Quantization of audio parameters

Abstract

The present invention particularly discloses a device for audio encoding, which is configured to compare an audio parameter with a threshold value and a value depending on a previously quantized audio parameter; calculate a quantized audio parameter as the previously quantized audio parameter increased by a predetermined value; and calculate the quantized audio parameter as the previously quantized audio parameter multiplied by a factor value.

Description

Technical Field

[0001] The present application relates to apparatus and methods for quantizing low-frequency audio channels, but is not specifically for quantizing low-frequency audio within audio encoders and decoders. Background Art

[0002] A typical speaker layout for multi-channel reproduction (such as 5.1) includes "normal" speaker channels and low-frequency effects (LFE) channels. The normal speaker channels (e.g., Section 5) include broadband signals. Using these channels, audio engineers can, for example, localize auditory objects in a desired direction. The LFE channel (e.g., Section 1) includes only low-frequency signals (<120Hz), which are usually reproduced using a subwoofer. LFE was originally developed to reproduce separate low-frequency effects, but has also been used to route part of the low-frequency energy of the sound field to the subwoofer.

[0003] All common multi-channel speaker layouts, such as 5.1, 7.1, 7.1+4 and 22.2, include at least one LFE channel. Therefore, it is desirable for any spatial audio processing system with speaker reproduction to utilize an LFE channel.

[0004] If the input to the system is a multichannel mix (e.g. 5.1) and the output is to a multichannel speaker setup (e.g. 5.1), the LFE channel does not require any specific processing and it can be routed directly to the output, however, a multichannel signal may be sent and typically the audio signal requires compression in order to have a reasonable bit rate.

[0005] Parametric spatial audio processing is an area of ​​audio signal processing where a set of parameters is used to describe the spatial aspects of the sound. For example, when capturing parametric spatial audio from a microphone array, a common and effective choice is to estimate from the microphone array signal a set of parameters such as the direction of the sound in a frequency band, and the ratio between the directed and non-directed parts of the captured sound in the frequency band. These parameters are known to describe the perceived spatial properties of the sound captured at the microphone array locations very well, and thus can be exploited in the synthesis of spatial sound, for binaural headphones, for loudspeakers, or for other formats such as Ambisonics. Summary of the invention

[0006] In a fundamental first aspect, the present invention provides an apparatus for encoding audio parameters, comprising: a component for comparing an audio parameter with a threshold value and a value depending on a previously quantized audio parameter; a component for calculating a quantized audio parameter as the previously quantized audio parameter increased by a predetermined value when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized audio parameter; and a component for calculating the quantized audio parameter as the previously quantized parameter multiplied by a factor value when the audio parameter is less than the threshold value or less than the value depending on the previously quantized audio parameter.

[0007] The apparatus may further include: a component for encoding into a bitstream an indication that the audio parameter is greater than a threshold and greater than a value dependent on a previously quantized audio parameter; a component for encoding into a bitstream an indication that the audio parameter is less than a threshold or less than a value dependent on a previously quantized audio parameter.

[0008] The device may also include: a component for determining that a previously quantized audio parameter has also been determined by adding a predetermined value; and a component for calculating the quantized audio parameter as the previously quantized audio parameter increased by a predetermined value when the audio parameter is greater than a threshold value and greater than a value depending on the previously quantized audio parameter. The component may include: a component for calculating the quantized audio parameter as the previously quantized parameter increased by a predetermined value multiplied by a gain factor when the audio parameter is greater than a threshold value and greater than a value depending on the previously quantized audio parameter. The gain factor may have an absolute value greater than 1.

[0009] Dependent on the value of the previously quantized audio parameter may include a combination of the previously quantized audio parameter increased by a predetermined value and the previously quantized audio parameter multiplied by a damping factor.

[0010] The damping factor may have an absolute value less than 1.

[0011] The audio parameters may be spatial audio parameters.

[0012] The audio parameter may be a low frequency effect to total energy ratio.

[0013] According to a second aspect, an apparatus for decoding an audio parameter comprises a component for decoding an indication from a bitstream; a component for calculating a quantized audio parameter as the previously quantized audio parameter increased by a predetermined value when the indicator indicates that the audio parameter is greater than a threshold and greater than a value depending on the previously quantized audio parameter; and a component for calculating the quantized audio parameter as the previously quantized parameter multiplied by a factor value when the indicator indicates that the audio parameter is less than a threshold or less than a value depending on the previously quantized audio parameter.

[0014] The apparatus may further include: a component for decoding an indication related to a previous audio parameter from a bitstream; a component for determining that the indication related to the previous audio parameter indicates that the quantized previous audio parameter has also been determined by increasing a predetermined value; and a component for calculating the quantized audio parameter as the previous quantized audio parameter increased by a predetermined value when the audio parameter is greater than a threshold value and greater than a value dependent on the previously quantized audio parameter. The component may include: a component for calculating the quantized audio parameter as the previous quantized parameter increased by a predetermined value multiplied by a gain factor when the audio parameter is greater than a threshold value and greater than a value dependent on the previously quantized audio parameter.

[0015] The gain factor may have an absolute value greater than 1.

[0016] The value depending on the previously quantized audio parameter may include a combination of the previously quantized audio parameter increased by a predetermined value and the previously quantized audio parameter multiplied by a damping factor.

[0017] The damping factor may have an absolute value less than 1.

[0018] The audio parameters may be spatial audio parameters.

[0019] The audio parameter may be a low frequency effect to total energy ratio.

[0020] According to a third aspect, a method for encoding an audio parameter comprises: comparing an audio parameter with a threshold value and a value depending on a previously quantized audio parameter; when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by a predetermined value; and when the audio parameter is less than the threshold value or less than the value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized parameter multiplied by a factor value.

[0021] The method may further include encoding into a bitstream an indication that the audio parameter is greater than a threshold and greater than a value that depends on a previously quantized audio parameter; encoding into a bitstream an indication that the audio parameter is less than a threshold or less than a value that depends on a previously quantized audio parameter

[0022] The method may also include: determining that a previously quantized audio parameter has also been determined by adding a predetermined value; and when the audio parameter is greater than a threshold value and greater than a value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by a predetermined value may include: when the audio parameter is greater than a threshold value and greater than a value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized parameter increased by a predetermined value multiplied by a gain factor.

[0023] The gain factor may have an absolute value greater than 1.

[0024] The value depending on the previously quantized audio parameter may include a combination of the previously quantized audio parameter increased by a predetermined value and the previously quantized audio parameter multiplied by a damping factor.

[0025] The damping factor may have an absolute value less than 1.

[0026] The audio parameters may be spatial audio parameters.

[0027] The audio parameter may be a low frequency effect to total energy ratio.

[0028] According to a fourth aspect, a method for decoding an audio parameter includes: decoding an indication from a bitstream; when the indicator indicates that the audio parameter is greater than a threshold and greater than a value depending on a previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by a predetermined value; and when the indicator indicates that the audio parameter is less than a threshold or less than a value depending on a previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized parameter multiplied by a factor value.

