Spatial parameter signaling

Abstract

An apparatus comprising means for obtaining at least one audio signal; respectively obtaining at least one parameter for each of the at least two frequency bands associated with the at least one audio signal; selecting a frequency band of the at least two frequency bands based on comparing at least one other respective parameter for each frequency band of the at least two frequency bands, where the at least one other respective parameter is determined from each frequency band of the at least two frequency bands; and generating an output comprising a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands such that the selection of the at least one parameter associated with the selected frequency band is configured to reduce a bit rate or size of the output, the at least one parameter of the selected frequency band is configured to represent respective parameters of the at least two frequency bands.

Description

[0001] This application is a divisional application of the Chinese invention patent application with the invention name “Spatial Parameter Signaling” (application number 201980070712.1, application date August 8, 2019). Technical Field

[0002] The present application relates to apparatus and methods for spatial parameter signaling, but not exclusively to apparatus and methods for spatial parameter signaling within and between spatial audio encoders and decoders. Background Art

[0003] Parametric spatial audio processing is a field of audio signal processing in which a set of parameters is used to describe the spatial aspects of sound. For example, in parametric spatial audio capture from a microphone array, estimating a set of parameters from the microphone array signal, such as the direction of the sound in the frequency band, and the ratio of the directional to non-directional parts of the captured sound in the frequency band, is a typical and effective choice. It is well known that these parameters describe the perceived spatial characteristics of the captured sound at the position of the microphone array. These parameters can be used accordingly in the synthesis of spatial sound for binaural headphones, speakers, or other formats such as Ambisonics. Summary of the invention

[0004] According to a first aspect, a device is provided, comprising components for performing the following operations: obtaining at least one audio signal; obtaining at least one parameter for each of at least two frequency bands associated with the at least one audio signal; selecting a frequency band of the at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on each of the at least two frequency bands; and generating an output, including a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands, so that the selection of the at least one parameter associated with the selected frequency band is configured to reduce the bit rate or size of the output, wherein the at least one parameter of the selected frequency band is configured to represent the corresponding parameters of the at least two frequency bands.

[0005] The component for obtaining at least one parameter respectively for each of at least two frequency bands associated with at least one audio signal can also be used to obtain an energy ratio and an energy respectively for each of the at least two frequency bands, and wherein the component for selecting a frequency band of the at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands can also be used to: determine an energy weighting factor for each of the at least two frequency bands based on the energy ratio and the energy for each of the at least two frequency bands, wherein the energy weighting factor is at least one other corresponding parameter for each of the at least two frequency bands; determine a weight limiting factor based on the average energy; compare the energy weighting factor for each of the at least two frequency bands with the weight limiting factor; and select the highest frequency band where the energy weighting factor is greater than the weight limiting factor.

[0006] The energy may be a normalized energy.

[0007] The means for selecting a frequency band of the at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands may also be used to select a highest frequency band of the at least two frequency bands.

[0008] The means for obtaining at least one parameter for each of at least two frequency bands associated with at least one audio signal, respectively, may also be used to obtain at least one of: a direction parameter; a distance parameter; an energy parameter; and an energy ratio parameter.

[0009] The component for selecting a frequency band from among at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands may also be used to: save at least one parameter for one of the at least two frequency bands; and discard any other parameters from the at least one parameter for the at least two frequency bands, wherein the component for generating an output including a selection of at least one parameter associated with a selected frequency band from among the at least two frequency bands may also be used to generate an output including the saved at least one parameter for one of the at least two frequency bands and excluding other parameters from the discarded at least one parameter for the at least two frequency bands.

[0010] The component for selecting a frequency band from among at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands may also be used to: save at least one parameter for one of the at least two frequency bands; and determine a difference between any other parameter of the at least one parameter for the at least two frequency bands and at least one parameter for one of the at least two frequency bands, wherein the component for generating an output including a selection of at least one parameter associated with a selected frequency band from among the at least two frequency bands may also be used to generate an output including a difference between any other parameter of the at least one parameter for the at least two frequency bands and at least one parameter for one of the at least two frequency bands.

[0011] The means may also be used to generate at least one transmission signal based on at least one audio signal, and wherein the means for generating a selected output comprising at least one parameter associated with a selected frequency band of at least two frequency bands may also be used to generate a data stream for storage / transmission based on a combination of the at least one parameter and the at least one transmission signal.

[0012] The component for generating a data stream for storage / transmission based on a combination of at least one parameter and at least one transmission signal can also be used to: encode at least one transmission signal; encode at least one parameter associated with a selected frequency band among at least two frequency bands; and combine the encoded transmission signal with the encoded at least one parameter associated with the selected frequency band among at least two frequency bands.

[0013] The component for generating at least one transmission signal based on at least one audio signal can also be used for at least one of the following: downmixing at least one audio signal; when the at least one audio signal includes two or more audio signals, selecting at least one audio signal from the at least one audio signal; when the at least one audio signal includes a first-order panoramic surround sound (Ambisonic) audio signal, generating directional signals directed to different directions; when the at least one audio signal includes a first-order panoramic surround sound audio signal, generating cardioid signals directed to different directions; when the at least one audio signal includes a first-order panoramic surround sound audio signal, generating cardioid signals directed in opposite directions; and when the at least one audio signal includes at least one transmission audio signal, transmitting at least one transmission audio signal.

[0014] According to a second aspect, a device is provided, comprising components for performing the following operations: obtaining at least one signal, the at least one signal comprising at least one parameter associated with a selected frequency band from at least two frequency bands, and at least one transmission signal; based on at least one parameter for one of the at least two frequency bands, and the transmission signal, copying at least one parameter for at least one other frequency band of the at least two frequency bands; and synthesizing at least two audio signals based on at least one parameter associated with a selected frequency band from the at least two frequency bands, at least one copied parameter for at least one other frequency band of the at least two frequency bands, and the transmission signal, wherein the at least two audio signals are configured to provide spatial audio reproduction.

[0015] The component for obtaining at least one signal including at least one parameter associated with a selected frequency band from at least two frequency bands and at least one transmission signal can also be used to obtain at least one of the following: a direction parameter; a distance parameter; an energy parameter; and an energy ratio parameter.

[0016] The component for copying at least one parameter for at least one other of the at least two frequency bands based on at least one parameter for one of the at least two frequency bands and a transmission signal can also be used to copy at least one parameter for one of the at least two frequency bands as at least one other parameter of the at least two frequency bands.

[0017] At least one signal may also include at least one parameter associated with the difference between at least one other parameter of the at least two frequency bands and at least one parameter for one of the at least two frequency bands, wherein the component for copying at least one parameter for at least one other of the at least two frequency bands based on the at least one parameter for one of the at least two frequency bands and the transmission signal may also be used to copy at least one parameter for at least one other of the at least two frequency bands based on a combination of at least one parameter for one of the at least two frequency bands and at least one parameter associated with the difference between at least one other parameter of the at least two frequency bands and at least one parameter for one of the at least two frequency bands.

[0018] According to a third aspect, a method is provided, comprising: obtaining at least one audio signal; obtaining at least one parameter for each of at least two frequency bands associated with the at least one audio signal; selecting a frequency band of the at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on each of the at least two frequency bands; and generating an output, including a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands, so that the selection of at least one parameter associated with the selected frequency band is configured to reduce the bit rate or size of the output, wherein the at least one parameter of the selected frequency band is configured to represent the corresponding parameters of the at least two frequency bands.

[0019] Obtaining at least one parameter for each of at least two frequency bands associated with at least one audio signal may include obtaining an energy ratio and an energy for each of the at least two frequency bands, and wherein selecting a frequency band of the at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands may include: determining an energy weight factor for each of the at least two frequency bands based on the energy ratio and the energy for each of the at least two frequency bands, wherein the energy weight factor is at least one other corresponding parameter for each of the at least two frequency bands; determining a weight limiting factor based on the average energy; comparing the energy weight factor for each of the at least two frequency bands with the weight limiting factor; and selecting the highest frequency band where the energy weight factor is greater than the weight limiting factor.

[0020] The energy may be a normalized energy.

[0021] Selecting a frequency band of the at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands may include selecting a highest frequency band of the at least two frequency bands.

[0022] Obtaining at least one parameter for each of at least two frequency bands associated with the at least one audio signal, respectively, may include obtaining at least one of: a direction parameter; a distance parameter; an energy parameter; and an energy ratio parameter.

[0023] Selecting a frequency band from among the at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands may include: saving at least one parameter for one of the at least two frequency bands; and discarding any other parameters from among the at least one parameter for the at least two frequency bands, wherein generating an output including a selection of at least one parameter associated with the selected frequency band from among the at least two frequency bands may also include generating an output including the saved at least one parameter for one of the at least two frequency bands and excluding other parameters from among the discarded at least one parameter for the at least two frequency bands.

