route and chmap

route and chmap

[Jonas Holmberg]

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?

BR
/Jonas

Re: route and chmap

[Jonas Holmberg]

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?
> 
> BR
> /Jonas

Re: 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