[pulseaudio-discuss] module-remap-source, module-virtual-source, and latencies

[Georg Chini]

Hi,

re-reading, it seems that you don't want to mix your microphone with 
some application
data, but just send the application data to Chrome. Without !661, you 
would use
module-remap-source with the master pointing to the monitor of a null 
sink, with !661
you have the additional option of using module-null-source and let 
module-remap-source
create your sink with the uplink_sink parameter.

Regards
        Georg

On 17.04.22 11:44, Georg Chini wrote:
> Hi,
>
> module-virtual-source is only an example of how a filter source should 
> be implemented and
> is very rarely used. Module-remap-source is intended to be used if you 
> want to change the
> channel map of your source. Module-remap-source has much less 
> overhead, so it is probably
> the better option for your use case.
> On the other hand, module-virtual-source provides the uplink_sink 
> option, which creates a
> sink that is mixed into the virtual source, which means you would not 
> need the null sink.
>
> If you are able to compile your own pulseaudio, you might want to try
> https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/661
> This MR generalizes the uplink_sink feature so that you can also use 
> it with module-remap-sink
> which should provide the lowest possible latency.
>
> Regards
>        Georg
>
> On 17.04.22 06:48, Chase Lambert wrote:
>> Hi,
>>
>> I'm trying to make a low latency Virtual microphone. What that means 
>> is I make a null sink, and then a module-virtual-source 
>> or module-remap-source that has a master pointing to the sink's monitor.
>>
>> Then I can write to that sink, and get data to show up in this 
>> virtual microphone.
>>
>> I've found that module-remap-source has a lower latency 
>> than module-virtual-source, (~400ms lower it seems), but I don't have 
>> any idea why. And more generally -- what is the difference between 
>> these two modules? I looked at their source and also the git history, 
>> but that didn't clear much up for me.
>>
>> Also, is this the best way to make a low latency microphone? I have 
>> an application that I want to send data to Chrome, with as low 
>> latency as possible. Chrome operates directly with pulseaudio[0].
>>
>> Thanks,
>> Chase
>>
>> [0] 
>> https://source.chromium.org/chromium/chromium/src/+/main:media/audio/pulse/audio_manager_pulse.cc 
>> <https://source.chromium.org/chromium/chromium/src/+/main:media/audio/pulse/audio_manager_pulse.cc> 
>>
>
>