[pulseaudio-discuss] Passthrough support and sink channel count

[Tanu Kaskinen]

On Tue, 2013-09-10 at 09:47 +0300, Anssi Hannula wrote:
> 10.09.2013 09:08, Tanu Kaskinen kirjoitti:
> > On Mon, 2013-09-09 at 22:14 +0300, Anssi Hannula wrote:
> >> Hi,
> >>
> >> I was looking at using the PA passthrough support (and adding support
> >> for TrueHD, DTS-HD), but it seems there is another issue that has to be
> >> resolved first:
> >>
> >> Pulseaudio passthrough (with ALSA) does not currently work unless a
> >> stereo profile is in use.
> >>
> >> If a HDMI surround profile is in use, the device seems to be permanently
> >> in a 6 channel mode. As passthrough of e.g. 48kHz AC-3/DTS requires the
> >> device to opened in 2 channel 48kHz mode, pa_sink_input_new() will
> >> always fail with "Could not update sink sample spec to match passthrough
> >> stream".
> > 
> > The HDMI surround profile is a 6-channel profile, so it's expected that
> > you can't open the device in 2-channel mode. If you want 2 channels, you
> > need to activate a 2-channel profile.
> > 
> > It would probably be good to change the profile automatically when a
> > passthrough stream appears.
> 
> That could seem a bit confusing to users ("Why does the HDMI sink switch
> to stereo mode if I'm playing a surround DTS stream?"), but OK, better
> than nothing of course.
> 
> I guess the profile would switch back when the stream ends? Otherwise it
> wouldn't seem very nice as the user would have to re-set it after every
> passthrough stream.

Yes, it should switch back automatically.

-- 
Tanu