The key to remember is that liquidsoap is not develop based on realtime priority but on buffers and clocks.
If you are using both the inputs and outputs then make sure your script do not have conflicts with clocks that concerns crossfades ,fallback and rotations.
you will want to read this
http://savonet.sourceforge.net/doc-1.1.0/clocks.html
Here is a solution
Here is some references
https://forum.sourcefabric.org/discussion/16077/alsa-underruns-and-mp3-stream-issues/p1
https://forum.sourcefabric.org/discussion/14678/endless-stuttering-alsa-frame-with-liquidsoap/p1
https://forum.sourcefabric.org/discussion/16245/underrun-maybe-it-helps-someone-else/p1
Voisses
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