PulseAudio doesn't allow AC3 output through S/PDIF

[Id2ndR]

Binary package hint: pulseaudio

Version: lucid
Hardware : sound card with an optical (or coaxial) output connected to an external amplifier with Dolby Digital or DTS decoder

First step : check that you can correctly send a DTS sound to you amplifier with ALSA . For example :
1/ Find your IEC958 (S/PDIF) Digital Audio Output : $ aplay -L
2/ Download a sample DTS (or Dolby) file at http://www.sr.se/multikanal/english/e_index.stm (the smallest one is at the bottom)
2/ Try to play this file directly through ALSA : $ aplay -D <iec958_device> <surround_file.wav> (example : $ aplay -D iec958:CARD=Aureon51MkII,DEV=0 SURROUNDTEST_011212.wav)

Current status :
- gnome-volume-control allows to use digital stereo output
- a digital stereo output is produced even when gnome-volume-control is set to analog output (so pulseaudio is configured this way too).

Expected status :
- gnome-volume-control should allow to use digital AC3 output
- no digital stereo should be produced when analog output is set in gnome-volume-control
- AC3 output of VLC should be sended instead of the digital stereo output of pulseaudio

More tests to be describe/to do :
- configuration of asound to encode the sound of application through ac3 in asound.conf (this may help : http://pulseaudio.org/ticket/655 and http://pulseaudio.org/ticket/570) and test application that use 5.1 output throught pulseaudio
- configure multimedia backend like gstreamer to pass-through AC3 directly to alsa
- use AC3 output in VLC

[tomeq_ (t-glowacki)]

I have exactly the same problem here. I'm unable to produce any AC3/DTS output out of S/PDIF interface. Only PCM digital stereo.The same thing happened in 9.04 an 9.10 release.

$ aplay -l
**** Lista PLAYBACK urządzeń ****
karta 0: Intel [HDA Intel], urządzenie 0: AD198x Analog [AD198x Analog]
  Urządzenia podrzędne: 1/1
  Urządzenie podrzędne #0: subdevice #0
karta 0: Intel [HDA Intel], urządzenie 1: AD198x Digital [AD198x Digital]
  Urządzenia podrzędne: 1/1
  Urządzenie podrzędne #0: subdevice #0

$ lsb_release -rd
Description: Ubuntu lucid (development branch)
Release: 10.04

[Id2ndR (id2ndr)]

Just for information to those who encounter this trouble: you can get AC3/DTS output working on VLC and SMplayer by using ALSA directly:
- VLC : chose "use S/PDIF if possible" and "Alsa" as output. If you've got several sound card, then chose "show settings" -> "ALL" at the bottom, chose Audio->output modules->ALSA and then chose the correct sound card.
- SMplayer : open preferences->General->Audio. Then chose the correct alsa sound card (not just alsa) and enable "AC3/DTS passtrough S/PDIF".

I can't get it working with Totem even choosing ALSA output on gstreamer-properties because gstreamer output still is redirected to pulseaudio doing this.

[tomeq_ (t-glowacki)]

Unfortunately your method doesn't work and never worked before, since I remember.

SMplayer ends up with an mplayer error "[format] Sample format big-endian AC3 not yet supported" no matter what you change in mplayer config (like disabling audio equalizer).

VLC is crashing my... amplituner. I'm getting no sound and speakers setup icons on the amp flashing constantly :)

[Id2ndR (id2ndr)]

Maybe you can try with an other media (dvd or file) that use DTS or Dolby sound instead of AC3. In my case my external amplifier doesn't support AC3 but support the two others.

[madbiologist (me-again)]

Does gst-plugins-good0.10 0.10.22-1 (available in Debian testing) fix this?

I contains the following new feature:

* directsoundsink: Implement SPDIF support for AC3

Note that if you want to try this you will first need to update GStreamer core/base to >= 0.10.29

[tomeq_ (t-glowacki)]

It's not amp's fault, it supports AC3. It decodes the same streams on Win7 on the same PC flawlessly.... Still cannot get any DD/AC3/DTS whatever you name it "surround sound" from my files using any of available players...

