route and chmap

[Takashi Iwai]

On Fri, 27 Mar 2020 16:50:13 +0100,
Jonas Holmberg wrote:
> 
> CC Takashi.
> 
> On Thu, Mar 26, 2020 at 02:41:11PM +0100, Jonas Holmberg wrote:
> > Hi,
> > I use the route plugin to copy mono to both FL and FR (front left and 
> > front right stereo) of the slave during playback. When get_chmap() is 
> > called in the route plugin it will call get_chmap() of the slave, 
> > which returns 2 channels with FL and FR positions, and then route 
> > itself returns 1 channel with FL position. But the application that 
> > called snd_pcm_get_chmap() on the playback device expected to get 
> > position MONO instead of FL since the number of channels is 1.
> > 
> > Is the application wrong in not accepting the chmap or should the 
> > route plugin have changed position from FL to MONO? Is it possible to 
> > add something to the config (asound.conf) to make FL become MONO in 
> > the reply of get_chmap() or solve the problem in any other way?

Well, that's a small missing piece in the route plugin
implementation.  It may have a capability to translate the destination
channel map, e.g. by extending the config syntax.

If anyone has a patch proposal, I'm willing to apply :)


thanks,

Takashi