[0024] Selecting a frequency band from among at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands may include: saving at least one parameter for one of the at least two frequency bands; and determining a difference between any other parameter from among the at least one parameter for the at least two frequency bands and at least one parameter for one of the at least two frequency bands, wherein generating an output including a selection of at least one parameter associated with a selected frequency band from among the at least two frequency bands may also include generating an output including a difference between any other parameter from among the at least one parameter for the at least two frequency bands and at least one parameter for one of the at least two frequency bands.

[0025] The method may further comprise generating at least one transmission signal based on the at least one audio signal, and wherein generating an output comprising a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands may further comprise generating a data stream for storage / transmission based on a combination of the at least one parameter and the at least one transmission signal.

[0026] Generating a data stream for storage / transmission based on a combination of at least one parameter and at least one transmission signal may also include: encoding at least one transmission signal; encoding at least one parameter associated with a selected frequency band among at least two frequency bands; and combining the encoded transmission signal with the encoded at least one parameter associated with the selected frequency band among at least two frequency bands.

[0027] Generating at least one transmission signal based on at least one audio signal may also include at least one of the following: downmixing the at least one audio signal; selecting at least one audio signal from the at least one audio signal when the at least one audio signal includes two or more audio signals; generating directional signals directed to different directions when the at least one audio signal includes a first-order panoramic surround sound audio signal; generating cardioid signals directed to different directions when the at least one audio signal includes a first-order panoramic surround sound audio signal; generating cardioid signals directed in opposite directions when the at least one audio signal includes a first-order panoramic surround sound audio signal; and transmitting the at least one transmission audio signal when the at least one audio signal includes at least one transmission audio signal.

[0028] According to a fourth aspect, a method is provided, comprising: obtaining at least one signal comprising at least one parameter associated with a selected frequency band from at least two frequency bands, and at least one transmission signal; based on at least one parameter for one of the at least two frequency bands, and the transmission signal, copying at least one parameter for at least one other frequency band of the at least two frequency bands; and synthesizing at least two audio signals based on at least one parameter associated with a selected frequency band from the at least two frequency bands, at least one copied parameter for at least one other frequency band of the at least two frequency bands, and the transmission signal, wherein the at least two audio signals are configured to provide spatial audio reproduction.

[0029] Obtaining at least one signal including at least one parameter associated with a selected frequency band from among at least two frequency bands and at least one transmission signal may also include obtaining at least one of: a direction parameter; a distance parameter; an energy parameter; and an energy ratio parameter.

[0030] Based on at least one parameter for one of the at least two frequency bands and the transmission signal, copying at least one parameter for at least one other of the at least two frequency bands may include copying at least one parameter for one of the at least two frequency bands as at least one other parameter of the at least two frequency bands.

[0031] The at least one signal may also include at least one parameter associated with the difference between at least one other parameter of the at least two frequency bands and at least one parameter for one of the at least two frequency bands, wherein, based on the at least one parameter for one of the at least two frequency bands and the transmission signal, copying at least one parameter for at least one other frequency band of the at least two frequency bands may also include copying at least one parameter for at least one other frequency band of the at least two frequency bands based on a combination of at least one parameter for one of the at least two frequency bands and at least one parameter associated with the difference between at least one other parameter of the at least two frequency bands and at least one parameter for one of the at least two frequency bands.

[0032] According to a fifth aspect, a device is provided, comprising at least one processor and at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, enable the device to at least: obtain at least one audio signal; obtain at least one parameter for each of at least two frequency bands associated with the at least one audio signal; select a frequency band of the at least two frequency bands based on comparison of at least one other corresponding parameter for each of the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on each of the at least two frequency bands; and generate an output, comprising a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands, so that the selection of at least one parameter associated with the selected frequency band is configured to reduce the bit rate or size of the output, wherein the at least one parameter of the selected frequency band is configured to represent the corresponding parameters of the at least two frequency bands.

[0033] The device that is enabled to obtain at least one parameter respectively for each of at least two frequency bands associated with at least one audio signal can also be enabled to obtain an energy ratio and an energy respectively for each of the at least two frequency bands, and wherein the device that is enabled to select a frequency band of at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands can also be enabled to: determine an energy weight factor for each of the at least two frequency bands based on the energy ratio and the energy for each of the at least two frequency bands, wherein the energy weight factor is at least one other corresponding parameter for each of the at least two frequency bands; determine a weight limiting factor based on the average energy; compare the energy weight factor for each of the at least two frequency bands with the weight limiting factor; and select the highest frequency band where the energy weight factor is greater than the weight limiting factor.

[0034] The energy may be a normalized energy.

[0035] The means caused to select a frequency band of the at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands may further be caused to select a highest frequency band of the at least two frequency bands.

[0036] The means caused to obtain at least one parameter for each of at least two frequency bands associated with at least one audio signal may further be caused to obtain at least one of: a direction parameter; a distance parameter; an energy parameter; and an energy ratio parameter.

[0037] The device that is caused to select a frequency band from at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands may also be caused to: save at least one parameter for one of the at least two frequency bands; and discard any other parameters from the at least one parameter for the at least two frequency bands, wherein the device that is caused to generate an output including a selection of at least one parameter associated with a selected frequency band from the at least two frequency bands may also be caused to generate an output including the saved at least one parameter for one of the at least two frequency bands and excluding the other parameters from the at least one parameter for the at least two frequency bands that were discarded.

[0038] The device that is caused to select a frequency band from at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands may also be caused to: save at least one parameter for one of the at least two frequency bands; and determine the difference between any other parameter of the at least one parameter for the at least two frequency bands and at least one parameter for one of the at least two frequency bands, wherein the device that is caused to generate an output including a selection of at least one parameter associated with a selected frequency band from the at least two frequency bands may also be caused to generate an output including the difference between any other parameter of the at least one parameter for the at least two frequency bands and at least one parameter for one of the at least two frequency bands.

[0039] The apparatus may also be caused to generate at least one transmission signal based on at least one audio signal, and wherein the apparatus caused to generate a selected output comprising at least one parameter associated with a selected frequency band of at least two frequency bands may also be caused to generate a data stream for storage / transmission based on a combination of the at least one parameter and the at least one transmission signal.

[0040] The device that is caused to generate a data stream for storage / transmission based on a combination of at least one parameter and at least one transmission signal can also be caused to: encode at least one transmission signal; encode at least one parameter associated with a selected frequency band among at least two frequency bands; and combine the encoded transmission signal with the encoded at least one parameter associated with the selected frequency band among at least two frequency bands.

[0041] The device configured to generate at least one transmission signal based on at least one audio signal may also be configured to perform at least one of the following: downmixing the at least one audio signal; selecting at least one audio signal from the at least one audio signal when the at least one audio signal includes two or more audio signals; generating directional signals directed to different directions when the at least one audio signal includes a first-order panoramic surround sound audio signal; generating cardioid signals directed to different directions when the at least one audio signal includes a first-order panoramic surround sound audio signal; generating cardioid signals directed in opposite directions when the at least one audio signal includes a first-order panoramic surround sound audio signal; and transmitting the at least one transmission audio signal when the at least one audio signal includes at least one transmission audio signal.

[0042] According to a sixth aspect, a device is provided, comprising at least one processor and at least one memory comprising computer program code, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, enable the device to at least: obtain at least one signal, the at least one signal comprising at least one parameter associated with a selected frequency band from at least two frequency bands, and at least one transmission signal; based on at least one parameter for one of the at least two frequency bands, and the transmission signal, copy at least one parameter for at least one other frequency band of the at least two frequency bands; and based on at least one parameter associated with a selected frequency band from the at least two frequency bands, at least one copied parameter for at least one other frequency band of the at least two frequency bands, and the transmission signal, synthesize at least two audio signals, wherein the at least two audio signals are configured to provide spatial audio reproduction.

[0043] The device is caused to obtain at least one signal, the at least one signal including at least one parameter associated with a selected frequency band from at least two frequency bands, and at least one transmission signal can also be caused to obtain at least one of the following: a direction parameter; a distance parameter; an energy parameter; and an energy ratio parameter.

[0044] The device that is caused to copy at least one parameter for at least one other frequency band of at least two frequency bands based on at least one parameter for one of the at least two frequency bands and a transmission signal can also be caused to copy at least one parameter for one of the at least two frequency bands as at least one other parameter of the at least two frequency bands.

[0045] At least one signal may also include at least one parameter associated with the difference between at least one other parameter of the at least two frequency bands and at least one parameter for one of the at least two frequency bands, wherein the device that is caused to copy at least one parameter for at least one other of the at least two frequency bands based on the at least one parameter for one of the at least two frequency bands and the transmission signal may also be caused to copy at least one parameter for at least one other of the at least two frequency bands based on a combination of at least one parameter for one of the at least two frequency bands and at least one parameter associated with the difference between at least one other parameter of the at least two frequency bands and at least one parameter for one of the at least two frequency bands.