[0029] The method may also include: decoding an indication associated with a previous audio parameter from a bitstream; determining that the indication associated with the previous audio parameter indicates that the quantized previous audio parameter has also been determined by increasing a predetermined value; and when the audio parameter is greater than a threshold and greater than a value dependent on the previously quantized audio parameter, a component for calculating the quantized audio parameter as the previously quantized audio parameter increased by a predetermined value may include a component for calculating the quantized audio parameter as the previously quantized parameter increased by a predetermined value multiplied by a gain factor when the audio parameter is greater than a threshold and greater than a value dependent on the previously quantized audio parameter.

[0030] The gain factor may have an absolute value greater than 1.

[0031] The value depending on the previously quantized audio parameter may include a combination of the previously quantized audio parameter increased by a predetermined value and the previously quantized audio parameter multiplied by a damping factor.

[0032] The damping factor may have an absolute value less than 1.

[0033] The audio parameters may be spatial audio parameters.

[0034] The audio parameter may be a low frequency effect to total energy ratio.

[0035] According to a fifth aspect, a device for decoding audio parameters is provided, comprising at least one processor and at least one memory comprising computer code, wherein the at least one memory and the computer code are configured, together with the at least one processor, to cause the device to at least perform: comparing the audio parameter with a threshold value and a value depending on the value of the previously quantized audio parameter; when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by a predetermined value; and when the audio parameter is less than the threshold value or less than the value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized parameter multiplied by a factor value.

[0036] According to a sixth aspect, a device for decoding audio parameters is provided, comprising at least one processor and at least one memory comprising computer code, wherein the at least one memory and the computer code are configured, together with the at least one processor, to cause the device to at least perform: decoding an indication from a bitstream; when the indicator indicates that the audio parameter is greater than a threshold and greater than a value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by a predetermined value; and when the indicator indicates that the audio parameter is less than a threshold or less than a value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized parameter multiplied by a factor value.

[0037] A computer program includes program instructions for causing a computer to execute the above method.

[0038] A computer program product stored on a medium may cause an apparatus to perform the methods described herein.

[0039] An electronic device may comprise an apparatus as described herein.

[0040] A chipset may include the apparatus described herein.

[0041] The embodiments of the present application are intended to solve the problems associated with the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] For a better understanding of the present application, reference will now be made by way of example to the accompanying drawings, in which:

[0043] Figure 1 A system of apparatus suitable for implementing some embodiments is schematically shown;

[0044] Figure 2 According to some embodiments, Figure 1 A flowchart of the operation of the system shown;

[0045] Figure 3 Schematically illustrates a capture / encoding device suitable for implementing some embodiments;

[0046] Figure 4 Schematically shows a method suitable for implementing some embodiments. Figure 3 The low frequency effects channel analyzer device shown;

[0047] Figure 5 a flow chart showing the operation of a low frequency effects quantizer apparatus according to some embodiments;

[0048] Figure 6 schematically illustrates a reproduction device suitable for implementing some embodiments; and

[0049] Figure 7 An exemplary device suitable for implementing the illustrated means is schematically illustrated. DETAILED DESCRIPTION

[0050] Suitable apparatus and possible mechanisms for providing efficient analysis of derived metadata parameters for microphone array and other input format audio signals are described in more detail below.

[0051] The device has been designed to send a spatial audio model of the sound field using N (usually 2 or in some cases N can be mono) transmission audio signals and spatial metadata. The transmission audio signal is typically compressed using a suitable audio coding mechanism (e.g. Advanced Audio Coding AAC or Enhanced Voice Service EVS codec). The spatial metadata may include parameters such as direction (e.g. azimuth, elevation) in the time-frequency domain, and the ratio of direct to total energy (or energy or ratio parameter) in the time-frequency domain.

[0052] In the following disclosure, such parameterization may be expressed as a sound field related parameterization. In the following disclosure, the use of direction and the direct-to-total energy ratio may be expressed as a directional ratio parameterization. In addition to these parameters, other parameters may be used (e.g., diffusivity is not a direct-to-total energy ratio or a distance parameter is added to the direction parameter). Using such a sound field related parameterization, a spatial perception similar to that which occurs in the original sound field may be reproduced. As a result, the listener may perceive the direction and distance of multiple sources, as well as the properties of the surrounding physical space, and other spatial sound characteristics.

[0053] The following disclosure proposes methods how to convey LFE information together with (directional and ratio) spatial parameterization. Thus, for example in case of multi-channel speaker input, embodiments aim to faithfully reproduce the perception of the original LFE signal. In some embodiments, in case of microphone array or Ambisonics input, apparatus and methods are proposed to determine reasonable LFE related signals.

[0054] Since the directional and direct to total energy ratio parameterization (in other words the directional ratio parameterization) is related to the human perception of the sound field, its purpose is to convey information that can be used to reproduce a sound field perceived as the original. The parameterization is generic for reproduction systems, as it can be designed to work for loudspeaker reproduction with any loudspeaker setup as well as headphone reproduction. Therefore, this parameterization is useful for generic audio codecs, where the input can come from various sources (microphone arrays, multi-channel loudspeakers, Ambisonics) and the output can go to various reproduction systems (headphones, various loudspeaker setups).

[0055] However, since the directional ratio parameterization is independent of the reproduction system, this also means that there is no direct control over what audio should be reproduced from a certain speaker. The directional ratio parameterization determines the directional distribution of the sound to be reproduced, which is usually sufficient for wideband speakers. However, the LFE channel does not usually have any "direction". Instead, it is just a channel where the audio engineer has decided to place a certain amount of low-frequency energy (and / or a certain low-frequency signal).

[0056] In the following embodiments, LFE information may be generated. In embodiments involving multi-channel input (e.g., 5.1), LFE channel information is readily available. However, in some embodiments, such as microphone array input, LFE channel information is not present (because the microphones are capturing the actual sound scene). Therefore, in some embodiments LFE channel information is generated or synthesized (in addition to encoding and transmitting the information).

[0057] Embodiments implementing the generation or synthesis of the LFE enable the reproduction system to avoid using only broadband speakers to reproduce the low frequencies and enable the use of a subwoofer or similar output device. Furthermore, these embodiments may allow the reproduction or synthesis system to avoid using a fixed energy portion of the low frequencies for reproduction using the LFE speaker, which may lose all directionality at those frequencies since there is typically only one LFE speaker. However, using the embodiments described herein, the LFE signal (which does not have directionality) may be reproduced using the LFE speaker and the other portion of the signal (which may have directionality) may be reproduced using the broadband speaker, thereby maintaining directionality.

[0058] Similar observations are valid for other inputs such as Ambisonics inputs.

