[mythtv] [mythtv-commits] Ticket #1104: multi channelaudio support

[Mark Spieth]

>There was actually one problem, when playing a stereo recording
>with 5.1 up mixing  the front speaker volume was about 6 db too
>low in volume when compared to an AC3 recording.

Ive noticed variations in how this is encoded. perhaps MP3 sound works 
differently to AC32 and AC35.1

I noticed with the AC3 5.1->2.0 switching clip that centre was low in 5.1 
mode and ok in 2.0 mode. this means there may be a problem with 5.1 decode 
in the internal ac3dec. not sure yet. I dont have too many 5.1 non HD 
recordings to test with.
no dts 5.1 clips to test with.

>
>I'm just testing to make sure there are no regressions in other output
>methods. They don't actually have to have 5.1 sound available.

ac3passthru may be slightly broken in 47 so Ill attach 48 which has this 
fix. untested of course for pasthru because I cant :-)

otherwise if seems fine on my 2ch frontend so far. all 2chmode stuff should 
be identical.

note for AC3 passthru setup, always set maxchannels to 2 as otherwise the 
alsa sound device doesnt open correctly.

mark