[0046] According to a seventh aspect, there is provided a computer program [or a computer-readable medium comprising program instructions], the instructions being used to cause an apparatus to perform at least the following operations: obtain at least one audio signal; obtain at least one parameter for each of at least two frequency bands associated with the at least one audio signal; select a frequency band of the at least two frequency bands based on comparison of at least one other corresponding parameter for each of the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on each of the at least two frequency bands; and generate an output comprising a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands, so that the selection of the at least one parameter associated with the selected frequency band is configured to reduce a bit rate or size of the output, wherein the at least one parameter of the selected frequency band is configured to represent a corresponding parameter of the at least two frequency bands.

[0047] According to an eighth aspect, there is provided a computer program [or a computer-readable medium comprising program instructions], the instructions being used to cause an apparatus to perform at least the following operations: obtain at least one signal comprising at least one parameter associated with a selected frequency band from at least two frequency bands, and at least one transmission signal; based on at least one parameter for one of the at least two frequency bands, and the transmission signal, copy at least one parameter for at least one other frequency band of the at least two frequency bands; and based on at least one parameter associated with a selected frequency band from the at least two frequency bands, at least one copied parameter for at least one other frequency band of the at least two frequency bands, and the transmission signal, synthesize at least two audio signals, wherein the at least two audio signals are configured to provide spatial audio reproduction.

[0048] According to the ninth aspect, a non-transitory computer-readable medium comprising program instructions is provided, which are used to cause an apparatus to perform at least the following operations: obtain at least one audio signal; obtain at least one parameter for each of at least two frequency bands associated with the at least one audio signal; select a frequency band of the at least two frequency bands based on comparison of at least one other corresponding parameter for each of the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on each of the at least two frequency bands; and generate an output, including a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands, so that the selection of at least one parameter associated with the selected frequency band is configured to reduce the bit rate or size of the output, wherein the at least one parameter of the selected frequency band is configured to represent the corresponding parameters of the at least two frequency bands.

[0049] According to the tenth aspect, a non-transitory computer-readable medium comprising program instructions is provided, which are used to cause an apparatus to perform at least the following operations: obtain at least one signal, the at least one signal comprising at least one parameter associated with a selected frequency band from at least two frequency bands, and at least one transmission signal; based on at least one parameter for one of the at least two frequency bands, and the transmission signal, copy at least one parameter for at least one other frequency band of the at least two frequency bands; and based on at least one parameter associated with a selected frequency band from the at least two frequency bands, at least one copied parameter for at least one other frequency band of the at least two frequency bands, and the transmission signal, synthesize at least two audio signals, wherein the at least two audio signals are configured to provide spatial audio reproduction.

[0050] According to an eleventh aspect, a computer-readable medium comprising program instructions is provided, which are used to cause an apparatus to perform at least the following operations: obtain at least one audio signal; obtain at least one parameter for each of at least two frequency bands associated with the at least one audio signal; select a frequency band of the at least two frequency bands based on comparison of at least one other corresponding parameter for each of the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on each of the at least two frequency bands; and generate an output comprising a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands, so that the selection of at least one parameter associated with the selected frequency band is configured to reduce the bit rate or size of the output, wherein the at least one parameter of the selected frequency band is configured to represent the corresponding parameters of the at least two frequency bands.

[0051] According to the twelfth aspect, a computer-readable medium comprising program instructions is provided, which are used to cause the device to perform at least the following operations: obtain at least one signal, the at least one signal comprising at least one parameter associated with a selected frequency band from at least two frequency bands, and at least one transmission signal; based on at least one parameter for one of the at least two frequency bands, and the transmission signal, copy at least one parameter for at least one other frequency band of the at least two frequency bands; and based on at least one parameter associated with a selected frequency band from the at least two frequency bands, at least one copied parameter for at least one other frequency band of the at least two frequency bands, and the transmission signal, synthesize at least two audio signals, wherein the at least two audio signals are configured to provide spatial audio reproduction.

[0052] According to the thirteenth aspect, a computer-readable medium comprising program instructions is provided, which are used to cause an apparatus to perform at least the following operations: obtain at least one audio signal; obtain at least one parameter for each of at least two frequency bands associated with the at least one audio signal; select a frequency band of the at least two frequency bands based on comparison of at least one other corresponding parameter for each of the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on each of the at least two frequency bands; and generate an output comprising a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands, so that the selection of at least one parameter associated with the selected frequency band is configured to reduce the bit rate or size of the output, wherein the at least one parameter of the selected frequency band is configured to represent the corresponding parameters of the at least two frequency bands.

[0053] According to the fourteenth aspect, a computer-readable medium comprising program instructions is provided, which are used to cause the device to perform at least the following operations: obtain at least one signal, the at least one signal comprising at least one parameter associated with a selected frequency band from at least two frequency bands, and at least one transmission signal; based on at least one parameter for one of the at least two frequency bands, and the transmission signal, copy at least one parameter for at least one other frequency band of the at least two frequency bands; and based on at least one parameter associated with a selected frequency band from the at least two frequency bands, at least one copied parameter for at least one other frequency band of the at least two frequency bands, and the transmission signal, synthesize at least two audio signals, wherein the at least two audio signals are configured to provide spatial audio reproduction.

[0054] According to the fifteenth aspect, a device is provided, comprising: an acquisition circuit configured to obtain at least one audio signal; an acquisition circuit configured to obtain at least one parameter for each of at least two frequency bands associated with the at least one audio signal; a selection circuit configured to select a frequency band of the at least two frequency bands by comparing at least one other corresponding parameter of each of the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on each of the at least two frequency bands; and an output generation circuit configured to generate an output, including a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands, so that the selection of at least one parameter associated with the selected frequency band is configured to reduce the bit rate or size of the output, wherein the at least one parameter of the selected frequency band is configured to represent the corresponding parameters of the at least two frequency bands.

[0055] According to the sixteenth aspect, a device is provided, comprising: an acquisition circuit configured to obtain at least one signal, the at least one signal including at least one parameter associated with a selected frequency band from at least two frequency bands, and at least one transmission signal; a replication circuit configured to replicate at least one parameter for at least one other frequency band of the at least two frequency bands based on at least one parameter for one of the at least two frequency bands, and the transmission signal; and a synthesis circuit configured to synthesize at least two audio signals based on at least one parameter associated with a selected frequency band from the at least two frequency bands, at least one replicated parameter for at least one other frequency band of the at least two frequency bands, and the transmission signal, wherein the at least two audio signals are configured to provide spatial audio reproduction.

[0056] An apparatus comprises means for performing the actions of the method as described above.

[0057] A device is configured to perform the actions of the method described above.

[0058] A computer program comprises program instructions for causing a computer to execute the method described above.

[0059] A computer program product stored on a medium can cause an apparatus to execute the method as described herein.

[0060] An electronic device may include the device described herein.

[0061] A chipset may include the device described herein.

[0062] The embodiments of the present application are intended to solve the problems associated with the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] For a better understanding of the present application, reference will now be made by way of example to the accompanying drawings, in which:

[0064] Figure 1 schematically illustrates a system suitable for implementing the apparatus of some embodiments;

[0065] Figure 2 According to some embodiments, Figure 1 A flowchart of the operation of the system shown;

[0066] Figure 3 A capture / encoding device is schematically shown;

[0067] Figure 4 Shown as Figure 3 A flowchart of the operation of the capture / encoding device shown;

[0068] Figure 5 schematically illustrates a capture / encoding apparatus according to some embodiments;

[0069] Figure 6 According to some embodiments, Figure 5 A flowchart of the operation of the capture / encoding device shown;

[0070] Figure 7 A flowchart illustrating the operation of an encoding apparatus according to some embodiments to encode an obtained transmission signal and metadata;

[0071] Figure 8 According to some embodiments, Figure 5 A flowchart of the frequency band selection operation of the capture / encoding device shown;

[0072] Fig. 9 Exemplary devices suitable for implementing the means described herein are schematically shown. DETAILED DESCRIPTION

[0073] Suitable apparatus and possible mechanisms for providing efficient spatial analysis derived metadata parameters associated with energy ratios of microphone array and other input format audio signals are described in further detail below.

[0074] The device has been designed to send a spatial audio modeling of the sound field using Q (usually 2) transmission audio signals and spatial metadata. The transmission audio signals are usually compressed using a suitable audio coding scheme (e.g., Advanced Audio Coding - AAC or Enhanced Voice Service - EVS codec). The spatial metadata may contain parameters such as direction in the time-frequency domain (e.g., azimuth, elevation).