[0059] The concepts expressed in the embodiments below relate to audio encoding and decoding using sound field related parameterization (e.g., directional and direct to total energy ratios in frequency bands), wherein embodiments utilize this parameterization to transmit (generate or receive) low frequency effects (LFE) channel information in addition to (wideband) audio signals. In some embodiments, the transmission of LFE channel (and wideband audio signal) information can be achieved by obtaining an audio signal; calculating the ratio of LFE energy to total energy of the audio signal in one or more frequency bands; using the audio signal to determine directional parameters, energy ratio parameters 110 (including the ratio of direct to total energy and the ratio of diffuse to total energy for each direction), and coherence parameters 112; quantizing and transmitting these LFE to total energy ratios (in other words, LFE metadata) together with the associated audio signal and directional and direct to total energy ratio parameters. Furthermore, in such an embodiment, audio may be synthesized for an LFE channel using the LFE to total energy ratio and the associated audio signal; and audio for other channels may be synthesized using the LFE to total energy ratio (LFE metadata), directionality, direct to total energy ratio, and coherence parameters, and the associated audio signal.

[0060] Embodiments disclosed herein also present an apparatus and method for quantizing the ratio of LFE to total energy associated with an LFE channel using a low bit rate representation. This enables the LFE channel to be transmitted with an encoded multi-channel audio signal operating at a relatively low bit rate. For example, a multi-channel audio coding system operating at a total bit rate of approximately 13 kb / s may require the LFE channel to be quantized in the range of 50-200 b / s.

[0061] In some embodiments, the input audio signal of the system may be a multi-channel audio signal, a microphone array signal, or an Ambisonic audio signal.

[0062] The transmitted related audio signals (1-N, for example 2 audio signals) may be obtained by any suitable means, for example by down-mixing, selecting or processing the input audio signals.

[0063] Any suitable method or apparatus may be used to determine the directional and direct to total energy ratio parameters.

[0064] As above, in some embodiments where the input is a multi-channel audio input, the LFE energy and the total energy may be estimated directly from the multi-channel signal. However, in some embodiments, an apparatus and method for determining the ratio of LFE to total energy is disclosed, wherein the ratio of LFE to total energy may be used to generate appropriate LFE information in the absence of LFE channel information received, such as a microphone array or Ambisonics input. Thus, this may be based on the analyzed direct to total energy ratio: if the sound is directional, the ratio of LFE to total energy is smaller; if the sound is non-directional, the ratio of LFE to total energy is larger.

[0065] In some embodiments, an apparatus and method for transmitting LFE information from a multi-channel signal together with an Ambisonic signal is provided. This is based on the method discussed in detail below, where the transmission is performed together with the parameterization related to the sound field and the associated audio signal, but in this case, the Ambisonic signal is used to transmit the spatial aspects, and the ratio of LFE to total energy is used to transmit the LFE information.

[0066] In addition, in some embodiments, an apparatus and method are provided for transcoding a first data stream (audio and metadata) (wherein the metadata does not contain a ratio of LFE to total energy) into a second data stream (audio and metadata) (wherein a synthesized LFE to total energy ratio is injected into the metadata).

[0067] refer to Figure 1 , shows an example apparatus and system for implementing embodiments of the present application. The system 171 is shown as having an 'analysis' part 121 and a 'synthesis' part 131. The 'analysis' part 121 is the part from receiving the input (multi-channel loudspeaker, microphone array, Ambisonics) audio signal 100 up to encoding metadata and a transmission signal 102 that can be transmitted or stored 104. The 'synthesis' part 131 can be the part from decoding of the encoded metadata and transmission signal 104 to presentation of the reproduced signal (e.g. in a multi-channel loudspeaker form 106 via loudspeaker 107).

[0068] The inputs to the system 171 and the 'analysis' part 121 are therefore audio signals 100. These may be suitable input multi-channel loudspeaker audio signals, microphone array audio signals or Ambisonics audio signals.

[0069] The input audio signal 100 may be passed to an analysis processor 101. The analysis processor 101 may be configured to receive the input audio signal and generate a suitable data stream 104 including a suitable transmission signal. The transmission audio signal may also be referred to as a related audio signal and is based on the audio signal. For example, in some embodiments, the transmission signal generator 301 is configured to downmix or otherwise select or combine the input audio signal to a determined number of channels, such as by beamforming technology, and output these as transmission signals. In some embodiments, the analysis processor is configured to generate a 2-audio channel output of a microphone array audio signal. The determined number of channels may be two or any suitable number of channels.

[0070] In some embodiments, the analysis processor is configured to pass the received unprocessed input audio signal 100 to the encoder in the same manner as the transmission signal. In some embodiments, the analysis processor 101 is configured to select one or more of the microphone audio signals and output the selection for transmission or storage 104. In some embodiments, the analysis processor 101 is configured to apply any suitable encoding or quantization to the transmission audio signal.

[0071] In some embodiments, the analysis processor 101 is also configured to analyze the input audio signal 100 to generate metadata associated with the input audio signal (and therefore associated with the transmission signal). The analysis processor 101 can be, for example, a computer (running appropriate software stored on a memory and at least one processor), a mobile device, or alternatively can be a specific device utilizing, for example, an FPGA or ASIC. As shown in more detail herein, for each time-frequency analysis interval, the metadata can include directional parameters, energy ratio parameters, and low-frequency effects channel parameters (and in some embodiments also surrounding coherence parameters, as well as extended coherence parameters and other parameters). In some embodiments, the directional parameters and energy ratio parameters can be considered as spatial audio parameters. In other words, the spatial audio parameters include parameters intended to characterize the sound field of the input audio signal.

[0072] In some embodiments, the analysis processor 101 comprises a time-frequency domain transformer.

[0073] In some embodiments, the time-frequency domain converter is configured to receive an input multi-channel signal and apply an appropriate time-frequency domain transform, such as a short-time Fourier transform (STFT), to convert the input time domain signal into an appropriate time-frequency signal. These time-frequency signals can be passed to the spatial analyzer 303.

[0074] Thus, for example, a time-frequency signal can be represented in the time-frequency domain as

[0075] si (b, n),

[0076] Where b is the frequency point index, n is the time-frequency block (frame) index, and i is the channel index. In another expression, n can be considered as a time index with a sampling rate lower than the sampling rate of the original time domain signal. The frequency points can be grouped into subbands that group one or more points into subbands with band index k=0,...,K-1. Each subband k has the lowest point b k，low and the highest point b k，high , and the subband contains k，low to b k，high The width of the subband can be approximated by any suitable distribution. For example, the equivalent rectangular bandwidth (ERB) scale or the Bark scale.

[0077] Thus, a time-frequency (TF) tile (or block) is a specific subband within a subframe of a frame.

[0078] It will be appreciated that the number of bits required to represent the spatial audio parameters may depend at least in part on the TF (time frequency) block resolution (i.e., the number of TF subframes or blocks). For example, a 20 ms audio frame may be divided into 4 time domain subframes of 5 ms each, and each time domain subframe may have up to 24 frequency subbands divided in the frequency domain according to the Bark scale, its approximation, or any other suitable division. In this particular example, the audio frame may be divided into 96 TF subframes / blocks, in other words, 4 time domain subframes with 24 frequency subbands. Therefore, the number of bits required to represent the spatial audio parameters of an audio frame may depend on the TF block resolution.

