Support AC3 Passthrough

[FireRabbit]

It would be great if PulseAudio could pass AC3 audio streams directly to a SPDIF/IEC958 alsa device without modifying them. This enables surround sound receivers to function properly.

I could dig up some free 5.1 channel sample files if this would help.

Thanks!

[X04D]

What's the status on this? Is true passthrough available yet?

[candrews]

Another vote for this one!

[Garlic]

I vote for this, too

[hackeron]

Hmm, you can't do passthrough in pulseaudio? -- Looks like I'm moving back to plain alsa for now.

[hackeron]

Why is the only way to support 5.1, 7.1 or any other kind of surround sound changed to a low priority feature?

[coling]

Pulse supports surround just fine. Just not via AC3 passthrough.

[hackeron]

OK, how would I get surround sound through SPDIF (optical or coaxial) with pulseaudio?

[coling]

Replying to hackeron:

OK, how would I get surround sound through SPDIF (optical or coaxial) with pulseaudio?

I'd ask this on the PA mailing list as Trac is not the correct medium to discuss this. The short answer is load an alsa sink with a device=spdif:0 or something like that (/me has not tried). If you look at the ML archives, there are people discussing exactly this over the last few days (and me jumping in with an incorrect comment to muddy the waters ;))

[coling]

My last comment here: You probably want to see Jim Duda's thread: "0.9.8 - Invalid value for card". HTHs

[lennart]

SPDIF doesn't support uncompressed audio with more than two channels. Only AC3 via SPDIF supports more than two.

For analog audio however, we do support surround just fine.

[ari]

+1 for AC3 passthrough support over SPDIF in pulseaudio. This is the only feature I really miss in pulseaudio in my soon-to-be linux media center.

When playing back a movie that has ac3 / dolby audio and spdif is being used, and there is no other audio stream active (no mixing) then it would be great for pulseaudio to let the ac3 stream go through spdif with no decoding/encoding overhead... which I'm guessing would affect the stream quality.

[fa5hion]

16 months since last comment. Any estimate on when this feature is going to be implemented? AC3 passthrough with PA would be awesome. Lennart?

[ppc52776]

Any new change about this issue?

[Zajec]

Lennart sounded quite optimistic for me about this feature:

http://www.mail-archive.com/pulseaudio-discuss@mail.0pointer.de/msg04936.html

[andee_em]

The lack of this feature makes using Fedora, Ubuntu et al useless as the basis for custom multifunction AV/Internet Server machines. The maintainers have decided to make pulseaudio mandatory. This has now set my project back considerably. This feature request is now the primary red line for me.

[mdelorme]

we can see that it is now a work in progress http://git.0pointer.de/?p=pulseaudio.git;a=commit;h=9b6c84ad6e572854f199379177226e24c317d0d8 For the moment the best I found to play 5.1 channel on SPDIF/IEC958 is to mute PA thanks to pavucontrol and set my movies player (gxine) to passthough by avoiding using PA

[mdelorme]

This feature is to be done see PassthroughSupport in about 1 mounth or 3 http://colin.guthr.ie/meetings/pulseaudio-meeting/2011/pulseaudio-meeting.2011-02-24-21.02.log.html#l-724

[hadess]

Required for Totem: https://bugzilla.gnome.org/show_bug.cgi?id=331875

[Ford_Prefect]

This is essentially done. The main thing that's left is to add some UI to pavucontrol for the user to tell PA what formats the receiver supports.

[Ford_Prefect]

SuperColin? added the bits to module-device-restore to save/restore formats and UI to pavucontrol. I've hooked this up into alsa-sink and added a command-line interface using pactl.

There's probably some amount of iterating required to make the entire user experience smooth, but all the bits are there to do this now.