Efficient encoding and decoding of multi-channel audio signal with multiple substreams

1. An audio encoder configured to encode a multi-channel audio signal according to a total available data-rate; wherein the multi-channel audio signal is representable as a basic group of channels for rendering the multi-channel audio signal in accordance to a basic channel configuration, and as an extension group of channels, which —in combination with the basic group —is for rendering the multi-channel audio signal in accordance to an extended channel configuration; wherein the basic channel configuration and the extended channel configuration are different from one another; the audio encoder comprising

a basic encoder configured to encode the basic group of channels according to an IS data-rate, thereby yielding an independent substream, referred to as IS;

an extension encoder configured to encode the extension group of channels according to a DS data-rate, thereby yielding a dependent substream, referred to as DS; and

a data rate controller that regularly adapts the IS data-rate and the DS data-rate based on a momentary IS coding quality indicator for the basic group of channels and/or based on a momentary DS coding quality indicator for the extension group of channels, such that the sum of the IS data-rate and the DS data-rate substantially corresponds to the total available data-rate.

2. The encoder of claim 1 , wherein the data rate controller is configured to determine the IS data-rate and the DS data-rate such that a difference between the momentary IS coding quality indicator and the momentary DS coding quality indicator is reduced.

3. The encoder of claim 1 , wherein the basic encoder and the extension encoder are frame-based audio encoders configured to encode a sequence of frames of the multi-channel audio signal, thereby yielding corresponding sequences of IS frames and DS frames of the independent substream and the dependent substream, respectively.

4. The encoder of claim 3 , wherein the data rate controller is configured to adapt the IS data-rate and the DS data-rate for each frame of the sequence of frames of the multi-channel audio signal.

5. The encoder of claim 3 , wherein

the IS coding quality indicator comprises a sequence of IS coding quality indicators for the corresponding sequence of IS frames;

the DS coding quality indicator comprises a sequence of DS coding quality indicators for the corresponding sequence of DS frames;

the rate controller is configured to determine the IS data-rate for an IS frame of the sequence of IS frames and the DS data-rate for a DS frame of the sequence of DS frames based on the sequence of IS coding quality indicators and the sequence of DS coding quality indicators, such that the sum of the IS data-rate for the IS frame and the DS data-rate for the DS frame is substantially the total available data-rate.

6. A method for encoding a multi-channel audio signal according to a total available data-rate; wherein the multi-channel audio signal is representable as a basic group of channels for rendering the multi-channel audio signal in accordance to a basic channel configuration, and as an extension group of channels, which —in combination with the basic group —is for rendering the multi-channel audio signal in accordance to an extended channel configuration; wherein the basic channel configuration and the extended channel configuration are different from one another; the method comprising

encoding the basic group of channels according to an IS data-rate, thereby yielding an independent substream, referred to as IS;

encoding the extension group of channels according to a DS data-rate, thereby yielding a dependent substream, referred to as DS; and

regularly adapting the IS data-rate and the DS data-rate based on a momentary IS coding quality indicator for the basic group of channels and/or based on a momentary DS coding quality indicator for the extension group of channels, such that the sum of the IS data-rate and the DS data-rate substantially corresponds to the total available data-rate.

7. The method of claim 6 , further comprising

determining the IS coding quality indicator based on one or more frames of the basic group of channels, and/or determining the DS coding quality indicator based on one or more corresponding frames of the extension group of channels.

8. A non-transitory computer readable medium containing a software program adapted for execution on a processor and for performing the method steps of claim 6 when carried out on the processor.

9. A non-transitory storage medium comprising a software program adapted for execution on a processor and for performing the method steps of claim 6 when carried out on the processor.

10. A non-transitory computer readable medium containing a computer program product comprising executable instructions for performing the method steps of claim 6 when executed on a computer.

11. A method for decoding encoded audio data, including the steps of:

receiving a signal indicative of the encoded audio data; and

decoding the encoded audio data to generate a signal indicative of the audio data,

wherein the encoded audio data have been generated by:

(a) encoding a basic group of channels according to an IS data-rate, thereby yielding an independent substream;

(b) encoding an extension group of channels according to a DS data-rate, thereby yielding a dependent substream; and

(c) regularly adapting the IS data-rate and the DS data-rate based on a momentary IS coding quality indicator for the basic group of channels and/or based on a momentary DS coding quality indicator for the extension group of channels, such that the sum of the IS data-rate and the DS data-rate substantially corresponds to a total available data-rate.

12. The method of claim 11 , wherein the encoded audio data have been further generated by determining the momentary IS coding quality indicator based on an excerpt of the basic group of channels, and/or determining the momentary DS coding quality indicator based on a corresponding excerpt of the extension group of channels.

13. A non-transitory computer readable medium containing a software program adapted for execution on a processor and for performing the method steps of claim 11 when carried out on the processor.

14. A non-transitory storage medium comprising a software program adapted for execution on a processor and for performing the method steps of claim 11 when carried out on the processor.

15. An audio decoder configured to decode audio data in accordance with the method steps of claim 11 .