Curious slow audio fade-in with certain USB audio card ... SDL-related?

[Harald Albrecht]

Hi,
here's a difficult question, I couldn't solve so far despite extensive research. Maybe someone here from devs/users can help?
Some weeks ago I got myself a Steinberg UR22mkII USB audio mic preamp+playback for recording voice overs. So far, I were using a more bulky Behringer 12chan USB audio mixwr with mic preamps.
I'm noticing a strange audio behavior when using the UR22mkII in Kdenlive, which I don't see in Audacity: whenever stopping playing the project timeline, and then a few seconds later restarting it, there's a 1s-2s clearly audible audio fade in. This doesn't happen with the Behringer. This fade in basically makes editing and arranging audio clips impossible. For reference, when I'm using the Steinberg UR22mkII with my Android tablet to record audio, there's no such unwanted audio fade-in, and playback immediately is at the correct level.
Could the unwanted fade be related to how MLT/Kdenluve use SDL?
Yes, my question may, erm, sound strange. But after checking drivers, aufio setup, et cetera, this is the best educated guess I can make at the moment. Maybe the devs can, erm, chime in?
Best regards, Harald
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