[0079] In some embodiments, the parameters generated may differ from frequency band to frequency band and may depend in particular on the transmission bit rate. Thus, for example in frequency band X all parameters are generated and sent, while in frequency band Y only one parameter is generated and sent and furthermore no parameters are generated and sent in frequency band Z. A practical example of this may be that for some frequency bands, such as the highest frequency band, some parameters are not needed for perceptual reasons.

[0080] The transmission signal and metadata 102 may be transmitted or stored. Figure 1 104. Before the transmission signal and metadata are transmitted or stored, in some embodiments, they may be encoded to reduce the bit rate and multiplexed into one stream. Any suitable scheme may be used to achieve encoding and multiplexing.

[0081] At the decoder side 131, the received or acquired data (stream) may be input to the synthesis processor 105. The synthesis processor 105 may be configured to demultiplex the data (stream) into coded transport and metadata. The synthesis processor 105 may then decode any coded streams to obtain the transport signal and metadata.

[0082] The synthesis processor 105 may then be configured to receive the transmission signal and metadata and create a suitable multi-channel audio signal output 106 (which may be any suitable output format, such as a binaural, multi-channel speaker or Ambisonics signal, depending on the use case) based on the transmission signal and metadata. In some embodiments with speaker reproduction, an actual physical sound field with desired perceptual characteristics is reproduced (using speaker 107). In other embodiments, reproduction of the sound field may be understood to refer to reproducing the perceptual characteristics of the sound field by other means than reproducing the actual physical sound field in the space. For example, the desired perceptual characteristics of the sound field may be reproduced on headphones using the binaural reproduction method described herein. In another example, the perceptual characteristics of the sound field may be reproduced as Ambisonic output signals, and these Ambisonic signals may be reproduced using an Ambisonic decoding method to provide, for example, a binaural output with desired perceptual characteristics.

[0083] In some embodiments, the synthesis processor 105 may be a computer (running appropriate software stored on memory and at least one processor), a mobile device, or alternatively, may be a specialized device utilizing, for example, an FPGA or ASIC.

[0084] about Figure 2 , showing Figure 1 An example flow chart of the overview shown.

[0085] First, the system (analysis part) is configured to receive an input audio signal or a suitable multi-channel input, such as Figure 2 As shown in step 201.

[0086] Then, the system (analysis part) is configured to generate a transmission signal channel or transmission signal (e.g. based on channel downmixing / selection / beamforming of a multi-channel input audio signal), such as Figure 2 As shown in step 203

[0087] The system (analysis part) is also configured to analyze the audio signal to generate metadata: direction; energy ratio, LFE ratio (and in some embodiments other metadata such as ambient coherence; propagation coherence), such as Figure 2 As shown in step 205.

[0088] The system is then configured to (optionally) encode the transmission signal and metadata with coherent parameters for storage / transmission, such as Figure 2 As shown in step 207.

[0089] Thereafter, the system may store / send the transmission signal and metadata (which may include coherence parameters), such as Figure 2 As shown in step 209.

[0090] The system can acquire / receive transmission signals and metadata, such as Figure 2 As shown in step 211.

[0091] Then, the system is configured to extract from the transmission signal and metadata, e.g. Figure 2 As shown in step 213.

[0092] The system (synthesis part) is configured to synthesize an output spatial audio signal (which, as previously discussed, may be any suitable output format, such as a binaural, multi-channel speaker or Ambisonics signal, depending on the use case) based on the extracted audio signal and metadata, such as Figure 2 As shown in step 215.

[0093] refer to Figure 3 , shows an example analysis processor 101 according to some embodiments, wherein the input audio signal is a multi-channel speaker input. In this example, the multi-channel speaker signal 300 is passed to a transmission audio signal generator 301. The transmission audio signal generator 301 is configured to generate a transmission audio signal according to any of the aforementioned options. For example, the transmission audio signal can be down-mixed from the input signal. The number of transmission audio signals can be any number, and can be 2 or more or less than 2.

[0094] exist Figure 3 In the example shown, the multi-channel loudspeaker signal 300 is also input to a spatial analyzer 303. The spatial analyzer 303 may be configured to generate appropriate spatial metadata outputs, such as direction 304 and direct to total energy ratio 306. The implementation of the analysis may be any suitable implementation as long as it can provide a direction, such as an azimuth angle θ(k,n) and a direct to total energy ratio ratio r(k,n) in the time-frequency domain (k is a frequency band index and n is a time frame index).

[0095] For example, in some embodiments, the spatial analyzer 303 transforms the multi-channel speaker signals into first order ambisonics (FOA) signals and performs directionality and ratio estimation in the time-frequency domain.

[0096] A FOA signal consists of four signals: omnidirectional w(t) and three figure-of-eight patterns x(t), y(t), and z(t) arranged orthogonally. Let us assume that they are transformed in time-frequency form: w(k,n), x(k,n), y(k,n), z(k,n). The SN3D normalization scheme is used, where the maximum directional response of each pattern is 1.

[0097] From the FOA signal, the vector pointing to the direction of arrival can be estimated:

[0098]

[0099] The direction of this vector is the direction θ(k,n). Brackets <.> denote averaging of potentials over time and / or frequency. Note that when averaging is performed, the direction data may not need to be represented or stored for each time and frequency.

[0100] The ratio parameter can be obtained as follows:

[0101]

[0102] To apply the above formula to the loudspeaker input, the loudspeaker signal Si(t) (where i is the channel index) can be transformed into the FOA signal:

[0103]

[0104] The w, x, y and z signals are for each loudspeaker with its own azimuth and elevation direction. i The output signal combining all these signals is

[0105] The multi-channel loudspeaker signal 300 may also be input to an LFE analyzer 305. The LFE analyzer 305 may be configured to generate an LFE to total energy ratio 308 (which may also be generally referred to as a ratio of low or lower frequency effects to total energy).

[0106] The output of LFE analyzer 305 may be passed to LFE quantizer 309 so that LFE to total energy ratio 308 may be quantized to provide quantized LFE to total energy ratio 311 .

[0107] The spatial analyzer may also include a multiplexer 307 configured to combine and encode the transmit audio signal 302, the direction 304, the direct to total energy ratio 306, the coherence 310, and the quantized LFE to total energy ratio 311 to generate the data stream 102. The multiplexer 307 may be configured to compress the audio signal using a suitable codec (e.g., AAC or EVS) and, in addition, compress the metadata as described above.

[0108] for Figure 4 , as shown previously Figure 3 An example LFE analyzer 305 is shown.

