[mythtv-users] Can myth DVD output 7.1 audio?

Michael T. Dean mtdean at thirdcontact.com
Sat Jan 12 22:28:14 UTC 2008

On 01/12/2008 05:06 PM, Paul Catchpole wrote:
> Michael T. Dean wrote:
>> On 01/10/2008 05:36 PM, Seth Daniel wrote:
>>> On Thu, Jan 10, 2008 at 05:31:39PM -0500, Michael T. Dean wrote:
>>>> On 01/10/2008 05:07 PM, Michelle Dupuis wrote:
>>>>> Back when my home theatre PC was running windows, I bought DVD player
>>>>> software that would output 7.1 channels to my amp (8 discrete channels).
>>>>> Although I'm very happy with Myth, I'm wondering if I've given up a nice
>>>>> feature....
>>>>> Does Myth's DVD player decode 8 discrete channels?  I've confirmed using
>>>>> speaker-test that my 8 channels are working, but movies like Gladiator
>>>>> (which are in DTS 6.1) don't seem to provide anything beyond 2 channels in
>>>>> myth.
>>>> http://svn.mythtv.org/trac/ticket/1104
>>> Reading this ticket was interesting, but I don't get it.  How would such
>>> a setup be...setup?  I can do 7.1 now if I simply pass-thru to my sound
>>> card (at least I think I can) and my receiver can deal with it.  So what
>>> does the work this ticket describes do?  Can someone explain it, please?
>> Allows 5.1-channel audio output through analog (or 5.1-channel 
>> re-encoding for timestretch).  Without the patch, you have 2 choices, 
>> 2-channel analog and/or AC-3/DTS passthrough.
> Isn't there a third choice here? Without the patch, setting myth to use 
> the 6-channel device and setting maxchannels to 6 will cause myth to 
> output 6-channel audio correctly. The patch addresses the problem that 
> then occurs with 2-channel audio sources where the same 6-channel device 
> is used, leading to 2-speaker output - whereas the current version of 
> the patch will upmix for you. The old version of the patch would let you 
> choose an alternative output device for using your own upmixer.
> That's how it works for me, anyhoo... :-)

Without the patch, if Myth decodes the audio, it only outputs 
2-channels.  If you do any kind of external upmixing/copying (i.e. using 
ALSA's ttable), you're not getting 5.1 or 7.1 channel audio, but you 
could get audio out on 6 or 8 speakers...

However, technically, you could say that 2-channel digital output is a 
3rd choice (because i forgot the "or digital" in my response).

Note that there is no 'MaxChannels' without the patch.


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