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

Robin Gilks g8ecj at gilks.org
Wed Jan 16 02:25:49 UTC 2008


>>
>> Does the patch merge the 5.1 tracks to an S/PDIF output or does it
>> assume
>> 6 discrete analog outputs to the ALSA output layer.
>>
>> I ask because my theatre amp never sees anything other than PCM48 stereo
>> from my frontend.
>>
>> If its 6 channels, can ALSA be set up to merge them to a single S/PDIF
>> stream?
>>
>
> use passthrough mode for spdif output. it should work still as this has
> remained the same.
> leave as 2ch and enable passthru
> if there is AC3 or DTS then the result will be digital, otherwise 2ch is
> analog to the amp.
> havent tried this myself but other use it. I have to assume it still
> works.
> timestretch will reencode to AC3 if necessary in this mode. upmix not
> required as the amp will do a similar job with DPL2 or NEO6
>
>> I still don't quite have enough horsepower with my Epia SP13000 but its
>> close enough for me to pursue if I can find out how to drive it
>> properly.
>>
>> Also, with the latest patch, the help in setup screen implies that the
>> 2/5.1 channel selection is related to the source of the audio rather
>> than
>> what it will be munged into (number of channels to decode implies the
>> width of the source to me!) - but then again maybe I'm just terminally
>> confused :-(
>
> It refers to the output #channels. the new upmix will then make the output
> chan count correct.
>

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?


-- 
Robin Gilks




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