Method and apparatus for sending auxiliary data on a TMDS-like link

• US 7,558,326 B1
• Filed: 09/12/2001
• Issued: 07/07/2009
• Est. Priority Date: 09/12/2001
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Silicon Image, Inc. (Lattice Semiconductor Corporation)
• Inventors: Tan, Ken-Sue, Wolf, Paul Daniel, Lyle, James D., Kim, Min-Kyu, Kim, Gyudong, Martin, Russel A., Altmann, William C.
• Primary Examiner(s): Ghayour; Mohammad H
• Assistant Examiner(s): Vlahos; Sophia
• Application Number:
  US09/954,663
• Time in Patent Office: 2,855 Days
• Field of Search: 375/244, 375/295, 375/296, 375365-366, 375/368, 375/219, 375/240, 375/242, 375/286, 375/288, 375/292, 375/314, 375/316, 375/319, 375/324, 375/342, 375/259, 348/5.5, 348/11, 348/14, 348/17, 348/512, 348/515, 348/469, 348/473, 348476-478, 348484-485, 347/472, 347/473, 347/471, 347/469, 370/464, 370/535, 370/536
• US Class Current: 375/244
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER
• CPC Class Codes: H04L 1/206 for modulated signals
• CPC Class Codes: H04L 25/49 using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems spectral shaping H04L25/03828
• CPC Class Codes: H04N 19/89 involving methods or arrangements for detection of transmission errors at the decoder

Abstract

A communication system including a transmitter, a receiver, and a TMDS-like link, in which video data and auxiliary data (typically including timing data associated with other auxiliary data) are transmitted from the transmitter to the receiver, or in which video data are transmitted over the link from the transmitter to the receiver, and auxiliary data (typically including timing data associated with other auxiliary data) are transmitted from the receiver to the transmitter. In typical embodiments the auxiliary data include one or more streams of audio data. Other aspects are transmitters and receivers for use in such a system, methods for sending auxiliary data and video data over a TMDS-like link, methods for transmitting and recovering clocks for auxiliary data transmitted over such a link, methods for synchronizing auxiliary data transmitted over such a link with video data transmitted over such a link, and methods for generating clocks having frequency closely matching the rate at which the auxiliary data are transmitted over such a link.

Claims

1. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over the link to the receiver, and the transmitter is configured to transmit auxiliary data to the receiver by modulating DC disparity of a channel of the communication link, wherein the transmitter is configured to transmit a stream of encoded data words over the channel, the words determine the video data and include bits indicative of accumulated DC disparity of the stream, and said bits determine the auxiliary data, and wherein the receiver is configured to determine a sequence of differences between successive values of the accumulated DC disparity, thereby determining the auxiliary data.

2. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over the link to the receiver, and the transmitter is configured to transmit auxiliary data to the receiver by modulating DC disparity of a channel of the communication link, wherein the transmitter is configured to transmit a stream of encoded data words over the channel, the words determine the video data and include bits indicative of accumulated DC disparity of the stream, and said bits determine the auxiliary data, and wherein a sequence of differences between successive values of the DC disparity determines the auxiliary data.

3. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over the link to the receiver, and the transmitter is configured to transmit auxiliary data to the receiver by modulating DC disparity of a channel of the communication link, wherein the transmitter is configured to transmit a stream of encoded data words over the channel, the words determine the video data and include bits indicative of accumulated DC disparity of the stream, and said bits determine the auxiliary data, and wherein the auxiliary data are digital audio data.

4. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over the link to the receiver, at least one of the transmitter and the receiver is configured to transmit a stream of data words determining auxiliary data over the link to the other one of the transmitter and the receiver, and a data structure of each of at least a subset of the words is indicative of DC disparity, and wherein the auxiliary data are determined by one of a sequence of values of the DC disparity and a sequence of differences between successive ones of the values of the DC disparity, wherein the transmitter is configured to transmit the stream of data words over a channel of the link, the data words of the stream are encoded data words that determine the video data and have an accumulated DC disparity, each said data structure has at least one bit indicative of a value of the accumulated DC disparity, and a sequence of differences between successive values of the accumulated DC disparity determines the auxiliary data.

5. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over the link to the receiver, at least one of the transmitter and the receiver is configured to transmit a stream of data words determining auxiliary data over the link to the other one of the transmitter and the receiver, and a data structure of each of at least a subset of the words is indicative of DC disparity, and wherein the auxiliary data are determined by one of a sequence of values of the DC disparity and a sequence of differences between successive ones of the values of the DC disparity, wherein a first accumulated DC disparity value followed by a second accumulated DC disparity value for two sequentially occurring ones of the words indicates an auxiliary data bit having a first logical value if the absolute value of the second accumulated DC disparity value is greater than the absolute value of the first accumulated DC disparity value, and an auxiliary data bit having a second logical value if the absolute value of the first accumulated DC disparity value is greater than the absolute value of the second accumulated DC disparity value.

6. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over the link to the receiver, at least one of the transmitter and the receiver is configured to transmit a stream of data words determining auxiliary data over the link to the other one of the transmitter and the receiver, and a data structure of each of at least a subset of the words is indicative of DC disparity, and wherein the auxiliary data are determined by one of a sequence of values of the DC disparity and a sequence of differences between successive ones of the values of the DC disparity, wherein the values of the DC disparity include values in at least two distinct ranges of positive DC disparities and at least two distinct ranges of negative DC disparities, and wherein a sequence of differences between successive values in one of the ranges of positive DC disparities determines values of the auxiliary data but differences between successive values in another one of the ranges of positive DC disparities do not determine values of the auxiliary data.

7. A transmitter for use in data transmission over a TMDS-like link, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

an input for receiving auxiliary data;

an output configured to be coupled to a channel of the link; and

circuitry coupled to the input and configured for generating an output signal in response to the auxiliary data, and asserting the output signal to the output for transmission over the channel, wherein the output signal modulates DC disparity of the channel and is indicative of the auxiliary data, wherein the auxiliary data are audio data.

8. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over the link to the receiver, at least one of the transmitter and the receiver is configured to transmit a stream of encoded words over the link to the other one of the transmitter and the receiver, each of the words has a data structure and is encoded in accordance with one of a first encoding operation and a second encoding operation,

and wherein the data structure of each of the words having nonzero DC disparity is indicative of whether said each of the words has been encoded in accordance with the first encoding operation or the second encoding operation, and the data structure of each of the words having zero DC disparity is indicative of at least one bit of the auxiliary data.

9. The system of claim 8, wherein the transmitter is configured to transmit the stream of encoded words over the link to the receiver, each of the encoded words is a TMDS-encoded word that comprises N bits and determines a word of the video data, and the data structure of said each of the encoded words is an M-bit subset of the N bits, where N is an integer and M is an integer less than N.

10. The system of claim 9, wherein N is equal to ten and M is equal to one.

11. The system of claim 8, wherein the auxiliary data are digital audio data.

12. The system of claim 8, wherein the auxiliary data determine at least one control signal.

13. A transmitter for use in data transmission over a TMDS-like link, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

an input for receiving auxiliary data;

an output configured to be coupled to a channel of the link; and

circuitry coupled to the input and configured for generating an output signal in response to the auxiliary data and asserting the output signal to the output for transmission over the channel, wherein the output signal is indicative of a stream of encoded data words, wherein each of the words includes a data structure and is encoded in accordance with one of a first encoding operation and a second encoding operation, the data structure of each of the words having nonzero DC disparity is indicative of whether said each of the words has been encoded in accordance with the first encoding operation or the second encoding operation, and the data structure of each of the words having zero DC disparity is indicative of at least some of the auxiliary data.

14. A method for sending data over a TMDS-like communication link, where “

TMDS”

denotes “

transition minimized differential signaling,”

comprising the steps of;

(a) transmitting a stream of encoded data words over at least one channel of the link, wherein each of the words is indicative of auxiliary data and includes a data structure, each of the words having nonzero DC disparity is encoded in accordance with one of a first encoding operation and a second encoding operation, each of the words having zero DC disparity is encoded in accordance with the first encoding operation, the data structure of each of the words having nonzero DC disparity is indicative of whether said each of the words has been encoded in accordance with the first encoding operation or the second encoding operation, and the data structure of each of the words having zero DC disparity is indicative of at least one bit of the auxiliary data; and

(b) recovering the auxiliary data from the transmitted stream of encoded data words.

15. The method of claim 14, wherein the encoded words are also indicative of video data, and also including the step of:

(c) decoding the transmitted stream of encoded data words to recover the video data.

16. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over the link to the receiver, wherein the video data are transmitted as a stream of binary data words that determine an analog auxiliary signal as well as the video data, wherein each of the binary data words is an encoded word that has been encoded in accordance with a first encoding operation when accumulated DC disparity of the stream exceeds a positive threshold, and has been encoded in accordance with a second encoding operation when the accumulated DC disparity of the stream exceeds a negative threshold, and instantaneous values of the stream'"'"'s accumulated DC disparity determine the analog auxiliary signal.