I'll try gst-plugins-good0.10 0.10.22-1 but this is far from optimal solution...

[Groening (vonbehren-c)]

I have the same problem, neither AC3, DTS nor DD works through IEC958!
"aplay -D iec958:CARD=SB,DEV=0 DEMO2_DTS.wav" does though...

[Groening (vonbehren-c)]

installed this ppa without changes : ppa:gstreamer-developers/ppa
(https://launchpad.net/~gstreamer-developers/+archive/ppa)

no changes at all using gst-plugins-good0.10 v 0.10.23-4~lucid1 so I switched back

[Samuli Kärkkäinen (skarkkai-ubuntu-launchpad)]

In case someone is having this problem with mplayer, it can be worked around as following at least on my Ubuntu 10.04:

mplayer -ao alsa -ac hwac3 file.avi

[David Guest (david-guest)]

This is still an issue in 10.10 as well. As other people have commented, you can use ALSA directly and it will work. This still needs to be fixed though.

[Luke Yelavich (themuso)]

Work is going on upstream to address this issue, but is not considered stable/ready enough yet for maverick. WIth any luck, natty should have this functionality.

[Jason Osbourne (it-blows)]

Hi! This is my first time posting here (hope this is in the right thread).

I'm currently running Ubuntu 10.04.

aplay -l lists:
**** List of PLAYBACK Hardware Devices ****
card 0: NVidia [HDA NVidia], device 0: VT1708B Analog [VT1708B Analog]
  Subdevices: 2/2
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
card 0: NVidia [HDA NVidia], device 1: VT1708B Digital [VT1708B Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 3: NVIDIA HDMI [NVIDIA HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

However, when I go into system>preferences>sound>hardware tab
My only surround options are Analog.
"Digital Stereo Duplex (IEC958)" works fine (over SPDIF), I just have no Digital Surround Options to choose from.

[tomeq_ (t-glowacki)]

I did some testing on 10.10. No surround sound on S/PDIF no matter what I've tried. VLC gives static noise instead of surround sound. mplayer with -ao alsa -ac hwac3 gives nothing, just silence, using Alsa directly in any media player with possibility of S/PDIF passthrough gives silence. Only using pulseaudio defaults gives just stereo output and system sounds working, but on very low volume level.

Everything unmuted, set to 100%, tried and checked two times.....

[pascal (pascal-pascallen)]

For mp3 to work directly with alsa add this in /etc/asound.conf
pcm.!default {
type plug
slave {
pcm "iec958"
rate 48000
format S16_LE
}
}
Resamples the stream to 48000 khz and puts it in "little indian" format so the receiver can pick it up.
In smplayer choose "AC3/DTS pass-through S/PDIF.
SMplayer should play all soundformats now.

Rhytmbox should play.

No sounds threw pulse.
IEC958 in pulse is shit.

Skype won't work. Uses pulse audio. Which dislikes a digital stream to your receiver.
No system sound either. Nice and quiet.
Don't think support will be implemented for a long time to.

[Kevin (kkd)]

Here is what works for me:

Use pasuspender to temporarily stop pulseaudio and let vlc/mplayer access the sound card directly.

pasuspender -- vlc yourfile.avi

[madbiologist (me-again)]

Is this problem still occurring on Ubuntu 11.04 "Natty Narwhal"?

[tomeq_ (t-glowacki)]

As far as I testedrecently it is still there, and still no support for digital multichannel output in sound control panel.

[madbiologist (me-again)]

The pulseaudio part of this bug has been fixed in Ubuntu 11.10 "Oneiric Ocelot" thanks to the update to pulseaudio 1:1.0-0ubuntu1.

Currently, the only client to support passthrough output is the GStreamer PulseAudio plugin. This will be available in the next release (0.10.31) of gst-plugins-good. Once this is installed, you should be able to have passthrough output just work with Totem and most other players that use playbin2.

See http://pulseaudio.org/wiki/Passthrough for more info on passthrough configuration.

[David Henningsson (diwic)]

AC3 Passthrough was initial supported in Ubuntu 11.10, and with 12.04 we can also set it up using pavucontrol. I am however a little unaware of which client applications that supports this new functionality.