Video playback from Instagram stalls on Firefox when selecting a USB DAC via pavucontrol

[GitHub issues - opened <github@alsa-project.org>]

alsa-project/alsa-lib issue #503 was opened from RJVB:

This is a very weird one, and I'm not certain where the actual bug is but hope that the devs here might have an idea. The context is "retro-computing" though...

'm setting up a refurb G3 Elitebook (6th Gen i7 with HD520 GPU) with a retro install based on a self-updated "FrankUbuntu" 14.04LTS. 5.15.95 xanmod kernel, mesa v21.3.9, recent intel-media and intel-vaapi libraries, pulseaudio 17 and current alsa-libs. I'm hesitant to update libc so that has remained on 2.19 .
Video works and uses the HD driver from the intel-media package, but there is an issue with playback of Instagram videos. As soon as I select a USB DAC (e.g. via pavucontrol), playback halts but resumes as soon as switch back to the internal audio interface. Or to a USB audio->bluetooth dongle (= an audio interface that probably contains neither DAC nor amp but sends the incoming PCM data to a BT radio). The issue disappears when I boot an older (5.6) kernel but also when I boot a newer distro (Devuan "Chimaera") with the same kernel (but earlier Alsa and pulseaudio versions and a newer libc).

The only thing hinting at the possible error that I get appears in the syslog, from pulseaudio:
```
[ [alsa-sink-USB Audio] alsa-sink.c: Resume failed, couldn't restore original fragment settings. (Old: 576000/288000, New 529200/264600)]
```
That suggests something goes wrong in `pa_alsa_set_hw_params()` but could that explain the video halting too?

Fun fact: with alsa 1.2.15.2 the issue only affected IG "stories"; with 1.2.15.3 all videos are affected.

Video playback is fine on all other sites I tested (YT, Prime Video) and also in my standalone multimedia player (QMPlay2), all routed directly via PulseAudio or via ALSA's pulseaudio plugin.
Sadly there are no recent enough Chromium builds that I can test (other than via flatpak).

I'm aware that this could be a bug in PulseAudio or even Firefox, but given the intricate dependencies on hardware, kernel and possibly ALSA versions I thought I'd ask here first as I expect there'll be more devs who might be able to (guide me) put a finger on the underlying issue.

Issue URL     : https://github.com/alsa-project/alsa-lib/issues/503
Repository URL: https://github.com/alsa-project/alsa-lib