17. The system of claim 16, wherein the analog auxiliary signal is an analog audio signal.

18. The system of claim 16, wherein the transmitter is configured to change dynamically at least one of the positive threshold and the negative threshold, so that the accumulated DC disparity has an envelope of disparity wander, and said envelope of disparity wander determines the analog auxiliary signal.

19. A transmitter for use in data transmission over a TMDS-like link, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

a first input for receiving auxiliary data;

at least one video input for receiving video data;

an output configured to be coupled to a channel of the link; and

circuitry coupled to the first input and to the video input and configured for generating an output signal in response to the auxiliary data and asserting the output signal to the output for transmission over the channel, wherein the output signal is indicative of a stream of binary data words that determine a DC disparity that varies over time within a time-varying envelope, the binary data words also determine the video data, and variation of the envelope over time determines an analog auxiliary signal, wherein the analog auxiliary signal is indicative of the auxiliary data.

20. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over the link to the receiver, the link includes at least one multi-purpose line, the transmitter and the receiver are operable in a first mode in which one of the transmitter and the receiver transmits a first signal indicative of auxiliary data over the at least one multi-purpose line to the other one of the transmitter and the receiver, and the transmitter and the receiver are operable in a second mode in which one of the transmitter and the receiver transmits a second signal over the at least one multi-purpose line to the other one of the transmitter and the receiver, wherein the auxiliary data are digital audio data, wherein the at least one multi-purpose line is at least one downstream device status line, the second mode is a monitoring mode in which the transmitter monitors the at least one downstream device status line to determine whether a downstream device is coupled to the receiver, and the first mode is an auxiliary data transmission mode in which the transmitter transmits the first signal over the at least one downstream status line to the receiver.

21. The system of claim 20, wherein the transmitter and the receiver operate simultaneously in the first mode and the second mode, the transmitter transmits the first signal over the at least one downstream status line to the receiver while operating in the first mode, and the transmitter also monitors the at least one downstream device status line while operating in the first mode to determine whether a downstream device is coupled to the receiver.

22. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over the link to the receiver, the link includes at least one multi-purpose line, the transmitter and the receiver are operable in a first mode in which one of the transmitter and the receiver transmits a first signal indicative of auxiliary data over the at least one multi-purpose line to the other one of the transmitter and the receiver, and the transmitter and the receiver are operable in a second mode in which one of the transmitter and the receiver transmits a second signal over the at least one multi-purpose line to the other one of the transmitter and the receiver, wherein the at least one multi-purpose line is at least one power line, the second mode is a power supply mode in which the transmitter provides DC power to the receiver over the at least one power line, the link also comprises at least one digital video channel, and the first mode is a data transmission mode in which the transmitter transmits digital video data to the receiver over the digital video channel and at least one of the transmitter and the receiver transmits the first signal over the at least one power line to the other one of the transmitter and the receiver.

23. The system of claim 22, wherein the transmitter and the receiver operate simultaneously in the first mode and the second mode, the transmitter is configured to send modulated DC power to the receiver over the at least one power line while operating in the first mode, and the receiver is configured to extract the auxiliary data from the modulated DC power while operating in the first mode.

24. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data over a video channel of the link to the receiver, wherein the link includes an additional channel for bidirectional communication between the transmitter and at least one of the receiver and a device associated with the receiver, wherein at least one of the transmitter and the receiver is operable in a mode in which it transmits auxiliary data over the additional channel to the other one of the transmitter and the receiver, the auxiliary data are audio data, and the additional channel is a serial bus configured to allow bidirectional communication between the transmitter and a monitor associated with the receiver, including transmission from the receiver to the transmitter of monitor identification data specifying characteristics of the monitor.

25. The system of claim 24, wherein the TMDS-like communication link is a Digital Video Interface, the additional channel is a Display Data Channel including power and ground lines, and the auxiliary data are transmitted over at least one line of the power and ground lines.

26. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link comprises at least two video channels, the transmitter is operable in a first mode in which it transmits video data to the receiver over a first subset of the video channels but not a second subset of the video channels, the transmitter is operable in another mode in which it transmits video data to the receiver over all of the video channels, and the transmitter is configured to transmit auxiliary data to the receiver over the second subset of the video channels during the first mode, wherein the auxiliary data are digital audio data.

27. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data to the receiver over the link, the transmitter is configured to transmit encoded words indicative of auxiliary data to the receiver over the link, at least one bit of each of the encoded words determines at least one auxiliary data bit, and the remaining bits of said each of the encoded words determine a word of the video data, wherein the remaining bits of said each of the encoded words determine all bits of an in-band, TMDS-encoded word other than a transition control bit, the TMDS-encoded word has a transition control bit slot, and said at least one bit of each of the encoded words is a single auxiliary data bit transmitted in the transition control bit slot.

28. The system of claim 27, wherein the receiver is configured to ignore a bit having a first binary value, in the transition control slot of one of the received words, in response to identifying a bit having a second binary value in the transition control slot each of the two previously received ones of the received words.

29. The system of claim 27, wherein the transmitter is also configured to transmit out-of-band, TMDS-encoded words to the receiver, and wherein each of the out-of-band, TMDS-encoded words has a transition control bit slot containing a transition control bit, and the receiver is configured to process received words including said encoded words and said out-of-band, TMDS-encoded words, and

wherein the receiver is configured to identify, as an auxiliary data bit or a transition control bit, each bit in the transition control slot of each of the received words as a result of analyzing a short past history of said each of the received words.

30. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link comprises at least one video channel, the transmitter is configured to transmit video data and auxiliary data to the receiver over the video channel, the video data are determined by a first set of code words, the auxiliary data are determined by a second set of code words, and none of the code words in the second set is a member of the first set, wherein each of the code words in the first set is an in-band TMDS-encoded word, and each of the code words in the second set is an out-of-band TMDS-encoded word.

31. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link comprises at least one digital video channel and at least one analog video channel, the transmitter is configured to transmit digital video data to the receiver over the digital video channel, and at least one of the transmitter and the receiver is configured to operate in a mode in which it transmits auxiliary data to the other of the transmitter and the receiver over the analog video channel.

32. The system of claim 31, wherein the auxiliary data are digital audio data, and the transmitter is configured to operate in a mode in which said transmitter transmits the audio data to the receiver over the analog video channel while transmitting the digital video data to the receiver over the digital video channel.

33. The system of claim 31, wherein the transmitter is configured to transmit an analog video signal over the analog video channel, and the transmitter is configured to transmit the auxiliary data over said analog video channel during blanking intervals of the analog video signal.

34. A transmitter for use in data transmission over a TMDS-like link having at least one digital video channel and at least one analog video channel, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

a first input for receiving auxiliary data;

at least one video input for receiving video data;

a first output configured to be coupled to the digital video channel;

a second output configured to be coupled to the analog video channel; and

circuitry, coupled to the first input and to the video input, and configured to operate in a selected one of a first mode and a second mode, wherein in the first mode, the circuitry generates an analog video signal indicative of at least some of the video data, and asserts the analog video signal to the second output for transmission over the analog video channel, and

wherein in the second mode, the circuitry generates an auxiliary data signal indicative of at least some of the auxiliary data and a video signal indicative of at least some of the video data, asserts the video signal to the first output for transmission over the digital video channel, and asserts the auxiliary data signal to the second output for transmission over the analog video channel.

35. A transmitter for use in data transmission over a TMDS-like link having at least one power line for providing DC power from the transmitter to another device, and at least one video channel, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

a first input for receiving auxiliary data;

at least one video input for receiving video data;

a first output configured to be coupled to the video channel;

a second output configured to be coupled to the power line; and

circuitry, coupled to the first input and to the video input, and configured to operate in a mode in which it generates a video signal indicative of at least some of the video data and an auxiliary data signal indicative of at least some of the auxiliary data, asserts the video signal to the first output for transmission over the video channel, and asserts the auxiliary data signal to the second output for transmission over the power line.

36. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link has multiple data transmission channels, the transmitter is configured to transmit video data to the receiver over at least a first channel of the link, and at least one of the transmitter and the receiver is configured to transmit a first stream of auxiliary data over a second channel of the link to the other one of the transmitter and the receiver, and at least one of the transmitter and the receiver is configured to transmit a second stream of auxiliary data over one of the first channel of the link and a third channel of the link to the other one of the transmitter and the receiver, and wherein the first stream of auxiliary data is a stream of digital audio data, the second stream of auxiliary data is a second stream of digital audio data, the transmitter is configured to transmit the stream of digital audio data over the second channel of the link to the receiver, the transmitter is configured to transmit the second stream of digital audio data over the third channel of the link to the receiver, the TMDS-like communication link is a Digital Video Interface link, the second channel is a video clock channel of the Digital Video Interface link and the third channel is a downstream device status line of the Digital Video Interface link.

37. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link has multiple data transmission channels, the transmitter is configured to transmit video data to the receiver over at least a first channel of the link, and at least one of the transmitter and the receiver is configured to transmit a first stream of auxiliary data over a second channel of the link to the other one of the transmitter and the receiver, and at least one of the transmitter and the receiver is configured to transmit a second stream of auxiliary data over one of the first channel of the link and a third channel of the link to the other one of the transmitter and the receiver, and wherein the first stream of auxiliary data comprises audio data, the transmitter is configured to transmit the first stream of auxiliary data over the second channel of the link to the receiver, and the receiver is configured to transmit the second stream of auxiliary data over the first channel of the link to the transmitter.

38. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link has multiple data transmission channels, the transmitter is configured to transmit video data to the receiver over at least a first channel of the link, at least one of the transmitter and the receiver is configured to transmit a first stream of auxiliary data over a second channel of the link to the other one of the transmitter and the receiver, at least one of the transmitter and the receiver is configured to transmit a second stream of auxiliary data over one of the first channel of the link and a third channel of the link to the other one of the transmitter and the receiver, the first stream of auxiliary data comprises audio data, the TMDS-like communication link is a Digital Video Interface link, the transmitter is configured to transmit the first stream of auxiliary data over the second channel of the link to the receiver, the transmitter is configured to transmit the second stream of auxiliary data over the first channel of the link to the receiver, the first channel is video channel of a first TMDS-link of the Digital Video Interface link, and the second channel is a video channel of a second TMDS-like link of the Digital Video Interface link.

39. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link has multiple data transmission channels, the transmitter is configured to transmit video data to the receiver over at least a first channel of the link, and at least one of the transmitter and the receiver is configured to transmit a first stream of auxiliary data over a second channel of the link to the other one of the transmitter and the receiver, and at least one of the transmitter and the receiver is configured to transmit a second stream of auxiliary data over one of the first channel of the link and a third channel of the link to the other one of the transmitter and the receiver, and wherein the first stream of auxiliary data comprises audio data, the transmitter is configured to transmit the first stream of auxiliary data over the second channel while the system employs the second channel for an additional function, the transmitter is configured to transmit over the second channel a first signal having no frequency components outside a frequency range and at least one signal having no frequency components in said frequency range, and said first signal is indicative of the first stream of auxiliary data.

40. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link has multiple data transmission channels, the transmitter is configured to transmit video data to the receiver over at least a first channel of the link, the transmitter and the receiver are configured to operate in a first mode in which one of the transmitter and the receiver asserts a signal indicative of auxiliary data over a second channel of the link to the other one of the transmitter and the receiver, and the transmitter and the receiver are configured to operate in a second mode in which said one of the transmitter and the receiver asserts a second signal over the second channel to the other one of the transmitter and the receiver, wherein the auxiliary data comprise audio data, the receiver asserts the signal indicative of auxiliary data to the transmitter over the second channel during the first mode, the receiver asserts said second signal to the transmitter over the second channel during the second mode, and said second signal is indicative of presence of a device coupled to the receiver.

41. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link has multiple data transmission channels, the transmitter is configured to transmit video data to the receiver over at least a first channel of the link, the transmitter and the receiver are configured to operate in a first mode in which one of the transmitter and the receiver asserts a signal indicative of auxiliary data over a second channel of the link to the other one of the transmitter and the receiver, and the transmitter and the receiver are configured to operate in a second mode in which said one of the transmitter and the receiver asserts a second signal over the second channel to the other one of the transmitter and the receiver, wherein the auxiliary data comprise audio data, the transmitter asserts the signal indicative of auxiliary data to the receiver over the second channel during the first mode, the transmitter asserts said second signal to the receiver over the second channel during the second mode, and said second signal provides power to at least one of the receiver and a device coupled to the receiver.

42. The system of claim 41, wherein the second mode is a sleep mode and the auxiliary data are audio data.

43. A transmitter for use in data transmission over a TMDS-like link, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

at least one video input for receiving video data;

an auxiliary data input for receiving auxiliary data;

a video output configured to be coupled to a first channel of the link;

a second output configured to be coupled to a second channel of the link;

circuitry, coupled between the video input and the video output and configured to assert a signal indicative of at least some of the video data to the video output in response to the video data; and

circuitry, coupled between the second output and the auxiliary data input and configured to operate in a first mode in which it asserts a signal indicative of the auxiliary data to the second output in response to the auxiliary data, and to operate in a second mode in which it asserts to the output a signal capable of providing power to a device coupled to the second channel of the link.

44. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link has multiple data transmission channels, the transmitter is configured to transmit video data to the receiver over at least a first channel of the link, and at least one of the transmitter and the receiver is configured to transmit auxiliary data over a second channel of the link, to the other one of the transmitter and the receiver, while at least one of the transmitter and the receiver asserts a signal over the second channel, wherein the transmitter is configured to transmit a first signal indicative of the auxiliary data over the second channel while said at least one of the transmitter and the receiver transmits a second signal over the second channel, wherein the first signal has no frequency components outside a frequency range and the second signal has no frequency components in said frequency range.

45. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link has multiple data transmission channels, the transmitter is configured to transmit video data to the receiver over at least a first channel of the link, and at least one of the transmitter and the receiver is configured to transmit auxiliary data over a second channel of the link, to the other one of the transmitter and the receiver, while at least one of the transmitter and the receiver asserts a signal over the second channel, wherein the receiver is configured to transmit a first signal indicative of the auxiliary data over the second channel while said at least one of the transmitter and the receiver transmits a second signal over the second channel, wherein the first signal has no frequency components outside a frequency range and the second signal has no frequency components in said frequency range.

46. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link has multiple data transmission channels, the transmitter is configured to transmit video data to the receiver over at least a first channel of the link, and at least one of the transmitter and the receiver is configured to transmit auxiliary data over a second channel of the link, to the other one of the transmitter and the receiver, while at least one of the transmitter and the receiver asserts a signal over the second channel, wherein the transmitter is configured to transmit a first signal indicative of the auxiliary data over the second channel while said at least one of the transmitter and the receiver transmits a second signal over the second channel, wherein the first signal has an amplitude that varies within a first amplitude range, and the second signal has an amplitude that varies between a first value and one or more additional values, wherein the difference between the first value and each of said additional values is greater than the difference between any two amplitudes in the first amplitude range.

47. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link has multiple data transmission channels, the transmitter is configured to transmit video data to the receiver over at least a first channel of the link, and at least one of the transmitter and the receiver is configured to transmit auxiliary data over a second channel of the link, to the other one of the transmitter and the receiver, while at least one of the transmitter and the receiver asserts a signal over the second channel, wherein the receiver is configured to transmit a first signal indicative of the auxiliary data over the second channel while said at least one of the transmitter and the receiver transmits a second signal over the second channel, wherein the first signal has an amplitude that varies within a first amplitude range, and the second signal has an amplitude that varies between a first value and one or more additional values, wherein the difference between the first value and each of said additional values is greater than the difference between any two amplitudes in the first amplitude range.

48. A communication system, including:

a transmitter;

a receiver; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link comprises at least one video channel, the transmitter is configured to transmit video data to the receiver over the link during data transmission periods separated by blanking intervals, wherein the data transmission periods include first periods each having duration within a first range and second periods each having duration within a second range distinct from the first range, the transmitter is configured to transmit the video data to the receiver over the video channel only during the first periods and to transmit auxiliary data to the receiver over the video channel only during the second periods, the receiver is configured to recognize each of the second periods and operate in an auxiliary data reception mode during each of the second periods, and the receiver is configured to recognize each of the first periods and operate in a video data reception mode during each of the first periods, wherein the video data and the auxiliary data are determined by code words of a first code word set, and the transmitter is configured to transmit code words of a second code word set only during the blanking intervals, wherein no member of the first code words set is a member of the first code word set.

49. The system of claim 48, wherein each code word of the first code word set is an in-band TMDS-encoded word, and each code word of the second code word set is an out-of-band TMDS-encoded word.

50. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link includes at least a first conductor pair and a second conductor pair between the transmitter and the receiver, wherein at least one of the transmitter and the receiver is configured to transmit a differential signal to the other of the transmitter and the receiver over the first conductor pair, at least one of the transmitter and the receiver is configured to transmit a second differential signal to the other of the transmitter and the receiver over the second conductor pair, and at least one of the transmitter and the receiver is configured to transmit a third differential signal indicative of auxiliary data to the other of the transmitter and the receiver over the conductor pairs, wherein the third differential signal is generated as a result of common mode modulation of both the first conductor pair and the second conductor pair such that the difference between common mode level of the first conductor pair and common mode level of the second conductor pair determines said third differential signal.

