Method and apparatus for controlling the transition of an audio converter between two operative modes in the presence of link impairments in a data communication channel

• US 6,721,707 B1
• Filed: 12/22/1999
• Issued: 04/13/2004
• Est. Priority Date: 05/14/1999
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Rabipour, Rafi, Chu, Chung Cheung C., Sloan, David G.
• Primary Examiner(s): Dorvil, Richemond
• Assistant Examiner(s): HARPER, V PAUL
• Application Number:
  US09/469,464
• Time in Patent Office: 1,574 Days
• Field of Search: 704/239, 704/233, 704/228, 704/221, 704/500, 704/219, 704/214, 704/212, 455/560
• US Class Current: 704/500
• CPC Class Codes: H04L 1/0014 by adapting the source coding
• CPC Class Codes: H04L 1/0019 in which mode-switching is based on a statistical approach

Abstract

A signal processor for effecting the conversion of an audio data signal from one format to another. The signal processor has a signal converter that can selectively acquire two operative modes, namely a first operative mode and a second operative mode. In the first operative mode, the signal converter transforms the audio data signal from one format to another and releases the converted audio data signal from the output of the signal processor. In the second operative mode, the signal converter is disabled and permits passage of the audio data signal to the output without conversion. The signal processor has a control unit for controlling the transition of the signal converter between operative modes. The control unit enables the signal converter to pass from the first operative mode to the second operative mode when at least one operating condition has been satisfied. The control unit reacts to a link impairment occurring on the data communication channel to alter the operating condition to be satisfied to enable passage from the first operative mode to the second operative mode. In a specific example of implementation, the modification to the operating condition can be such as to “tighten” the requirements to be met for switching from the first to the second operative mode.

Claims

1. A signal processor, comprising:

an input for receiving an audio data signal;

an output for connection to a data communication channel;

a signal converter coupled to said input for processing the audio data signal at said input, said signal converter capable to selectively acquire a first operative mode and a second operative mode, in said first operative mode said signal converter converting the audio data signal from a first format to a second format and releasing the audio data signal in said second format from said output, in said second operative mode said signal converter permitting passage of the audio data signal to said output without conversion to said second format;

a control unit coupled to said signal converter, said control unit being operative to enable said signal converter to pass from said first operative mode to said second operative mode when at least one operating condition has been satisfied, said control unit being responsive to the detection of a link impairment on the data communication channel to alter the at least one operating condition that must be satisfied in order to enable passage from said first operative mode to said second operative mode.

2. A signal processor as defined in claim 1, wherein said signal processor is operative for establishing a bi-directional communication with a remote entity over a duplex communication channel including a forward link and a return link, said output being operative for coupling to the forward link for transmitting the audio data signal toward the remote entity on the forward link, said signal processor being operative for receiving an audio data signal from the remote entity on the return link, said control unit being responsive to the detection of a link impairment occurring on the return link of the data communication channel to alter the at least one operating condition that must be satisfied in order to enable passage from said first operative mode to said second operative-mode.

3. A signal processor as defined in claim 2, wherein the audio data signal is conveying speech sound information.

4. A signal processor as defined in claim 3, wherein the first format is a compressed version of the audio data signal in the second format.

5. A signal processor as defined in claim 4, wherein said signal converter includes a decoder.

6. A signal processor as defined in claim 5, wherein said decoder is a VSELP decoder.

7. A signal processor as defined in claim 4, wherein said control unit includes a link impairment monitor for monitoring audio data signal in the first format on the return link of the data communication channel for the presence of impairments over the return link.

8. A signal processor as defined in claim 7, wherein said control unit includes a link impairment response unit coupled to said link impairment monitor for receiving from said link impairment monitor a data signal conveying link impairment information.

9. A signal processor as defined in claim 8, wherein said link impairment response unit includes a data structure holding data elements representative of operating conditions to be satisfied to enable passage from said first operative mode to said second operative mode, said link impairment response unit being operative to alter at least one of the data elements representative of the operating conditions to be satisfied to enable passage from said first operative mode to said second operative mode in response to reception from said link impairment monitor of a data signal indicative of occurrence of a link impairment.

10. A signal processor as defined in claim 9, wherein at least one of the data elements representative of the operating conditions to be satisfied to enable passage from said first operative mode to said second operative mode is altered such as to tighten a tolerance level with respect to the occurrence of a link impairment on the return link of the data communication channel.

11. A signal processor as defined in claim 10, wherein said link impairment monitor is operative to detect a link impairment on the return link of the data communication channel by detecting data transmission errors on the return link of the data communication channel.

12. A signal processor as defined in claim 11, wherein said link impairment monitor is operative to detect data transmission errors on the return link of the data communication channel by observing parity information contained in the audio data signal in the first format on the return link of the data communication channel.