[0075] In addition, other parameters that can be determined and signaled to the renderer or receiver are one or more direct-to-total energy ratios (in the time-frequency domain) that represent the energy distribution between each specific direction and the total audio energy. Another parameter can be one (or multiple where feasible) diffuse-to-total energy ratios (in the time-frequency domain) that represent the energy distribution between the ambient or diffuse signal (i.e., a non-directional signal such as reverberation) and the total energy.

[0076] The parametric spatial audio signal can be represented as a Q channel + metadata. This format can be compressed in the encoding to store it efficiently for later retrieval or to send it over a suitable transmission channel. Various methods can be used, depending on how the channels are configured and what the metadata contains.

[0077] A common procedure is to define a constant bitrate budget for the entire bitstream containing audio channels and metadata. This bitrate budget can then be allocated statically or adaptively (dynamically) between the audio channels and metadata.

[0078] For example, a bitrate budget of 64kb / s for 2 channels + metadata can be used in various ways. Using the full 64kb / s for 2 audio channels will provide excellent quality for encoding a stereo signal (e.g. using the EVS codec), but in this example the metadata will not be sent. Using 56kb / s for audio and 8kb / s for metadata will generally provide a higher overall quality, as the difference in audio encoding quality is not that great, but the metadata sent with the signaling can provide a full 3D surround sound reproduction.

[0079] At lower bit rates, it becomes more difficult to divide the bitrate budget. For example, based on a 16kb / s budget, the following encoding modes are possible:

[0080] One channel audio 16kb / s

[0081] One channel audio 15kb / s + 1kb / s metadata

[0082] One channel audio 11kb / s + 5kb / s metadata

[0083] Two channels audio 16kb / s

[0084] Two channels audio 15kb / s + 1kb / s metadata

[0085] Two channels audio 11kb / s + 5kb / s metadata

[0086] Optimizing between these example modes may require listening experimentation. However, previous experiments have shown that providing more bitrate for pristine audio quality across multiple channels tends to provide better perceived quality based on such low bitrates. The role of the metadata bitrate budget is to reduce the metadata bitrate so that the audio signal receives at least 90% of the total bitrate budget which is considered a good goal.

[0087] However, the amount of metadata generated, as well as the amount of data defining the spatial parameters, is frequency band dependent. For example, for B (e.g., 5, 10, 20, or 30) frequency bands per time frame and two parameters (direction and energy ratio), there may be at least 2*B*K (K is the number of bits per parameter) metadata bits per time frame. Assuming a common number of frames per second of 50, B=5, K=10, 5kb / s of metadata can be generated. With low bitrate applications (e.g., IVAS), the total target bitrate for audio can be as low as 14kb / s, so even after entropy coding, metadata will take up a large portion of the bitrate budget (which may reduce the bitrate to half of the total generated).

[0088] Currently, attempts to reduce generation include reducing the bit precision per parameter, or even removing less important parameters when the bitrate budget is low. Another approach is to reduce the number of bands used for metadata, for example, only generating one parameter per time frame, resulting in a reduction in the generated metadata times B. One way to achieve this is to perform a wideband analysis (in other words, assume only one band over the entire audible frequency range) and encode this wideband group.

[0089] The concepts discussed in this article attempt to improve upon these approaches, and in particular, instead of broadband analysis, attempt to:

[0090] · requiring a single analysis system for different bit rates (so no need for one-band analysis for low bit rates and multi-band analysis for high bit rates); and

[0091] Improve the temporal and frequency resolution of sound scenes in a practical way that is compatible with the human hearing range.

[0092] Thus, the concepts discussed in greater detail in the embodiments herein implement an analysis system having multiple frequency bands, and thereby selecting the best frequency band to represent the current time frame.

[0093] Therefore, the embodiments discussed herein attempt to reduce the bit rate by selecting one band to represent all bands based on the analyzed metadata. This can reduce the bit rate usage by a factor B (where B is the original number of bands). Therefore, in some embodiments, the selection process can involve audio encoding and decoding using parameterization related to the sound field (e.g., directional and direct to total energy ratio in the band), wherein a solution is provided to automatically reduce the bit rate of the directional parameters by sending only one directional value for all bands, and the one directional value sent is determined by the following operations:

[0094] Obtaining an audio signal;

[0095] Determine the (spatial parameters) directional and direct to total energy ratios in the frequency band;

[0096] determining normalized energy in a frequency band;

[0097] determining a directional energy weighting factor (e.g., energy multiplied by the direct to total energy ratio);

[0098] determining the highest frequency band having a directional energy weight factor above a threshold;

[0099] Only the direction of the determined frequency band is encoded / stored / transmitted.

[0100] When the analysis device is configured to perform the following operations, the above content may be further expanded or concretized as follows:

[0101] Obtaining a multi-channel audio signal (e.g., capturing a spatial audio signal);

[0102] applying time-frequency transforms to multi-channel audio signals;

[0103] performing spatial analysis on the transformed signal;

[0104] For each frequency band of the transformed signal, normalized energy is calculated;

[0105] For each frequency band of the transformed signal, a band weight factor (energy multiplied by energy ratio) is calculated;

[0106] Selecting or choosing the highest frequency band whose weight factor exceeds a defined limit (e.g., 0.5);

[0107] Discard other metadata and only save metadata of the selected frequency band;

[0108] Create a transmission signal;

[0109] Encodes and sends / stores transmission signals and metadata.

[0110] For the synthesis device, it is then configured as follows:

[0111] Obtain (receive / acquire) sent / stored transmission signals and metadata;

[0112] copying the selected / chosen metadata to all bands; and

[0113] The output is synthesized using the transport signal and the copied metadata.

[0114] The directional and direct to total energy ratios may be estimated using any suitable method (eg, SPAC) and depends on the type of audio signal (eg, microphone array, Ambisonics, multi-channel audio signal).

[0115] The normalized energy may be estimated in a suitable manner as discussed in the embodiments herein, for example by calculating the sum of squares of the frequency domain samples and dividing by the maximum energy.

[0116] In some embodiments, the threshold may be determined, for example, by multiplying the average normalized energy by a factor.

[0117] In addition to the direction, the same scheme can be used to encode all other parameters (e.g., direct to total energy ratio). In other words, only one parameter value is sent for all frequency bands. The same process can be used to select the value to be sent.

[0118] The decoding may be performed using any suitable method, for example by using the same parameter values ​​in all frequency bands.

[0119] In some embodiments, when encoding, the selected frequency band may be used as a reference frequency band, and very low bit rate difference encoding with respect to the selected frequency band may be determined for other frequency bands.

[0120] about Figure 1 , shows an exemplary apparatus and system for implementing embodiments of the present application. System 171 is shown as having an "analysis" portion 121 and a "synthesis" portion 131. The "analysis" portion 121 is the portion from receiving the input (multi-channel speaker, microphone array, Ambisonics, or mobile device capture) audio signal 100 to encoding metadata and transmission signal 102 that can be sent or stored 104. The "synthesis" portion 131 is the portion from decoding the encoded metadata and transmission signal 104 to the presentation of the synthesized signal (e.g., in the form of a multi-channel speaker 106, via a speaker 107 or binaural or Ambisonics format).

[0121] Thus, the inputs to the system 171 and the "analysis" part 121 are audio signals 100. They may be suitable input multi-channel loudspeaker audio signals, microphone array audio signals, Ambisonics audio signals, or audio signals captured by a mobile device.

[0122] 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 an associated audio signal and is based on the audio signal. For example, in some embodiments, the transmission signal generator 103 is configured to down-mix or otherwise select or combine the input audio signal to a determined number of channels, such as by beamforming technology, and output it as a transmission signal. 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.

[0123] 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 microphone audio signals and output the selection as the transmission signal 104. In some embodiments, the analysis processor 101 is configured to apply any suitable encoding or quantization to the transmission audio signal.

[0124] In some embodiments, the analysis processor 101 is further 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 suitable software stored on a memory and at least one processor), a mobile device, or alternatively a dedicated device such as an FPGA or ASIC. As shown in more detail herein, for each time-frequency analysis interval, the metadata may include at least one directional parameter and at least one energy ratio parameter. In some embodiments, the at least one directional parameter and the at least one energy ratio parameter may 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.

[0125] In some embodiments, the parameters generated may differ between frequency bands and may depend 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 in frequency band Z any other number of parameters is generated or sent. A practical example may be that for some frequency bands (e.g. the highest frequency band) certain parameters are not needed for perceptual reasons.

[0126] The transmission signal and metadata 102 may be transmitted or stored. Figure 1104. In some embodiments, before the transmission signal and metadata are sent or stored, they may be encoded to reduce the bit rate and multiplexed into one stream. Any suitable scheme may be used to implement encoding and multiplexing.

[0127] At the decoder side 131, the received or acquired data (stream) may be input into the synthesis processor 105. The synthesis processor 105 may be configured to demultiplex the data (stream) into encoded transport and metadata. The synthesis processor 105 may then decode any encoded stream to obtain the transport signal and metadata.

