Hello, It seems that clock_thread may be setting its timestamp incorrectly as a result of an incorrect setting for samples_per_frame in pjmedia_clock_create: Shouldn't clock->samples_per_frame = samples_per_frame; be this instead? clock->samples_per_frame = samples_per_frame / channel_count; Cheers, Yann ps note that if anyone is interested in correct PortAudio timestamps for AdaptingInputOnlyProcess you may want the -r1408 patch in portaudio/trunk/src/common/pa_process.c from 03/13/09 12:41:39