For pulseaudio what does tsched do (and what are the defaults)?

Solution 1:

There is a nice (technical) discussion here :

http://www.alsa-project.org/~tiwai/lk2k/lk2k.html

What's Sequencer?

The role of sequencer =
Delivers events at the right time (sequence) to the right destination (device).

So this has to do with how the kernel manages your hardware , in this case your sound card. Some sound cards (commonly Intel ones) need real time sqeuencing.

The Arch Wiki's page on PulseAudio/Troubleshooting says:

The newer implementation of the PulseAudio sound server uses timer-based audio scheduling instead of the traditional, interrupt-driven approach.

Timer-based scheduling may expose issues in some ALSA drivers. On the other hand, other drivers might be glitchy without it on, so check to see what works on your system.