[pulseaudio-discuss] {PATCH][RFC] AC3 passthrough support

Tanu Kaskinen tanuk at iki.fi
Sat Jul 10 03:13:13 PDT 2010

On Sat, 2010-07-10 at 08:05 +0000, Michael Rans wrote:
> Even with these "hacks", I found that sometimes I see:
> I: module.c: Unloading "module-alsa-sink" (index: #4).
> D: module-always-sink.c: Autoloading null-sink as no other sinks
> detected.
> After I see that, the sink disappears and cannot be selected any more
> in sound properties.
> 1. Does the ac3-iec958 profile resolve any of these issues?

What's "the ac3-iec958 profile"? The iec958-ac3-surround-* mappings that
currently exist in pulseaudio use the a52 alsa plugin, which may or may
not work with Colin's patch[1]. (It didn't work for Colin.)

> 2. Jack has ac3jack. What would be the pros and cons of doing the AC3
> encoding in Pulseaudio instead of in Alsa?

I think it would make sense to do AC3 encoding in Pulseaudio, although
in theory I don't see what difference it would make. Maybe it's somehow
benefical to handle all the buffering inside Pulseaudio. If there are
timing related bugs in the a52 plugin, as Colin seems to think there
are, then it's also a matter of who volunteers first: a person who knows
how to fix the a52 plugin, or a person who knows how to hack AC3
encoding support into Pulseaudio.

[1] https://tango.0pointer.de/pipermail/pulseaudio-discuss/2010-June/007311.html

Tanu Kaskinen

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