Pulseaudio surround with a52 (Dolby Digital)

[msilveira]

Hi all.

I'm amazed not to find any post with the keyword "a52" in this forum!

So, I'd like to invite everyone trying this setup or those who had successfully got it working to this discussion.

Goals:

• First and the mother of all problems: Output encoded 5.1 to the digital out of the sound card, to a DTS/Dolby Digital capable receiver.
• Have a52 encoded sound like DD (Dolby Digital) Live working on Windows
• Be as compatible as possible for multiple programs (alsa dmix style)
• Achieve a successful setup with both ALSA and Pulseaudio if possible

First Notes:

• The a52 plugin requires access to the sound hardware
• Pulseaudio already handles the mixing and rate conversion over alsa
• My setup is with an ALC883(HDA-Intel) (Gigabyte GA-EP45-UD3P)

Let's begin with my current setup (for testing):
.asoundrc

pcm.pulseaudio {
  type pulse
}
ctl.pulseaudio {
  type pulse
}

pcm.pulsea52enc {
  type a52
  @args.0 {
    type integer
    default 0
  }
}
ctl.pulsea52enc {
type hw
card 0
}
pcm.pulseaudioplug {
  type plug
  slave.pcm "pulsea52enc"
}

pcm.!default {
  type upmix
  slave.pcm "pulsea52enc"
#  slave.pcm "pulseaudioplug"
  channels 6
}
ctl.!default {
    type pulse
}

The tail of my default.pa

load-module module-alsa-sink device=pulsea52enc rate=48000 channels=6 tsched=0 sink_name=alsa_a52
set-default-sink alsa_a52

My changes into default.pa (by default, everything is commented)

realtime-scheduling = yes
disable-lfe-remixing = no
default-fragments = 5
default-fragment-size-msec = 25

Linux, ALSA, programs just don't cease to amuse me...
Testing using xine with alsa as sound plugin and into pcm.!default I use slave.pcm "pulsea52enc", the sound distorts a bit, but if i change the slave to slave.pcm "pulseaudioplug" the "distortion" isn't there any more.
Changing the audio plugin to pulseudio, quality is good for both slaves.

If you get a message that audio device is no available, wait 2sec and try playing again.

Some notes:

• mpg321 with -ao alsa09 is unable to spawn pulseaudio
• audacious simply doesn't work (sound is "pausing"), using either pulse or alsa as output plugin
• xmms works with pulseaudio plugin only; alsa plugin seems to try to use direct hardware access (damn ool unmaintained codes!)
• Looks like amarok works fine!
• Xine works fine, both stereo, ac3, dts, all works fine.
• Totem didn't work
• Not sure, but it looks like xine doesn't remember volume!?
• I'm still trying to get pulseaudio device chooser/volume manager to work
• Will try later with 4 channels instead of 6

I believe that pulseaudio already creates a 6 channel stream with this config, thus, making the pulseaudioplug and upmix pcms useless or might be guilty to some extent.

That's it for the moment, I hope those who want the same setup participate, so we may find the guilty for all this a52 mess... any component might be buggy: alsa-a52-plugin, pulseaudio or alsa. And surely there will still remain bugs in the programs we use.

Later, I will upload some audio samples recorded from my cell phone for you to compare with your results.

[boxxy]

can someone confirm if workaround from msilviera working? thanks