Codec system and method

• US 7,239,253 B1
• Filed: 09/16/2004
• Issued: 07/03/2007
• Est. Priority Date: 09/18/2003
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Denninghoff, Karl
• Primary Examiner(s): Jeanglaude; Jean Bruner
• Application Number:
  US10/943,112
• Time in Patent Office: 1,020 Days
• Field of Search: 341/155, 341/50, 341/118, 341/126, 341/200, 704/204, 382/239, 382/240, 370/522
• US Class Current: 341/50
• CPC Class Codes: G10L 19/0208 Subband vocoders
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components

Abstract

A sound codec including a compression portion and a decompression portion. The compression portion separates the incoming sound packet bandwidth into frequency sub-bands using a bank of infinite impulse response (IIR) filters. In accordance with the invention, the lower frequency signals are divided into more sub-bands than the higher frequency signals. Once the signals are divided into sub-bands, each sub-band signal is quantized. The resulting signals of all of the quantized sub-bands are then sent out over a communications link along with the filter state at the end of each sound packet. The decompression portion recombines the individual sub-band signals together (using a bank of infinite impulse response (IIR) filters) to form the audio data using the filter states to configure the reconstruction.

Claims

1. An apparatus for compressing a data stream, the apparatus comprising:

a first level bank of filters to separate a data stream into a higher frequency portion and a lower frequency portion;

a second level bank of filters to separate the higher frequency data stream portion into a first plurality of sub-band portions and to separate the lower frequency data stream portion into a second plurality of sub-band portions, wherein the lower frequency portion is divided into more sub-bands than the higher frequency portion; and

a plurality of quantizers wherein each quantizer receives a particular sub-band from a particular filter, the quantizer quantizing the particular sub-band signal to generate a sub-band quantized signal wherein the signals of the plurality of quantizers are combined together to form a compressed output signal.

2. The apparatus of claim 1, wherein the data stream further comprises audio data.

3. The apparatus of claim 1, wherein the higher frequency portion further comprises a frequency range of 2000–

4000 Hz and wherein the lower frequency portion further comprises a frequency range of 0–

2000 Hz.

4. The apparatus of claim 3, wherein the lower frequency sub-bands further comprise a 0–

500 Hz subband, a 500–

1000 Hz subband, a 1000–

1500 Hz subband and a 1500–

2000 Hz subband and wherein the higher frequency sub-bands further comprise a 2000–

3000 Hz subband and a 3000–

4000 Hz subband.

5. The apparatus of claim 1, wherein each filter further comprises an infinite impulse response filter.

6. The apparatus of claim 1, wherein each filter further comprise a software-implemented filter and wherein each quantizer further comprises a software-implemented quantizer.

7. A method for compressing a data stream, the method comprising:

separating a data stream having a higher frequency portion and a lower frequency portion, using a first bank of filters;

separating the higher frequency portion into a first plurality of sub-bands and separating the lower frequency portion into a second plurality of sub-bands, wherein the lower frequency portion is divided into more sub-bands than the higher frequency portion;

quantizing each sub-band signal to generate a sub-band quantized signal having quantizer noise wherein the quantizer noise for a particular sub-band signal is masked by the amplitude of the signal in the sub-band and wherein the sub-band quantized signals of the plurality of quantizers are combined together to form a compressed output signal.

8. The method of claim 7, wherein the data stream further comprises audio data.

9. The method of claim 7, wherein separating the data stream further comprises generating the higher frequency portion having a frequency of 2000–

4000 Hz and generating the lower frequency portion having a frequency of 0–

2000 Hz.

10. The method of claim 9, wherein the lower frequency sub-bands further comprise a 0–

500 Hz subband, a 500–

1000 Hz subband, a 1000–

1500 Hz subband and a 1500–

2000 Hz subband and wherein the higher frequency sub-bands further comprise a 2000–

3000 Hz subband and a 3000–

4000 Hz subband.

11. An apparatus for decompressing a compressed data stream having a plurality of quantized frequency sub-bands, the apparatus comprising:

a plurality of decoders wherein each decoder receives a particular quantized frequency sub-band of the compressed data stream, each decoder reverse quantizing the particular quantized frequency sub-band to generate a decoded frequency sub-band signal wherein the quantizer noise for a particular sub-band signal is masked by the amplitude of the signal in the sub-band and wherein the plurality of decoders generate a plurality of decoded frequency sub-band signals at a plurality of sub-bands; and

a bank of filters wherein the bank of filters reconstruct the plurality of decoded frequency sub-band signals at a plurality of sub-bands into an uncompressed data stream wherein each sub-band signal comprises a portion of the data stream within a particular frequency range so that the plurality of sub-bands cover the frequency range of the data stream and wherein a lower frequency portion is divided into more sub-bands than a higher frequency portion, each filter receives a filter state from the compressed data stream in order to reconstruct a sequence of data packets in the particular decoded frequency sub-band signal in reverse order to generate the uncompressed data stream.