13. A signal processor as defined in claim 12, wherein said link impairment monitor includes a statistical analysis unit for generating data indicative of information selected in the group consisting of time during which said control unit has stayed in said second operative mode, frequency of occurrence of data transmission errors on the return link of the data communication channel, bit error rate during negotiation for passage from said first operative state to said second operative state, bit error rate while in said second operative state, run-length, energy level during negotiation for passage from said first operative state to said second operative state.

14. A signal processor as defined in claim 13, wherein the data signal conveying link impairment information conveys at least in part to said link impairment response unit the data generated by said statistical analysis unit.

15. A signal processor as defined in claim 14, wherein said control unit when in said second operative mode is responsive to the detection of a link impairment occurring on the data communication channel to switch to said first operative mode.

16. A signal processor as defined in claim 15, wherein an operating condition to be satisfied to enable passage from said first operative mode to said second operative mode corresponds to a maximal time interval within which to complete successful negotiation for passage from said first operative state to said second operative state.

17. A signal processor as defined in claim 16, wherein said operating condition may be altered such as to tighten a tolerance level with respect to the occurrence of a link impairment on the return link of the data communication channel by decreasing the maximal time interval within which successful negotiation for passage from said first operative state to said second operative state must be completed.

18. A signal processor, comprising:

input means for receiving an audio data signal;

output means for connection to a data communication channel;

signal converter means coupled to said input for processing the audio data signal at said input means, said signal converter means capable to selectively acquire a first operative mode and a second operative mode, in said first operative mode said signal converter means converting the audio data signal from a first format to a second format and releasing the audio data signal in said second format from said output means, in said second operative mode said signal converter means permitting passage of the audio data signal to said output means without conversion to said second format;

control means coupled to said signal converter means, said control means being operative to enable said signal converter means to pass from said first operative mode to said second operative mode when at least one operating condition has been satisfied, said control means being responsive to the detection of a link impairment on the data communication channel to alter the at least one operating condition that must be satisfied to enable passage from said first operative mode to said second operative mode.

19. A method for processing an audio data signal, said method comprising:

providing an input for receiving the audio data signal;

providing an output for connection to a data communication channel;

providing a signal converter coupled to said input for processing the audio data signal at said input, said signal converter capable to selectively acquire a first operative mode and a second operative mode, in said first operative mode said signal converter converting the audio data signal from a first format to a second format and releasing the audio data signal in said second format from said output, in said second operative mode said signal converter permitting passage of the audio data signal to said output without conversion to said second format;

providing a control unit coupled to said signal converter, said control unit being operative to enable said signal converter to pass from said first operative mode to said second operative mode when at least one operating condition has been satisfied;

in response to detection of a link impairment on the data communication channel, altering the at least one operating condition that must be satisfied to enable passage from said first operative mode to said second operative mode.

20. A method as defined in claim 19, wherein said signal processor is operative for establishing a bi-directional communication with a remote entity over a duplex communication channel including a forward link and a return link, said output being operative for coupling to the forward link for transmitting the audio data signal toward the remote entity on the forward link, said method comprising:

receiving an audio data signal from the remote entity on the return link;

in response to the detection of a link impairment occurring on the return link of the data communication channel, altering the at least one operating condition that must be satisfied to enable passage from said first operative mode to said second operative mode.

21. A method as defined in claim 20, wherein the audio data signal is conveying speech sound information.

22. A transmission system, comprising:

a first signal processor;

a second signal processor; and

a duplex data communication linking said first signal processor to said second signal processor, said duplex data communication channel including a forward link and a return link;

said first signal processor being operable to convert an audio data signal from a first signal format to a second signal format for transmission on said forward link to said second signal processor,

said second signal processor being operable to reconvert said audio data signal from said second signal format to said first signal format;

said first signal processor including;

a) an input for receiving the audio data signal;

b) an output coupled to said forward link for transmitting the audio data signal in either one of the first and second format to said second signal processor;

c) a control unit operative to enable said signal processor to pass the audio data signal without conversion to the second signal format to said output, when at least one operating condition has been satisfied, said control unit being responsive to the detection of a link impairment on said duplex data communication channel to alter the at least one operating condition that must be satisfied in order to enable said signal processor to pass the audio data signal without conversion to the second signal format.

23. A signal processor, comprising:

an input for receiving an audio data signal;

an output for connection to a data communication channel;

a signal converter coupled to said input for processing the audio data signal at said input, said signal converter capable to selectively acquire a first operative mode and a second operative mode, in said first operative mode said signal converter converting the audio data signal from a first format to a second format and releasing the audio data signal in said second format from said output, in said second operative mode said signal converter permitting passage of the audio data signal to said output without conversion to said second format;

a control unit coupled to said signal converter, said control unit being operative to enable said signal converter to pass from said first operative mode to said second operative mode when at least one operating condition has been satisfied, said control unit including;

a link impairment monitor for monitoring the audio data signal in the first format on the return link of the data communication channel for the presence of impairments over the return link;

said control unit being responsive to the detection by said link impairment monitor of a link impairment occurring on the data communication channel to alter the operating condition that must be satisfied in order to enable passage from said first operative mode to said second operative mode.