HDMI Handshaking for Audio vs. Video
htnut -- Fri, 12/22/2006 - 13:50
There is an unanswered specific concern for anyone who is considering the purchase of a display at this time. Given that the 3-way "handshaking" between source, A/V receiver and display results in a default to the weakest link in the chain, is the "handshaking' separate for audio and video, or are both audio and video limited collectively by the oldest HDMI version in the chain? More specifically, if a person purchases a currently-available display (i.e., Sony VPL-VW50 or other 1080p projector) that supports either version 1.1 or 1.2, and waits to buy an A/V receiver that supports version 1.3, will the "handshaking" link with the older display restrict the source component from sending the new HD lossless audio formats to the A/V receiver, or will the HD lossless formats be sent to the A/V receiver because audio and video capabilities are independently determined and transmitted as a result of the "handshaking"? Anyone considering the purchase of a high-end display at this time needs the answer to determine whether or not to wait for a display that supports version 1.3.
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Here is a response from Joe Lee, HDMI Evangelist at HDMI Licensing, LLC:
The short answer is that audio and video capabilities are completely distinct fields in the EDID (Extended Display Identification Data) of all relevant devices, so these capabilities do not have a relationship effect on each other. HDMI is designed such that when a series of devices are chained together (such as a Blu-ray player + A/V receiver + HDTV), the source device (Blu-ray player in this example) will automatically adjust its audio and video output to be the best formats that are mutually supported by all the devices in the chain. An easy way to think about it is that you will experience the highest common denominator. This is logical, as you cannot enjoy the 8-channel audio soundtrack on a Blu-ray disc if your A/V receiver can only support 6-channel audio.
We recommend that consumers do not think about the HDMI version number; this has little meaning regarding a device's capabilities since most features are optional. Rather, consumers should focus on specific features that they are interested in experiencing. For example, there can be an "HDMI 1.0" A/V receiver that supports 8-channel 192kHz PCM audio, which can support lossless audio formats such as 8-channel Dolby TrueHD. On the other hand, there can be an "HDMI 1.3" A/V receiver that only supports 2-channel PCM audio and none of the surround-sound formats. Again, this is because the vast majority of features in each HDMI version are optional and do not have to be supported. We recently released a new HDMI Trademark and Logo Usage Guideline that prohibits a product to be marketed purely by its HDMI revision number, and we hope this will help dispel they confusion that has resulted from the heavy branding of HDMI revisions numbers instead of the actual features.
One final technical clarification: the lossless surround-sound audio formats (Dolby TrueHD and DTS-HD Master Audio) can be enjoyed by any older (i.e., HDMI 1.0) A/V receiver that supports 6 or 8 channels of high-bitrate PCM audio, provided that the playback device decodes the audio. This is explained in greater detail in the HDMI FAQ here:
http://www.hdmi.org/learningcenter/faq.aspx#q2