Abstract:
In an embodiment, a transmitter generates a self-generated video signal when retrieving only audio input signal from an audio source to replace an video input signal expected by the HDMI system. In another embodiment, a transmitter sets a flag when retrieving only an audio input signal, wherein the flag configures preamble transmitted in control periods to allow audio data to be transmitted to a receiver without incorporated with video data.

Description:
BACKGROUND  
       [0001]     The invention relates to high-definition multimedia interface (HDMI), and more specifically, to methods and systems for transmission of audio data that is originally not associated with video data using HDMI.  
         [0002]     HDMI, an industry-supported, uncompressed, all-digital audio/video interface, provides an interface between a source device, such as a set-top box, digital video disc (DVD) player, computer, or a digital-video home system (D-VHS), and a destination device, such as a digital television (DTV), projector, plasma panel or a liquid crystal display (LCD) display. HDMI integrates audio and video information into a single digital interface. HDMI development is overseen by the HDMI Working Group, including Hitachi, Panasonic, Philips, Sony, Thomson (RCA), Toshiba, and Silicon Image. LLC, a subsidiary of Intel, as developed High-bandwidth Digital Content Protection (HDCP) for HDMI, providing a secure audio/video interface that meets the security requirements of content providers and system operators.  
         [0003]     As an example shown in  FIG. 1 , a DVD player  12  is connected to a digital television or monitor  14  via an HDMI cable  13 . A DVD player  12  comprises an MPEG decoder chip  122  and an HDMI transmitter chip  124 . The MPEG decoder chip  122  acquires video data  161  and audio data  181  from a video source  16  and audio source  18  respectively. The HDMI transmitter chip  124  receives decoded video data  123   a  (such as 24-bit RGB) and decoded audio data  123   b  from the MPEG decoder chip  122 , and encrypts the decoded video data  123   a  and decoded audio data  123   b  in a HDCP encryption block  1242 . The encrypted HDMI data is output to the HDMI cable  13  and sent to an HDMI receiver  142  in the digital television  14 . The HDMI receiver  142  comprises a corresponding HDCP decryption block  1422  for decrypting the received HDMI data. The HDMI receiver  14  recovers the received HDMI data and outputs the recovered video data  143   a  and audio data  143   b.    
         [0004]     HDMI utilizes core technologies provided by the Digital Visual Interface (DVI). DVI is a 24-bit RGB interface, which utilizes transition minimized differential signaling (TMDS). TMDS is a signaling technique that produces a transition controlled, DC balanced series of characters from an input series of data bytes. In a long string of logic zeros and logic ones, bits are selectively manipulated to maintain a particular DC biased signal. A DVI link utilizes three pairs of differential digital signals, each pair carrying low voltage signals representative of the red (R), green (G), and blue (B) signal components. A fourth pair of wires carries a pixel clock signal. A serial 8-bit RGB signal carries information at a speed of up to 1.65 Gbps with an aggregate link speed of 4.95 Gbps, but an effective transfer rate of 3.96 Gbps. A 10 bit encoding scheme is utilized to minimize transitions at such high data rates.  
         [0005]     HDMI has potential beyond the scope of DVI. The HDMI specifications allow up to 5 Gbps bandwidth, compatible with future technology expansions, as current uncompressed HD movies only require 2.2 Gbps for both multi-channel audio and video. DVI has drawbacks that can be solved by HDMI, for example, DVI does not support digital audio data and digital chrominance signals (YCbCr). HDMI is fully backward-compatible with DVI using the CEA-861 profile for DTVs, however, the limitation of DVI makes a DVI device connected to an HDMI device unable to provide audio capability. One of the most important capabilities of HDMI is the ability to carry digital multi-channel audio in addition to digital video.  
