[mythtv-users] ALSA:plug:surround51 works, but only two channels used?

[Michael T. Dean]

On 01/08/2008 12:11 AM, Keller Giacomarro wrote:
> Hello!  I've always appreciated help from you guys in the past, and 
> know I can expect the same this time.  Thanks in advance.
>
> I'm trying to setup analog surround sound from my frontend, out my 
> SBLive, to my receiver.  I know that 6ch analog out works, since I can 
> watch a DVD in VLC with 5.1 selected and all is correct.
>
> I'm seeing strange behavior by Myth.  Please see the following from 
> 'mythfrontend -v audio' run on SVN revision 15283.
>
> Compile string:
> ./configure --prefix=/usr --enable-proc-opt --disable-firewire 
> --disable-audio-arts --disable-audio-jack --enable-opengl-vsync 
> --disable-xvmc --enable-opengl-video --disable-dvb --disable-dbox2 
> --disable-hdhomerun --disable-iptv --disable-v4l --disable-ivtv
>
>    2008-01-07 22:52:21.279 AFD: Opened codec 0x841c3a0, id(MPEG2VIDEO)
>    type(Video)
>    2008-01-07 22:52:21.280 AFD: Opened codec 0x841c720, id(AC3) 
> type(Audio)
>    2008-01-07 22:52:21.280 AFD: Audio Track #1 is A/V stream #1 and has
>    6 channels in the English language(6647399).
>    2008-01-07 22:52:21.287 AFD: Selected track 1: English AC3 5.1ch
>    (A/V Stream #1)
>    2008-01-07 22:52:21.287 AFD: Initializing audio parms from audio
>    track #1
>    2008-01-07 22:52:21.287 AFD: Audio format changed
>                            from id(NONE)    -1Hz -1ch   0bps    ;
>    id(NONE)    -1Hz -1ch   0bps                             to   id( 
> AC3) 48000Hz  6ch  16bps    ; id(
>    AC3) 48000Hz  2ch  16bps     2008-01-07 22:52:21.291 AO: Killing 
> AudioOutputDSP
>    2008-01-07 22:52:21.292 Opening ALSA audio device 'plug:surround51'.
>    2008-01-07 22:52:21.293 in SetParameters(format=2, channels=2,
>    rate=48000, buffer_time=500000, period_time=125000)
>    2008-01-07 22:52:21.295 get_buffer_size returned 16384
>    2008-01-07 22:52:21.295 set_period_time_near returned 170666
>    2008-01-07 22:52:21.295 get_period_size returned 8192
>
> Myth can see the audio streams, sees that Audio Track 1 has 6 
> channels, selects the English AC3 5.1 track, and changes the format to 
> 6ch.  It then opens the (working) alsa:plug:surround51 device.  Then, 
> for some reason, it sets the ALSA parameters to only two channels.  It 
> seems like all the prereqs for 6ch surround have been satisfied, but 2 
> channels is all I get.
>
> If I take the raw MPEG file and open it in VLC, I can select 5.1 
> surround and it works correctly.  Any ideas anyone has would be 
> GREATLY appreciated!  Thanks in advance once again! 

http://svn.mythtv.org/trac/ticket/1104

Mike