run 'pactl list sinks' and look at 'Latency'. You'll see a value in usec displayed for your currently active output. Take this value, devide by 1000 and pass it to snapclient as the latency parameter, e.g. for a value of 30000 usec in your pulseaudio playback latency you run 'snapclient --latency=30' and everything will be in sync again.
thanks for that, unfortunately it just says 0 usec in the pactl list sinks command:
Latency: 0 usec, configured 48219 usec - setting it to 48 is too little, I have put it up to the maximum of 100 and it's almost in sync now, although not 100%. I guess some more msec would be necessary