         [0006]     HDMI has the capability to support existing high-definition video formats (720 p, 1080 i, and 1080 p). It also has the flexibility to support enhanced definition formats such as 480 p and 576 p, as well as standard definition formats such as National Television System Committee (NTSC) or Phase Alternating Line (PAL). The HDMI specifications allow for up to 8 channels of audio with 24 bits at sampling rates for up to 192 kHz, supporting all current forms of pulse code modulation (PCM) audio including DVD-Audio and compressed audio formats. HDMI allows connection from source to receiver, or receiver to display, all via one cable type for both video and audio.  
       SUMMARY  
       [0007]     The invention provides methods and systems for transmission of audio data that is originally not associated with video data using High-definition Multimedia Interface (HDMI). In one embodiment, an HDMI transmitting system receives audio input signal, and self-generates video signal if the video input signal is absence. The HDMI transmitting system thus transmits audio data in data island periods and self-generated video data in video data periods. According to the HDMI specification, audio must be transmitted and played with video, such that the self-generated video data provided by the HDMI transmitting system replaces the absent input video data expected by the HDMI system. The audio data is transmitted in the data island periods within periods of horizontal or vertical blanking. Exemplary self-generated video data is a static (or still) picture, such as a logo or a trademark.  
         [0008]     In another embodiment, an HDMI transmitting system receives an audio input signal, and sets a flag if a video input signal is not available. The HDMI transmitting system transmits audio data in data island periods within periods of horizontal or vertical blanking, and the flag configures the HDMI protocol to replace video data periods with data island periods and control periods. The flag extends horizontal or vertical blanking by configuring the beginning and end points thereof. The HDMI transmitting system can also send a signal instructing the corresponding HDMI receiver to turn off the display to conserve power.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:  
         [0010]      FIG. 1  is a schematic diagram illustrating a conventional HDMI system with HDCP protection scheme.  
         [0011]      FIG. 2  is a block diagram of an HDMI system.  
         [0012]      FIG. 3  shows an exemplary TMDS period placement in a 720×480 p video frame.  
         [0013]      FIG. 4A  is a block diagram illustrating an embodiment of a system for audio transmission using HDMI.  
         [0014]      FIG. 4B  is a block diagram illustrating an embodiment of a system for audio transmission using HDMI.  
     
    
     DETAILED DESCRIPTION  
       [0015]      FIG. 2  is a block diagram of an HDMI system, comprising a plurality of sources and sinks, wherein an HDMI source denotes a device with an HDMI output, and an HDMI sink denotes a device with an HDMI input. As shown in  FIG. 2 , the HDMI cable and connectors carry four differential pairs that make up the transition minimized differential signaling (TMDS) clock channel  233  for carrying timing information for video data (“video pixel clock”), and three TMDS data channels  230 ˜ 232  carrying video data  211 , audio data  212 , and auxiliary data. The auxiliary data herein includes any data that is neither video data, audio data, nor timing information for video data, for example, timing information for audio data, text data, control signals for power supply, monitor control information (such as audio volume, brightness, or power state), and non-audio or video control information.  
         [0016]     A video electronics standard association (VESA) display data channel (DDC)  234  configures and exchanges status between a single source and a single sink. An optional consumer electronics association (CEC) protocol provides high-level control functions between all audiovisual products in a user&#39;s environment. The video pixel clock is transmitted via the TMDS clock channel  233 , and is used by the receiver  24  as a frequency reference for data recovery on the other three TMDS data channels  230 ˜ 232 . In order to transmit audio data  212  and auxiliary data across the TMDS data channels  230 ˜ 232 , HDMI uses a packet structure. As previously mentioned, the data can be protected with HDCP to attain higher reliability.  
         [0017]     Various serial links for transmitting data and clock signals from a transmitter  22  to a receiver  24  are well known to those skilled in the art. One conventional serial links is known as a TMDS link, in which video data  211  are encoded and transmitted as encoded words, and the encoded video data and a video clock signal are transmitted as differential signals. The TMDS link operates in video data period, data island period, or control period.  FIG. 3  depicts an exemplary TMDS period placement in a 720×480 p video frame  30 . The active pixels of an active video line are transmitted during the video data periods, marked by pattern C in  FIG. 3 . Audio and auxiliary data is transmitted using a series of packets during data island periods, marked by pattern A. The control periods, marked by pattern B, are used when no video, audio, or auxiliary data needs to be transmitted, required between any other two periods.  