[0128] The synthesis processor 105 can then be configured to receive the transmission signal and metadata, and create a suitable multi-channel audio signal output 106 based on the transmission signal and metadata (which can be any suitable output format, such as binaural, multi-channel speaker or Ambisonics signal, depending on the use case). In some embodiments, the actual physical sound field with the desired perceptual characteristics is reproduced using headphones or speakers (using output device 107, such as speakers / headphones, etc.). In other embodiments, the reproduction of the sound field can be understood to refer to the reproduction of the perceptual characteristics of the sound field by other means other than reproducing the actual physical sound field in space. For example, the desired perceptual characteristics of the sound field can be reproduced on headphones using the binaural reproduction method described herein. In another example, the perceptual characteristics of the sound field can be reproduced as Ambisonics output signals, and these Ambisonics signals can be reproduced using Ambisonics decoding methods to provide, for example, binaural outputs with desired perceptual characteristics.

[0129] In some embodiments, the synthesis processor 105 may be a computer (running suitable software stored on memory and at least one processor), a mobile device, or alternatively a dedicated device such as using an FPGA or ASIC.

[0130] about Figure 2 , showing Figure 1 An exemplary flow chart of the overview shown.

[0131] 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.

[0132] The system (analysis part) is then configured to generate a transmission signal channel or transmission signal (e.g., based on down-mixing / selection / beamforming of the multi-channel input audio signal), such as Figure 2 As shown in step 203.

[0133] In addition, the system (analysis part) is configured to analyze the audio signal to generate metadata: direction, energy ratio, e.g. Figure 2 As shown in step 205.

[0134] Furthermore, the system is configured to (optionally) encode the transmission signal and metadata for storage / transmission, such as Figure 2 As shown in step 207.

[0135] Thereafter, the system can store / send the transmission signal and metadata, e.g. Figure 2 As shown in step 209.

[0136] The system can acquire / receive transmission signals and metadata, such as Figure 2 As shown in step 211.

[0137] The system is then configured to extract from the transmission signal and metadata, e.g. Figure 2 As shown in step 213.

[0138] The system (synthesis part) is configured to synthesize an output spatial audio signal (which, as previously discussed, may be in any suitable output format, e.g., 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.

[0139] about Figure 3 , an exemplary analysis processor 101 is shown, wherein an input audio signal is provided from an audio source 301, which in this example is a spatial capture device configured to generate a multi-channel audio signal from a plurality of microphones. In this example, the multi-channel audio signal is passed to a transmission (audio) signal generator 311. The transmission signal generator 311 is configured to generate a transmission audio signal according to any of the options previously described. For example, the transmission signal may be down-mixed from the input signal. The number of transmission audio signals may be any number, may be 2, or more or less than 2.

[0140] exist Figure 3 In the example shown, the multi-channel audio signal is also input to the time-frequency transform 303. The time-frequency transform 303 may be configured to generate a suitable time-frequency representation of the multi-channel audio signal and pass it to the frequency band processor 307.

[0141] The band processor 305 is configured to generate spatial metadata outputs, such as shown as directions, direct-to-total energy ratios, and in some embodiments other types of energy ratios, e.g., diffuse-to-total energy ratios, and remainder-to-total energy ratios.

[0142] The implementation of the analysis may be any suitable implementation that produces the described metadata output.

[0143] Thus, for example, in some embodiments, the frequency band processor 305 includes a direction analyzer 307 configured to generate direction metadata and an energy ratio analyzer 309 configured to generate energy ratio metadata.

[0144] In turn, the direction and energy ratio metadata of all analyzed frequency bands may be passed to the transmit / storage encoder 313. The transmit / storage encoder 313 may be configured to combine and encode the transmission signal, direction, and energy ratio to generate the data stream 102.

[0145] For example, in some embodiments, the transmit / storage encoder 313 may include a suitable transmission signal compressor / encoder configured to compress the audio signal using a suitable codec (eg, AAC or EVS).

[0146] about Figure 4 , a flow chart showing the operation of the analysis processor.

[0147] The first operation is to receive an audio signal (multi-channel loudspeaker or other) such as Figure 4 As shown in step 401.

[0148] In some embodiments, the audio signal is processed in some form to generate a transmission audio signal, such as Figure 4 As shown in step 403.

[0149] The next operation is to perform a spatial analysis of the (multi-channel loudspeaker) signal in order to determine directional metadata, such as Figure 4 As shown in step 405.

[0150] Then, the energy ratios (e.g., direct, diffuse, and residual energy ratios) are determined, such as Figure 4 As shown in step 407.

[0151] In some embodiments, the metadata and the transmitted audio signal are processed (compressed / encoded). For example, the number of directions and ratios is further controlled (and can be selected and / or combined). Figure 4 Step 409 shows the processing of metadata / transmitted audio signal.

[0152] Furthermore, the processed transmission audio signal and metadata can be further combined to generate a suitable data stream, such as Figure 4 As shown in step 411.

[0153] about Figure 5 , shows an exemplary analysis processor 101 suitable for implementing some embodiments, and Figure 3The examples provided in this document are supplemented.

[0154] Again, an exemplary analysis processor 101 is shown with an input audio signal provided from an audio source 301, which in this example is a spatial capture device configured to generate a multi-channel audio signal from a plurality of microphones. For example, the spatial audio signal may be captured using any known capture device. For example, an Eigenmike or Nokia 8 mobile phone are suitable capture devices. As previously mentioned, the multi-channel (spatial) audio signal may be in any format that may produce relevant spatial audio parameters, such as hybrid content (e.g., a multi-channel audio format such as 5.1) and Ambisonics content.

[0155] In this example, the multi-channel audio signal is passed to a transmission (audio) signal generator 311 .

[0156] and Figure 3 The transmission signal generator 311 similar to the example in is configured to generate a transmission audio signal according to any of the options described previously. For example, the transmission signal can be down-mixed from the input signal. The number of transmission audio signals can be any number, which can be 2, or more or less than 2.

[0157] exist Figure 5 In the example shown, the multi-channel audio signal is also input to the time-frequency transform 303. The time-frequency transform 303 may be configured to generate a suitable time-frequency representation of the multi-channel audio signal and pass it to the frequency band processor 505.

[0158] The band processor 505 is configured to generate spatial metadata outputs, such as shown as direction, direct to total energy ratio, and in some embodiments other types of energy ratios, for example, diffuse to total energy ratio, and residual to total energy ratio.

[0159] The implementation of the analysis may be any suitable implementation that produces the described metadata output.

[0160] Thus, for example, in some embodiments, the frequency band processor 505 includes a direction analyzer 307 configured to generate direction metadata and an energy ratio analyzer 309 configured to generate energy ratio metadata.

[0161] These can be determined by performing spatial analysis on the time-frequency transformed multi-channel audio signal.

[0162] An example of spatial analysis may be eg DirAC (Directional Audio Coding) spatial analysis.

[0163] DirAC can estimate the directional and diffuse ratios (equivalent information of the direct-to-total ratio parameters) from First Order Ambisonic (FOA) signals or its variant B-format signals.

[0164]

[0165] The signal is transformed into frequency bands, for example, by STFT, thereby generating time-frequency signals w(k,n), x(k,n), y(k,n), z(k,n), where k is the frequency bin index and n is the time index. DirAC estimates the intensity vector by the following formula:

[0166]

[0167] Here, Re represents the real part and the asterisk * represents the complex conjugate.

[0168] The direction parameter is opposite to the direction of the real part of the intensity vector.Before determining the direction parameter, the intensity vector may be averaged over several time and / or frequency indices.

[0169] DirAC determines the diffusion as:

[0170]

[0171] Diffusivity is a ratio value: when the sound is completely ambient, the ratio is 1, and when the sound is completely directional, the ratio is 0. In addition, all parameters in this formula are usually averaged over time and / or frequency. In practical systems, the expectation operator E[] can be replaced by an average operator.

[0172] When averaging is performed, several frequency bins k are typically combined in a frequency band (eg, approximately Bark frequency resolution) to determine the diffuseness (and direction) parameters.

[0173] As determined above, DirAC is only one of the options for determining directional and ratio metadata, and obviously other methods can be used to determine metadata, for example, using a spatial audio capture (SPAC) algorithm and a microphone array signal (real or simulated). In addition, there are many variations of DirAC analysis in the literature. For example, if the input content is not FOA, appropriate modifications can be made to transform the signal into FOA format to perform the analysis. Other analysis methods are also applicable as long as directional metadata and energy ratio metadata are generated.

[0174] Furthermore, the direction and energy ratio metadata of all analyzed frequency bands may be passed to the metadata selector 521 .

[0175] Furthermore, the output of the energy ratio analyzer 309 is output to the weight factor determiner 517 .

