Bitstream syntax for multi-process audio decoding

1. A method of decoding a compressed audio bitstream containing syntax elements conforming to a bitstream syntax, the bitstream syntax being partitioned in tiles and defining a base coding layer for coding a base band spectrum region of audio content and optional coding layers comprising a base plus coding layer, a base peak coding layer, a frequency extension coding layer and a channel extension coding layer, the method comprising:

reading the compressed audio bitstream in tiles;

decoding a base coding layer of the tiles;

parsing a first syntax element from a header portion of the tile that signals a superframe header;

upon reaching a tile in which the first syntax element signals a superframe header, decoding configuration parameters signaling which of the optional coding layers are present;

decoding any optional coding layers signaled to be present;

reconstructing an output audio signal from the decoded coding layers; and

playing the output audio signal.

2. The method of claim 1 , further comprising:

reading the base plus coding layer of the compressed audio bitstream;

parsing a first syntax element from the base plus coding layer specifying a coding mode of the base plus coding layer from among at least an exclusive mode and an overlay mode;

in case of the exclusive mode, processing coded audio content of the base plus coding layer alone to reconstruct the base band spectrum region portion of an output audio signal; and

in case of the overlay mode, processing coded audio content of the base coding layer and the base plus coding layer to reconstruct the base band spectrum region portion of an output audio signal, wherein the coded audio content of the base plus coding layer is combined to fill spectral holes in the coded audio content of the base coding layer.

3. The method of claim 2 , further comprising, in the case of the extend mode:

reading a plurality of syntax elements specifying parameters for processing the coded audio content of the base plus coding layer in the extend mode; and

processing the coded audio content of the base plus coding layer using the parameters.

4. The method of claim 2 , further comprising, in the case of the exclusive mode:

reading a plurality of syntax elements specifying parameters for processing the coded audio content of the base plus coding layer in the exclusive mode; and

processing the coded audio content of the base plus coding layer using the parameters.

5. The method of claim 4 , wherein the parameters for the exclusive mode comprise a scale factor, an entropy coding scheme, and a tool box set of coding features used in coding the audio content of the base plus coding layer.

6. The method of claim 2 , further comprising, in the case of the overlay mode:

reading a plurality of syntax elements specifying parameters for processing the coded audio content of the base plus coding layer in the overlay mode; and

processing the coded audio content of the base plus coding layer using the parameters.

7. The method of claim 6 , wherein the parameters for the overlay mode comprise a weight factor and power of a coded channel of the audio content in the base plus coding layer.

8. The method of claim 1 , wherein the coding mode of the base plus coding layer is from among choices further comprising an extend mode, and the method further comprises:

in case of the extend mode, processing coded audio content of the base coding layer and the base plus coding layer to reconstruct portions of an output audio signal comprising the base band spectrum region and an extended spectrum region above an upper bound of the base band spectrum region, wherein the coded audio content of the base plus coding layer is used to fill the extended spectrum region.

9. The method of claim 1 , further comprising:

reading a base peak coding layer of the compressed audio bitstream;

parsing a plurality of syntax elements from the base peak coding layer specifying parameters used in the sparse spectral peak coding; and

processing coded audio content of the base peak coding layer to reconstruct the portion of audio content in an output audio signal.

10. The method of claim 9 , wherein the parameters comprise:

a coded peak type from among at least a choice of no peak data, intra-frame coded peak, and inter-frame coded peak;

in the case of an intra-frame coded peak, a zero run length and subsequent two coefficient levels; and

in the case of an inter-frame coded peak, a shift from a predicted position of the peak and two coefficient levels.

11. The method of claim 1 , further comprising:

reading a frequency extension coding layer of the compressed audio bitstream;

parsing a plurality of syntax elements from the frequency extension coding layer specifying parameters used in the frequency extension coding, wherein the parameters comprise parameters specifying frequency extension coding using a different transform window size than a base coding layer; and

processing coded audio content of the frequency extension coding layer to reconstruct the portion of audio content in an output audio signal.

