[pulseaudio-discuss] [PATCH]: High-definition audio pass-through support

[Kelly Anderson]

On 11/21/2011 03:35 AM, David Henningsson wrote:
> On 11/17/2011 10:14 PM, Kelly Anderson wrote:
>> Hi,
>>
>> I finally got around to working out the kinks to pass-through
>> high-definition audio
>> in Xbmc. Funny how long it took me to get back to it. I was 
>> re-reading some
>> emails on the list from way back in March and one of the emails turned
>> me on to
>> a proper solution. One thing that I wasn't able to do was to get 
>> PulseAudio
>> to pass-through 8 channel audio when the device's sink was set as
>> hdmi-stereo.
>>
>> So I patched PulseAudio 1.1 for hdmi-surround-71 and lo and behold it
>> worked.
>> Here's a patch, hopefully we can get this added in the next official
>> release
>> of PulseAudio. I know that there are quite a few Xbmc users that have
>> been anxiously
>> waiting for high-definition audio pass-through to work correctly. Of
>> course if someone
>> has a better solution, that would be fine too.
>>
>> --- ./src/modules/alsa/mixer/profile-sets/default.conf.orig 2011-10-20
>> 06:54:16.000000000 -0600
>> +++ ./src/modules/alsa/mixer/profile-sets/default.conf 2011-11-17
>> 02:16:00.038900536 -0700
>> @@ -173,6 +173,12 @@ channel-map = left,right
>> priority = 4
>> direction = output
>>
>> +[Mapping hdmi-surround-71]
>> +device-strings = hdmi:%f
>> +channel-map =
>> front-left,front-right,rear-left,rear-right,front-center,lfe,side-left,side-right 
>>
>
> I've been experimenting with enabling such stuff in Ubuntu, but never 
> got any positive or negative feedback about it. FYI, I'm attaching 
> what we're shipping for Nvidia and Intel (as part of the jack 
> detection stuff) in Ubuntu 11.10.
>
> And Colin, you're right: this isn't passthrough, this is multichannel 
> PCM.
>
It's not specifically pass-through, but high-def (i.e, DTS-HD) 
pass-through requires an 8 channel mapping.  I've got Xbmc/PulseAudio 
pass-through working well.  It passes low bit rate data through as 2 
channel and high bit rate data as 8 channel.  Specifically what I have 
to do in the Xbmc/PulseAudio code is switch the sink to 8 channels when 
requiring high bit rates and switch back to 2 channels for standard bit 
rates.  The last couple of commits pertain to the 2/8 channel switching.

git://github.com/cbxbiker61/xbmc.git