[0176] Additionally, the frequency band processor 505 includes a normalized energy determiner 515 configured to generate a normalized energy determination and pass the normalized energy determination to the weight factor determiner 517 and the weight limit determiner 519 .

[0177] In some embodiments, the normalized energy determination can be performed as a two-step operation. The first step is to calculate the average energy for each frequency band at this time, for example using the following formula:

[0178]

[0179] Where N is the number of time samples in the time frame, Kb and Kt are the lowest and highest frequency bins of the current frequency band, and I is the number of input channels of the signal. S(i,k,n) is the time-frequency domain representation of the transmitted signal.

[0180] The second step is to normalize the average energy of each band so that the maximum energy of any band is found, and then all energies are divided by the maximum energy value. This can be viewed as a band with a maximum energy of 1 (always) and other bands with smaller energies, or expressed as the following formula:

[0181]

[0182] In some embodiments, any suitable alternative normalization method may be used (e.g., normalizing with total energy instead of maximum energy), and the limiting parameters may be adjusted appropriately (as discussed subsequently). Additionally, in some embodiments, non-normalized energies may be used, but the limiting parameters require more careful adjustment.

[0183] In some embodiments, the frequency band processor 505 further includes a weight factor determiner 517 configured to receive the normalized energy and the energy ratio and determine at least one weight factor to be output to the metadata selector 521 .

[0184] When the normalized energy is known, the weight factor can be determined based on the product of the energy ratio and the normalized energy in the frequency band. Therefore, the weight factor can be determined by the following formula:

[0185] w=rEnorm

[0186] Where r is the energy ratio parameter.

[0187] The weight factor is a number between 0 and 1. When there is a directional impulse onset in the scene, the weight factor has a very high value because both the energy ratio and the normalized energy are high. Likewise, if there is no onset, these values ​​will tend to be lower for higher frequencies. The use of the product ensures that, for example, high normalized energy but low energy ratio (i.e., loud reverberation) does not result in a high weight value because the direction and metadata in this case are not optimally represented.

[0188] In some embodiments, the weighting factor may be any other suitable weighting factor, such as just the energy ratio parameter r.

[0189] In some embodiments, the analysis processor 101 includes a weight limit determiner 519 configured to receive the normalized energy determination and output a weight limit value to the metadata selector 521 .

[0190] The weight limit can be a constant value (e.g., 0.5), or it can be based on the average normalized energy of all frequency bands in the time frame (e.g., the average normalized energy multiplied by a constant (such as 0.5)). The latter option is preferred and has the form:

[0191]

[0192] Where c is an adjusted threshold constant (eg, 0.5) and B is the total number of frequency bands.

[0193] In some embodiments, the weight limit may be any other suitable value.

[0194] In some embodiments, the analysis processor 101 includes a metadata selector 521 configured to receive the output of the direction analyzer 307 (the direction metadata for each frequency band), the output of the energy ratio analyzer 309 (the energy ratio metadata for each frequency band), the output of the weight factor determiner 517 (the weight factor), and the output of the weight limit determiner 519. In turn, the metadata selector 521 is configured to select one of the direction and the energy ratio based on the weight factor and the weight factor limit, and pass the selected metadata to the transmission / storage encoder 513.

[0195] The metadata selector may be configured to select or choose the highest frequency band whose weight factor exceeds the weight limit. If for some reason no frequency band's weight exceeds the limit, then in some embodiments the metadata selector is configured to select the lowest frequency band.

[0196] In some embodiments, once the metadata selector determines the selected frequency band, it may be configured to discard metadata associated with other frequency bands.

[0197] In some embodiments, the metadata selector is configured to prioritize and discard only a portion of the metadata. For example, in some embodiments, directional information for other frequency bands is discarded, but energy ratio parameters for all frequency bands are retained.

[0198] In some embodiments, two or more frequency bands (but less than the total number of frequency bands) are selected to represent other frequency bands. For example, two frequency bands may be selected so that the two (or N, where N is less than the total number of frequency bands) highest frequency bands whose weights exceed a threshold (or weight limit) are selected. In turn, the parameters associated with the selected higher frequency band are used to represent the parameters of the frequency bands above it, the parameters associated with the lower frequency band are used to represent the parameters of the frequency bands below it, and both are used simultaneously to represent the frequency bands between them.

[0199] In some embodiments, the "best" frequency band is selected, but differential encoding techniques are employed to represent other frequency bands.

[0200] For example, for each frequency band:

[0201] Direction can be encoded separately for azimuth and elevation

[0202] o Azimuth has 2 bits and indicates 0°, 90°, 180°, or 270° from the selected frequency band azimuth

[0203] Offset

[0204] o Elevation has 2 bits and represents an offset of 0°, 45°, and -45° (one value is not used)

[0205] Each ratio parameter has 2 bits and represents an offset of 0, 0.25, -0.25, -0.5

[0206] In some embodiments, some bits are used to signal which band is the reference band for differential encoding. Using this approach can still significantly reduce the bit rate, but can provide a more accurate representation.

[0207] In some embodiments, the highest frequency band is selected and metadata associated with the highest frequency band is used to "represent" all frequency bands. This is not optimal in quality, but can be achieved in a computationally efficient manner.

[0208] The analysis processor 101 may further include a transmission / storage encoder 513. The transmission / storage encoder 513 may be configured to combine and encode the transmission signal, the selected direction, and the energy ratio to generate the data stream 102.

[0209] For example, in some embodiments, the transmit / storage encoder 513 may include a suitable transmission signal compressor / encoder configured to compress the audio signal using a suitable codec (e.g., AAC or EVS) and to encode the metadata using an entropy coding method (e.g., codebook coding).

[0210] about Figure 6 , showing Figure 5 The analysis processor shown (also shown Figure 1 Flowchart of the operation of the synthesis processor) shown.

[0211] The first operation is to obtain a (multi-channel loudspeaker or other) audio signal, such as Figure 6 As shown in step 601.

[0212] Audio signals can be processed by applying time-frequency transforms, such as Figure 6 As shown in step 603.

[0213] In some embodiments, the time-frequency domain audio signal is processed in some form to generate a transmission signal, such as Figure 6 As shown in step 617.

[0214] Furthermore, in some embodiments, the time-frequency domain audio signal is processed and a spatial analysis is performed to determine parameters for each frequency band, such as direction (and / or distance) and energy ratio, e.g. Figure 6 As shown in step 607.

[0215] In addition, in some embodiments, the time-frequency domain audio signal is processed and the normalized energy of each frequency band is calculated, such as Figure 6 As shown in step 605.

[0216] After the normalized energy per frequency band has been determined and the spatial analysis has been performed, in some embodiments, a weighting factor per frequency band is formed or determined, such as Figure 6 As shown in step 609.

[0217] Additionally, after the normalized energy per frequency band has been determined, in some embodiments, weight factor constraints are formed or determined, such as Figure 6 As shown in step 611.

[0218] Based on the weight factor for each frequency band and the weight factor limit, the highest frequency band whose weight exceeds the limit is selected, e.g. Figure 6 As shown in step 613.

[0219] Then, other metadata are discarded and the selected band metadata is saved, such as Figure 6 As shown in step 615.

[0220] Prior to storage and / or transmission, selected metadata and transmission signals are compressed / encoded (and combined), such as Figure 6 As shown in step 619.

[0221] Regarding the synthesis processor operation, the transmitted / acquired signal is decoded and metadata is copied for all frequency bands, such as Figure 6 As shown in step 621.

[0222] Then, appropriate spatial synthesis is performed, such as Figure 6 As shown in step 623.

[0223] As mentioned above, the audio signal input format can be any suitable format. Figure 7 , shows a flow chart of the operation of an encoder suitable for encoding the obtained transmission audio signal and metadata. In such an embodiment, the frequency band processor may only include a normalized energy determiner and a weighting factor determiner, since the direction and energy ratio have already been determined.

[0224] The first operation is to obtain the transmission audio signal and metadata, such as Figure 7 As shown in step 701.

[0225] In this example, parameters for each frequency band (such as direction (and / or distance) and energy ratio) have been obtained and the normalized energy per frequency band is calculated, as Figure 7 As shown in step 705.

[0226] After the normalized energy per frequency band has been determined and the spatial analysis has been performed, in some embodiments, a weighting factor per frequency band is formed or determined, such as Figure 7 As shown in step 709.

[0227] Additionally, after the normalized energy per frequency band has been determined, in some embodiments, weight factor constraints are formed or determined, such as Figure 7 As shown in step 711.

[0228] Based on the weight factor for each frequency band and the weight factor limit, the highest frequency band whose weight exceeds the limit is selected, e.g. Figure 7 As shown in step 713.

[0229] Then, other metadata are discarded and the selected frequency band metadata is saved, such as Figure 7 As shown in step 715.

