[mythtv-users] DVI to HDMI what about th eaudio???

[Simon Hobson]

Nick Rout wrote:

>my question was really to do with how the sound got from the video
>card to the hdmi cable, given the intervening DVI step, when DVI is
>not supposed to be able to carry audio.
>
>As I see it the audio passes this route on these cards:
>
>MB-->graphicscard-->DVI-->DVI/HDMI convertor-->HDMIcable-->TV (or amp)
>
>How does the audio pass through the DVI cable to the HDMI cable?

The thing is that in DVI or HDMI, sound is not really "another 
signal" with it's own wires. DVI and HDMI are a fully digital system 
- essentially a fast serial link.

I would surmise that when DVI was designed, audio wasn't included. 
When HDMI was designed, it was made backwards compatible with DVI and 
things like audio were added as a separate stream in the digital 
multiplex. Older DVI recipient devices will probably just ignore the 
unknown stream.

The DVI-HDMI adapter doesn't actually do anything to the signals - 
it's really just a change of connector. So, if a manufacturer outputs 
an "HDMI" signal (ie with audio), but uses a DVI connector, you get 
audio over DVI - but it's not really true DVI, it really something 
later using the older connector.

At least, that's what I'm assuming is going on.

-- 
Simon Hobson

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