[0109] The example LFE analyzer 305 may include a time-frequency transformer 401 configured to receive a multi-channel loudspeaker signal and transform the multi-channel loudspeaker signal into the time-frequency domain using an appropriate transform, such as a short-time Fourier transform (STFT), a complex modulated quadrature mirror filter bank (QMF), or a hybrid QMF, which is a complex QMF bank with cascaded band-splitting filters at the lowest frequency band to improve frequency resolution. The resulting signal may be represented as S i (b,n), where i is the speaker channel, b is the frequency point index and n is the time frame index.

[0110] In some embodiments, the LFE analyzer 305 may include an energy (for each channel) determiner 403 configured to receive the time-frequency audio signal and determine the energy of each channel by:

[0111] E i (b, n) = S i (b, n) 2

[0112] The energy of the frequency points can be grouped into frequency bands that group one or more points into frequency band index k=0, ..., k-1

[0113]

[0114] Each frequency band k has the lowest point b k，low and the highest point b k，high , and the frequency band includes k，low to b k，high The width of the frequency band can be approximated by any suitable distribution. For example, the Equivalent Rectangular Bandwidth (ERB) scale or the Bark scale is commonly used in spatial audio processing.

[0115] In some embodiments, the LFE analyzer 305 may include a ratio (between the LFE channel and all channels) determiner 405 configured to receive the energy 404 from the energy determiner 403. The ratio (between the LFE channel and all channels) determiner 405 may be configured to determine the ratio of the LFE to the total energy by selecting low frequency bands in a manner that preserves the perception of the LFE. For example, in some embodiments, two bands may be selected at low frequencies (0-60 and 60-120 Hz), or if a minimum bit rate is desired, only one band (0-120 Hz) may be used. In some embodiments, a large number of bands may be used, and the frequency boundaries of the bands may be different or may partially overlap. In addition, in some embodiments, the energy estimates may be averaged over the time axis.

[0116] The LFE to total energy ratio Ξ(k,n) may then be calculated as the ratio of the sum of the energies of the LFE channel to the sum of the energies of all channels, for example by using the following calculation:

[0117]

[0118] The ratio of LFE to total energy Ξ(k,n) 308 may then be output and passed to the LFE quantizer 309. Sometimes the LFE signal may be downmixed with a subset of channels. In this case, the above expression may be written in the form of a ratio of the sum of the energies of the LFE channels to the sum of the energies of the channel subsets.

[0119] In an embodiment, the LFE quantizer 309 may be arranged with a multi-quantizer approach whereby a specific quantizer may be used to quantize the LFE to total energy ratio depending on the operating bit rate of the LFE channel and the results of the analysis performed on the LFE to total energy ratio itself.

[0120] For example, the LFE quantizer 309 may be arranged to have the following functions:

[0121] o Determine the maximum LFE to total energy ratio of the frame, keeping in mind that each frame may be divided into multiple TF partitions. That is, the maximum LFE to total energy ratio of all LFE to total energy ratios in the frame, whereby each TF partition (k, n) in the frame may have a calculated LFE to total energy ratio Ξ(k, n).

[0122] o If the determined maximum LFE to total energy ratio for a frame is below a predetermined threshold, sending one bit (for that frame) indicating that the frame has no quantized LFE to total energy ratio.

[0123] o If the determined maximum LFE to total energy ratio of a frame is above a predetermined threshold, determine the average LFE to total energy ratio over the TF partitions of the frame.

[0124] o Depending on the encoding bit rate, the ratio of average LFE to total energy is quantized and transmitted using one of a plurality of bit rates. For example, the ratio of average LFE to total energy may be scalar quantized according to a plurality of different ratios. A vector quantizer (VQ) based on the quantized ratio of average LFE to total energy may then be selected from a set of vector quantizers (VQ). The selected vector quantizer may then be used to quantize the ratio of average removed LFE to total energy for each subframe.

[0125] Figure 5 It is shown how the LFE quantizer 309 can be configured to have a quantization scheme of the ratio of LFE to total energy that can quantize the ratio of LFE to total energy according to a plurality of different quantization schemes. In this case, there is a quantization scheme of the ratio of LFE to total energy that incorporates a decision loop that allows scalar or vector quantization of the ratio of LFE to total energy in a frame.

[0126] Figure 5 The decision is initially made based on the encoding bit rate, where if the available encoding bit rate is above a threshold bit rate value (Thresh_bitrate), a higher rate scheme for quantization of the ratio of LFE to total energy of the frame can be selected. The higher rate scheme can be based on scalar or vector quantization or both. This decision path is in Figure 5 However, if the available encoding bitrate for the frame is less than the threshold bitrate value, a low rate quantization scheme based on tracking the amount of energy associated with the LFE channel is used with the goal of maintaining the perception of the original sound (within the LFE channel). This path is in Figure 5 It is shown as 504 in the figure.

[0127] Use a low-rate quantization method (according to Figure 5 One solution for encoding the ratio of LFE to total energy is to simply use a bit to indicate whether the ratio of LFE to total energy of a subframe or frame is above a predetermined threshold. This method can use 1 bit per subframe to signal / quantize the ratio of LFE to total energy.

[0128] Another solution to encode / quantize the ratio of LFE to total energy at low rate (according to Figure 5 503) is a method using a delta-sigma type, whereby a single bit is used to modulate the value of the ratio of LFE to total energy from one frame to the next frame (or from one subframe to the next subframe).

[0129] On the encoding side, this can be achieved by comparing the current LFE to total energy ratio (the ratio of LFE to total energy of the current frame or subframe) to a predetermined threshold and a value derived from the ratio of the previously quantized LFE to the total energy. The derived value can be a combination of one term that increases the ratio of the previously (stored) quantized LFE to the total energy by a fixed amount (β) and a second term that adds a certain degree of hysteresis that eliminates any sudden changes in the ratio of the currently quantized LFE to the total energy. The second term can be formulated by multiplying the ratio of the previously quantized LFE to the total energy by a damping factor (α).

[0130] On the encoding side, when the current LFE to total energy ratio is greater than a predetermined threshold and a value derived from the previously quantized LFE to total energy ratio, the LFE quantizer 309 may be configured to increase the previously quantized LFE to total energy ratio by a fixed amount β. This increased previously quantized LFE to total energy ratio becomes the quantized LFE to total energy ratio of the current frame, which is stored in preparation for use as the previously quantized LFE to total energy ratio of the next frame. The increase (by amount β) applied to the previously quantized LFE to total energy ratio may be represented by the state of a single bit. For example, a state of "1" may represent an increase in the previously quantized LFE to total energy ratio.

[0131] Conversely, at the encoding side, when the current LFE to total energy ratio is less than (or equal to) a predetermined threshold or a value derived from the previously quantized LFE to total energy ratio, then the LFE quantizer 309 may be arranged not to increase the previously quantized LFE to total energy ratio by a fixed amount β. In this case, the previously quantized LFE to total energy ratio may be damped by a damping factor α. In other words, the previously quantized LFE to total energy ratio of the next frame is the quantized LFE to total energy ratio of the current frame multiplied by a factor α. An effective reduction in the previously quantized LFE to total energy ratio (which forms the currently quantized LFE to total energy ratio) may also be represented by the state of a single bit. For example, a state of "0" may represent a decrease in the previously quantized LFE to total energy ratio.

