[pulseaudio-discuss] can rewindings in the null sink produce noises in programs recording its monitor?

[wellington wallace]

Hi! PulseEffects developer here again.

Like the title says I'd like to know if rewinds can cause crackling noises
when we are recording from a null sink monitor. In PulseEffecs I use the
plugin pulsesrc from GStreamer to record the null sink monitor and whenever
there is a change in the null sink volume or in the volume of a sink input
playing to the null sink I can here noises. Looking at Pulseaudio's logs I
can see lines with:

[null-sink] module-null-sink.c: Requested to rewind 3528 bytes.
[null-sink] sink.c: Processing rewind...
[null-sink] sink-input.c: Have to rewind 2840 bytes on render memblockq.
[null-sink] sink-input.c: Have to rewind 1420 bytes on implementor.
[null-sink] source.c: Processing rewind...
[null-sink] module-null-sink.c: Rewound 2840 bytes.
[pulseaudio] module-stream-restore.c: Storing volume/mute/device for stream
sink-input-by-media-role:music.
[pulseaudio] protocol-native.c: Client spotify changes volume of sink input
Spotify.

whenever the application volume is changed. At the same time they are shown
I can hear cracklings. So it seems related. I noticed that forcing pulsesrc
to use lower latencies help but do not fix the problem. Changing volumes
with pulsesrc latency-time parameter set to 1000 us produces less noises
than when it is set to 10000 us.

I tried my best to see if there is anything I can do on my side to remove
this noise I found nothing. Is that how things are or is there anything
that can be done to remove this noises?

Best regards,

                  Wellington

-- 
Prof.° Wellington Wallace Miguel Melo

CEFET/RJ Uned Nova Iguaçu
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