Method and apparatus for low cost error recovery in predictive coding

Abstract

To provide a method, apparatus, decoder and computer program for replacing decoded parameters of a received multi-channel signal.SOLUTION: The decoder decodes multi-channel parameters of a frame of the signal, determines that a parameter memory is corrupted if a bad frame is indicated, derives a location measurement of a reconstructed sound source based on the decoded multi-channel parameters when the parameter memory is not corrupted if a bad frame is not indicated, and determines whether the reconstructed sound source is stationary and primarily concentrated within a subset of channels of the multi-channels of the received multi-channel signal based on the location measurement when the parameter memory is corrupted; If it is stable and concentrated in the subset, parameter recovery is activated to replace the decoded multi-channel parameters with the stored multi-channel parameters.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] This application relates to methods and apparatus for error resilience in predictive coding for stereo or multi-channel audio encoding and decoding. [Background technology]

[0002] Although capacity within communication networks is continuously increasing, limiting the required bandwidth per communication channel remains a major concern. In mobile networks, smaller transmission bandwidth for each call results in lower power consumption in both mobile devices and base stations. This translates into energy and cost savings for mobile operators, while end users experience longer battery life and increased talk time. Furthermore, with less bandwidth consumed per user, mobile networks can serve more users in parallel.

[0003] Through current music playback systems and movie theaters, most listeners are accustomed to high-quality immersive audio. In mobile communication services, constraints on radio resources and processing delays have kept quality at a lower level, and most voice services still deliver only mono sound. In recent years, stereo and multi-channel sound for communication services has gained momentum in the context of virtual / augmented / augmented reality, which requires immersive sound reproduction beyond mono sound. Rendering high-quality spatial sound within the bandwidth constraints of communication networks still presents challenges. Sound reproduction also needs to deal with variable channel conditions, where occasional data packets may be lost due to, for example, network congestion or insufficient cell coverage.

[0004] In a typical stereo recording, channel pairs may exhibit a high degree of similarity, or correlation. Some embodiments of stereo coding schemes may exploit this correlation by employing parametric coding, in which a single channel is coded with high quality and complemented by a parametric description that allows reconstruction of the complete stereo image, such as the scheme discussed in C. Faller, "Parametric multichannel audio coding: synthesis of coherence cues," in IEEE Transactions on Audio, Speech, and Language Processing, vol. 14, no. 1, pp. 299-310, January 2006. The process of reducing a channel pair to a single channel is often called downmixing, and the resulting channel is often called the downmix channel. Downmix procedures typically attempt to preserve energy by aligning inter-channel time differences (ITDs) and inter-channel phase differences (IPDs) before mixing the channels. Inter-channel level differences (ILDs) may also be measured to maintain energy balance in the input signal. The ITD, IPD, and ILD can then be coded and used in an inverted upmix procedure to reconstruct the stereo channel pair at the decoder. The ITD, IPD, and ILD parameters describe the correlated components of the channel pair, while the stereo channel pair may also contain uncorrelated components that cannot be reconstructed from the downmix. These uncorrelated components can be represented by an inter-channel coherence parameter (ICC). The uncorrelated components can be synthesized at the stereo decoder by passing the decoded downmix channels through a decorrelator filter, which outputs a signal with low correlation with the decoded downmix. The strength of the uncorrelated components can be controlled by the ICC parameters.

[0005] Similar principles apply to multi-channel audio such as 5.1 and 7.1.4, as well as spatial audio representations such as Ambisonics or spatial audio object coding. The number of channels can be reduced by exploiting correlation between channels and bundling a reduced channel set and metadata or parameters for channel reconstruction or spatial audio rendering at the decoder.

[0006] To overcome the problems of transmission errors and packet loss, communication services utilize packet loss concealment (PLC) techniques. When a data packet is lost or corrupted due to a poor connection, network congestion, etc., the missing information of the lost or corrupted data packet at the receiver side is replaced by a decoder with a synthetic signal to conceal the lost or corrupted data packet. Some embodiments of PLC techniques are often closely coupled with the decoder, in which case the internal state can be used to generate signal continuation or extrapolation to cover packet loss. For multi-mode codecs with several operating modes for different signal types, there are often several PLC techniques that can be implemented to handle the concealment of lost or corrupted data packets.

[0007] Missing or corrupted packets are identified by the transport layer handling the connection and conveyed to the decoder as "bad frames" through a Bad Frame Indicator (BFI), which may be in the form of a flag. The decoder stores this flag in its internal state and may also track the history of bad frames, e.g., a "previous Bad Frame Indicator" (PREV BFI). Note that one transmitted packet may contain one or more speech or audio frames. This means that one lost or corrupted packet will cause all of the frames it contains to be labeled as "bad."

[0008] For stable audio scenes, parameters may show a high degree of similarity between adjacent frames. To exploit this similarity, predictive coding schemes may be applied. In such schemes, predictions of current frame parameters are derived based on past decoded parameters, and the difference from the true parameters is coded. A simple but effective prediction is to use the last decoded parameters as predictions; in this case, the predictive coding scheme can be referred to as a differential coding scheme.

[0009] One problem with predictive coding schemes is that they can be sensitive to errors. For example, if one or more elements of a predicted sequence are lost, the decoder will have a prediction error that can persist for a long time after the error occurs. This problem, called error propagation, can exist in any predictive coding scheme. An illustration of error propagation is provided in FIG. 1. In FIG. 1, an absolute coding frame is lost before a sequence of consecutive predictive coding frames (i.e., a predictive coding streak). The memory that would have been updated with parameters from the lost frame stores the previous parameters and is therefore corrupted. Because the memory is corrupted by the frame loss, the error will continue for the entire duration of the predictive coding streak and will only end when a new absolute coding frame is received. One consequence of such a loss is an effect on the synthesized signal, which can be an unwanted, even dramatic, change in the perceived location of the source. This is particularly noticeable when the source has a static and extreme position, such as a sound source located at either the far right or far left in a stereo scene.

[0010] One improvement is to force non-predictive coding at regular time intervals, which will terminate error propagation. Another solution is to use a partial redundancy scheme, where a low-resolution encoding of the parameters is transmitted along with adjacent audio frames. If the decoder detects a frame loss in a predictive coding streak, the low-resolution parameters can be used to reduce error propagation. Summary of the Invention

[0011] One drawback of the predictive coding improvements mentioned above is that they consume bandwidth, which is wasted bandwidth when the transmission channel is error-free.

[0012] According to some embodiments, a method for replacing decoded parameters in a received multi-channel signal is provided. The method includes decoding multi-channel parameters of a frame of the received multi-channel signal. The method further includes determining whether a bad frame is indicated. In response to the bad frame indication, the method includes determining that the parameter memory is corrupted. In response to the bad frame not being indicated and the parameter memory not being corrupted, the method includes deriving a location measurement of a reconstructed sound source based on the decoded multi-channel parameters. In response to the parameter memory being corrupted, the method includes determining based on the location measurement whether the reconstructed sound source is stable and primarily centered within a subset of channels of the multi-channel signal. In response to the reconstructed sound source being centered within a subset of channels of the multi-channel signal and being stable, the method includes initiating parameter recovery to replace the decoded multi-channel parameters with the stored multi-channel parameters.

[0013] A potential advantage of using parameters from memory instead of decoded parameters is that the operation can reduce predictive coding problems without transmitting redundant parameter information that would be wasted in error-free channel operation. Furthermore, using estimated parameters only during stable audio scene periods avoids the audio scene being "frozen" in an unnatural manner during unstable audio scene periods.

[0014] Another potential advantage of using parameters from memory instead of decoded parameters is that when a bad frame is indicated, the perceived location of the reproduced sound using parameters from memory may be closer to the actual location of the sound compared to the decoded parameters. In particular, using parameters from memory may reduce undesired or unnatural shifts in sound location when the source is stable and concentrated within one channel or a subset of channels.

[0015] According to some embodiments of the inventive concept, a decoder for a communication network is provided. The decoder has a processor and a memory coupled to the processor, the memory including instructions that, when executed by the processor, cause the processor to perform operations including decoding multi-channel parameters of a frame of a received multi-channel signal. The operations further include determining whether a bad frame is indicated. The operations further include determining that the parameter memory is corrupted in response to the bad frame being indicated. The operations further include deriving a location measurement of a reconstructed sound source based on the decoded multi-channel parameters in response to the bad frame not being indicated and the parameter memory not being corrupted. The operations further include determining, in response to the parameter memory being corrupted, based on the location measurement whether the reconstructed sound source is stable and whether it is primarily centered within a subset of channels of the multi-channel signal. In response to the reconstructed sound source being centered within a subset of channels of the multi-channel signal and being stable, the operations include initiating parameter recovery to replace the decoded multi-channel parameters with the stored multi-channel parameters.

[0016] According to some embodiments of the inventive concept, there is provided a decoder configured to operate in a communications network. The decoder is adapted to perform operations including decoding multi-channel parameters of a frame of a received multi-channel signal. The operations include determining whether a bad frame is indicated. The operations include determining that a parameter memory is corrupted in response to the bad frame indication. The operations include deriving a location measurement of a reconstructed sound source based on the decoded multi-channel parameters in response to the bad frame not being indicated and the parameter memory not being corrupted. The operations include determining whether the reconstructed sound source is stable and primarily centered within a subset of channels of the multi-channel signal based on the location measurement in response to the parameter memory being corrupted. In response to the reconstructed sound source being centered within a subset of channels of the multi-channel signal and being stable, the operations include initiating parameter recovery to replace the decoded multi-channel parameters with the stored multi-channel parameters.

[0017] According to some embodiments of the inventive concept, there is provided a computer program comprising computer-executable instructions, which, when executed on a processor included in a device, cause the device to perform operations. The operations include decoding multi-channel parameters of a frame of a received multi-channel signal. The operations further include determining whether a bad frame is indicated. The operations further include determining that the parameter memory is corrupted in response to the bad frame being indicated. The operations include deriving a location measurement of a reconstructed sound source based on the decoded multi-channel parameters in response to the bad frame not being indicated and in response to the parameter memory not being corrupted. The operations include determining, in response to the parameter memory being corrupted, based on the location measurement whether the reconstructed sound source is stable and whether it is primarily concentrated within a subset of channels of the multi-channel signal. In response to the reconstructed sound source being concentrated within a subset of channels of the multi-channel signal and being stable, the operations include initiating parameter recovery to replace the decoded multi-channel parameters with the stored multi-channel parameters.

[0018] According to some embodiments of the inventive concept, a computer program product is provided comprising a non-transitory computer-readable storage medium having computer-executable instructions that, when executed on a processor included in a device, cause the device to perform operations including decoding multi-channel parameters of a frame of a received multi-channel signal. The operations further include determining whether a bad frame is indicated. The operations further include determining, in response to the bad frame being indicated, that the parameter memory is corrupted. The operations include, in response to the bad frame not being indicated and in response to the parameter memory not being corrupted, deriving a location measurement of the reconstructed sound source based on the decoded multi-channel parameters. The operations, in response to the parameter memory being corrupted, include determining, based on the location measurement, whether the reconstructed sound source is stable and whether it is primarily concentrated within a subset of the channels of the multi-channel signal. In response to the reconstructed sound source being centered and stable within a subset of the channels of the multi-channels, the operations include invoking parameter recovery to replace the decoded multi-channel parameters with the stored multi-channel parameters.