[0132] The above algorithm for quantifying the ratio of the current frame LFE to the total energy at time t can be represented by the following pseudo code:

[0133] pseudocode:

[0134]

[0135]

[0136] In further embodiments, it may be desirable to react more quickly to changes in the ratio of LFE to total energy on a frame-by-frame basis. This may be arranged by storing whether the decision previously taken was to increase or decrease the previous quantized ratio of LFE to total energy for the previous frame. That is, at time t, in the case of a decision made for the current frame, the previous decision may refer to the decision made for the frame at time t-1. The result of whether a faster reaction to changes in the ratio of LFE to total energy is desired may then be based on whether both the previous update decision and the current update decision indicate that the ratio of quantized LFE to total energy should be increased.

[0137] In other words, if the previous update decision indicated that the ratio of quantized LFE to total energy increased, and the update decision for the current frame also indicates that the ratio of quantized LFE to total energy increased, then it can be determined that the ratio of quantized LFE to total energy should be increased by a larger amount, such as an amount given by β*θ, where θ is greater than 1.

[0138] With respect to the above pseudo code, the condition for the increase (rate of change) of the ratio of quantized LFE to total energy is generated by the decision to send a "1" for the current frame together with the decision to send a "1" for the previous frame. This further embodiment can be reflected in the pseudo code as

[0139] pseudocode:

[0140]

[0141]

[0142] Back to Figure 5 , if the available coding rate for the ratio of LFE to total energy is greater than a threshold bitrate (Thresh_bitrate), path 502 may be taken. Path 502 encodes the ratio of LFE to total energy for each subframe of the frame using a higher rate quantization scheme that may be a combination of scalar and vector quantization. Initially, the ratio of LFE to total energy of the subframe is checked against an LFE activity threshold ( Figure 5 , 505). If the threshold is exceeded, a quantization process is entered to quantize the ratio of LFE to total energy of each (sub) frame ( Figure 5 , 506). However, if the threshold is not exceeded, the ratio of LFE to total energy of the entire frame is not quantized ( Figure 5 , 507).

[0143] After entering the quantization process for quantizing the ratio of LFE to total energy of each subframe (path 506, Figure 5 ), the process can use a scalar quantizer in the log2 domain to quantize the ratio of the average LFE to the total energy of the frame. Figure 5 This is shown as processing block 509.

[0144] The process can then check whether the available coding rate is above a higher threshold bit rate (H_Thresh_Bitrate, 511, Figure 5 ). If the check at 511 indicates that the available coding rate (of the frame) is above the upper threshold bit rate, then quantization of the ratio of LFE to total energy for all subframes of the frame may proceed to a further processing stage. The further processing stage may include forming a residual LFE to total energy ratio vector for each frame, whereby each component of the vector is formed by subtracting the quantized average LFE to total energy ratio (formed in block 509) from the ratio of LFE to total energy corresponding to each subframe in the frame. Figure 5 Also depicted in FIG. 5 is a processing block 513 which indicates that when the available coding rate for a frame is below an upper threshold bit rate, no further quantization is performed.

[0145] The LFE to total energy ratio vector may then be quantized using one of a plurality of different codebooks. The size of the codebook used to quantize the LFE to total energy ratio vector may depend on the size of the quantized average LFE to total energy ratio. Thus, an LFE to total energy ratio vector derived from a low value quantized average LFE to total energy ratio may use a smaller sized codebook to encode the LFE to total energy ratio vector, and an LFE to total energy ratio vector derived from a high value quantized average LFE to total energy ratio may use a larger sized codebook to encode the LFE to total energy ratio vector. Processing block 515 depicts forming Figure 5 The ratio of the residual LFE to the total energy in the vector steps.

[0146] about Figure 5 , the process of selecting the codebook size according to the size of the quantized average LFE to total energy ratio is arranged according to the actual implementation. In this example, the index of the quantized average LFE to total energy ratio is used to select the codebook. The selected codebook is then used to quantize the LFE to total energy ratio vector. In this example, the low value index 1 will correspond to the lowest quantized average LFE to total energy ratio, which in turn leads to the selection of the smallest 1-bit codebook (in Figure 5 However, in contrast, a quantized average LFE to total energy ratio index of "4 and above" will correspond to a higher quantized average LFE to total energy ratio, which in turn results in the selection of a maximum 4-bit codebook (in Figure 5 In between these two extremes are processing blocks 521 and 523 corresponding to quantizing the LFE to total energy ratio vector with a 2-bit codebook, and processing blocks 525 and 527 corresponding to quantizing the LFE to total energy ratio vector with a 3-bit codebook.

[0147] It should be understood that Figure 5Each quantization routine described in can be implemented as a separate process for quantizing the ratio of LFE to total energy of a frame and requires Figure 5 In other words, this means that the low rate quantization scheme of Figure 5503 can be implemented as a separate independent routine without having to enter the vector quantization scheme according to path 502. Therefore, the delta-sigma type method described in the context of 503 can be implemented as a separate feature for quantizing the ratio of LFE to total energy of a frame.

[0148] about Figure 6 , shows an example synthesis processor 105 suitable for processing the output of a multiplexer according to some embodiments.

[0149] like Figure 6 The synthesis processor 105 shown shows a demultiplexer 600. The demultiplexer 600 is configured to receive the data stream 102 and demultiplex and / or decompress or decode the audio signal and / or metadata. Direction 604, direct to total energy ratio 606 and coherence 614 can also be demultiplexed from the demultiplexer 600 and passed to the spatial synthesizer 605.

[0150] The transmission audio signal 602 can then be output to a filter bank 603. The filter bank 603 can be configured to perform a time-frequency transform (e.g., STFT or complex QMF). The filter bank 603 is configured to have sufficient frequency resolution at low frequencies so that the audio can be processed according to the frequency resolution of the ratio of LFE to total energy. For example, in the case of a complex QMF filter bank implementation, if the frequency resolution is not good enough (i.e., the frequency point is too wide in frequency), a cascade filter can be used to further divide the frequency point into narrower bands at low frequencies, and the high frequencies can be delayed accordingly. Therefore, in some embodiments, a hybrid QMF can implement the method.

[0151] In some embodiments, the LFE to total energy ratio 608 output by the demultiplexer 601 is for two frequency bands (associated with the filter bank bands b0 and b1). The filter bank transforms the signal so that the time-frequency domain transmits the audio signal T i The (b, n) two (or any defined number identifying the LFE frequency range) lowest frequency points correspond to these frequency bands and are input to the LFE determiner 609 .

