Hi Benny, I compiled pjsip (svn trunk) with visual express 2005. I just changed in pjmedia/include/pjmedia/config.h the following line to use direct sound : # define PJMEDIA_SOUND_IMPLEMENTATION PJMEDIA_SOUND_WIN32_DIRECT_SOUND /* define PJMEDIA_SOUND_IMPLEMENTATION PJMEDIA_SOUND_PORTAUDIO_SOUND*/ When I run pjsua_vc8d with this option --play-file file.wav I obtain this message : 08:30:54.713 wav_player.c File player 'file.wav' created: samp.rate=22050, ch=1, bufsize=4KB, filesize=5977KB 08:30:54.713 pjsua_media.c Unable to add file to conference bridge: Invalid operation (PJ_EINVALIDOP) [status=70013] 08:30:54.729 pjsua_core.c Shutting down... If I didn't define play-file option, and I make a new call, I obtain the following message : 08:54:16.432 pjsua_call.c Unable to create media session: Invalid operation (PJ_EINVALIDOP) [status=70013] before I can read in the log file : 08:54:04.338 dsound.c DirectSound initialized, found 5 devices: 08:54:04.338 dsound.c dev_id 0: Pilote de capture audio principal (in=2, out=2) 08:54:04.338 dsound.c dev_id 1: C-Media Rear Panel Audio (in=0, out=2) 08:54:04.338 dsound.c dev_id 2: Lecture sur modem n? 0 (?mul?) (in=0, out=2) 08:54:04.338 dsound.c dev_id 3: C-Media Rear Panel Audio (in=2, out=0) 08:54:04.338 dsound.c dev_id 4: Enreg. sur modem n? 0 (?mul?) (in=2, out=0) 08:54:04.338 pjlib select() I/O Queue created (00CBCC0C) 08:54:04.338 conference.c Creating conference bridge with 32 ports I obtained the same messages with portaudio. Do you have an idea to resolve my problem Best regards Samuel