[0019] According to some embodiments of the inventive concept, there is provided an apparatus configured to replace decoded parameters with estimated parameters in a received multi-channel signal. The apparatus includes at least one processor and a memory communicatively coupled to the processor, the memory including instructions executable by the processor, the instructions causing the processor to perform operations. The operations include decoding multi-channel parameters of a frame of the received multi-channel signal. The operations further include determining whether a bad frame is indicated. The operations further include determining, in response to the bad frame indication, that the parameter memory is corrupted. In response to the bad frame not being indicated and in response to the parameter memory not being corrupted, the operations include deriving a location measure of the reconstructed sound source based on the decoded multi-channel parameters. In response to the parameter memory being corrupted, the operations include determining, based on the location measure, whether the reconstructed sound source is stable and whether it is primarily concentrated within a subset of the channels of the multi-channel signal. In response to the reconstructed sound source being centered and stable within a subset of the channels of the multi-channels, the operations include invoking parameter recovery to replace the decoded multi-channel parameters with the stored multi-channel parameters.

[0020] According to another embodiment of the inventive concept, there is provided a method for replacing decoded parameters in a received multi-channel signal. The method includes determining whether a coding mode is an absolute coding mode or a predictive coding mode. In response to the coding mode being a predictive coding mode, the method includes determining whether a memory corruption flag is set. In response to the memory corruption flag being set, the method includes determining whether the reconstructed sound source is a stable source and whether location measurements of the reconstructed sound source are primarily centered within a subset of channels. In response to the reconstructed sound source being a stable source and the location measurements of the reconstructed sound source are primarily centered within a subset of channels of the multi-channel signal, the method includes replacing the decoded multi-channel parameters with stored multi-channel parameters. In response to the memory corruption flag not being set, the method includes analyzing location measurements of the source position to update the location measurements, and updating the stored multi-channel parameters with the decoded multi-channel parameters.

[0021] According to some other embodiments of the inventive concept, a decoder for a communications network is provided. The decoder includes a processor and a memory coupled to the processor, the memory comprising instructions that, when executed by the processor, cause the processor to perform operations. The operations include determining whether a coding mode is an absolute coding mode or a predictive coding mode. The operations include determining whether a memory corruption flag is set in response to the coding mode being the predictive coding mode. The operations include determining whether a reconstructed sound source is a stable source and whether location measurements of the reconstructed sound source are primarily centered within a subset of channels in response to the memory corruption flag being set. The operations include replacing decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being a stable source and the location measurements of the reconstructed sound source being primarily centered within a subset of channels of the multi-channel. The operations include analyzing location measurements of source positions to update the location measurements and updating the stored multi-channel parameters with the decoded multi-channel parameters in response to the memory corruption flag not being set.

[0022] According to some other embodiments of the inventive concept, there is provided a decoder configured to operate in a communications network. The decoder is adapted to perform operations including determining whether a coding mode is an absolute coding mode or a predictive coding mode. The operations include determining whether a memory corruption flag is set in response to the coding mode being the predictive coding mode. The operations include determining whether a reconstructed sound source is a stable source and whether location measurements of the reconstructed sound source are primarily centered within a subset of channels in response to the memory corruption flag being set. The operations include replacing decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being a stable source and the location measurements of the reconstructed sound source being primarily centered within a subset of channels of the multi-channel. The operations include analyzing location measurements of the source position to update the location measurements and updating the stored multi-channel parameters with the decoded multi-channel parameters in response to the memory corruption flag not being set.

[0023] According to some other embodiments of the inventive concept, there is provided a computer program comprising computer-executable instructions that, when executed on a processor included in a device, cause the device to perform operations. The operations include determining whether a coding mode is an absolute coding mode or a predictive coding mode. The operations include determining whether a memory corruption flag is set in response to the coding mode being the predictive coding mode. The operations include determining whether the reconstructed sound source is a stable source and whether location measurements of the reconstructed sound source are primarily centered within a subset of channels in response to the memory corruption flag being set. The operations include replacing decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being a stable source and the location measurements of the reconstructed sound source being primarily centered within a subset of channels of the multi-channel. The operations include analyzing location measurements of the source position to update the location measurements and updating the stored multi-channel parameters with the decoded multi-channel parameters in response to the memory corruption flag not being set.

[0024] According to some other embodiments of the inventive concept, there is provided a computer program product comprising a non-transitory computer-readable storage medium having computer-executable instructions, which, when executed on a processor included in a device, cause the device to perform operations. The operations include determining whether a coding mode is an absolute coding mode or a predictive coding mode. The operations include determining whether a memory corruption flag is set in response to the coding mode being the predictive coding mode. The operations include determining whether the reconstructed sound source is a stable source and whether location measurements of the reconstructed sound source are primarily centered within a subset of channels in response to the memory corruption flag being set. The operations include replacing decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being a stable source and the location measurements of the reconstructed sound source being primarily centered within a subset of channels of the multi-channel. The operations include analyzing location measurements of the source position to update the location measurements and updating the stored multi-channel parameters with the decoded multi-channel parameters in response to the memory corruption flag not being set.

[0025] According to some other embodiments of the inventive concept, there is provided an apparatus configured to replace decoded parameters in a received multi-channel signal with estimated parameters. The apparatus includes at least one processor and a memory communicatively coupled to the processor, the memory including instructions executable by the processor, causing the processor to perform operations. The operations include determining whether a coding mode is an absolute coding mode or a predictive coding mode. The operations include determining whether a memory corruption flag is set in response to the coding mode being the predictive coding mode. The operations include determining whether a reconstructed sound source is a stable source and whether location measurements of the reconstructed sound source are primarily centered within a subset of channels in response to the memory corruption flag being set. The operations include replacing the decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being a stable source and the location measurements of the reconstructed sound source are primarily centered within a subset of channels of the multi-channel signal. The operations include, in response to the memory corruption flag not being set, analyzing location measurements of the source position to update the location measurements and updating the stored multi-channel parameters with the decoded multi-channel parameters.

[0026] The accompanying drawings, which are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this application, illustrate certain non-limiting embodiments of the inventive concepts. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is an exemplary diagram of error propagation. [Figure 2] FIG. 1 is a block diagram illustrating an example of a decoder system environment in which error recovery in predictive coding may be performed, according to some embodiments. [Figure 3]1 is a block diagram illustrating components of a stereo encoder and decoder according to some embodiments. [Figure 4] 10 is a flowchart illustrating the operation of a decoder according to some embodiments of the inventive concept. [Figure 5] FIG. 1 is a block diagram illustrating the operation of a decoder by providing error recovery according to some embodiments of the inventive concept. [Figure 6] FIG. 1 is a block diagram illustrating a state machine according to some embodiments of the inventive concept. [Figure 7] FIG. 10 is a block diagram illustrating operations for generating substitution parameters according to some embodiments of the inventive concept. [Figure 8] FIG. 1 is a block diagram illustrating a decoder according to some embodiments of the inventive concept. [Figure 9] 10 is a flowchart illustrating the operation of a decoder according to some embodiments of the inventive concept. [Figure 10] 10 is a flowchart illustrating the operation of a decoder according to some embodiments of the inventive concept. DETAILED DESCRIPTION OF THE INVENTION

[0028] The inventive concepts will now be described more fully hereinafter with reference to the accompanying drawings, in which example embodiments of the inventive concepts are shown. However, the inventive concepts may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concepts to those skilled in the art. It should also be noted that these embodiments are not mutually exclusive. Elements from one embodiment may be implicitly contemplated as being present / used in another embodiment.

[0029] The following description presents various embodiments of the disclosed subject matter. These embodiments are presented as instructional examples and should not be construed as limiting the scope of the disclosed subject matter. For example, certain details of the described embodiments can be modified, omitted, or expanded without departing from the scope of the described subject matter.

[0030] The described inventive concept maintains a memory of the most recently received parameters corresponding to the source location. If the decoder detects an error in the predictive coding streak and the location analysis determines that the source is stable and has an extreme position (i.e., the source location measurements are primarily concentrated within a subset of channels of the multi-channel signal being decoded), the parameters from the memory may be used instead of the decoded parameters until the predictive coding streak is terminated by an absolute coding frame.

[0031] In cases where the audio scene is unstable and exhibits large variations in the stereo parameters, replacing the decoded parameters with frozen estimated parameters may be unpleasant for the listener.

[0032] To achieve these goals, a method in one embodiment includes a location analyzer for determining source locations, a parameter memory for storing parameters for the last observed active source, a memory corruption detector for determining whether the parameter memory is corrupted, and a decision mechanism for initiating parameter recovery (replacing decoded parameters with parameters stored in the memory) based on at least a history of bad frame indicators and, in a further embodiment, the output of the location analyzer. Here, an active source refers to a source intended to be reconstructed, such as a voice in a speech conversation. When a source is inactive (quiet), the captured sound is typically dominated by background noise, which is considered less relevant for sound reconstruction. The background noise may consist of many different sources that may render an unstable audio scene with large variations in the parametric description. When estimating active source locations, this large variation should be ignored. Therefore, it may be beneficial to estimate the location only when the source is active.

[0033] One advantage that may be provided by the inventive concept includes reducing the problem of channel errors during predictive coding without transmitting redundant parameter information that would be wasted in error-free channel operation. Another advantage that may be provided is that parameter estimation in predictive decoding operation is not enabled for unstable audio scenes, which leads to avoiding unnaturally frozen audio scenes. Yet another advantage that may be provided is that if the source location is stable and concentrated within a subset of the channels of the multi-channel signal, this may reduce unnatural or undesirable instability at the source location.

[0034] FIG. 2 illustrates an example operating environment for a decoder 200 that may be used to decode a multi-channel bitstream as described herein. The decoder 200 may be part of a media player, a mobile device, a set-top device, a desktop computer, etc. In other embodiments, the decoder 200 may be embodied in hardware and / or software of a standalone server, a cloud-implemented server, a distributed server, or as a processing resource in a server farm. For example, the decoder may be part of a cloud-implemented videoconferencing application. The decoder 200 receives an encoded bitstream transmitted over a transport layer of a network. The bitstream may be sent from an encoder, from a storage device 204, from a device on the cloud via the network 202, etc. During operation, the decoder 200 receives and processes frames of the bitstream as described herein. The decoder 200 may output a multi-channel audio signal and transmit the multi-channel audio signal to a multi-channel audio player 206 having at least one loudspeaker for playback of the multi-channel audio signal. The storage device 204 may be part of a storage repository of multi-channel audio signals, e.g., a store or streaming music service, a separate storage component, a component of a mobile device, a multi-channel audio player, a Bluetooth speaker, a device with at least one loudspeaker, a mobile device, a streaming music service, etc.

[0035] While parametric stereo reproduction provides good quality at low bit rates, this quality tends to saturate as the bit rate increases due to limitations of the parametric model. To overcome this problem, decorrelated components can be coded. This encoding is achieved by simulating stereo reconstruction in the encoder and subtracting the reconstructed signal from the input channels to produce a residual signal. If the downmix conversion is invertible, the residual signal can be represented by only a single channel for the stereo channel case. Typically, residual signal encoding targets lower frequencies, which are more psychoacoustically important, while higher frequencies can be synthesized using a decorrelator method. Figure 3 is a block diagram illustrating one embodiment of a setup for a parametric stereo codec including a residual coder. In FIG. 3 , the encoder 310 may receive an input signal, perform the above-described processing in the stereo processing and downmix block 312, encode an output via the downmix encoder 314, encode a residual signal via the residual encoder 316, and encode ITD parameters, IPD parameters, ILD parameters, and ICC parameters via the parameter encoder 318. The decoder 320 may receive the encoded output, the encoded residual signal, and the coded parameters. The decoder 320 may decode the residual signal via the residual decoder 326 and the downmix signal via the downmix decoder 324. The parameter decoder 328 may decode the coded parameters. The stereo synthesizer 322 may receive the decoded output signal and the decoded residual signal and output stereo channels CH1 and CH2 based on the decoded parameters.