[0152] The determiner 609 may be configured to receive the transmission audio signal T iThe LFE determiner 609 may be configured to form a quantized LFE to total energy ratio from the LFE to total energy ratio index. In an embodiment, this may be performed by a dequantization operation. For embodiments in which a delta-sigma method is used to quantize the LFE to total energy ratio, the LFE determiner 609 may be arranged to receive a bit (or indication) indicating whether the value of the quantized LFE to total energy ratio of the current frame is formed by increasing the quantized LFE to total energy of the previous frame or decreasing the quantized LFE to total energy of the previous frame.

[0153] In the case where a bit is received indicating that the ratio of the quantized LFE to the total energy of the current frame is calculated by increasing the quantized LFE to the total energy of the previous frame, in the context of the above pseudo code, the signaling bit is received as "1". The ratio of the quantized LFE to the total energy of the current frame can be calculated by obtaining the stored ratio of the quantized LFE to the total energy from the previous frame and increasing its value by the value of β.

[0154] In another embodiment, the signaling bits of the previous frame are also considered during the calculation of the ratio of the quantized LFE to the total energy of the current frame. In the case where the signaling bits of the previous frame also indicate "1" (i.e. the previous frame also has an increase in the ratio of the quantized LFE to the total energy). Then, the ratio of the quantized LFE to the total energy of the current frame can be calculated by obtaining the stored ratio of the quantized LFE to the total energy from the previous frame and increasing its value by the larger value of β*θ.

[0155] In the case where a bit is received indicating that the ratio of the quantized LFE to the total energy of the current frame is calculated by reducing the quantized LF to the total energy of the previous frame, in the context of the above pseudo code, the signaling bit is received as "0". The ratio of the quantized LFE to the total energy of the current frame can be calculated by taking the stored ratio of the quantized LFE to the total energy from the previous frame and damping its value by the damping factor α.

[0156] The process for dequantizing the ratio of LFE to total energy for the current frame at time t at the LFE determiner 609 may be represented by the following pseudo code:

[0157]

[0158] The LFE determiner may then generate the LFE channel, for example, by calculating:

[0159]

[0160] Where p is, for example, 0.5. In some embodiments, the inverse filter bank 611 is configured to receive the multi-channel loudspeaker signal from the spatial synthesizer 605 and the LFE signal time-frequency signal 610 output from the LFE determiner 609. These signals may be combined or merged and further converted to the time domain.

[0161] In some embodiments, the transmission signal may be modified before being fed to the spatial synthesizer 605. For each channel i, the modification may take the following form:

[0162] T′ i (b,n)=(1-Ξ(b,n)) p T i (b, n)

[0163] The resulting multi-channel speaker signal (eg 5.1) 612 may be reproduced using a speaker setup.

[0164] about Figure 7 , shows an example electronic device that can be used as an analysis or synthesis device. The device can be any suitable electronic device or apparatus. For example, in some embodiments, the device 1400 is a mobile device, a user device, a tablet computer, a computer, an audio playback device, etc.

[0165] In some embodiments, device 1400 includes at least one processor or central processing unit 1407. Processor 1407 may be configured to execute various program codes, such as the methods described herein.

[0166] In some embodiments, the device 1400 includes a memory 1411. In some embodiments, at least one processor 1407 is coupled to the memory 1411. The memory 1411 can be any suitable storage component. In some embodiments, the memory 1411 includes a program code segment for storing program code that can be implemented on the processor 1407. In addition, in some embodiments, the memory 1411 can also include a storage data segment for storing data, such as data that has been processed or is to be processed according to the embodiments described herein. Whenever needed, the processor 1407 can retrieve the implemented program code stored in the program code segment and the data stored in the stored data segment via the memory-processor coupling.

[0167] In some embodiments, device 1400 includes a user interface 1405. In some embodiments, user interface 1405 can be coupled to processor 1407. In some embodiments, processor 1407 can control the operation of user interface 1405 and receive input from user interface 1405. In some embodiments, user interface 1405 can enable a user to enter commands to device 1400, for example, via a keyboard. In some embodiments, user interface 1405 can enable a user to obtain information from device 1400. For example, user interface 1405 can include a display configured to display information from device 1400 to a user. In some embodiments, user interface 1405 can include a touch screen or touch interface, both of which can enable information to be input to device 1400 and further display information to a user of device 1400.

[0168] In some embodiments, the device 1400 includes an input / output port 1409. In some embodiments, the input / output port 1409 includes a transceiver. The transceiver in such embodiments can be coupled to the processor 1407 and configured to communicate with other devices or electronic devices, for example, via a wireless communication network. In some embodiments, the transceiver or any suitable transceiver or transmitter and / or receiver device can be configured to communicate with other electronic devices or devices via a wired or wired coupling.

[0169] The transceiver can communicate with other devices via any suitable known communication protocol. For example, in some embodiments, the transceiver or transceiver device can use a suitable Universal Mobile Telecommunications System (UMTS) protocol, a wireless local area network (WLAN) protocol such as IEEE 802.X, a suitable short-range radio frequency communication protocol such as Bluetooth, or an infrared data communication path (IRDA).

[0170] The transceiver input / output port 1409 may be configured to receive the speaker signal and in some embodiments determine parameters as described herein using the processor 1407 executing appropriate code. In addition, the device may generate appropriate transmission signals and parameter outputs for transmission to a synthesis device.

[0171] In some embodiments, device 1400 may be used as at least part of a synthesis device. Thus, input / output port 1409 may be configured to receive a transmission signal, and in some embodiments receive parameters determined at a capture device or processing device as herein, and generate a suitable audio signal format output by executing suitable code using processor 1407. Input / output port 1409 may be coupled to any suitable audio output, such as to a multi-channel speaker system and / or headphones, etc.

[0172] In general, various embodiments of the present invention may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be executed by a controller, microprocessor, or other computing device, but the present invention is not limited thereto. Although various aspects of the present invention may be shown and described as block diagrams, flow charts, or using some other graphical representation, it is well understood that the boxes, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general hardware or controllers or other computing devices, or some combination thereof as non-limiting examples.

[0173] Embodiments of the present invention may be implemented by computer software executable by a data processor of a mobile device (e.g., in a processor entity), or by hardware, or by a combination of software and hardware. In addition, it should be noted at this point that any box of the logic flow in the figure may represent program steps, or interconnected logic circuits, boxes and functions, or a combination of program steps and logic circuits, boxes and functions. The software may be stored on a physical medium such as a memory chip or a memory block implemented within a processor, a magnetic medium such as a hard disk or a floppy disk, and an optical medium such as a DVD and its data variants, a CD.

[0174] The memory may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. As non-limiting examples, the data processor may be of any type suitable for the local technical environment and may include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a gate-level circuit, and a processor based on a multi-core processor architecture.

