[pulseaudio-discuss] How to control the right and left channel for a specific application using CLI ?

[01ivier at labomedia.org]

Le 2020-11-04 18:28, Tanu Kaskinen a écrit :
> On Wed, 2020-11-04 at 14:56 +0100, 01ivier at labomedia.org wrote:
>> Le 2020-11-04 01:17, Arun Raghavan a écrit :
>> > On Tue, 3 Nov 2020, at 7:09 PM, 01ivier at labomedia.org wrote:
>> > > Le 2020-11-03 23:49, Arun Raghavan a écrit :
>> > > > On Tue, 3 Nov 2020, at 5:28 PM, 01ivier at labomedia.org wrote:
>> > > > > Hello again,
>> > > > >
>> > > > > I want to know if there is a way, still in command line, to control
>> > > > > the
>> > > > > right and left volumes of an application.
>> > > > > With Pulseaudio Volume Control, you can click on the lock icon related
>> > > > > to a launched application, and two sliders appear to do so.
>> > > > > Is it possible in CLI ?
>> > > > >
>> > > > > My goal is to run two applications on the same card, but to assign
>> > > > > right
>> > > > > channel for one and left for the other.
>> > > > >
>> > > > > Possible complication : the output of my application is in mono and
>> > > > > with
>> > > > > Pulseaudio Volume Control I don't get the two sliders if I click on
>> > > > > the
>> > > > > lock icon.
>> > > >
>> > > > You can use pactl to do this:
>> > > >
>> > > >   pactl set-sink-input <sink input index> <volume for channel 1>
>> > > > <volume for channel 2> ...
>> > > >
>> > > > You can look up the sink input index and channel map for channel order
>> > > > with:
>> > > >
>> > > >   pactl list sink-inputs
>> > > >
>> > > > -- Arun
>> > >
>> > > Hello Arun and thanks for the quick answer.
>> > >
>> > > It's exactly the command I was looking for.
>> > > Unfortunately, as I thought, it doesn't work in my case because my
>> > > output is in mono.
>> > > Here's what I get:
>> > > Failed to set volume: You tried to set volumes for 2 channels, whereas
>> > > channel(s) supported = 1
>> > >
>> > > I can't change the output of the software.
>> > > Is there possibly a way to create a virtual stereo output from the
>> > > mono
>> >
>> > Yup, check out module-remap-sink:
>> > https://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/User/Modules/#module-remap-sink
>> >
>> > -- Arun
>> 
>> Thank you,
>> 
>> Your answer is good... I just asked the wrong question... Sorry...
>> 
>> What could help me, in my case, is to remap the mono sink-input (the
>> ouput of my application) into a stereo one, so that I could control 
>> the
>> volume of each channel with set-sink-input.
>> Maybe I missed something but module-remap-sink doesn't like to do it.
>> 
>> I tried to use module-remap-source but "Name or index of the master
>> source" seems to concern sink listed with "pacmd list-sinks" not 
>> "pactl
>> list sink-inputs".
>> 
>> Is there a solution to get a stereo sink-input from a mono one ?
> 
> There's no way to change the channel map of a sink input. It sounds
> like you could load one remap-sink for the left channel and one remap-
> sink for the right channel, and point the application to the
> appropriate remap-sink.

A BIG THANK YOU !
It perfectly works !

I'm going to try in few days with many more sound cards but is there a 
known limit to the number of sink which can be create this way ?
Is 40 something completely crazy to think about ?

Thanks again for your helps.

°1ivier