[pulseaudio-discuss] cannot set volume in c++

Tanu Kaskinen tanuk at iki.fi
Sun Jun 5 12:02:48 UTC 2016

On Sun, 2016-06-05 at 10:16 +0200, pfl wrote:
> hello everyone,
> for a raspberrry applicance I need to setup the input volume of the 
> microphone programaticaly
> in c++, I can read the actual value (changed if I change it in the pa 
> mixer), but as I set it, it does not seem to work...
> after I launched my code, I check in the pa panel mixer, the volume is 
> not changed
> below, the sources with their chanels and volumes
> :[0]'alsa_output.usb-0d8c_C-Media_USB_Headphone_Set-00-Set.analog-stereo.monitor''Monitor 
> of Audio Adapter Analog Stereo'(0)=65536(1)=65536SOURCE 
> :[1]'alsa_input.usb-0d8c_C-Media_USB_Headphone_Set-00-Set.analog-mono''Audio 
> Adapter Analog Mono'(0)=26281SOURCE 
> :[2]'alsa_output.0.analog-stereo.monitor''Monitor of bcm2835 ALSA Analog 
> Stereo'(0)=65536(1)=65536|
> so I try to change volume of source index #1
> > voidsetVolume(intindex,intvolume){pa_operation*o;currentVolume.values[0]=volume;if(!(o 
> =pa_context_set_source_output_volume(context,index,¤tVolume,NULL,NULL))){printf("pa_context_set_source_output_volume() 
> failed");return;}printf("new volume: 
> %d\n",currentVolume.values[0]);pa_operation_unref(o);}|
> please can someone help ?

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The problem is that you set the volume for a "source output" rather
than for a "source". A source output means a recording stream, while a
source is a device such as a microphone. Use
pa_context_set_source_volume_by_index() or


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