[0230] Prior to storage and / or transmission, selected metadata and transmission signals are compressed / encoded (and combined), such as Figure 7 As shown in step 719.

[0231] Regarding the synthesis processor operation, the transmitted / acquired signal is decoded and metadata is copied for all frequency bands, such as Figure 7 As shown in step 721.

[0232] Then, appropriate spatial synthesis is performed, such as Figure 7 As shown in step 723.

[0233] about Figure 8 , further details exemplary operations of the metadata selector. The first operation is to start and receive inputs such as weight factors, weight limits, and parameters, such as Figure 8 As shown in step 801.

[0234] The next operation is to set the index i=B, such as Figure 8 As shown in step 803.

[0235] The next operation is to test the index weight factor wi against the weight limit wthr, such as Figure 8 As shown in step 803.

[0236] If wi>wthr, the next operation is to determine i as the selected frequency band, such as Figure 8 As shown in step 809, the operation is then terminated. Figure 8 As shown in step 813.

[0237] If wi does not > wthr, the next operation is to reduce i by 1, such as Figure 8 As shown in step 807.

[0238] After i has been decremented by 1, the next operation is to check whether i = 1, such as Figure 8 As shown in step 811.

[0239] If i=1, the next operation is to determine whether i is the selected frequency band, such as Figure 8 As shown in step 809, the operation is then terminated. Figure 8 As shown in step 813.

[0240] If i is not equal to 1, then the next operation can test the new index against the weight limit wthr, the index weight factor wi, such as Figure 8 As shown in step 803, the process then continues until for index, wi>wthr, or index=1.

[0241] The above assumes that the band index starts at 1. The above can be modified to accommodate any other indexing system (eg starting at 0).

[0242] With respect to the synthesis processor, a single band metadata value may be obtained and then replicated for all bands. This will result in a common complete set of metadata that can be used for further synthesis.

[0243] In turn, the synthesis operation may use the transmitted signal and the copied metadata to generate a suitable rendering of the audio signal. The process may be performed using any suitable means, for example, using a method such as DirAC-based spatial audio signal synthesis. An exemplary process for synthesizing the loudspeaker audio signal is to use a 3D panning technique (e.g., Vector Basis Amplitude Panning (VBAP)) to synthesize the direction into a specific direction multiplied by The non-directional ambient signal is decorrelated with a phase scrambling filter and reproduced in all directions by multiplying Where r is the energy ratio parameter and C is the number of speaker channels.

[0244] In this way, some embodiments can be achieved that reduce bitrate usage while providing a quality that is at least reasonable in many cases and can be nearly transparent (and in many cases transparent) to the complete metadata transmission of many signals. The bitrate reduction of the main method is reduced by a factor of B (where B is the original number of bands). That is, if the original metadata bitrate is 5kb / s and B=5, this method will achieve a bitrate of 1kb / s.

[0245] Furthermore, such embodiments may be able to produce a signal at least as good or better than using a single wideband parameter analysis.

[0246] Additionally, in some embodiments, this implementation is a computationally efficient way to reduce the bit rate, since it only requires determining the energy (which is usually already part of the analysis) and the weighting factors, thereby discarding data.

[0247] In some embodiments, spatial sound transmission storage is even achieved at very low bit rates.

[0248] For example, a teleconferencing system may use parameterized spatial audio (e.g., DirAC) as the primary analysis and synthesis method. Spatial capture may be obtained using Eigenmike, which produces first-order Ambisonics for this use. Spatial audio is analyzed in the time-frequency (20ms frames and 30 frequency bands) domain, and directional parameters (such as azimuth and elevation) and energy ratio parameters (in the form of diffuseness) are generated. Instead of encoding these parameters using a determined number of bits per parameter (i.e., 8 bits) to produce metadata at a bit rate of 36kb / s (before other compression), applications of certain embodiments may produce a bit rate of only 1.2kb / s for the metadata (before other compression). This leaves more bits for encoding the audio signal, which directly results in better perceived audio quality.

[0249] Another example is that using a time-frequency resolution such as 10 ms time frame, 12 frequency bands would result in the following comparative bit rates: According to some embodiments, 24 kb / s compared to 2.4 kb / s.

[0250] Since the reduction in metadata bitrate is so large, it is particularly advantageous for use cases with very low bitrate budgets. For example, if only raw audio encoding is used, 24kb / s is typically mixed in mono or in the stereo domain with a very high compression rate. If spatial metadata is introduced using, for example, the second time-frequency resolution above, the full spatial metadata will have difficulty fitting into the bitrate budget, even after the expected 50% entropy encoding of it (the metadata will take up 12kb / s of the available 24kb / s). However, by using the provided embodiment, the metadata can be reduced to one-fifth, and in this case a very reasonable bitrate division is achieved after entropy encoding (1.2kb / s for metadata and 22.8kb / s for audio), thereby providing full spatial audio even at low bitrates, rather than mono or stereo. This means that at low bitrates, the sound quality can be significantly improved compared to sending the full metadata.

[0251] about Fig. 9 , shows an exemplary electronic device that can be used as an analysis or synthesis device. The device can be any suitable electronic device or device. For example, in some embodiments, the device 1900 is a mobile device, a user device, a tablet computer, a computer, an audio playback device, etc.

[0252] In some embodiments, the apparatus 1900 includes at least one processor or central processing unit 1907. The processor 1907 may be configured to execute various program codes such as the methods described herein.

[0253] In some embodiments, the device 1900 includes a memory 1911. In some embodiments, at least one processor 1907 is coupled to the memory 1911. The memory 1911 can be any suitable storage component. In some embodiments, the memory 1911 includes a program code portion for storing program codes that can be implemented on the processor 1907. In addition, in some embodiments, the memory 1911 may also include a storage data portion for storing data (e.g., data that has been processed or will be processed according to the embodiments described herein). Whenever necessary, the processor 1907 can obtain the implementation program code stored in the program code portion and the data stored in the storage data portion via the memory-processor coupling.

[0254] In some embodiments, the device 1900 includes a user interface 1905. In some embodiments, the user interface 1905 may be coupled to a processor 1907. In some embodiments, the processor 1907 may control the operation of the user interface 1905 and receive input from the user interface 1905. In some embodiments, the user interface 1905 may enable a user to input commands to the device 1900, for example, via a keyboard. In some embodiments, the user interface 1905 may enable a user to obtain information from the device 1900. For example, the user interface 1905 may include a display configured to display information from the device 1900 to the user. In some embodiments, the user interface 1905 may include a touch screen or touch interface that enables information to be input to the device 1900 and also displays information to a user of the device 1900.

[0255] In some embodiments, the device 1900 includes an input / output port 1909. In some embodiments, the input / output port 1909 includes a transceiver. In such embodiments, the transceiver may be coupled to the processor 1907 and configured to enable communication 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 may be configured to communicate with other electronic devices or devices via a wired or wired coupling.

[0256] The transceiver may communicate with other devices via any suitable known communication protocol. For example, in some embodiments, the transceiver or transceiver component may use a suitable Universal Mobile Telecommunications System (UMTS) protocol, a wireless local area network (WLAN) protocol such as, for example, IEEE 802.X, a suitable short-range radio frequency communication protocol such as Bluetooth, or an infrared data communication path (IRDA).

[0257] The transceiver input / output port 1909 may be configured to receive a speaker signal (or other input format audio signal) and in some embodiments determine parameters as described herein using the processor 1907 executing appropriate code. In addition, the device may generate appropriate transmission signals and parameter outputs to send to the synthesis device.

[0258] In some embodiments, the device 1900 may be used as at least part of a synthesis device. Thus, the input / output port 1909 may be configured to receive the transmission signal, and in some embodiments receive the parameters determined at the capture device or processing device as described herein, and generate a suitable audio signal format output by using the processor 1907 executing appropriate code. The input / output port 1909 may be coupled to any suitable audio output, such as being coupled to a multi-channel speaker system and / or headphones or the like.

[0259] Generally, 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 that 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 illustrated or described using some other graphical representation, it should be fully 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.

[0260] Embodiments of the present invention may be implemented by computer software, or by hardware, or by a combination of software and hardware, the computer software being executable by a data processor of the mobile device, such as in a processor entity. In addition, in this regard, it should be noted that any box of the logic flow in the accompanying drawings may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks 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.

[0261] 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. The data processor may be of any type suitable for the local technical environment and may include, as non-limiting examples, 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.

[0262] Embodiments of the present invention may be practiced in various components such as integrated circuit modules. The design of integrated circuits is essentially 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.

[0263] Programs, such as those offered by Synopsys, Inc. of Mountain View, Calif., and Cadence Design, Inc. of San Jose, Calif., can 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 design, in a standardized electronic format (e.g., Opus, GDSII, etc.), can be transmitted to a semiconductor manufacturing facility or "fab" for fabrication.