12. The apparatus of claim 11, wherein the data stream further comprised audio data.

13. The apparatus of claim 11, wherein the higher frequency portion further comprises 2000–

4000 Hz and wherein the lower frequency portion further comprises 0 –

2000 Hz.

14. The apparatus of claim 13, wherein the lower frequency sub-bands further comprise a 0–

500 Hz subband, a 500–

1000 Hz subband, a 1000–

150 Hz subband and a 1500–

2000 Hz subband and wherein the higher frequency sub-bands further comprise a 2000–

3000 subband and a 3000–

4000 Hz subband.

15. The apparatus of claim 11, wherein each filter further comprises an infinite impulse response filter.

16. The apparatus of claim 11, wherein each filter further comprise a software-implemented filter and wherein each quantizer further comprises a software-implemented quantizer.

17. A method for decompressing a compressed data stream having a plurality of quantized frequency sub-bands, the method comprising:

decoding, using reverse quantization, a particular quantized frequency subband of the compressed data stream to generate a decoded frequency sub-band signal wherein the quantizer noise for a particular sub-band signal is masked by the amplitude of the signal in the sub-band and wherein the plurality of decoders generate a plurality of decoded frequency sub-band signals at a plurality of sub-bands; and

reconstructing, using a bank of filters, the plurality of decoded frequency sub-band signals at a plurality of sub-bands into an uncompressed data stream wherein each sub-band signal comprises a portion of the data stream within a particular frequency range so that the plurality of sub-bands cover the frequency range of the data stream and wherein a lower frequency portion is divided into more sub-bands than a higher frequency portion, each filter receives a filter state from the compressed data stream in order to reconstruct a sequence of data packets in the particular decoded frequency sub-band signal in reverse order to generate the uncompressed data stream.

18. The method of claim 17, wherein the data stream further compresses audio data.

19. The method of claim 17, wherein reconstructing the data stream further comprises generating the higher frequency data stream having a frequency of 2000–

4000 Hz and generating the lower frequency data stream having a frequency of 0–

2000 Hz.

20. The method of claim 19, wherein the lower frequency sub-bands further comprise a 0–

500 Hz subband, a 500–

1000 Hz subband, a 1000–

1500 Hz subband and a 1500–

2000 Hz subband and wherein the higher frequency sub-bands further comprise a 2000–

3000 Hz subband and a 3000–

4000 Hz subband.

21. A personal computing device for use within a communications network, the device comprising:

a communications application, being executed by a processor of the personal computing device, that can establish a communication session with a communications application of another personal computing device over a communications network;

a sound manager module, part of the communications application that receives outgoing sound data and incoming sound data, the sound manager module having a codec with a compression module and a decompression module,

a first bank of filters, part of the compression module wherein the bank of filters separate a data stream having a higher frequency portion and a lower frequency portion;

a second bank of filters, part of the compression module, to separate the higher frequency portion into a first plurality of sub-band portions and to separate the lower frequency portion into a second plurality of sub-band portions, wherein the plurality of sub-bands cover the frequency range of the data stream and wherein the lower frequency portion is divided into more sub-bands than the higher frequency portion; and

a plurality of quantizers wherein each quantizer receives a particular sub-band from a particular filter, the quantizer quantizing the particular sub-band signal to generate a sub-band quantized signal having quantizer noise wherein the quantizer noise for a particular sub-band signal is masked by the amplitude of the signal in the sub-band and wherein the sub-band quantized signals of the plurality of quantizers are combined together to form a compressed output signal; and

the decompression module further comprises a plurality of decoders that receive a compressed data stream wherein each decoder receives a particular quantized frequency sub-band of the compressed data stream, each decoder reverse quantizing the particular quantized frequency sub-band to generate a decoded frequency sub-band signals at a plurality of sub-bands; and

a bank of filters wherein the bank of filters reconstruct the plurality of decoded frequency sub-band signals at a plurality of sub-bands into an uncompressed data stream having a plurality of frequencies corresponding to the frequencies of the sub-band signals wherein each filter receives a filter state from the compressed data stream in order to reconstruct a sequence of data packets in the particular decoded frequency sub-band signal in reverse order to generate the uncompressed data stream.

22. The device of claim 21, wherein the data stream further comprises audio data.

23. The device of claim 21, wherein the higher frequency portion further comprises 2000–

4000 Hz and wherein the lower frequency portion further comprises 0 –

2000 Hz.

24. The device of claim 23, wherein the lower frequency sub-bands further comprise a 0–

500 Hz subband, a 500–

1000 Hz subband, a 1000–

1500 Hz subband and a 1500–

2000 Hz subband and wherein the higher frequency sub-bands further comprise a 2000–

3000 Hz subband and a 3000–

4000 Hz subband.

25. The device of claim 21, wherein each filter further comprises an infinite impulse response filter.

26. The device of claim 21, wherein each filter further comprise a software-implemented filter and wherein each quantizer further comprises a software-implemented quantizer.