i'm trying to pin down a crackling audio issue that, the more i dig into, the more things i find that are possibly at fault and the more it confuses me. firstly i should mention that i run gentoo and all packages are compiled with gcc 6.4/7.2 -march=znver1. i haven't yet tried to reproduce the issue on another distro but i will try and do so when i find the time. my cpu is a ryzen 5 1600 and the codec is a realtek alc892. pulseaudio is compiled with +realtime for rtkit. usually pulse sound output works fine in firefox, spotify, mpv, but when i join a voice channel in the linux native version of discord all output and, i am told, the input heard on the other end, sounds crackly and horrific and the crackling rises and falls with the actual sound. if you aren't familiar with discord, it's a proprietary chat service of which the desktop client is a web application that uses webrtc and uses electron which through chromium i believe uses libpulse directly. when i stop the audio by either leaving the channel or pausing music, the last heard sound plays twice. when i leave the channel though all audio returns to normal. i set the loglevel to debug in daemon.conf and i saw pulse crying out about buffer underruns. however, the crackling only persists temporarily, and resolves itself in a few minutes. adding tsched=0 to module-udev-detect removed the initial crackling but introduced a staticky noise in the microphone input. interestingly the amount of time it took to resolve itself depended on the running kernel. very unscientifically after a couple of kernel upgrades i noticed that a linux-ck kernel seemed to resolve itself in more time than a mainline kernel, and that changing the tickrate to 1000hz reduced the amount of time to less than either of the last two kernels. this and that it works with tsched=0 caused me to suspect timer scheduling was possibly an issue. the other thing that i thought of is that activating resampling causes the crackling since pulse logs that resampling gets activated when i join the channel and the crackling stops when i leave. finally i decided to instead try running discord inside chromium, and it works perfectly. at this point i believe the root of the issue could be in either pulse, libpulse, discord, discord's version of electron or in fact revert to the alsa driver, and i'm leaning more towards an issue with build options/configuration of pulse. i'm happy to provide any more logs and run any more tests if needed.
