Hi Chase,
let me know the results of your tests. I would especially be interested
in the
difference between using module-null-sink with module-remap-source
and module-null-source with the uplink sink of module-remap-source.
Regards
Georg
On 19.04.22 01:32, Chase Lambert wrote:
Thanks for the replies!
guest271314 - Huh, that's odd that you would see any audio
differences. My stab in the dark guess would be some sort of
PulseAudio resampling? Otherwise I would think the PCM data would be
the same. I'll double check that the audio quality is as expected.
Georg - I can see how that MR could reduce latency, interesting.
I'm kind of just thinking out loud here, but the latency can get very
low (say to 10ms), right? As long as I have small numbers
in pa_buffer_attr, I would think that:
- My application would get a callback from PulseAudio, telling it to
write something
- My application writes something
- Immediately thereafter, Chrome gets a callback to read data
- Chrome reads the data
- There isn't a risk of an underrun here by Chrome, because it will
only get callbacks when data is ready (hazy guess!)
I ask this because my alternative is modifying Chromium and sending
data directly to it over a custom IPC channel. But in theory that IPC
channel should not be faster than PulseAudio. PulseAudio is just
acting as a queue, and ultimately just a form of IPC between my
application and Chrome.
In any case, I'll soon find the answer myself. Thanks!
On Sun, Apr 17, 2022 at 9:13 AM guest271314 <guest271...@gmail.com
<mailto:guest271...@gmail.com>> wrote:
I am not sure about different latencies re module-remap-source and
module-virtual-source. From my testing the quality of audio output
when using a remapped source with getUserMedia() is inferior
compared to getting the raw PCM using pactl or parec with fetch()
on the browser side then using AudioWorklet or
MediaStreamTrackGenerator in Chrome/Chromium to output the audio.
On Sat, Apr 16, 2022 at 9:49 PM Chase Lambert
<chaselam...@gmail.com <mailto:chaselam...@gmail.com>> 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>
