Silence description coding for multi-rate speech codecs

• US 7,120,578 B2
• Filed: 04/24/2001
• Issued: 10/10/2006
• Est. Priority Date: 11/30/1998
• Status: Expired due to Fees

• Current Assignee: WIAV Solutions LLC
• Original Assignee: Mindspeed Technologies Inc. (MACOM Technology Solutions Holdings, Inc.)
• Inventors: Shlomot, Eyal, Thyssen, Jes, Su, Huan-Yu, Benyassine, Adil
• Primary Examiner(s): ARMSTRONG, ANGELA A
• Application Number:
  US09/841,764
• Publication Number:
  US 20010016811A1
• Time in Patent Office: 1,995 Days
• Field of Search: 704201-501
• US Class Current: 704/221
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding

Abstract

Speech coding systems include multi-rate speech codecs having an encoder and a decoder. Silence description coding for multi-rate speech coding systems that employ discontinued transmission is performed in either the encoder or the decoder of the multi-rate speech codec. It may also be performed in a distributed manner wherein it is performed partially in the encoder and partially in the decoder. The silence description coding is performed on a speech signal having a substantially non-speech-like characteristic. Voice activity detection classifies the speech signal as being either substantially speech-like or substantially non-speech-like. The silence description coding is selected from a plurality of coding modes. In certain embodiments of the invention, the silence description coding is a source coding mode that operates at a bit rate that fits within a bit rate budget as determined by all of the available source coding modes within the plurality of coding modes. The silence description coding is also accompanied with signaling coding and channel coding of the speech signal. Error checking is performed using an unused portion of a bandwidth of the multi-rate speech codec'"'"'s bit rate. This error checking involves majority voting in certain embodiments of the invention.

Claims

1. A communication device having a multi-rate speech coder that performs silence description coding of a speech signal having varying characteristics, comprising:

a voice activity detection circuit that is capable of identifying a substantially speech-like characteristic of a segment of the speech signal; and

a processing circuit communicatively coupled to the voice activity detection circuit, the processing circuit being capable of selectively applying one of a plurality of coding modes to the segment of the speech signal,

wherein the plurality of coding modes comprises a plurality of speech coding modes and a silence description coding mode,

wherein the processing circuit selects the silence description coding mode upon the identification of the absence of a substantially speech-like characteristic of the segment of the speech signal independent of the speech coding mode applied before the segment.

2. The communication device of claim 1, wherein the communication device comprises a wireless communication device.

3. The communication device of claim 2, wherein the wireless communication device comprises a telephone.

4. The communication device of claim 3, wherein the telephone comprises a cellular telephone.

5. The communication device of claim 1, wherein the communication device comprises a handheld wireless communication device.

6. The communication device of claim 1, wherein the communication device comprises a computer network-based communication device.

7. The communication device of claim 6, wherein the computer network-based communication device is capable of communicating via an internet-based network.

8. The communication device of claim 6, wherein the computer network-based communication device is capable of transmitting an encoded speech signal via the internet-based network.

9. The communication device of claim 1, wherein the communication device is capable of communicating via a computer network and telephone network.

10. The communication device of claim 9, wherein the telephone network is a cellular telephone network.

11. The communication device of claim 1, wherein the communication device comprises a data processor.

12. The communication device of claim 1, wherein the communication device comprises a network interface device that is capable of interfacing a cellular telephone to a computer network.

13. The communication device of claim 1, wherein the processing circuit selects a discontinuous transmission mode after the silence description coding mode.

14. A method of coding a speech signal, comprising:

coding a first segment of the speech signal using a speech coding mode selected from a plurality of speech coding modes; and

coding a second segment of the speech signal using a silence description coding mode independent of the speech coding mode used to code the first segment of the speech signal.

15. The method of claim 14, further comprising:

transmitting the coded first and second segments of the speech signal.

16. The method of claim 15, further comprising:

transmitting an error checking signal with the coded second segment of the speech signal.

17. The method of claim 16, wherein the transmitting the error checking signal comprises transmitting redundant data.

18. A communication system, comprising:

a coder;

a decoder; and

a communication network selectively interconnecting the coder and the decoder;

wherein the coder comprises a voice activity detector, a processor coupled with the voice activity detector, and a transmitter coupled with the processor,

wherein the voice activity detector receives first and second segments of a speech signal and identifies a substantially speech-like characteristic of the first segments and an absence of a substantially speech-like characteristic of the second segment of the speech signal,

wherein the processor selectively applies one of a plurality of coding modes to the first and second segments, the plurality of coding modes comprises a plurality of speech coding modes and a silence coding mode,

wherein the processor applies the silence description coding mode to the second segment of the speech signal independent of the speech coding mode applied to the first segments of the speech signal.

19. The communication system of claim 18, wherein the decoder generates a reproduced speech signal that is substantially imperceptible from the first and second segments of the speech signal.

20. The communication system of claim 19, wherein the coder selects a discontinuous transmission mode after the silence description coding mode.

21. The communication system of claim 19, wherein the communication network comprises a wireless communication network.

22. The communication system of claim 19, wherein the communication network comprises a computer network.

23. The communication system of claim 22, wherein the computer network comprises a local area network.

24. The communication system of claim 22, wherein the communication network further comprises a wireline communication network connected with the computer network.

25. A multi-rate codec that encodes a first speech signal having a first plurality of segments and receives a second speech signal having a plurality of encoded segments, comprising:

a multi-rate coder, wherein the multi-rate coder is capable of coding each of the segments of the first speech signal via one of a plurality of speech coding modes and a silence description coding mode, wherein the multi-rate coder selects the silence description mode when an absence of a substantially speech-like characteristic is detected in a segment independent of the speech coding mode applied to an earlier segment; and

a multi-rate decoder operatively coupled to the multi-rate coder, wherein the multi-rate decoder is capable of receiving and decoding the second plurality of encoded segments, wherein the multi-rate decoder selectively adds comfort noise to the decoded segment.

26. The multi-rate codec of claim 25, further comprising an error checking mechanism that reduces erroneous transmission by transmitting redundant data and performing majority voting on the redundant data.

27. The multi-rate codec of claim 26, wherein the multi-rate codec transmits the redundant data when the first speech signal is being coded with the silence description coding mode.

28. The multi-rate codec of claim 27, wherein the amount of the redundant data transmitted is a function of an available communication bandwidth.

29. The multi-rate codec of claim 28, wherein the multi-rate coder comprises a perceptual weighting filter.

30. The multi-rate codec of claim 25, wherein the multi-rate coder selects a speech coding mode from the plurality of speech coding modes as a function of a power consumption level associated with each speech coding mode.

31. The multi-rate codec of claim 25, wherein the multi-rate coder selects a speech coding mode from the plurality of speech coding modes as a function of a electromagnetic interference level associated with each speech coding mode.

32. The multi-rate codec of claim 25, wherein the multi-rate coder selects a speech coding mode from the plurality of speech coding modes as a function of a radio frequency interference level associated with each speech coding mode.