[0036] 8 is a block diagram illustrating elements of a decoder 200 configured to decode multi-channel audio frames and provide error recovery for lost or corrupted frames in a predictive coding mode, according to some embodiments of the inventive concept. As shown, the decoder 200 may include a network interface circuit 805 (also referred to as a network interface) configured to provide communication with other devices / entities / functions, etc. The decoder 200 may also include a processor circuit 801 (also referred to as a processor) coupled to the network interface circuit 805, and a memory circuit 803 (also referred to as a memory) coupled to the processor circuit. The memory circuit 803 may include computer-readable program code that, when executed by the processor circuit 801, causes the processor circuit to perform operations according to embodiments disclosed herein.

[0037] According to other embodiments, the processor circuit 801 may be defined to include memory such that a separate memory circuit is not required. As discussed herein, the operations of the decoder 200 may be performed by the processing circuit 801 (also referred to as the processor) and / or the network interface circuit 805 (also referred to as the network interface). For example, the processing circuit 801 may control the network interface 805 to send communications to the multi-channel audio player 206 and / or to receive communications through the network interface 805 from one or more other network nodes / entities / servers, such as an encoder node, a depository server, etc. Additionally, modules may be stored within the memory circuit 803, and these modules may provide instructions such that, when the instructions of the modules are executed by the processing circuit 801, the processing circuit 801 performs respective operations.

[0038] In the following description, a stereo decoder of a stereo encoder and decoder system such as that outlined in FIG. 3 may be used. To illustrate the embodiments, two channels will be used. These embodiments may also be used with more than two channels. The multi-channel encoder 310 may process the input left and right channels in segments called frames. The stereo analysis and downmix block 312 may perform a parametric analysis and produce a downmix. For a given frame m, the two input channels are , N represents the sample number in frame m, and N is the length of the frame. In one embodiment, frames may be extracted with overlaps at the encoder so that a decoder can reconstruct a multi-channel audio signal using an overlap-add strategy. The input channels may be windowed with an appropriate window function w(n) and transformed to the Discrete Fourier Transform (DFT) domain. TIFF2026016503000003.tif34170It should be noted that other frequency domain representations may also be used here, such as a quadrature mirror filter (QMF) filter bank, a hybrid QMF filter bank, or an odd DFT (ODFT) representation composed of MDCT (Modified Discrete Cosine Transform) and MDST (Modified Discrete Cosine Transform) transform components.

[0039] For parametric analysis, the frequency spectrum can be partitioned into bands b, where each band b has a range of frequency coefficients k=k start(b) ...k end(b) ,b=0,1,2,...N bands -1 corresponds to, where N bandsrepresents the total number of bands. The band limits are set to reflect the resolution of human hearing, which typically suggests narrow bands for low frequencies and wider bands for high frequencies. Note that different band resolutions may be used for different parameters.

[0040] The signal can then be analyzed to extract ITD, IPD, and ILD parameters. Note that ILD can have a significant effect on the perceived location of a sound. Therefore, in some embodiments, it can be important to reconstruct ILD parameters with high accuracy in order to maintain a stable and accurate location of the sound.

[0041] Also, channel coherence may be analyzed and ICC parameters may be derived. The set of multi-channel audio parameters for frame m may contain the complete set of ITD, IPD, ILD, and ICC parameters used in the parametric representation. The parameters may be encoded by the parameter encoder 318 and added to a bitstream, which may be stored and / or transmitted to a decoder.

[0042] Before producing the downmix channels, in one embodiment, it may be beneficial to compensate for the ITD and IPD to reduce cancellation and maximize the energy of the downmix. ITD compensation can be implemented in both the time domain before frequency conversion or the frequency domain, but ITD compensation essentially performs a time shift on one or both channels to remove the ITD. Phase alignment may be implemented in different ways, but the goal is to align the phase so that cancellation is minimized, which ensures maximum energy in the downmix. ITD and IPD adjustments may be made in frequency bands or across the entire frequency spectrum, and the adjustments may be made using quantized ITD and IPD parameters to ensure that the transformations can be inverted at the decoder stage.

[0043] The embodiments described below are independent of the implementation of IPD and ITD parameter analysis and compensation. In other words, the embodiments are independent of how IPD and ITD are analyzed and compensated. In such embodiments, ITD and IPD adjusted channels may be represented using an apostrophe ('). TIFF2026016503000004.tif13170

[0044] The ITD and IPD adjusted input channels may then be downmixed by the parametric analysis and downmix block 312 to produce a center / side representation, also called a downmix / side representation. One approach to performing the downmix is ​​to use sums and differences of signals. TIFF2026016503000005.tif25170

[0045] Downmix signal X M(m, k) may be encoded by the downmix encoder 314 and stored and / or transmitted to the decoder. This encoding may be performed in the frequency domain, but may also be performed in the time domain. In the latter case, a DFT synthesis stage is required to produce a time-domain version of the downmix signal, which is then provided to the downmix encoder 314. However, the conversion to the time domain may introduce delay misalignment with the multi-channel audio parameters, which would require additional handling. In one embodiment, this delay misalignment is resolved by introducing additional delays or by interpolating the parameters to ensure that the decoder synthesis of the downmix and the multi-channel audio parameters is aligned.

[0046] Side signal X S The reconstruction of (m, k) can be generated from the obtained multi-channel audio parameters through downmixing and local parametric synthesis. TIFF2026016503000006.tif7170 is the downmix signal TIFF2026016503000007.tif7170, where p(·) is a predictor function, which may be implemented as a single scale factor α that minimizes the mean squared error (MSE) between the side signal and the predicted side signal. Furthermore, the prediction may be applied to frequency bands, with prediction parameters for each frequency band b. TIFF2026016503000008.tif7170

[0047] The coefficients of band b are expressed as a column vector TIFF2026016503000009.tif7170 and X M,b If specified as (m), the minimum MSE predictor is It can be derived as TIFF2026016503000010.tif14170.

[0048] However, this expression can be simplified to yield more stable prediction parameters. b does not represent a level difference, but may control the portion of the downmix signal that is routed to the left and right channels. Thus, with respect to the ILD parameters, the prediction parameter α b (m) can have a significant effect on the perceived sound location. Further details are explained in the prediction modes section of Breebaart, J., Herre, J., Faller, C., Roden, J., Myburg, F., Disch, S., ...& Oomen, W. (2005). "MPEG spatial audio coding / MPEG surround: Overview and current status," 2005 In Preprint 119th Conv. Aud. Eng. Soc. (No. LCAV-CONF-2005-029). The prediction parameter α b (m) is then coded using an inter-frame predictive coding scheme, where the differences between frames m are taken into account. For each band b, the reconstructed parameters of the previous frame The difference from TIFF2026016503000011.tif6170 can be calculated. TIFF2026016503000012.tif8170

[0049] The encoder uses α b (m) or Δα b (m) may be chosen to encode, depending on which of these produces the lowest bit consumption. b (m) and Δα b (m) may be quantized using a scalar quantizer on the quantizer index followed by an entropy coder. Arithmetic coding, Huffman coding, and Golomb-Rice coding are examples of coding that may be used as entropy coders. An entropy coder is one that can tolerate small variations, i.e., Δα bFor small values ​​of (m), we assign smaller codewords. b This means that predictive coding using (m) will be used for stable audio scenes. b In the case of fast scene changes, which leads to (m), α b The bit consumption for encoding (m) can be lower by using a non-predictive, or absolute, encoding scheme. Therefore, the encoding scheme can have two modes. TIFF2026016503000013.tif16170

[0050] Encoding mode alpha mode (m)∈{ABSOLUTE, PREDICTIVE} is a value that is encoded as TIFF2026016503000014.tif16170.

[0051] Further variations of this encoding scheme are possible. For example, the prediction parameter α b If (m) shows a high correlation with another parameter, such as the residual coding energy or a corresponding representation, it may be beneficial to jointly code these parameters. The important part is that if the encoding scheme has a predictive coding mode and an absolute (non-predictive) coding mode, this decision is coded and conveyed to the decoder. A sequence of consecutive PREDICTIVE coding modes may be referred to as a "predictive coding streak" or "predictive streak" and will be observed for audio segments where the scene is stable. If an audio frame at the start of a predictive streak is lost, the parameters may suffer from error propagation throughout the entire duration of the streak (see FIG. 1). To reduce the effects of error propagation, absolute coding may be enforced at regular intervals, which effectively limits the predictive streak to a maximum length in time.

[0052] After encoding, the parameters A local reconstruction of TIFF2026016503000015.tif6170 is derived in the encoder, stored in memory, and used when encoding the next frame. TIFF2026016503000016.tif6170

[0053] The decoding step may be similar to the encoder step. TIFF2026016503000017.tif14170

[0054] It should be noted that although the predictive coding is described for reconstructed values, it is also possible to perform the predictive coding step on the quantizer indices, however the principles of memory dependency remain the same.

[0055] During error-free operation, the local reconstruction at the encoder is It is the same as TIFF2026016503000018.tif6170. Memory TIFF2026016503000019.tif6170 is frame m-1, Note also that the reconstructed parameter values ​​for TIFF2026016503000020.tif6170 will be identical. For the first frame, the parameter memory may be set to some predefined value, e.g., all zeros, or the average expected value of the parameters.

[0056] Details regarding residual coding are discussed here. Given a predicted side signal, the prediction residual X R (m, k) can be created. TIFF2026016503000021.tif6170

[0057] The prediction residual may be input to the residual encoder 316. Encoding may be performed directly in the DFT domain or in the time domain. Similarly, with respect to a downmix encoder, a time-domain encoder would require DFT synthesis, which may require signal alignment at the decoder. The residual signal represents diffuse components that are uncorrelated with the downmix signal. If the residual signal is not transmitted, a solution in one embodiment may be to replace the signal for the residual signal in stereo synthesis at the decoder with a signal derived from a decorrelated version of the decoded downmix signal. Substitution is typically used for low bitrates, where the bit budget is too low to represent the residual signal with any useful resolution. For intermediate bitrates, it may be common to encode a portion of the residual. In this case, lower frequencies are often encoded, as they may be more perceptually important. For the remaining part of the spectrum, a decorrelator signal may be used as a substitute for the residual signal at the decoder. This approach is often referred to as a hybrid coding mode. Further details are provided in the decoder description below.

[0058] The encoded downmix representation, the encoded multi-channel audio parameters, and the encoded residual signal may be multiplexed into a bitstream (not shown), which may be transmitted to a decoder 320 or stored on a medium for future decoding.

[0059] In the decoder, a downmix decoder 328 generates a reconstructed downmix signal TIFF2026016503000022.tif7170, which is segmented into DFT analysis frames m, where n=0, 1, 2, ..., N-1 represents the sample number within frame m. The analysis frames are typically extracted with overlap to allow for an overlap-add strategy in the DFT synthesis stage. The corresponding DFT spectrum is then extracted using the DFT transform TIFF2026016503000023.tif16170, where w(n) represents an appropriate window function. The shape of the window function can be designed using a trade-off between frequency characteristics and algorithm delay due to the length of the overlap region. Similarly, the residual decoder 326 generates a residual image for frame m and time instance n=0, 1, 2, ...N R -1, the reconstructed residual signal TIFF2026016503000024.tif7170. The residual signal can be generated at different sampling rates, so the frame length N R Note that may be different from N. Since the residual coding may only cover a lower frequency range, it may be beneficial to express the residual coding at a lower sampling rate to save memory and computational complexity. The DFT representation of TIFF2026016503000025.tif6170 is obtained. If the residual signal is upsampled in the DFT domain to the same sampling rate as the reconstructed downmix, the DFT coefficients are N / N R It will need to be scaled by Note that TIFF2026016503000026.tif6170 will be zero-padded to match the length N. For simplicity of notation, and for purposes of better understanding, since the embodiment is not affected by the use of different sampling rates, in the following description, the sampling rates will be assumed to be equal and N R = N. Therefore, no scaling or zero padding shall be indicated.