[0175] Embodiments of the present invention may be implemented in various components such as integrated circuit modules. The design of integrated circuits is generally a highly automated process. Complex and powerful software tools are available to convert a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0176] Programs such as those offered by Synopsys, Inc. of Mountain View, Calif., and Cadence Design, of San Jose, Calif., automatically route conductors and position components on a semiconductor chip using well-established design rules and a library of pre-stored design modules. Once the design of a semiconductor circuit is complete, the resulting design in a standardized electronic format (e.g., Opus, GDSII, etc.) can be transmitted to a semiconductor manufacturing facility or "fab" of a semiconductor fabrication plant.

[0177] The foregoing description has provided a complete and informative description of exemplary embodiments of the present invention by way of exemplary and non-limiting examples. However, various modifications and adaptations may become apparent to those skilled in the relevant art in view of the foregoing description when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the present teachings will still fall within the scope of the present invention as defined by the appended claims.

Claims

1. A device for encoding audio parameters, comprising: means for comparing the audio parameter to a threshold value and to a value dependent on a previously quantized audio parameter; means for calculating the quantized audio parameter as the previously quantized audio parameter increased by a predetermined value when the audio parameter is greater than the threshold value and greater than a value dependent on the previously quantized audio parameter; as well as Means for calculating the quantized audio parameter as the previously quantized audio parameter multiplied by a factor value when the audio parameter is less than the threshold, or less than a value dependent on the previously quantized audio parameter.

2. The device according to claim 1, wherein the device further comprises: means for encoding into a bitstream an indication that the audio parameter is greater than the threshold and greater than a value dependent on the previously quantized audio parameter; as well as Means for encoding into a bitstream an indication that the audio parameter is less than the threshold, or less than a value dependent on the previously quantized audio parameter.

3. The device according to claim 1, wherein the device further comprises: means for determining that said previously quantized audio parameter has also been determined by increasing said predetermined value; as well as The component for calculating the quantized audio parameter as the previously quantized audio parameter increased by the predetermined value when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized audio parameter includes: a component for calculating the quantized audio parameter as the previously quantized audio parameter increased by the predetermined value multiplied by the gain factor when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized audio parameter. The apparatus of claim 3 , wherein the gain factor has an absolute value greater than 1.

5. The apparatus of claim 1 , wherein the value depending on the previously quantized audio parameter comprises: A combination of the previously quantized audio parameter increased by a predetermined value and the previously quantized audio parameter multiplied by a damping factor. The apparatus of claim 5 , wherein the damping factor has an absolute value less than 1. 7 . The apparatus of claim 1 , wherein the audio parameters are spatial audio parameters.

8. The apparatus according to any one of claims 1 to 6, wherein the audio parameter is a low frequency effects to total energy ratio.

9. An apparatus for decoding audio parameters, comprising: means for decoding an indication from a bitstream; means for calculating the quantized audio parameter as a previously quantized audio parameter increased by a predetermined value when the indicator indicates that the audio parameter is greater than a threshold value and greater than a value dependent on the previously quantized audio parameter; as well as Means for calculating the quantized audio parameter as the previously quantized audio parameter multiplied by a factor value when the indicator indicates that the audio parameter is less than the threshold, or less than a value dependent on the previously quantized audio parameter.

10. The apparatus according to claim 9, wherein the apparatus further comprises: means for decoding from said bitstream an indication relating to previous audio parameters; means for determining that said indication associated with said previous audio parameter indicates that the quantized previous audio parameter has also been determined by increasing said predetermined value; and The component for calculating the quantized audio parameter as the previously quantized audio parameter increased by the predetermined value when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized audio parameter includes: a component for calculating the quantized audio parameter as the previously quantized audio parameter increased by the predetermined value multiplied by the gain factor when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized audio parameter. The apparatus of claim 10 , wherein the gain factor has an absolute value greater than 1.

12. The apparatus of claim 9, wherein the value depending on the previously quantized audio parameter comprises: A combination of a previously quantized audio parameter to which a predetermined value is added and the previously quantized audio parameter multiplied by a damping factor. The apparatus of claim 12 , wherein the damping factor has an absolute value less than 1. The apparatus of claim 9 , wherein the audio parameters are spatial audio parameters.

15. An apparatus according to any one of claims 9 to 13, wherein the audio parameter is a low frequency effects to total energy ratio.

16. A method for encoding audio parameters, comprising: comparing the audio parameter to a threshold value and to a value dependent on a previously quantized audio parameter; When the audio parameter is greater than the threshold value and greater than a value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by a predetermined value; as well as When the audio parameter is less than the threshold, or less than a value dependent on the previously quantized audio parameter, the quantized audio parameter is calculated as the previously quantized audio parameter multiplied by a factor value.

17. The method according to claim 16, wherein the method further comprises: encoding into a bitstream an indication that the audio parameter is greater than the threshold and greater than a value dependent on the previously quantized audio parameter; as well as An indication that the audio parameter is less than the threshold, or less than a value that depends on the previously quantized audio parameter, is encoded into the bitstream.

18. The method according to claim 16, wherein the method further comprises: determining that the previously quantized audio parameter has also been determined by increasing the predetermined value; and Wherein when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by the predetermined value includes: when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by the predetermined value multiplied by the gain factor. The method of claim 18 , wherein the gain factor has an absolute value greater than 1.

20. The method of claim 16, wherein depending on the value of a previously quantized audio parameter comprises: A combination of the previously quantized audio parameter increased by a predetermined value and the previously quantized audio parameter multiplied by a damping factor. The method of claim 20 , wherein the damping factor has an absolute value less than 1.

22. The method according to any one of claims 16 to 21, wherein the audio parameters are spatial audio parameters.

23. A method according to any one of claims 16 to 21, wherein the audio parameter is a low frequency effects to total energy ratio.

24. A method for decoding audio parameters, comprising: decoding instructions from a bitstream; When the indicator indicates that the audio parameter is greater than the threshold value and greater than a value dependent on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by a predetermined value; as well as When the indicator indicates that the audio parameter is less than the threshold, or less than a value dependent on the previously quantized audio parameter, the quantized audio parameter is calculated as the previously quantized audio parameter multiplied by a factor value.

25. The method according to claim 24, wherein the method further comprises: decoding from the bitstream an indication associated with a previous audio parameter; determining that the indication associated with the previous audio parameter indicates that the quantized previous audio parameter has also been determined by increasing the predetermined value; as well as Wherein when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by the predetermined value includes: when the audio parameter is greater than the threshold value and greater than the value depending on the previously quantized audio parameter, calculating the quantized audio parameter as the previously quantized audio parameter increased by the predetermined value multiplied by the gain factor. The method of claim 25 , wherein the gain factor has an absolute value greater than 1.

27. The method of claim 24, wherein depending on the value of the previously quantized audio parameter comprises: A combination of the previously quantized audio parameter increased by a predetermined value and the previously quantized audio parameter multiplied by a damping factor.

28. The method of claim 27, wherein the damping factor has an absolute value less than 1.

29. The method according to any one of claims 24 to 28, wherein the audio parameters are spatial audio parameters.

30. A method according to any one of claims 24 to 28, wherein the audio parameter is a low frequency effects to total energy ratio.

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