[pulseaudio-discuss] Crackling audio with Pulseaudio 4.0 and the simple Pulse API.

[Luke Yelavich]

Hey folks.
I've been experiencing some weird  and infrequent crackling of audio with pulse 4, and applications that use the simple pulse API. The crackling tends to happen at the very start of the buffer, causing a varying amount of audio to be audible as noise, or not at all. This doesn't occur when other applications are playing audio at the same time, and it comes and goes, and I can never predict when it might start to happen, or when it will go away. Unfortunately I haven't been able to reliably log this, since it seems to occur very infrequently if not at all whilst being logged with full verbose output.

I haven't really been able to reproduce this problem outside of this single use case, since all the apps I've tried to test to reproduce the problem don't use the simple pulse API. My use case is the GNOME Orca screen reader, using the speech-dispatcher text to speech server, using its pulseaudio backend, with the espeak speech synthesizer. The sample rate of the audio from speech-dispatcher is 22050, and the pulseaudio backend in speech-dispatcher is using the simple pulse API.

The above combination worked just fine in pulseaudio 3 and earlier.

I'm sorry if this sounds vague, and I will keep trying to get a log during the bad audio crackle, but thats the best I have WRT this problem right now. Happy to test other config changes etc to help further narrow down the cause.

Luke