51. The system of claim 50, wherein the transmitter is configured to transmit the first differential signal to the receiver over the first conductor pair, and to transmit the second differential signal to the receiver over the second conductor pair, wherein each of the first differential signal and the second differential signal is indicative of digital video data, and wherein the transmitter is configured to transmit the third differential signal to the receiver by modulating both the common mode level of the differential signal and the common mode level of the second differential signal with respect to each other.

52. A transmitter for use in data transmission over a TMDS-like link, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

at least one video input for receiving video data;

an auxiliary data input for receiving auxiliary data;

outputs configured to be coupled to a conductor pair of the link;

circuitry, coupled to the outputs and the auxiliary data input and configured to assert a differential signal indicative of the auxiliary data to the output, such that modulation of the common mode level of the differential signal as a function of time is indicative of said auxiliary data.

53. The transmitter of claim 52, wherein the circuitry is also coupled to the video input and the differential signal is also indicative of at least some of the video data.

54. A transmitter for use in data transmission over a TMDS-like link, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

at least one video input for receiving video data;

an auxiliary data input for receiving auxiliary data;

first outputs configured to be coupled to a first conductor pair of the link;

second outputs configured to be coupled to a second conductor pair of the link; and

circuitry, coupled to the first outputs, the second outputs, and the auxiliary data input, and configured to assert a first differential signal having a first common mode level to the first outputs and a second differential signal having a second common mode level to the second outputs, wherein the difference between the first common mode level and the second common mode level determines a third differential signal, and the third differential signal is indicative of the auxiliary data.

55. The transmitter of claim 54, wherein the circuitry is also coupled to each said video input, the first differential signal is indicative of a first portion of the video data, and the second differential signal is indicative of a second portion of the video data.

56. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit TMDS-encoded words indicative of video data and binary auxiliary data to the receiver over the link, wherein each of the encoded words is indicative of a bit of the auxiliary data and at least one bit of the video data, at least some of the TMDS-encoded words are transition minimized words, at least some of the TMDS-encoded words are transition maximized words, and the receiver is configured to identify each of the transition minimized words as a first binary auxiliary data bit and to identify each of the transition maximized words as the complement of the first binary auxiliary data bit.

57. A transmitter for use in data transmission over a TMDS-like link, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

a video input for receiving video data;

an auxiliary data input for receiving binary auxiliary data;

an output configured to be coupled to a channel of the link; and

circuitry, coupled to the video input, the auxiliary data input, and the output, and configured to assert a stream of TMDS-encoded words to the output, wherein each of the TMDS-encoded words is indicative of a bit of the auxiliary data and at least one bit of the video data, at least some of the TMDS-encoded words are transition minimized words, at least some of the TMDS-encoded words are transition maximized words, each of the transition minimized words is indicative of a first binary auxiliary data bit, and each of the transition maximized words is indicative of the complement of the first binary auxiliary data bit.

58. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the transmitter is configured to transmit video data and a video clock to the receiver over the link, the receiver includes clock recovery circuitry coupled to receive the video clock, the clock recovery circuitry has an operating mode in which it generates a recovered clock in response to the video clock while the transmitter transmits said video clock to the receiver, and the clock recovery circuitry has a locking mode preliminary to the operating mode, wherein during the locking mode the clock recovery circuitry attempts to lock onto any video clock being transmitted by the transmitter to the receiver, the transmitter is configured to transmit the video data over a video channel when the receiver is in the operating mode, and at least one of the transmitter and the receiver is configured to transmit auxiliary data over the video channel to the other of the transmitter and the receiver when the receiver is in the locking mode.

59. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link comprises at least one video channel, the transmitter is configured to transmit video data and auxiliary data to the receiver over the video channel, the video data are determined by a first set of code words, the auxiliary data are determined by a second set of code words, none of the code words in the second set is a member of the first set, and each of the code words in the second set is determined by a robust encoding algorithm, wherein the robust encoding algorithm maps a different cluster of the code words in the second set to each different value of the auxiliary data, each value of the auxiliary data is determined by any one of the code words in one said cluster, and each code word in each said cluster has identical noncritical bits and different values of a critical bit set, wherein each said critical bit set comprises at least one critical bit, and each said critical bit is subject to greater error risk in transmission and recovery than is each said noncritical bit.

60. The system of claim 59, wherein each of the code words in the first set is an in-band TMDS-encoded word, each of the code words in the second set is an out-of-band TMDS-encoded word, and each said critical bit is one of a DC balancing bit and a transition control bit.

61. The system of claim 60, wherein the robust encoding algorithm maps each different one of sixty-four different clusters of the code words in the second set to a different one of sixty-four different values of the auxiliary data.

