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

Keller Giacomarro keller.g at gmail.com
Tue Jan 8 05:11:34 UTC 2008

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)
    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!

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mythtv.org/pipermail/mythtv-users/attachments/20080107/8f726875/attachment.htm 

More information about the mythtv-users mailing list