[mythtv] [mythtv-commits] Ticket #1104: multichannelaudio support

Mark Spieth mark at digivation.com.au
Wed Jan 16 04:13:40 UTC 2008

> Sorry Mark - still confused...
> Are you saying that if my only connection is S/PDIF from my frontend to my
> amp then it will only reencode if I change playback speed? Otherwise I
> have to use 6 analog connections?
> Example
> Standard def DVB-S recording with stereo sound. I have ALSA:Default as the
> output device for S/PDIF output to the amp. No analog connections at all.
> The amp analyses the stream as PCM48.
> If I select 5.1 in setup, the digital stream to the amp is always
> displayed as PCM48 stereo. It does not encode it to AC3. Will it become
> 5.1 if I change the playback speed?

I assume you have passthru enabled as you should have.
leave #channels set to stereo (2ch). you dont need 6ch mode at all.
any AC3 5.1 or DTS5.1 source material audio will be passed through as 
digital via spidf.
any 2ch source material audio is passed via spidf as 2ch PCM48 and your amp 
does the upmixing.

reencoding only occurs if the source material is 6ch and you have passthru 
enabled and timestretch != 1.0
In this case it still appears via spidf as AC3 encoded 5.1 to your amp.

hope this is clear.


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