[0060] It should be noted that if the downmix and / or the residual signal is coded in the DFT domain, a frequency transformation by DFT is not necessary. In this case, decoding of the downmix and / or the residual signal provides the necessary DFT spectrum for further processing.

[0061] In an error-free frame, often referred to as a good frame, a multi-channel audio decoder may use the decoded downmix signal together with the decoded multi-channel audio parameters in combination with the decoded residual signal to produce a multi-channel synthesis. b For case (m), the decoder uses the mode parameter α mode (m) to select the appropriate decoding mode and to obtain the reconstructed prediction parameters Produces TIFF2026016503000027.tif6170. TIFF2026016503000028.tif12170

[0062] The parameter memory stores the reconstructed predicted parameters. Updated with TIFF2026016503000029.tif6170. TIFF2026016503000030.tif6170

[0063] Decoded Downmix TIFF2026016503000031.tif6170 Stereo parameters and residual signal TIFF2026016503000032.tif7170 is fed into the parametric stereo synthesis block 322 to produce a reconstructed stereo signal. After stereo synthesis in the DFT domain is applied, the left and right channels are transformed into the time domain and output from the stereo decoder.

[0064] If a decoder detects a lost or corrupted frame, it may use one or several PLC modules to conceal the missing data. For example, there may be several dedicated PLC techniques to replace the missing information, as part of a downmix decoder, a residual decoder, or a parameter decoder. The goal of PLC is to generate an extrapolated audio segment similar to the missing audio segment, ensuring a smooth transition between the correctly decoded audio before and after the lost or corrupted frame.

[0065] PLC methods for stereo parameters may vary. One example is to simply repeat the parameters of the previous decoded frame. Another method is to use the average stereo parameters observed over a large audio database, or to slowly converge to the average stereo parameters for successive frame losses (burst losses). The PLC method may update the parameter memory with the concealment parameters, or may leave the parameter memory as it is, so that the last decoded parameters remain. In either case, the memory will be out of sync with the encoder.

[0066] 4, a flowchart of decoder operation in one embodiment of predictive parametric coding recovery is provided. If a bad frame is indicated through a bad frame indicator (BFI) in operation 400, the decoder may employ packet loss concealment methods in operation 402, and in some embodiments, may add a flag (e.g., α memory_corrupted_flag :=TRUE). If BFI is not active, normal decoding is used in operation 406. After normal decoding, parameter recovery operation 408 is performed.

[0067] More specifically, the error-free decoding operation can be explained as outlined by Fig. 5, which can be compared to the stereo decoder block 320 of Fig. 3. Fig. 5 provides a downmix decoder 510 and, optionally, a residual decoder 520. The decoder has a parameter decoder 530 with parameter recovery, which will be explained in more detail below.

[0068] The parameter decoder 532 may perform decoding of the stereo parameters using either an absolute coding mode or a predictive coding mode. In the following description, the reconstructed side signal prediction parameters TIFF2026016503000033.tif6170 shall be used for the error recovery method. In the location analyzer block 538, location measurements are derived that represent the positions of the sources. An example of a location measurement is the reconstructed prediction parameters σ across all subbands for each frame. Average value of TIFF2026016503000034.tif6170 The solution is to use TIFF2026016503000035.tif6170. TIFF2026016503000036.tif14170

[0069] The recovery solution will be triggered when the location is extreme and static (or stable). The extreme location can be expressed as a concentration of signal power in a certain channel or direction, where a shift in the direction of the concentrated energy has a large effect on the perceived location. For example, in a stereo signal, the extreme location represents a source concentrated in the left or right channel. In other words, the source location measurement (e.g., the reconstructed source signal) is primarily concentrated within a subset of channels of the multi-channel signal. In the case of a stereo signal, the source location measurement will be primarily concentrated in one of the two channels. The triggering mechanism will be based on a low-pass filtered location, e.g., It may be based on TIFF2026016503000037.tif11170.

[0070] Here, the threshold Any position value less than TIFF2026016503000038.tif6170 This will reset TIFF2026016503000039.tif6170 to zero.

[0071] A suitable value for the filter parameter γ may be γ=0.425, or in the range [0.3, 0.7]. The extreme location decision P(m) may be formed by comparing the low-pass filtered position with a fixed threshold: TIFF2026016503000040.tif12170However, TIFF2026016503000041.tif6170 is the parameter It depends on the range of TIFF2026016503000042.tif6170, where α b As a result, TIFF2026016503000043.tif6170 is [-1.0,1.0], An appropriate value for TIFF2026016503000044.tif6170 is 0.4. In other words, P(m) equal to 1 indicates that the sound source is panned to either the left or right channel, and is therefore a stable source at an extreme position. If the value of TIFF2026016503000045.tif6170 is 0.4, it is greater than 0.4 or less than -0.4. Any value of TIFF2026016503000046.tif6170 (i.e. TIFF2026016503000047.tif8170) would indicate that the sound source is at an extreme position (e.g., the location measurements are concentrated primarily in either the left or right channel). The value of TIFF2026016503000048.tif6170 may be set to another value.

[0072] The location measurements described above provide a solution that is computationally simple to implement. However, including a parameter difference weighting that takes into account the band energy of the downmix can make sense from a perceptual point of view. Furthermore, The weighting factors can be normalized to the [0.0,1.0] range so that TIFF2026016503000049.tif5170 remains in the [-0.1,0.1] range. Thus, an alternative representation for the location is TIFF2026016503000050.tif46170, provided that TIFF2026016503000051.tif6170 is the weighted location measure, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000052.tif6170 contains the weighted average of N bands is the number of subbands in frame m, and w b (m) and TIFF2026016503000053.tif6170 is the weighting factor, k end(b) is the end of the multiple summation, and k start(b) is the beginning of multiple sums, TIFF2026016503000054.tif6170 is the converted downmix signal.

[0073] The above expression is a panning measurement. Highlight high energy bands in TIFF2026016503000055.tif6170. It may be necessary to re-optimize the filter parameter γ by applying weighting to TIFF2026016503000056.tif6170. It may further be desirable to update the location measurements only during frame periods that are classified as coming from active sources, or to normalize the weighting by an estimate of the current peak energy or noise floor level.

[0074] The recovery decision logic depends on the outputs from the memory corruption detector 536 and the location analyzer 538. The memory corruption detector 536 may use at least the coding mode of parameters (predictive / absolute) and the bad frame indicator (BFI) in detecting memory corruption. The recovery decision logic can be further described by a state machine as outlined in FIG. 6.

[0075] 6, a starting state 610 represents the normal decoding mode. mode = PREDICTIVE and the preceding frame was a bad frame, this is the parameter The memory of TIFF2026016503000057.tif6170 is corrupted (α memory_corrupted_flag :=TRUE), the audio is at an extreme and stable position TIFF2026016503000058.tif7170 and transitions to recovery state 620. While in recovery state 620, the decoder enters absolute decoding mode α mode If the state transitions to ABSOLUTE, the state transitions to normal decoding state 610.

[0076] In the recovery state 620, the decoded parameters replace the parameters stored in memory. TIFF2026016503000059.tif7170 parameters Since TIFF2026016503000060.tif6170 is new from memory, it may be preferable not to update the parameter memory and position measurements. means TIFF2026016503000061.tif7170.

[0077] Returning to FIG. 5, the output of the parameter decoder with parameter recovery block 530, along with the outputs of the downmix decoder block 510 and potentially the residual decoder block 520, are input to the stereo synthesizer block 540, which synthesizes an audio signal for output on channels CH1 and / or CH2.

[0078] The operation of parameter recovery can also be explained by the flowchart of Figure 7. Now, turning to Figure 7, in operation 710, α is calculated to determine whether the coding mode is absolute or predictive. mode (m) Parameters can be checked.

[0079] In response to the coding mode being the absolute coding mode, at operation 720, the flag for indicating memory corruption is cleared, e.g., α memory_corrupted_flag :=Can be set to FALSE.

[0080] In response to the coding mode being a predictive coding mode, a memory state may be checked at operation 730. If the parameter memory is not corrupted (e.g., α memory_corrupted_flag =FALSE), the location of the sound source can be analyzed in operation 740. TIFF2026016503000062.tif6170 can be updated.

[0081] In operation 750, the memory of the decoded parameters may be updated. memory_corrupted_flag =TRUE), at operation 760 a determination is made as to whether the sound source is a stable source with an extreme position (e.g., TIFF2026016503000063.tif7170 shows that location measurements are primarily concentrated within a subset of channels of a multi-channel system).

[0082] In operation 770, in response to the sound source being a stable source with an extreme position, the decoded parameters are replaced with a memory of decoded parameters.

[0083] The operation of a decoder with parameter recovery can also be described by the flowchart in Figure 9. In operation 900, processing circuit 801 of decoder 200 may decode multi-channel parameters of a frame of a received multi-channel signal. This operation may be similar to operation 406 of Figure 4. In operation 902, decoder 200 may determine whether a bad frame is indicated. This operation may be similar to operation 400 of Figure 4. In one embodiment, this may be a flag derived from a flag in a data packet message.

[0084] In response to the bad frame being indicated, processing circuit 801 may perform a packet loss concealment operation in operation 904. This operation may be similar to operation 402 of Figure 4. For example, the packet loss concealment operation described above with respect to Figure 3 may be performed in operation 904.

[0085] At operation 906, the processing circuit 801 may determine whether the parameter memory is corrupted based on at least the coding mode and the preceding bad frame indicator. This operation may be similar to operation 730 of FIG. 7. In one embodiment, the coding mode may be one of an absolute coding mode or a predictive coding mode. In this embodiment, the determination is based on the coding mode being a predictive coding mode. Thus, determining whether the parameter memory is corrupted based on at least the coding mode and the preceding bad frame indicator is determined based on the coding mode being a predictive coding mode and the preceding bad frame indicator.

[0086] In operation 908, processing circuit 801 may derive a location measurement of the position of the source based on the decoded multi-channel parameters. This operation may be similar to operation 740 of Figure 7. In one embodiment, the location measurement is TIFF2026016503000064.tif14170, where: TIFF2026016503000065.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000066.tif6170 contains the average value, N bands is the number of subbands in frame m.

[0087] In another embodiment, the location measurement comprises: It may be derived based on TIFF2026016503000067.tif46170, provided TIFF2026016503000068.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000069.tif6170 contains the weighted average of N bands is the number of subbands in frame m, and w b (m) and TIFF2026016503000070.tif6170 is the weighting factor, k end(b) is the end of the multiple summation, and k start(b) is the beginning of multiple sums, TIFF2026016503000071.tif6170 is the converted downmix signal.

[0088] At operation 910, processing circuit 801 may determine whether the reconstructed sound source is stable and whether the location measurement is primarily centered within a subset of channels of the multi-channel signal. This operation may be similar to operation 760 of FIG. 7. In one embodiment, determining whether the reconstructed sound source is stable and whether the location measurement is primarily centered within a subset of channels of the multi-channel signal includes determining whether a low-pass filtered position exceeds a threshold, and determining that the location measurement is primarily centered within the subset of channels of the multi-channel signal in response to the low-pass filtered position exceeding the threshold. The low-pass filtered position may be TIFF2026016503000072.tif11170, where γ is a filter parameter, TIFF2026016503000073.tif6170 is the mean value of the reconstructed prediction parameters for frame m, TIFF2026016503000074.tif7170 is the low-pass filtered position.