[0264] 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 will 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 to the teachings of the present invention will still fall within the scope of the present invention as defined in the appended claims.

Claims

1. An apparatus comprising at least one processor and at least one memory storing computer program code, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the apparatus to at least: obtaining at least one audio signal; obtaining at least one parameter for at least two frequency bands associated with the at least one audio signal; selecting a frequency band from the at least two frequency bands based on comparing at least one other corresponding parameter for the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on the at least two frequency bands; and An output is generated including a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands, wherein the at least one parameter of the selected frequency band is configured to represent a parameter of the at least two frequency bands.

2. The device according to claim 1, wherein: Obtaining at least one parameter further causes the device to: obtain at least one parameter for each of at least two frequency bands associated with the at least one audio signal, respectively, and wherein selecting a frequency band among the at least two frequency bands further causes the device to: select a frequency band among the at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on each of the at least two frequency bands.

3. The device according to claim 1 or 2, wherein: Generating an output further causes the apparatus to: generate an output comprising a selection of at least one parameter associated with a selected frequency band among the at least two frequency bands, such that the selection of at least one parameter associated with the selected frequency band is configured to reduce a bit rate or size of the output, wherein the at least one parameter of the selected frequency band is configured to represent a corresponding parameter of the at least two frequency bands.

4. The device according to claim 2, wherein: Obtaining at least one parameter further causes the apparatus to obtain an energy ratio and an energy for each of the at least two frequency bands, respectively, and wherein selecting the frequency band causes the apparatus to: determining an energy weighting factor for each of the at least two frequency bands based on the energy ratio and the energy for each of the at least two frequency bands, wherein the energy weighting factor is at least one other corresponding parameter for each of the at least two frequency bands; Based on the average energy, a weight limiting factor is determined; comparing an energy weighting factor for each of the at least two frequency bands with the weight limiting factor; and The highest frequency band in which the energy weighting factor is greater than the weight limit factor is selected.

5. The device according to claim 4, wherein: The energy is the normalized energy.

6. The device according to claim 1, wherein: Selecting a frequency band among the at least two frequency bands causes the apparatus to select a highest frequency band among the at least two frequency bands.

7. The device according to claim 1, wherein: Obtaining at least one parameter further causes the apparatus to obtain at least one of: Direction parameters; Distance parameter; Energy parameters; and Energy ratio parameter.

8. The device according to claim 1, wherein: Selecting the frequency band further enables the device to: saving at least one parameter for one of the at least two frequency bands; and discarding any other parameters of the at least one parameter for the at least two frequency bands, wherein generating an output causes the apparatus to generate an output including the saved at least one parameter for one of the at least two frequency bands and excluding other parameters of the discarded at least one parameter for the at least two frequency bands.

9. The device according to claim 1, wherein: Selecting the frequency band further enables the device to: saving at least one parameter for one of the at least two frequency bands; and A difference between any other of the at least one parameter for the at least two frequency bands and the at least one parameter for one of the at least two frequency bands is determined, wherein the generated output includes the difference.

10. The device according to claim 1, wherein: The apparatus is further caused to generate at least one transmission signal based on the at least one audio signal, and generating an output causes the apparatus to generate a data stream for storage / transmission based on a combination of the at least one parameter and the at least one transmission signal.

11. The device according to claim 10, wherein: Generating a data stream for storage / transmission causes the apparatus to perform at least one of the following: encoding the at least one transmission signal; encoding at least one parameter associated with the selected frequency band of the at least two frequency bands; as well as The encoded transmission signal is combined with the encoded at least one parameter associated with the selected frequency band of the at least two frequency bands.

12. The device according to claim 10, wherein: Generating at least one transmission signal further causes the apparatus to perform at least one of the following: downmixing the at least one audio signal; When the at least one audio signal includes two or more audio signals, selecting at least one audio signal from the at least one audio signal; When the at least one audio signal comprises a first-order panoramic surround sound audio signal, generating directional signals directed to different directions; generating a cardioid signal directed to different directions when the at least one audio signal comprises a first order panoramic surround sound audio signal; generating a cardioid signal directed in opposite directions when the at least one audio signal comprises a first order panoramic surround sound audio signal; as well as When the at least one audio signal includes at least one transmission audio signal, the at least one transmission audio signal is delivered.

13. An apparatus comprising at least one processor and at least one memory storing computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least: obtaining at least one signal comprising at least one parameter associated with a selected frequency band from among at least two frequency bands and at least one transmission signal; replicating at least one parameter for at least one other frequency band of the at least two frequency bands based on at least one parameter for one of the at least two frequency bands and a transmission signal; as well as At least two audio signals are synthesized based on at least one parameter associated with the selected frequency band from at least two frequency bands, at least one replication parameter for at least one other frequency band of the at least two frequency bands, and the transmission signal, wherein the at least two audio signals are configured to provide spatial audio reproduction.

14. The device according to claim 13, wherein: Obtaining at least one signal causes the device to obtain at least one of the following: Direction parameters; Distance parameter; Energy parameters; and Energy ratio parameter.

15. The device according to claim 13, wherein: Copying at least one parameter causes the apparatus to copy at least one parameter for one of the at least two frequency bands as at least one other parameter for the at least two frequency bands.

16. The device according to claim 13, wherein: The at least one signal further comprises at least one parameter associated with a difference between at least one other parameter of the at least two frequency bands and at least one parameter for one of the at least two frequency bands, wherein Copying at least one parameter further causes the device to copy at least one parameter for at least one other of the at least two frequency bands based on a combination of the at least one parameter for one of the at least two frequency bands and at least one parameter associated with a difference between at least one other parameter of the at least two frequency bands and the at least one parameter for one of the at least two frequency bands.

17. A method comprising: obtaining at least one audio signal; obtaining at least one parameter for at least two frequency bands associated with the at least one audio signal; selecting a frequency band from the at least two frequency bands based on comparing at least one other corresponding parameter for the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on the at least two frequency bands; and An output is generated including a selection of at least one parameter associated with a selected frequency band of the at least two frequency bands, wherein the at least one parameter of the selected frequency band is configured to represent a parameter of the at least two frequency bands.

18. The method according to claim 17, wherein: Obtaining at least one parameter further comprises obtaining at least one parameter for each of at least two frequency bands associated with the at least one audio signal, respectively, and wherein selecting a frequency band of the at least two frequency bands further comprises selecting a frequency band of the at least two frequency bands based on comparing at least one other corresponding parameter for each of the at least two frequency bands, wherein the at least one other corresponding parameter is determined based on each of the at least two frequency bands.

19. The method according to claim 17 or 18, wherein: Generating an output also includes: generating an output including a selection of at least one parameter associated with a selected frequency band among the at least two frequency bands, so that the selection of at least one parameter associated with the selected frequency band is configured to reduce the bit rate or size of the output, wherein the at least one parameter of the selected frequency band is configured to represent the corresponding parameters of the at least two frequency bands.

20. The method of claim 17, further comprising: At least one transmission signal is generated based on the at least one audio signal, and generating the output includes generating a data stream for storage / transmission based on a combination of the at least one parameter and the at least one transmission signal.

21. The method according to claim 20, wherein: Generating a data stream for storage / transmission includes at least one of the following: encoding the at least one transmission signal; encoding at least one parameter associated with the selected frequency band of the at least two frequency bands; as well as The encoded transmission signal is combined with the encoded at least one parameter associated with the selected frequency band of the at least two frequency bands.

22. The method according to claim 20, wherein: Generating the at least one transmission signal comprises at least one of: downmixing the at least one audio signal; When the at least one audio signal includes two or more audio signals, selecting at least one audio signal from the at least one audio signal; When the at least one audio signal comprises a first-order panoramic surround sound audio signal, generating directional signals directed to different directions; generating a cardioid signal directed to different directions when the at least one audio signal comprises a first order panoramic surround sound audio signal; generating a cardioid signal directed in opposite directions when the at least one audio signal comprises a first order panoramic surround sound audio signal; as well as When the at least one audio signal includes at least one transmission audio signal, the at least one transmission audio signal is delivered.

23. A method comprising: obtaining at least one signal comprising at least one parameter associated with a selected frequency band from among at least two frequency bands and at least one transmission signal; replicating at least one parameter for at least one other frequency band of the at least two frequency bands based on at least one parameter for one of the at least two frequency bands and a transmission signal; as well as At least two audio signals are synthesized based on at least one parameter associated with the selected frequency band from at least two frequency bands, at least one replication parameter for at least one other frequency band of the at least two frequency bands, and the transmission signal, wherein the at least two audio signals are configured to provide spatial audio reproduction.

24. The method according to claim 23, wherein: Duplicating at least one parameter further comprises duplicating at least one parameter for one of the at least two frequency bands as at least one other parameter of the at least two frequency bands.

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