[mythtv] Internal DVD Player multichannel support

Dave Oxley dave at daveoxley.co.uk
Mon May 1 02:36:57 UTC 2006

I have a 5.1 system. My amp will mix from 2 channels to 6 channels 
automatically, so I'd rather MythTV doesn't do this. What would be handy 
is if you could specifiy what ouput you'd prefer (say DTS). And 
therefore when starting a DVD etc it'll automatically select DTS if 
possible, otherwise Dolby DIgital etc.


Mark Spieth wrote:
>> I'm working up to some changes on the audio code to neaten up a few
>> things which have been bothering me for a while
>> - What do we need to do to get multichannel audio working with the
>> internal DVD player?  Presumably some way to set the number of speakers
>> the user has is a pre-req?  I guess that libavcodec can do the
>> downmixing for us though?  I'm interested to do some work on this
> I assume you are talking about my patch #1104.
> AC3 and DTS both have downmixing support built in. just need to specify the 
> number of channels when decoding. also supports upmixing for 2 -> 6 channel 
> synthesised but not sure on this. still dont have a 6 channel system to 
> listen/test with. there is no generic downmixing component in libavcodec 
> though you could use liba52 or dts directly but the format is not 
> interleaved. not sure why you would want to do this outside of the decode 
> operation anyway.
> general setup part of the patch has the number of channels the user has.
> still havent found the time yet to clean up the audio bit and the 
> interaction with avformatdecoder. sorry about this.
> what I wanted to do was incorporate some way of the audio layer handling any 
> number of source channels without being explicitly configured for them. 
> output channels (analog) I thought just limit to 2 and 6 which alsa can 
> handle.
> cheers
> mark 
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