[0089] If the multi-channel is two channels (e.g., a stereo system having a left channel and a right channel), determining whether the location measurements are primarily concentrated within a subset of channels of the multi-channel of the received multi-channel signal includes determining whether the location measurements are primarily concentrated within one of the two channels.

[0090] At operation 912, processing circuit 801 may initiate parameter recovery to replace the decoded multi-channel parameters with the stored multi-channel parameters in response to the location measurements of the reconstructed sound source being centered within a subset of the channels of the multi-channels, the reconstructed sound source being stable, and the parameter memory being corrupted. This operation may be similar to operation 770 of FIG. 7.

[0091] The operation of the decoder with parameter recovery can also be further explained by the flowchart in FIG.

[0092] If a bad frame is indicated, one or more PLC methods are used to determine the parameters. The bad frame may be indicated by a BFI flag indicating that a bad frame has been received. In operation 1000, the processing circuit 801 may set a memory corruption flag to indicate that the parameter memory is corrupted in response to the bad frame being indicated.

[0093] If no bad frame is indicated, a parameter decoder operation with parameter recovery is used. In operation 1002, the processing circuit 801 of the decoder 200 may determine whether the coding mode is an absolute decoding mode or a predictive coding mode. The decoder 200 may receive the coding mode from the encoder. This operation may be similar to operation 710 of FIG. 7.

[0094] In response to the coding mode being the absolute coding mode, the processing circuit 801 clears the memory corruption flag in operation 1004. The memory corruption flag may be used to indicate that the parameter memory is corrupted. This may occur if the frame preceding the currently decoded frame was a bad frame, which means that the parameter memory is corrupted. An example of setting the memory corruption flag is also illustrated in FIG. 4.

[0095] In response to the coding mode being a predictive coding mode, the processing circuit 801 may determine whether a memory corruption flag is set in operation 1006. This operation may be similar to operation 730 in FIG.

[0096] In response to the memory corruption flag being set, the processing circuit 801 may determine, at operation 1008, whether the reconstructed sound source is a stable sound source and whether location measurements of the reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel signal being decoded. This operation may be similar to operation 760 of FIG. 7. In one embodiment, determining whether location measurements of the reconstructed sound source are primarily concentrated within the subset of channels includes determining whether an absolute value of a low-pass filtered position exceeds a threshold, and determining that the location measurements of the reconstructed sound source are primarily concentrated within the subset of channels in response to the absolute value of the low-pass filtered position exceeding the threshold. The low-pass filtered position may be TIFF2026016503000075.tif11170, where γ is a filter parameter, TIFF2026016503000076.tif6170 is the mean value of the reconstructed prediction parameters for frame m, TIFF2026016503000077.tif6170 is the low-pass filtered position.

[0097] If the multi-channel is two channels (e.g., a stereo system having a left channel and a right channel), determining whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of the channels includes determining whether the location measurements of the reconstructed sound source are primarily concentrated in one of the two channels.

[0098] At operation 1010, processing circuit 801 may replace the decoded multi-channel parameters with the stored multi-channel parameters in response to the reconstructed sound source being a stable source and the location measurements of the reconstructed sound source being primarily concentrated within a subset of the channels of the multi-channels. This operation may be similar to operation 770 of FIG. 7.

[0099] In response to the memory corruption flag not being set, processing circuit 801 may analyze the location measurements of the source position to update the location measurements in operation 1012. This operation may be similar to operation 740 of FIG. 7. In one embodiment, updating the location measurements includes: TIFF2026016503000078.tif15170, where: TIFF2026016503000079.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000080.tif7170 contains the average value of N bands is the number of subbands in frame m.

[0100] In another embodiment, updating the location measurements comprises: TIFF2026016503000081.tif47170, provided that: TIFF2026016503000082.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000083.tif6170 contains the weighted average of N bands is the number of subbands in frame m, and w b (m) and TIFF2026016503000084.tif6170 is the weighting factor, k end(b) is the end of the multiple summation, and k start(b) is the beginning of multiple sums, TIFF2026016503000085.tif6170 is the converted downmix signal.

[0101] In response to the memory corruption flag not being set, processing circuit 801 may update the stored multi-channel parameters with the decoded multi-channel parameters at operation 1014. This operation may be similar to operation 750 of FIG.

[0102] The above description describes parameter recovery using decoder 200. A potential advantage of using parameters from memory instead of decoded parameters is that the operation can reduce predictive coding problems without transmitting redundant parameter information that would be wasted in error-free channel operation. Furthermore, using estimated parameters only during stable audio scene periods avoids the audio scene being "frozen" in an unnatural manner during unstable audio scene periods.

[0103] Another potential advantage of using parameters from memory instead of decoded parameters is that when a bad frame is indicated, the perceived location of the reproduced sound using parameters from memory may be closer to the actual location of the sound compared to the decoded parameters.

[0104] List of Embodiments 1. A method for permuting decoded parameters in a received multi-channel signal, the method comprising: Decoding (900) multi-channel parameters of a frame of a received multi-channel signal; determining whether a bad frame is indicated (902); In response to the bad frame being indicated, performing a packet loss concealment operation (904); In response to no bad frame being indicated, determining whether the parameter memory is corrupted based on at least the coding mode and the preceding bad frame indicator (906); deriving (908) a location measure of the reconstructed sound source based on the decoded multi-channel parameters; determining (910) whether the reconstructed sound source is stable and primarily concentrated within a subset of channels of the multi-channel signal based on the location measurements; In response to the reconstructed sound source location measurements being centered and stable within a subset of the channels of the multi-channel and the parameter memory being corrupted, initiating parameter recovery (912) to replace the decoded multi-channel parameters with the stored multi-channel parameters; A method comprising:

[0105] 2. The method of embodiment 1, wherein the multi-channel includes two channels, and determining (910) based on the location measurements whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel includes determining (910) based on the location measurements whether the location measurements of the reconstructed sound source are primarily concentrated in one of the two channels.

[0106] 3. The method of embodiment 1 or 2, wherein the coding mode includes one of an absolute coding mode and a predictive coding mode, and determining whether the parameter memory is corrupted based on at least the coding mode and the preceding bad frame indicator includes determining whether the parameter memory is corrupted based on the coding mode being a predictive coding mode and the preceding bad frame indicator.

[0107] 4. Deriving location measurements deriving location measurements based on TIFF2026016503000086.tif14170, TIFF2026016503000087.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000088.tif6170 contains the average value of N bands 4. The method of any one of embodiments 1-3, wherein m is the number of subbands in frame m.

[0108] 5. Determining whether the reconstructed source location measurements are primarily concentrated within a subset of channels of the multi-channel The low-pass filtered position TIFF2026016503000089.tif11170, where γ is a filter parameter, TIFF2026016503000090.tif6170 is the mean value of the reconstructed prediction parameters for frame m, determining a low-pass filtered position, where TIFF2026016503000091.tif6170 is the low-pass filtered position; The absolute value of the low-pass filtered position is the threshold determining whether the file exceeds TIFF2026016503000092.tif6170; The absolute value of the low-pass filtered position is the threshold determining that the location measurements of the sound source are primarily concentrated within a subset of the channels of the multi-channel audio signal in response to exceeding TIFF2026016503000093.tif6170; and 5. The method of embodiment 4, comprising:

[0109] 6. Deriving location measurements deriving location measurements based on TIFF2026016503000094.tif45170, wherein: TIFF2026016503000095.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000096.tif6170 contains the weighted average of N bands is the number of subbands in frame m, and w b (m) and TIFF2026016503000097.tif7170 is the weighting factor, k end(b) is the end of the multiple summation, and k start(b) is the beginning of multiple sums, 2. The method of embodiment 1, wherein TIFF2026016503000098.tif6170 is the converted downmix signal.

[0110] 7. A method for substituting decoded multi-channel parameters for stored multi-channel parameters, said method comprising: determining whether the coding mode is an absolute coding mode or a predictive coding mode (1002); In response to the coding mode being a predictive coding mode, determining if a memory corruption flag is set (1006); In response to the memory corruption flag being set, determining (1008) whether the reconstructed sound source is a stable sound source and whether location measurements of the reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel signal being decoded; replacing the decoded multi-channel parameters with the stored multi-channel parameters in response to the reconstructed sound source being a stable sound source and the location measurements of the reconstructed sound source being primarily centered within a subset of the channels of the multi-channels (1010); In response to the memory corruption flag not being set, analyzing (1012) the location measurements of the reconstructed sound sources to update the location measurements; updating (1014) the stored multi-channel parameters with the decoded multi-channel parameters; A method comprising:

[0111] 8. The method of embodiment 7, wherein the multi-channel includes two channels, and determining whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of the channels includes determining whether the location measurements of the reconstructed sound source are primarily concentrated in one of the two channels (910).

[0112] 9. In response to the coding mode being the absolute coding mode, clearing the memory corruption flag (1004). 9. The method of embodiment 7 or 8, further comprising:

[0113] 10. In response to a bad frame being indicated, setting a memory corruption flag (1000). 10. The method of any one of embodiments 7 to 9, further comprising:

[0114] 11. Updating location measurements and updating the location measurements based on TIFF2026016503000099.tif15170, TIFF2026016503000100.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000101.tif6170 contains the average value, N bands 11. The method of any one of embodiments 7-10, wherein m is the number of subbands in frame m.

[0115] 12. Determining whether the reconstructed source location measurements are primarily concentrated within a subset of channels The low-pass filtered position is TIFF2026016503000102.tif12170, where γ is a filter parameter, TIFF2026016503000103.tif7170 is the mean value of the reconstructed prediction parameters for frame m, determining a low-pass filtered position, where TIFF2026016503000104.tif6170 is the low-pass filtered position; The absolute value of the low-pass filtered position is the threshold Determining whether TIFF2026016503000105.tif6170 is greater than The absolute value of the low-pass filtered position is the threshold determining that the reconstructed source location measurements are primarily concentrated within the subset of channels in response to exceeding TIFF2026016503000106.tif6170; and 12. The method of embodiment 11, comprising:

[0116] 13. Deriving location measurements deriving location measurements based on TIFF2026016503000107.tif45170, wherein: TIFF2026016503000108.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000109.tif6170 contains the weighted average of N bands is the number of subbands in frame m, and w b (m) and TIFF2026016503000110.tif6170 is the weighting factor, k end(b) is the end of the multiple summation, and k start(b) is the beginning of multiple sums, 8. The method of embodiment 7, wherein TIFF2026016503000111.tif6170 is the converted downmix signal.

[0117] 14. A decoder (200) for a communication network, the decoder (100) comprising: A processor (801); A decoder (200) comprising: a memory (803) coupled to the processor, the memory containing instructions that, when executed by the processor, cause the processor to perform the operations described in any one of embodiments 1 to 13.

[0118] 15. A decoder (200) configured to operate in a communications network, the decoder (200) being adapted to perform according to any one of embodiments 1 to 13.

[0119] 16. A computer program comprising computer-executable instructions configured to cause a device to perform a method according to any one of embodiments 1 to 13 when the computer-executable instructions are executed on a processor (801) included in the device.

[0120] 17. A computer program product comprising a non-transitory computer-readable storage medium (803), the non-transitory computer-readable storage medium having computer-executable instructions configured to cause the device to perform the method of any one of embodiments 1 to 13 when the computer-executable instructions are executed on a processor (801) included in the device.

