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

[Ma Begaj]

2008/1/8, Keller Giacomarro <keller.g at gmail.com>:
>
>  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!
>
>  -Keller

As I can remember, SB is already mixing sound, so you can use
ALSA:default. You just have to set up your alsamixer correctly. I used
it like that before and the sound was great.

But if you still have/want to use myth, use the patch from the Mike's
link. It is working great for me with Asus M2NPV-VM. I had some
problems with Mythmusic and this patch, but it is working