[mythtv-users] ALSA:plug:surround51 works, but only two channels used?
paul at paulcatchpole.co.uk
Thu Jan 10 18:41:20 UTC 2008
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)
> 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!
> mythtv-users mailing list
> mythtv-users at mythtv.org
There's a setting in the frontend setup somewhere which specifies the
number of channels to use. It defaults to 2 and if left, the logs look
like what you've posted. I fell into the trap when testing the #1104
patch. The new upmixer on recent #1104 patches is very worth trying if
you sometimes have 2-channel source material as well as the AC3 you show
above - although I'm having some problems with Mythmusic with the latest
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