[0121] 18. An apparatus configured to replace decoded parameters with estimated parameters in a received multi-channel signal, the apparatus comprising: At least one processor (801); a memory (803) communicatively coupled to the processor, the memory including instructions executable by the processor, the instructions causing the processor to: decoding (900) multi-channel parameters of a frame of a received multi-channel signal using one of an absolute coding mode or a predictive coding mode; determining whether a bad frame is indicated (902); performing a packet loss concealment operation in response to the bad frame being indicated; In response to no bad frame being indicated, determining whether the parameter memory is corrupted based on at least the coding mode and the preceding bad frame indicator (906); deriving (908) a location measure of the reconstructed sound source based on the decoded multi-channel parameters; determining (910) whether the reconstructed sound source is stable based on the location measurements and whether the location measurements are primarily centered within a subset of channels of the multi-channel signal; In response to the reconstructed sound source being stable and the location measurements being primarily centered within a subset of the channels of the multi-channel, and the parameter memory being corrupted, initiating parameter recovery (912) to replace the decoded multi-channel parameters with the stored multi-channel parameters; An apparatus for causing an operation including

[0122] 19. The apparatus of embodiment 18, wherein the coding mode includes one of an absolute coding mode and a predictive coding mode, and determining whether the parameter memory is corrupted based on at least the coding mode and the preceding bad frame indicator includes determining whether the parameter memory is corrupted based on the coding mode being a predictive coding mode and the preceding bad frame indicator.

[0123] 20. The apparatus of embodiment 18 or 19, wherein the multi-channel includes two channels, and determining (910) based on the location measurements whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of the channels of the multi-channel includes determining (910) based on the location measurements whether the location measurements of the reconstructed sound source are primarily concentrated in one of the two channels.

[0124] 21. Deriving location measurements includes: deriving location measurements based on TIFF2026016503000112.tif14170, wherein: TIFF2026016503000113.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000114.tif6170 contains the average value of N bands 21. The apparatus of any one of embodiments 18-20, wherein m is the number of subbands in frame m.

[0125] 22. Determining whether the reconstructed sound source is primarily concentrated within a subset of channels of the multi-channel The low-pass filtered position is determining in accordance with TIFF2026016503000115.tif11170, where γ is a filter parameter, TIFF2026016503000116.tif6170 is the mean value of the reconstructed prediction parameters for frame m, determining a low-pass filtered position, where TIFF2026016503000117.tif6170 is the low-pass filtered position; The absolute value of the low-pass filtered position is the threshold Determine whether TIFF2026016503000118.tif6170 is greater than The absolute value of the low-pass filtered position is the threshold determining that the reconstructed sound source is primarily concentrated within a subset of the channels of the multi-channel signal in response to exceeding TIFF2026016503000119.tif6170; and 22. The apparatus of embodiment 21, comprising:

[0126] 23. Deriving location measurements includes: deriving location measurements based on TIFF2026016503000120.tif46170, wherein: TIFF2026016503000121.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000122.tif6170 contains the weighted average of N bands is the number of subbands in frame m, and w b (m) and TIFF2026016503000123.tif6170 is the weighting factor, k end(b) is the end of the multiple summation, and k start(b) is the beginning of multiple sums, The apparatus of embodiment 18, wherein TIFF2026016503000124.tif6170 is the converted downmix signal.

[0127] 24. An apparatus configured to replace decoded parameters with estimated parameters in a received multi-channel signal, the apparatus comprising: At least one processor (801); a memory (803) communicatively coupled to the processor, the memory containing instructions executable by the processor, the instructions, when executed, causing the processor to: determining whether the coding mode is an absolute coding mode or a predictive coding mode (1002); In response to the coding mode being a predictive coding mode, determining if a memory corruption flag is set (1006); In response to the memory corruption flag being set, determining 1008 whether the reconstructed sound source is a stable sound source and whether location measurements of the reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel signal; responsive to the reconstructed sound source being a stable sound source and the location measurements of the reconstructed sound source being primarily concentrated within the subset of channels, replacing the decoded multi-channel parameters with the stored multi-channel parameters (1010); In response to the memory corruption flag not being set, analyzing (1012) the location measurements of the reconstructed sound sources to update the location measurements; updating (1014) the stored multi-channel parameters with the decoded multi-channel parameters; An apparatus for causing an operation including

[0128] 25. The memory includes further instructions executable by the processor, the further instructions, when executed, causing the processor to: In response to the coding mode being the absolute coding mode, clearing the memory corruption flag (1004) 25. The apparatus of embodiment 24, wherein the apparatus performs operations including:

[0129] 26. The memory includes further instructions executable by the processor, the further instructions, when executed, causing the processor to: Setting a memory corruption flag in response to a bad frame being indicated (1000). 25. The apparatus of embodiment 24, wherein the apparatus performs operations including:

[0130] 27. The device of any one of embodiments 24 to 26, wherein the multi-channel includes two channels, and determining whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of the channels includes determining whether the location measurements of the reconstructed sound source are primarily concentrated in one of the two channels (910).

[0131] 28. Updating location measurements and updating the location measurements based on TIFF2026016503000125.tif15170, TIFF2026016503000126.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000127.tif6170 contains the average value of N bands 28. The apparatus of any one of embodiments 24-27, wherein m is the number of subbands in frame m.

[0132] 29. Determining whether the reconstructed source location measurements are primarily concentrated within a subset of channels includes: The low-pass filtered position is TIFF2026016503000128.tif11170, where γ is a filter parameter, TIFF2026016503000129.tif6170 is the mean value of the reconstructed prediction parameters for frame m, determining a low-pass filtered position, where TIFF2026016503000130.tif6170 is the low-pass filtered position; The absolute value of the low-pass filtered position is the threshold determining whether it exceeds TIFF2026016503000131.tif6170; The absolute value of the low-pass filtered position is the threshold determining that the reconstructed source location measurements are primarily concentrated within the subset of channels in response to exceeding TIFF2026016503000132.tif6170; and 29. The apparatus of embodiment 28, comprising:

[0133] 30. Deriving a location measurement includes: deriving location measurements based on TIFF2026016503000133.tif46170, TIFF2026016503000134.tif6170 is the location measurement, which is the reconstructed prediction parameters across all subbands for each frame m TIFF2026016503000135.tif6170 contains the weighted average of N bands is the number of subbands in frame m, and w b (m) and TIFF2026016503000136.tif6170 is the weighting factor, k end(b) is the end of the multiple summation, and k start(b) is the beginning of multiple sums, The apparatus of embodiment 24, wherein TIFF2026016503000137.tif6170 is the converted downmix signal.

[0134] Explanations of abbreviations from the above disclosure are provided below. Abbreviation Explanation BFI Bad Frame Indicator PREV BFI Previous frame bad frame indicator DFT Discrete Fourier Transform LP Linear Prediction PLC Packet Loss Concealment ECU Error Concealment Unit FEC Frame Error Correction / Concealment MDCT Modified Discrete Cosine Transform MDST Modified Discrete Sine Transform MSE Mean Squared Error ODFT Odd Discrete Fourier Transform Long-term predictors of LTP ITD Inter-Channel Time Difference IPD inter-channel phase difference ILD Level difference between channels ICC Inter-Channel Coherence FD Frequency Domain TD Time Domain FLC Frame Loss Concealment

[0135] Citations for references from the above disclosures are provided below. [1] C. Faller, “Parametric multichannel audio coding: synthesis of coherence cues,” in IEEE Transactions on Audio, Speech, and Language Processing, vol. 14, no. 1, pp. 299–310, January 2006. [2].Breebaart, J., Herre, J., Faller, C., Roden, J., Myburg, F., Disch, S., ...&Oomen, W. (2005). “MPEG spatial audio coding / MPEG surround:Overview and current status,”2005 In Preprint 119th Conv.Aud.Eng.Soc.(No.LCAV-CONF-2005-029).

[0136] Further definitions and embodiments are discussed below.

[0137] In the above description of various embodiments of the inventive concept, it should be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the inventive concept. Unless otherwise specified, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of this specification and the related art, and will not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0138] When an element is referred to as being "connected," "coupled," "responsive," or variations thereof, to another element, the element can be directly connected, coupled, or responsive to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected," "directly coupled," or "directly responsive" to another element, or variations thereof, there are no intervening elements present. Like numbers refer to like elements throughout. Furthermore, as used herein, "coupled," "connected," "responsive," or variations thereof may include wirelessly coupled, wirelessly connected, or wirelessly responsive. As used herein, the singular forms "a," "an," and "the" are intended to include the plural unless the context clearly dictates otherwise. Well-known features or structures may not be described in detail for the sake of brevity and / or clarity. The term "and / or" includes any and all combinations of one or more of the associated listed items.

[0139] Terms such as first, second, third, etc. may be used herein to describe various elements / operations, but it will be understood that these elements / operations should not be limited by these terms. These terms are used only to distinguish one element / operation from another. Thus, a first element / operation in some embodiments may be termed a second element / operation in other embodiments without departing from the teachings of the inventive concept. The same reference numerals or symbols represent the same or similar elements throughout this specification.

[0140] As used herein, the terms "comprise," "comprising," "comprises," "include," "including," "includes," "have," "has," "having," or variations thereof, are open-ended and refer to the inclusion of one or more stated features, integers, elements, steps, components, or functions, but do not exclude the presence or addition of one or more other features, integers, elements, steps, components, functions, or groups thereof. Additionally, as used herein, the general abbreviation "eg," derived from the Latin phrase "exempli gratia," may be used to introduce or identify one or more general examples of the aforementioned items and is not intended to be limiting to such items. The general abbreviation "ie," derived from the Latin phrase "id est," may be used to identify a specific item from a more general description.

[0141] Exemplary embodiments are described herein with reference to block diagrams and / or flowchart illustrations of computer-implemented methods, apparatus (systems and / or devices), and / or computer program products. It will be understood that blocks of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by computer program instructions executed by one or more computer circuits. These computer program instructions can be provided to general-purpose computer circuits, special-purpose computer circuits, and / or processor circuits of other programmable data processing devices such that the instructions executed by the processor of the computer and / or other programmable data processing device transform and control transistors, values ​​stored in memory locations, and other hardware components within such circuits to implement the functions / acts identified in the block diagrams and / or one or more flowchart blocks, thereby producing a machine with the means (functionality) and / or structure for implementing the functions / acts identified in the block diagrams and / or flowchart blocks.

[0142] These computer program instructions may be stored in a tangible computer-readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture comprising instructions that implement the functions / acts identified in the block diagrams and / or one or more flowchart blocks. Thus, embodiments of the inventive concepts may be embodied in hardware and / or in software (including firmware, resident software, microcode, etc.) running on a processor, such as a digital signal processor, which may collectively be referred to as a "circuit," "module," or variations thereof.

[0143] It should also be noted that in some alternative implementations, the functions / acts noted in the blocks may occur out of the order noted in the flowcharts. For example, two blocks shown in succession may in fact be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending on the functionality / acts involved. Furthermore, the functionality of a given block of the flowcharts and / or block diagrams may be separated into multiple blocks, and / or the functionality of two or more blocks of the flowcharts and / or block diagrams may be at least partially integrated. Finally, other blocks may be added / inserted between the illustrated blocks, and / or blocks / acts may be omitted without departing from the scope of the inventive concepts. Furthermore, while some of the figures include arrows on communication paths to indicate the primary direction of communication, it should be understood that communication may occur in a direction opposite to that of the illustrated arrows.

[0144] Numerous variations and modifications can be made to the embodiments without substantially departing from the principles of the inventive concept. All such variations and modifications are intended to be included herein within the scope of the inventive concept. Accordingly, the subject matter disclosed above should be considered illustrative and not limiting, and the example embodiments are intended to cover all such modifications, enhancements, and other embodiments that fall within the spirit and scope of the inventive concept. Therefore, to the maximum extent permitted by law, the scope of the inventive concept should be determined by the broadest permissible interpretation of this disclosure, including the example embodiments and their equivalents, and should not be limited or constrained by the foregoing detailed description.

