[mythtv-users] How to debug "no sound" ?

[Michael T. Dean]

John P Poet wrote:

> I just did a fresh install of Fedora Core 4.  Everything is working 
> great, except I get no sound out of Myth.
>
> I had a similar problem when I first installed my maudio sound card 
> under FC2.  All "other" programs would produce sound out the S/PDIF 
> jack just fine, but Myth was mute.  I thought I had finally figured 
> out what needed to go into my asound.conf file, to make Myth happy.  I 
> have tried using that exact same asound.conf file under FC4, but Myth 
> is still silent.
>
> What is weird, is that mplayer works with the S/PDIF out perfectly, 
> even when a asound.conf file does not exist.  All I have to do is use 
> "mplayer -ao alsa -ac hwac3" and it just works.

-ac hwac3 tells MPlayer to use AC-3 passthrough, so it's not using any 
information from your ALSA configuration file.  It's simply dumping the 
AC-3 stream from the DVD/video to your digital output.  This will work 
regardless of the config file.  (MPlayer without an /etc/asound.conf 
will play stereo sound on the analog outputs--unless the user running 
MPlayer defines an ~/.asoundrc .)

> Xine and aplay require the asound.conf file, however.  For Xine and 
> aplay, this asound.conf file is sufficient:
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> pcm.!default {
>   type plug
>   slave.pcm iec958
> }
>
> pcm.ice1712 {
>    type hw
>    card 0
>    device 0
> }
>
> ctl.ice1712 {
>    type hw
>    card 0
> }
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> With the above asound.conf, I can play both AC3 and stereo material 
> via the S/PDIF port using any program *except* Myth.

Basically just says to output to iec958 unless otherwise specified 
(remaps default output).

> Under FC2, I thought I had solved the problem by adding:
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> pcm.ice1712_spdif {
>     type plug
>     ttable.0.8 1 # S/PDIF left...Delta 9
>     ttable.1.9 1 # S/PDIF right...Delta 10
>     slave.pcm ice1712
> }
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Funny...  That's a simplified version of the default definition for 
iec958 (see /usr/share/alsa/card/ICE1712.conf ).  I'd say try using 
ALSA:iec958 instead.  Even ALSA:default should work with a config file 
that remaps the default device (as above).

> And then telling Myth to use "ALSA:ice1712_spdif".  However, that does 
> not seem to be working under FC4.  I end up with this in my log:
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 2005-06-25 21:03:39.653 Using protocol version 17
> adding pes stream at pid 0x31 with type 2
> adding pes stream at pid 0x34 with type 129
> 2005-06-25 21:03:42.696 libavformat type mpegts
> 0: start_time: 4752.137 duration: 323.408
> 1: start_time: 4752.094 duration: 323.407
> stream: start_time: 52801.048 duration: 3593.896 bitrate=15577 kb/s
> 2005-06-25 21:03:43.472 Stream #1 (audio track #0) is an audio stream 
> with 2 channels.
> 2005-06-25 21:03:43.472 Auto-selecting AC3 audio track (stream #1).
> 2005-06-25 21:03:43.472 Initializing audio parms from audio track #0.
> 2005-06-25 21:03:43.603 Killing AudioOutputDSP
> 2005-06-25 21:03:43.604 Opening audio device 'ice1712_spdif'.
> 2005-06-25 21:03:43.612 in SetParameters(format=2, channels=2, 
> rate=48000, buffer_time=500000, period_time=125000)
> 2005-06-25 21:03:43.613 get_buffer_size returned 6553
> 2005-06-25 21:03:43.613 set_period_time_near returned 68250
> 2005-06-25 21:03:43.613 get_period_size returned 3276
> 2005-06-25 21:03:43.621 Audio fragment size: 4096
> 2005-06-25 21:03:43.623 Audio Stretch Factor: 1
> 2005-06-25 21:03:43.623 Ending reconfigure
> 2005-06-25 21:03:43.624 kickoffOutputAudioLoop: pid = 13790
> 2005-06-25 21:03:43.624 OutputAudioLoop: Play Event
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> I am not even sure the problem has anything to do with the S/PDIF 
> port.  Using the envy24control utility, I see that when Myth is 
> "playing", no audio is being generated on *any* of the soundcard's 
> jacks.  When I use mplayer,xine or aplay, the envy24control utility 
> shows me that audio is being routed to the S/PDIF jack.  If I remove 
> the asound.conf file, and use aplay, envy24control shows me that the 
> audio is being routed to the first two analog jacks.

Because the config file changed the definition of the default device to 
output to the digital port.

> So, how do I debug this?  How can I figure out why all other programs 
> will send sound to my audio card, but Myth is mute?  Since Myth is not 
> generating any errors, I have no idea where to look.

HTH.

Mike