[pulseaudio-discuss] HDMI passthrough request for help

Kelly Anderson kelly at silka.with-linux.com
Fri Feb 18 07:07:39 PST 2011

On 02/18/11 07:41, pl bossart wrote:
>> First of all I patched pulseaudio git with some updates to treat
>> hdmi-passthrough as it does iec958-passthrough.  That seems to work.  I can
>> use paplay to pass a dts-wav file through to the receiver and the receiver
>> triggers into dts mode and plays it.  A native dts file stripped from and
>> mkv movie file on the other hand doesn't play.
>> I made some minor changes to the Xbmc pulseaudio driver so that it does not
>> ignore passthrough requests.  Xbmc's pulseaudio driver assumes (without
>> patching) that passthrough is not available for pulseaudio.  Now I can
>> select the pulseaudio passthrough device.  Xbmc has code in it to manipulate
>> dts streams.
>> The problem is that I can start a movie, Xbmc will select the dts track and
>> play, but the receiver doesn't go into dts mode, but instead just buzzes the
>> speakers.
> Did you actually add the PASSTHROUGH flag when you create the pa_stream?
> When the receiver doesn't lock it's typically when the data was
> modified by the volume control.
> Another possibility is mismatch between frequencies. Make sure the
> sink and the stream sampling frequencies match.

Yeah, I added the passthrough flag.  The code dealing with volume 
control has a conditonal around it to ignore requests when using 
passthrough.  I'll look a bit more a sample frequencies.  I did change 
the default pulse frequency to 48000 in daemon.conf, not sure if that 
was necessary or not.

> Note that we are completely reworking this part, you may want to wait
> 1-2 months before the feature becomes more stable.
> -Pierre
Yeah, I know.  But I need it now! hehe, I've got quite a few blue-rays 
that have been put into mkv's and I just bought a very nice surround 
sound system.

Actually I though working on it now would be beneficial both for pulse 
and xbmc.  Xbmc should be able to rock out as soon as pulse is 
official.  I might uncover something useful to pulse while hacking xbmc.

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