[alsa-devel] USB-Audio.conf routing and dmix

[Alexander E. Patrakov]

15.05.2015 10:53, Alexander E. Patrakov wrote:
> 15.05.2015 07:07, sylvain.bertrand at gmail.com wrote:
>> On Wed, May 13, 2015 at 11:32:15AM +0000, sylvain.bertrand at gmail.com
>> wrote:
>>> On Wed, May 13, 2015 at 11:24:32AM +0200, Clemens Ladisch wrote:
>>>>>> I linked the surround51 and surround71 pcms with the
>>>>>> 'disable-able' dmix
>>>>>> section from the default pcm.
>>>>
>>>> These devices are not supposed to use plug or dmix.
>>>
>>> Ok. Then, there is no pcm to output 5.1 sound with dmix.
>>>
>>> Does it mean that the application is in charge to build a alsa-lib
>>> pipeline
>>> with dmix pcm and surround51 pcm, in order to let other applications
>>> output 5.1
>>> sound at the same time?
>>
>> Then what is the "Right"(tm) way to do that?
>>
>
> [this is my personal opinion, in no way official]
>
> The right way seems to be to use PulseAudio. Pure ALSA, in its default
> configuration, just does not support mixing 5.1 audio, on any card. This
> default cannot really be changed, because there are many people who use
> 5.1 cards for output to stereo headphones only, i.e. who need automatic
> downmixing if an app (such as VLC) starts a 5.1 stream. The default
> plug/dmix setup provides such downmixing.

I need to test things before posting. This is wrong, plug/dmix does not 
include the extra channels in the stereo mix.

> As an application developer, just tell your users "your default device
> needs to support 5.1, see you there", as mpv developers did. This will
> be the case either with PulseAudio or with a hacked .asoundrc.

This is still my position.

-- 
Alexander E. Patrakov