System and method for processing audio data

1. A sub-band coder for processing audio samples for use in a digital encoder, the sub-band coder comprising:

a computer-usable non-transitory storage resource; and

one or more processors communicatively coupled to the storage resource, wherein the processors are configured to execute application code instructions that are stored in the storage resource to cause the coder to:

filter audio samples into a plurality of frequency band components using at least one Pseudo-Quadrature Mirror Filter (PQMF);

modulate the plurality of frequency band components into a plurality of quantized band values using an adaptive pulse code modulation technique; and

decode zero or more of the plurality of quantized band values into an approximate signal using an inverse adaptive pulse code modulation technique and at least one Inverse Pseudo-Quadrature Mirror Filter (IPQMF);

wherein the sub-band coder generates an output that includes the plurality of quantized band values, the approximate signal, and a plurality of encoded quantized band values encoded by a lossless encoder.

2. The sub-band coder of claim 1 wherein the processor further executes application code instructions stored in the storage resource to cause the coder to:

detect pre-echo events adjacent to audio bearing data in the plurality of quantized band values.

3. The sub-band coder of claim 1 wherein the plurality of quantized band values includes pre-echo events.

4. The sub-band coder of claim 1 wherein the frequency band components are modulated using one of an Adaptive Pulse Code Modulation (APCM) techniques and modulated using Adaptive Differential Pulse Code Modulation (ADPCM) techniques.

5. The sub-band coder of claim 1 wherein at least one of the plurality of quantized band values has one value with an absolute value above a threshold and are decoded into the approximate signal using one of an Inverse APCM techniques and Inverse ADPCM techniques.

6. The sub-band coder of claim 1 wherein the audio samples are filtered into 16 frequency bands.

7. The sub-band coder of claim 6 wherein a highest frequency band is not modulated and only other frequency bands of the 16 frequency bands not outside a hearing range are modulated.

8. The sub-band coder of claim 1 wherein the plurality of encoded quantized band values are encoded using Huffman encoding techniques and encoded quantized band values from the plurality are encoded as Huffman encoded codewords.

9. A computer-aided method of sub-band coding data, the method comprising:

filtering audio samples into a plurality of frequency band components using at least one Pseudo-Quadrature Mirror Filter (PQMF);

modulating the plurality of frequency band components into a plurality of quantized band values using an adaptive pulse code modulation technique;

decoding zero or more of the plurality of quantized band values into an approximate signal using an inverse adaptive pulse code modulation technique and at least one Inverse Pseudo-Quadrature Mirror Filter (IPQMF); and

providing an output that includes the plurality of quantized band values, the approximate signal, and a plurality of encoded quantized band values.

10. The method according to claim 9 , further comprising:

detecting pre-echo events adjacent to audio bearing data in the plurality of quantized band values.

11. The method according to claim 9 , wherein the plurality of quantized band values includes pre-echo events.

12. The method according to claim 9 , wherein the frequency band components are modulated using one of an Adaptive Pulse Code Modulation (APCM) techniques and modulated using Adaptive Differential Pulse Code Modulation (ADPCM) techniques.

13. The method according to claim 9 , wherein the plurality of quantized band values are decoded into the approximation signal using one of an Inverse APCM techniques and Inverse ADPCM techniques.

14. The method according to claim 9 , wherein the audio samples are filtered into 16 frequency bands.

15. The method according to claim 9 , wherein a highest frequency band is not modulated and only other frequency bands of the 16 frequency bands not outside a hearing range are modulated.

16. A non-transitory computer readable storage medium comprising a set of computer instructions executable by a processor for instructing a computer to sub-band code data, the computer instructions configured to:

filter audio samples into a plurality of frequency band components using at least one Pseudo-Quadrature Mirror Filter (PQMF);

modulate the plurality of frequency band components into a plurality of quantized band values using an adaptive pulse code modulation technique; and

decode zero or more of the plurality of quantized band values into an approximate signal using an inverse adaptive pulse code modulation technique and at least one Inverse Pseudo-Quadrature Mirror Filter (IPQMF);

wherein the sub-band coder generates an output that includes the plurality of quantized band values, the approximation signal, and a plurality of encoded quantized band values encoded by a lossless encoder.

17. The non-transitory computer readable storage medium as recited in claim 16 further including computer instructions configured to:

detect pre-echo events adjacent to audio bearing data in the plurality of quantized band values.

18. The non-transitory computer readable storage medium as recited in claim 16 wherein the plurality of quantized band values includes pre-echo events.

19. The non-transitory computer readable storage medium as recited in claim 16 wherein the frequency band components are modulated using one of an Adaptive Pulse Code Modulation (APCM) techniques and modulated using Adaptive Differential Pulse Code Modulation (ADPCM) techniques.

20. The non-transitory computer readable storage medium as recited in claim 16 wherein the plurality of quantized band values are decoded into the approximation signal using one of an Inverse APCM techniques and Inverse ADPCM techniques.