62. The system of claim 60, wherein the receiver is configured to decode each said out-of-band TMDS-encoded word to determine one of the values of the auxiliary data by ignoring the least significant bit of said out-of-band TMDS-encoded word, toggling all bits of said out-of-band TMDS-encoded word other than said least significant bit and then shifting the toggled bits to the right by one bit if the most significant bit of said out-of-band TMDS-encoded word has a first value, and shifting all bits of said out-of-band TMDS-encoded word other than said least significant bit to the right by one bit without toggling said bits if the most significant bit of said out-of-band TMDS-encoded word has a second value.

63. A transmitter for use in data transmission over a TMDS-like link, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

a video input for receiving video data;

an auxiliary data input for receiving auxiliary data;

an output configured to be coupled to a channel of the link; and

circuitry, coupled to the video input, the auxiliary data input and the output, and configured to assert a stream of code words to the output in response to the video data and the auxiliary data, wherein the code words include a first set of code words and a second set of code words, each of the code words in the first set determines a word of the video data, each of the code words in the second set determines a word of the auxiliary data, none of the code words in the second set is a member of the first set, and each of the code words in the second set is determined by a robust encoding algorithm, wherein each of the code words in the first set is an in-band TMDS-encoded word, each of the code words in the second set is an out-of-band TMDS-encoded word.

64. A communication system, including:

a receiver;

a transmitter; and

a TMDS-like communication link between the transmitter and the receiver, wherein “

TMDS”

denotes “

transition minimized differential signaling,”

the link comprises at least one video channel, the transmitter is configured to transmit video data and auxiliary data to the receiver over the video channel, each word of the video data is determined by a code word of a first set of code words, each word of the auxiliary data is determined by a code word of a second set of code words, none of the code words in the second set is a member of the first set, and the transmitter is configured to transmit a sequence of N identical code words of the second set to indicate each word of the auxiliary data, where N is an integer greater than one.

65. The system of claim 64, wherein the receiver is configured to perform error correction on each said sequence of N identical code words.

66. The system of claim 64, wherein each of the code words of the second set is an out-of band, TMDS-encoded word.

67. The system of claim 66, wherein N is equal to three.

68. The system of claim 66, wherein N is greater than two.

69. The system of claim 64, wherein the transmitter is configured to transmit code words of the second set only during blanking intervals of the video data and to transmit code words of the first set only during active video periods between said blanking intervals.

70. The system of claim 69, wherein N is equal to three, whereby each said sequence of N identical code words includes an initial code word, a middle code word following the initial code word, and a final code word following the middle code word.

71. The system of claim 70, wherein the receiver is configured to perform error correction on each received sequence of N code words transmitted as a sequence of N identical code words, by replacing the middle code word of the received sequence with the initial code word of said received sequence when the initial word and the final word of said received sequence are identical but the middle code word is not identical to the initial code word, thereby generating corrected sequences.

72. The system of claim 71, wherein the receiver is configured to identify transitions between the active video periods and following ones of the blanking intervals, and to identify the words of auxiliary data determined by the corrected sequences by selecting the first middle code word of the first one of the corrected sequences following each of the transitions, and selecting the final code word of each subsequent one of the corrected sequences occurring in the same one of the blanking intervals as does said first one of the corrected sequences.

73. The system of claim 69, wherein the receiver is configured to identify transitions between the active video periods and following ones of the blanking intervals, and to identify the words of auxiliary data determined by each received sequence of code words transmitted as a sequence of N identical code words, by selecting the first middle code word of the first received sequence following each of the transitions and selecting the final code word of each subsequent received sequence occurring in the same one of the blanking intervals as does said first received sequence.

74. A transmitter for use in data transmission over a TMDS-like link, where “

TMDS”

denotes “

transition minimized differential signaling,”

said transmitter including;

a video input for receiving video data;

an auxiliary data input for receiving auxiliary data;

an output configured to be coupled to a channel of the link; and

circuitry, coupled to the video input, the auxiliary data input and the output, and configured to assert a stream of code words to the output in response to the video data and the auxiliary data, wherein the code words include a first set of code words and a second set of code words, each of the code words in the first set determines a word of the video data, a sequence of N identical ones of the code words in the second set determines a word of the auxiliary data, N is an integer greater than one, and none of the code words in the second set is a member of the first set.

75. The transmitter of claim 74, wherein the circuitry is configured to transmit code words of the second set only during blanking intervals of the video data and to transmit code words of the first set only during active video periods between said blanking intervals.