Run-time audio parameters change crashes UltraGrid

[MartinPulec]

Originally posted by @sogorman in https://github.com/CESNET/UltraGrid/issues/336#issuecomment-1722485367

Audio compression crashes on audio properties reconfiguration, steps to reproduce (commit 996d876 required):

$ ffmpeg -f lavfi -i sine=duration=5 -c:a pcm_s32le -t 5 -f lavfi -i testsrc -ar 48000 src2.mp4
$ uv -s embedded -t switcher:fallback -t testcard:fr=10 -t file:src2.mp4 -A opus -a bps=16

Explanation:

1. FFmpeg used to create 5 second input A/V file with 32 bit audio samples
2. using switcher in the fallback mode a. vidcap testcard captures 10 video frames with 16-bit audio b. vidcap file captures 32-bit audio after first 10 frames from testcard (because of the fallback switcher parameter)

Perhaps applicable only on development version, because audio with switcher is more or less usable since #318.

[MartinPulec]

Only BPS seem to be problematic – channel count or sampling rate seem to be fine.