         [0018]     As shown in  FIG. 3 , the primary data transmitted by a TMDS link are video data. The video data are not continuous, but with many blanking intervals, including vertical blanking  302  and horizontal blanking  306 . These blanking intervals provide an opportunity for audio data and auxiliary data to be transported.  
         [0019]     A preamble at the end of each control period indicates whether the next data period is a video data period or a data island period. Each video data period and data island period starts with a leading guard band providing determination of the transition from the control period to the data period.  
         [0020]     As shown in  FIG. 3 , audio data is transmitted during data island periods within horizontal blanking  306  and vertical blanking  302 . In conventional HDMI architecture, audio can only be transmitted along with video. The invention provides methods and systems allowing the audio data that is originally not associated with video data to be played by using an HDMI transmitter.  
         [0021]      FIG. 4A  is a block diagram illustrating an embodiment of a system for audio transmission using HDMI. As shown in  FIG. 4A , an HDMI transmitting system  44  comprises an HDMI transmitter  446 , an audio processor  444 , a video processor  442 , a video signal generator  440 , and a mode indicator  448 . The HDMI transmitting system  44  receives an audio input signal  421  from an audio source  42  and a video input signal  423  from a video source (not shown). The audio processor  444  receives and processes the audio input signal  421 , such as digitizing, coding, and compressing the audio input signal  421 , and subsequently outputs audio data  445  to the HDMI transmitter  446 . The mode indicator  448 , which could be a register or a control signal in practical implementation, is used to reflect if only audio input signal  421  is available or both audio input signal  421  and video input signal  423  are available. The video processor  442  receives either the external video input signal  423  or a self-generated video signal  441  output by the video signal generator  440  in accordance with the mode indicator  448 . The video processor  442  processes the video signal, such as digitizing, coding, and compressing the video signal, and subsequently outputs video data  443  to the HDMI transmitter  446 . The self-generated video signal  441  can carry any video, for example, a static picture such as a logo or a trademark. The HDMI transmitter  446  receives both the audio data  445  and the video data  443 , and outputs an HDMI signal  447  to the HDMI receiver  46  through an HDMI cable.  
         [0022]      FIG. 4B  is a block diagram illustrating an embodiment of a system for audio transmission using HDMI. An HDMI transmitting system  48  comprises an HDMI transmitter  486 , an audio processor  484 , and a video processor  482 . The HDMI system  44  receives an audio input signal  421  from an audio source  42  and a video input signal  423  from a video source (not shown). The audio processor  484  receives and processes the audio input signal  421 , and subsequently outputs audio data  485  to the HDMI transmitter  486 . The HDMI transmitter  486  comprises a mode indicator  4862 , which could be a register or a control signal. The mode indicator  4862  reflects whether there is only audio input signal  421  available, or there are both audio input signal  421  and video input signal  423  available at the input of the HDMI system. The video processor  482  receives and processes the video input signal  423  and outputs video data  483  to the HDMI transmitter  486 . The HDMI transmitter  486  receives the audio data  485  and the video data  483  if the input of the HDMI system contains both audio and video signals, and outputs an HDMI signal  487  to the HDMI receiver  46  through an HDMI cable. If the input of the HDMI system contains only audio signal, the mode indicator in the HDMI transmitter  486  sets a flag, and the HDMI transmitter  486  outputs an HDMI signal  487  to the HDMI receiver  46  according to the audio data  485 . The flag configures the preamble transmitted in the control period to always arrange a data island period after each control period. The video frame thus contains only control period and data island periods. In other words, the periods of horizontal or vertical blanking are extended and the video data periods are omitted from the video frame. In some embodiments, the flag can also signal the HDMI receiver to turn off the display since there is no video data to be played, thereby conserving power.  
         [0023]     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.