12. The method of claim 11 , wherein the parameters comprise parameters identifying tiles coded using frequency extension coding with a different transform window size than a based coding layer.

13. The method of claim 1 , further comprising:

reading a channel extension coding layer of the compressed audio bitstream;

parsing a plurality of syntax elements from the channel extension coding layer specifying parameters used in the channel extension coding; and

processing coded audio content of the channel extension coding layer to reconstruct the portion of audio content in an output audio signal.

14. The method of claim 13 , wherein the parameters comprise a band configuration parameterization, which comprises a number of bands, a size relation among bands, and a starting band of the channel extension coding.

15. An audio decoder, comprising:

a processing unit; and

a memory storing computer-executable instructions for performing a method of decoding a compressed audio bitstream containing syntax elements conforming to a bitstream syntax, the bitstream syntax being partitioned in tiles and defining a base coding layer for coding a base band spectrum region of audio content and optional coding layers comprising a base plus coding layer, a base peak coding layer, a frequency extension coding layer and a channel extension coding layer, the method including:

reading the compressed audio bitstream in tiles;

decoding a base coding layer of the tiles;

parsing a first syntax element from a header portion of the tile that signals a superframe header;

upon reaching a tile in which the first syntax element signals a superframe header,

decoding configuration parameters signaling which of the optional coding layers are present;

decoding any optional coding layers signaled to be present; and

reconstructing an output audio signal from the decoded coding layers.

16. The audio decoder of claim 15 , wherein the decoding method further includes:

reading the base plus coding layer of the compressed audio bitstream;

parsing a first syntax element from the base plus coding layer specifying a coding mode of the base plus coding layer from among at least an exclusive mode and an overlay mode;

in case of the exclusive mode, processing coded audio content of the base plus coding layer alone to reconstruct the base band spectrum region portion of an output audio signal; and

in case of the overlay mode, processing coded audio content of the base coding layer and the base plus coding layer to reconstruct the base band spectrum region portion of an output audio signal, wherein the coded audio content of the base plus coding layer is combined to fill spectral holes in the coded audio content of the base coding layer.

17. The audio decoder of claim 16 , wherein the decoding method further includes:

reading a base peak coding layer of the compressed audio bitstream;

parsing a plurality of syntax elements from the base peak coding layer specifying parameters used in the sparse spectral peak coding; and

processing coded audio content of the base peak coding layer to reconstruct the portion of audio content in an output audio signal.

18. At least one computer readable storage device containing computer-executable instructions for performing a method of decoding a compressed audio bitstream containing syntax elements conforming to a bitstream syntax, the bitstream syntax being partitioned in tiles and defining a base coding layer for coding a base band spectrum region of audio content and optional coding layers comprising a base plus coding layer, a base peak coding layer, a frequency extension coding layer and a channel extension coding layer, the method comprising:

reading the compressed audio bitstream in tiles;

decoding a base coding layer of the tiles;

parsing a first syntax element from a header portion of the tile that signals a superframe header;

upon reaching a tile in which the first syntax element signals a superframe header, decoding configuration parameters signaling which of the optional coding layers are present;

decoding any optional coding layers signaled to be present; and

reconstructing an output audio signal from the decoded coding layers.

19. The at least one computer readable storage device of claim 18 , wherein the method further comprises playing the output audio signal.

20. The at least one computer readable storage device of claim 18 , wherein the method further comprises:

reading the base plus coding layer of the compressed audio bitstream;

parsing a first syntax element from the base plus coding layer specifying a coding mode of the base plus coding layer from among at least an exclusive mode and an overlay mode;

in case of the exclusive mode, processing coded audio content of the base plus coding layer alone to reconstruct the base band spectrum region portion of an output audio signal; and

in case of the overlay mode, processing coded audio content of the base coding layer and the base plus coding layer to reconstruct the base band spectrum region portion of an output audio signal, wherein the coded audio content of the base plus coding layer is combined to fill spectral holes in the coded audio content of the base coding layer.