[0145] In general, all terms used herein should be interpreted according to their ordinary meaning in the relevant technical field unless a different meaning is clearly given and / or is suggested by the context in which the term is used. Any reference to an element, apparatus, component, means, step, etc. should be openly interpreted as referring to at least one instance of the element, apparatus, component, means, step, etc., unless expressly stated otherwise. The steps of any method disclosed herein need not be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and / or unless it is implied that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, where appropriate. Similarly, any advantage of any of the embodiments may be applied to any other embodiment, and vice versa.

[0146] Any appropriate step, method, feature, function, or advantage disclosed herein may be performed through one or more functional units or modules of one or more virtual devices. Each virtual device may include multiple of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessors or microcontrollers and other digital hardware, which may include digital signal processors (DSPs), special-purpose digital logic, etc. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory, such as read-only memory (ROM), random access memory (RAM), cache memory, flash memory devices, optical storage devices, etc. The program code stored in memory includes program instructions for implementing one or more communication and / or data communication protocols, as well as instructions for executing one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause each functional unit to perform corresponding functions according to one or more embodiments of the present disclosure.

Claims

1. 1. A method for permuting decoded parameters in a received multi-channel signal, the method comprising the steps of: decoding (900) multi-channel parameters of a frame of the received multi-channel signal; Determining whether a bad frame is indicated (902); determining (904) that a parameter memory is corrupted in response to the bad frame being indicated; In response to the bad frame not being indicated, deriving (908) a location measure of the reconstructed sound source based on the decoded multi-channel parameters in response to the parameter memory being uncorrupted (906); In response to the parameter memory being corrupted (906), determining (910) based on the location measurements whether the reconstructed sound source is stable and primarily concentrated within a subset of channels of the multi-channel signal; initiating parameter recovery (912) to replace decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being centered and stable within the subset of channels of the multi-channels; A method comprising:

2. The method of claim 1 , further responsive to the bad frame being indicated, performing a packet loss concealment operation.

3. The method of claim 1 or 2, further responsive to the bad frame not being indicated, storing the decoded multi-channel parameters as the stored multi-channel parameters.

4. 9. The method of claim 1, wherein the multi-channel signal includes two channels, and determining (910) based on the location measurements whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of the channels of the multi-channel signal includes determining (910) based on the location measurements whether the location measurements of the reconstructed sound source are primarily concentrated within one of the two channels.

5. 3. The method of claim 1, wherein the coding mode includes one of an absolute coding mode and a predictive coding mode, and wherein a memory corruption flag is cleared in response to the coding mode being the absolute coding mode, and in response to the memory corruption flag being set.

6. deriving the location measurement deriving the location measurement based on are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. Including the average value of N ｂａｎｄｓ The method of claim 1 , wherein m is the number of subbands in frame m.

7. Determining whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel audio signal comprises: The low-pass filtered position is determining based on where γ is a filter parameter, is the mean value of the reconstructed prediction parameters for frame m, determining a low-pass filtered position, where x is the low-pass filtered position; The absolute value of the low-pass filtered position is a threshold determining whether The absolute value of the low-pass filtered position is determining that the location measurements of the sound source are primarily concentrated within a subset of channels of the multi-channel sound source in response to exceeding The method of claim 6, comprising:

8. deriving the location measurement deriving the location measurement based on are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. and N ｂａｎｄｓ is the number of subbands in frame m, and w ｂ (m) and is a weighting coefficient, and k ｅｎｄ（ｂ） is the end of the multiple summation, and k ｓｔａｒｔ（ｂ） is the beginning of the plurality of sums, The method of claim 1 , wherein is the converted downmix signal.

9. A decoder (200) for a communication network, said decoder (100) comprising: A processor (801); a memory (803) coupled to the processor, the memory containing instructions that, when executed by the processor, cause the processor to: Decoding (900) multi-channel parameters of a frame of a received multi-channel signal; Determining whether a bad frame is indicated (902); determining (904) that a parameter memory is corrupted in response to the bad frame being indicated; In response to the bad frame not being indicated, deriving (908) a location measure of the reconstructed sound source based on the decoded multi-channel parameters in response to the parameter memory being uncorrupted (906); In response to the parameter memory being corrupted (906), determining (910) based on the location measurements whether the reconstructed sound source is stable and primarily concentrated within a subset of channels of the multi-channel signal; initiating parameter recovery (912) to replace decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being centered and stable within the subset of channels of the multi-channels; The decoder (200) performs operations including:

10. 10. The decoder (200) of claim 9, wherein the multi-channel signal includes two channels, and determining (910) based on the location measurements whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of the channels of the multi-channel signal comprises determining (910) based on the location measurements whether the location measurements of the reconstructed sound source are primarily concentrated within one of the two channels.

11. 11. The decoder (200) of claim 9 or 10, wherein the coding mode comprises one of an absolute coding mode and a predictive coding mode, and wherein in response to the coding mode being the absolute coding mode, a memory corruption flag is cleared in response to the memory corruption flag being set.

12. deriving the location measurement deriving the location measurement based on are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. Including the average value of N ｂａｎｄｓ 12. The decoder (200) of any one of claims 9 to 11, wherein m is the number of subbands in frame m.

13. Determining whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel audio signal comprises: The low-pass filtered position is determining based on where γ is a filter parameter, is the mean value of the reconstructed prediction parameters for frame m, determining a low-pass filtered position, where x is the low-pass filtered position; The absolute value of the low-pass filtered position is a threshold determining whether The absolute value of the low-pass filtered position is determining that the location measurements of the sound source are primarily concentrated within a subset of channels of the multi-channel sound source in response to exceeding The decoder (200) of claim 12, comprising:

14. deriving the location measurement deriving the location measurement based on are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. and N ｂａｎｄｓ is the number of subbands in frame m, and w ｂ (m) and is a weighting coefficient, and k ｅｎｄ（ｂ） is the end of the multiple summation, and k ｓｔａｒｔ（ｂ） is the beginning of the plurality of sums, The decoder (200) of claim 13, wherein is the transformed downmix signal.

15. A decoder (200) configured to operate in a communications network, said decoder comprising: Decoding (900) multi-channel parameters of a frame of a received multi-channel signal; Determining whether a bad frame is indicated (902); determining (904) that a parameter memory is corrupted in response to the bad frame being indicated; In response to the bad frame not being indicated, deriving (908) a location measure of the reconstructed sound source based on the decoded multi-channel parameters in response to the parameter memory being uncorrupted (906); In response to the parameter memory being corrupted (906), determining (910) based on the location measurements whether the reconstructed sound source is stable and primarily concentrated within a subset of channels of the multi-channel signal; initiating parameter recovery (912) to replace decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being centered and stable within the subset of channels of the multi-channels; A decoder (200) adapted to perform operations including:

16. The decoder (200) of claim 15, further adapted to perform the operations of any one of claims 2 to 8.

17. A computer program comprising computer-executable instructions that, when executed on a processor contained within a device, cause the device to: Decoding (900) multi-channel parameters of a frame of a received multi-channel signal; Determining whether a bad frame is indicated (902); determining (904) that a parameter memory is corrupted in response to the bad frame being indicated; In response to the bad frame not being indicated, deriving (908) a location measure of the reconstructed sound source based on the decoded multi-channel parameters in response to the parameter memory being uncorrupted (906); In response to the parameter memory being corrupted (906), determining (910) based on the location measurements whether the reconstructed sound source is stable and primarily concentrated within a subset of channels of the multi-channel signal; initiating parameter recovery (912) to replace decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being centered and stable within the subset of channels of the multi-channels; A computer program that causes a computer to perform operations including:

18. 18. A computer program product according to claim 17, comprising further computer-executable instructions which, when executed on a processor contained within a device, cause the device to perform the operations of any one of claims 2 to 8.

19. 1. A computer program product comprising a non-transitory computer-readable storage medium (803) having computer-executable instructions that, when executed on a processor (801) contained within a device, cause the device to: Decoding (900) multi-channel parameters of a frame of a received multi-channel signal; Determining whether a bad frame is indicated (902); determining (904) that a parameter memory is corrupted in response to the bad frame being indicated; In response to the bad frame not being indicated, deriving (908) a location measure of the reconstructed sound source based on the decoded multi-channel parameters in response to the parameter memory being uncorrupted (906); In response to the parameter memory being corrupted (906), determining (910) based on the location measurements whether the reconstructed sound source is stable and primarily concentrated within a subset of channels of the multi-channel signal; initiating parameter recovery (912) to replace decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being centered and stable within the subset of channels of the multi-channels; A computer program product for causing a computer to perform operations including:

20. 20. The computer program product of claim 19, wherein the non-transitory computer-readable storage medium has further computer-executable instructions that, when executed on a processor (801) included in a device, cause the device to perform the operations of any one of claims 2 to 8.

21. 1. A method for substituting decoded multi-channel parameters for stored multi-channel parameters, the method comprising: Determining whether the coding mode is an absolute coding mode or a predictive coding mode (1002); In response to the coding mode being a predictive coding mode, Determining if a memory corruption flag is set (1006); In response to the memory corruption flag being set, determining 1008 whether the reconstructed sound source is a stable sound source and whether location measurements of said reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel signal being decoded; responsive to the reconstructed sound source being a stable sound source and the location measurements of the reconstructed sound source being primarily centered within the subset of channels of the multi-channels, replacing the decoded multi-channel parameters with stored multi-channel parameters (1010); In response to the memory corruption flag not being set, - analyzing (1012) the location measurements of the reconstructed sound sources to update the location measurements; updating (1014) the stored multi-channel parameters with the decoded multi-channel parameters; A method comprising:

22. 22. The method of claim 21 , wherein the multi-channel signal includes two channels, and determining whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels includes determining whether the location measurements of the reconstructed sound source are primarily concentrated within one of the two channels (910).

23. clearing the memory corruption flag in response to the coding mode being an absolute coding mode (1004).

23. The method of claim 21 or 22, further comprising:

24. setting the memory corruption flag in response to a bad frame being indicated (1000); 24. The method of any one of claims 21 to 23, further comprising:

25. The location measurement and further including updating the information based on the are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. Including the average value of N ｂａｎｄｓ 25. The method of claim 21, wherein m is the number of subbands in frame m.

26. Determining whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels includes: The low-pass filtered position is determining based on where γ is a filter parameter, is the mean value of the reconstructed prediction parameters for frame m, determining a low-pass filtered position, where x is the low-pass filtered position; The absolute value of the low-pass filtered position is a threshold determining whether The absolute value of the low-pass filtered position is determining that the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels in response to the 26. The method of claim 25, comprising:

27. The location measurement and further comprising deriving the parameter based on: are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. and N ｂａｎｄｓ is the number of subbands in frame m, and w ｂ (m) and is a weighting coefficient, and k ｅｎｄ（ｂ） is the end of the multiple summation, and k ｓｔａｒｔ（ｂ） is the beginning of the plurality of sums, The method of claim 23, wherein is the converted downmix signal.

