It does not compile: replace rechne with callp_ptr or skip callp_ptr entirely by using mpv_set_wakeup_callback(ctx,(void (*)(void *) )callp,MY_CXT.callback);

When you get it compilable add OPTIMIZE => '-g' to your Makefile.PL and compile. Then run gdb -q --args perl <test-program.pl> For more info on debugging, see https://stackoverflow.com/questions/50643536/how-do-i-trace-through-an-xs-so-file

I have no idea about threads and XS but I would eliminate all the assignment from incompatible pointer type warnings before investigationg in that direction.

bw, bliako