28. A decoder (200) for a communication network, said decoder (100) comprising: A processor (801); a memory (803) coupled to the processor, the memory containing instructions that, when executed by the processor, cause the processor to: Determining whether the coding mode is an absolute coding mode or a predictive coding mode (1002); In response to the coding mode being a predictive coding mode, Determining if a memory corruption flag is set (1006); In response to the memory corruption flag being set, determining 1008 whether the reconstructed sound source is a stable sound source and whether location measurements of said reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel signal being decoded; responsive to the reconstructed sound source being a stable sound source and the location measurements of the reconstructed sound source being primarily centered within the subset of channels of the multi-channels, replacing the decoded multi-channel parameters with stored multi-channel parameters (1010); In response to the memory corruption flag not being set, - analyzing (1012) the location measurements of the reconstructed sound sources to update the location measurements; updating (1014) the stored multi-channel parameters with the decoded multi-channel parameters; The decoder (200) performs operations including:

29. 29. The decoder (200) of claim 28, wherein the multi-channel includes two channels, and determining whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels comprises determining (910) whether the location measurements of the reconstructed sound source are primarily concentrated in one of the two channels.

30. The memory includes further instructions that, when executed by the processor, cause the processor to: clearing the memory corruption flag in response to the coding mode being an absolute coding mode (1004).

30. The decoder (200) of claim 28 or 29, causing further operations to be performed, including:

31. The memory includes further instructions that, when executed by the processor, cause the processor to: setting the memory corruption flag in response to a bad frame being indicated (1000); 31. The decoder (200) of any one of claims 28 to 30, causing further operations to be performed, including:

32. The memory includes further instructions that, when executed by the processor, cause the processor to: updating the location measurements based on: are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. Including the average value of N ｂａｎｄｓ 32. The decoder (200) of any one of claims 28 to 31, further comprising: updating the location measurement, wherein m is the number of subbands in frame m.

33. Determining whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels includes: The low-pass filtered position is determining based on where γ is a filter parameter, is the mean value of the reconstructed prediction parameters for frame m, determining a low-pass filtered position, where x is the low-pass filtered position; The absolute value of the low-pass filtered position is a threshold determining whether The absolute value of the low-pass filtered position is determining that the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels in response to the 33. The decoder (200) of claim 32, comprising:

34. The memory includes further instructions that, when executed by the processor, cause the processor to: deriving the location measurement based on are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. and N ｂａｎｄｓ is the number of subbands in frame m, and w ｂ (m) and is a weighting coefficient, and k ｅｎｄ（ｂ） is the end of the multiple summation, and k ｓｔａｒｔ（ｂ） is the beginning of the plurality of sums, 29. The decoder (200) of claim 28, wherein the decoder (200) performs further operations including deriving the location measure, wherein the location measure is a transformed downmix signal.

35. A decoder (200) configured to operate in a communications network, said decoder comprising: Determining whether the coding mode is an absolute coding mode or a predictive coding mode (1002); In response to the coding mode being a predictive coding mode, Determining if a memory corruption flag is set (1006); In response to the memory corruption flag being set, determining 1008 whether the reconstructed sound source is a stable sound source and whether location measurements of said reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel signal being decoded; responsive to the reconstructed sound source being a stable sound source and the location measurements of the reconstructed sound source being primarily centered within the subset of channels of the multi-channels, replacing the decoded multi-channel parameters with stored multi-channel parameters (1010); In response to the memory corruption flag not being set, - analyzing (1012) the location measurements of the reconstructed sound sources to update the location measurements; updating (1014) the stored multi-channel parameters with the decoded multi-channel parameters; A decoder (200) adapted to perform operations including:

36. 36. The decoder (200) of claim 35, wherein the decoder is further adapted to perform the operations of any one of claims 22 to 27.

37. A computer program comprising computer-executable instructions that, when executed on a processor contained within a device, cause the device to: Determining whether the coding mode is an absolute coding mode or a predictive coding mode (1002); In response to the coding mode being a predictive coding mode, Determining if a memory corruption flag is set (1006); In response to the memory corruption flag being set, determining 1008 whether the reconstructed sound source is a stable sound source and whether location measurements of said reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel signal being decoded; responsive to the reconstructed sound source being a stable sound source and the location measurements of the reconstructed sound source being primarily centered within the subset of channels of the multi-channels, replacing the decoded multi-channel parameters with stored multi-channel parameters (1010); In response to the memory corruption flag not being set, - analyzing (1012) the location measurements of the reconstructed sound sources to update the location measurements; updating (1014) the stored multi-channel parameters with the decoded multi-channel parameters; A computer program that causes a computer to perform operations including:

38. 38. A computer program according to claim 37, comprising further computer-executable instructions which, when executed on a processor contained within a device, cause the device to perform the operations of any one of claims 22 to 27.

39. 1. A computer program product comprising a non-transitory computer-readable storage medium (803) having computer-executable instructions that, when executed on a processor (801) contained within a device, cause the device to: Determining whether the coding mode is an absolute coding mode or a predictive coding mode (1002); In response to the coding mode being a predictive coding mode, Determining if a memory corruption flag is set (1006); In response to the memory corruption flag being set, determining 1008 whether the reconstructed sound source is a stable sound source and whether location measurements of said reconstructed sound source are primarily concentrated within a subset of channels of the multi-channel signal being decoded; responsive to the reconstructed sound source being a stable sound source and the location measurements of the reconstructed sound source being primarily centered within the subset of channels of the multi-channels, replacing the decoded multi-channel parameters with stored multi-channel parameters (1010); In response to the memory corruption flag not being set, - analyzing (1012) the location measurements of the reconstructed sound sources to update the location measurements; updating (1014) the stored multi-channel parameters with the decoded multi-channel parameters; A computer program product for causing a computer to perform operations including:

40. 42. The computer program product of claim 41, wherein the non-transitory computer-readable storage medium has further computer-executable instructions that, when executed on a processor (801) included in a device, cause the device to perform the operations of any one of claims 22 to 27.

41. 1. An apparatus configured to replace decoded parameters with estimated parameters in a received multi-channel signal, the apparatus comprising: At least one processor (801); a memory (803) communicatively coupled to the processor, the memory including instructions executable by the processor, the instructions causing the processor to: decoding (900) multi-channel parameters of a frame of the received multi-channel signal using one of an absolute coding mode or a predictive coding mode; Determining whether a bad frame is indicated (902); performing a packet loss concealment operation in response to the bad frame being indicated; In response to the bad frame not being indicated, determining whether the parameter memory is corrupted based on at least the coding mode and the preceding bad frame indicator (906); Deriving (908) location measures of the reconstructed sound sources based on the decoded multi-channel parameters; determining (910) based on the location measurements whether the reconstructed sound source is stable and whether the location measurements are primarily centered within a subset of channels of the multi-channel signal; initiating parameter recovery (912) to replace decoded multi-channel parameters with stored multi-channel parameters in response to the reconstructed sound source being stable, the location measurements being primarily centered within a subset of channels of the multi-channel, and the parameter memory being corrupted; An apparatus for causing an operation including

42. 42. The apparatus of claim 41 , wherein the coding mode comprises one of an absolute coding mode and a predictive coding mode, and determining whether the parameter memory is corrupted based on at least the coding mode and the preceding bad frame indicator comprises determining whether the parameter memory is corrupted based on the coding mode being the predictive coding mode and the preceding bad frame indicator.

43. 43. The apparatus of claim 41 or 42, wherein the multi-channel includes two channels, and determining (910) based on the location measurements whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of the channels of the multi-channel includes determining (910) based on the location measurements whether the location measurements of the reconstructed sound source are primarily concentrated in one of the two channels.

44. The memory includes further instructions that, when executed by the processor, cause the processor to: deriving the location measurement based on are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. Including the average value of N ｂａｎｄｓ 44. The apparatus of claim 41, further comprising: deriving the location measure, wherein m is the number of subbands in frame m.

45. Determining whether the reconstructed sound source is primarily concentrated within the subset of channels of the multi-channel audio signal may include: The low-pass filtered position is determining in accordance with where γ is a filter parameter, is the mean value of the reconstructed prediction parameters for frame m, determining a low-pass filtered position, where x is the low-pass filtered position; The absolute value of the low-pass filtered position is a threshold determining whether The absolute value of the low-pass filtered position is determining that the reconstructed sound source is primarily concentrated within a subset of channels of the multi-channel audio signal in response to exceeding 45. The apparatus of claim 44, comprising:

46. The memory includes further instructions that, when executed by the processor, cause the processor to: deriving the location measurement based on are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. and N ｂａｎｄｓ is the number of subbands in frame m, and w ｂ (m) and is a weighting coefficient, and k ｅｎｄ（ｂ） is the end of the multiple summation, and k ｓｔａｒｔ（ｂ） is the beginning of the plurality of sums, 44. The apparatus of claim 43, wherein the apparatus performs further operations including: deriving the location measure is a transformed downmix signal.

47. 1. An apparatus configured to replace decoded parameters with estimated parameters in a received multi-channel signal, the apparatus comprising: At least one processor (801); a memory (803) communicatively coupled to the processor, the memory including instructions executable by the processor, the instructions, when executed, causing the processor to: Determining whether the coding mode is an absolute coding mode or a predictive coding mode (1002); In response to the coding mode being a predictive coding mode, Determining if a memory corruption flag is set (1006); In response to the memory corruption flag being set, determining 1008 whether the reconstructed sound source is a stable sound source and whether location measurements of the reconstructed sound source are primarily concentrated within a subset of channels of the multi-channels of the received multi-channel signal; responsive to the reconstructed sound source being a stable sound source and the location measurements of the reconstructed sound source being primarily centered within the subset of channels, replacing the decoded multi-channel parameters with stored multi-channel parameters (1010); In response to the memory corruption flag not being set, - analyzing (1012) the location measurements of the reconstructed sound sources to update the location measurements; updating (1014) the stored multi-channel parameters with the decoded multi-channel parameters; An apparatus for causing an operation including

48. The memory includes further instructions executable by the processor, the further instructions, when executed, causing the processor to: clearing the memory corruption flag in response to the coding mode being an absolute coding mode (1004).

48. The apparatus of claim 47, wherein the apparatus performs operations including:

49. The memory includes further instructions executable by the processor, the further instructions, when executed, causing the processor to: setting the memory corruption flag in response to a bad frame being indicated (1000); 48. The apparatus of claim 47, wherein the apparatus performs operations including:

50. 50. The apparatus of claim 47, wherein the multi-channel signal includes two channels, and determining whether the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels comprises determining whether the location measurements of the reconstructed sound source are primarily concentrated within one of the two channels (910).

51. The memory includes further instructions executable by the processor, the further instructions, when executed, causing the processor to: updating the location measurements based on: are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. Including the average value of N ｂａｎｄｓ 50. The apparatus of claim 47, wherein the apparatus is configured to perform operations including updating the location measurements such that m is the number of subbands in frame m.

52. Determining whether the location measurements of the reconstructed sound source are primarily concentrated within the subset of channels includes: The low-pass filtered position is determining based on where γ is a filter parameter, is the mean value of the reconstructed prediction parameters for frame m, determining a low-pass filtered position, where x is the low-pass filtered position; The absolute value of the low-pass filtered position is a threshold determining whether The absolute value of the low-pass filtered position is determining that the location measurements of the reconstructed sound source are primarily concentrated within a subset of channels in response to the 52. The apparatus of claim 51, comprising:

53. The memory includes further instructions executable by the processor, the further instructions, when executed, causing the processor to: deriving the location measurement based on are the location measurements, which are the reconstructed prediction parameters m across all subbands for each frame m. and N ｂａｎｄｓ is the number of subbands in frame m, and w ｂ (m) and is a weighting coefficient, and k ｅｎｄ（ｂ） is the end of the multiple summation, and k ｓｔａｒｔ（ｂ） is the beginning of the plurality of sums, 50. The apparatus of claim 49, wherein the apparatus is configured to perform operations including deriving the location measure, wherein: is a transformed downmix signal.

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