Après recherches, c'est en fait sur les playback() qu'il est recommandé (mais pas obligatoire) d'avoir un timer correct:
Dahdi, mais pas forcément son timer (qui peut provenir aussi de timerfd ou pthread), est nécessaire aussi pour les conférence avec MeetMe:The only functionality that requires internal timing is IAX2 trunking.
It may also be used when generating audio for playback, such as from a file.
One common misconception which has arisen is that since
timing can be provided elsewhere, DAHDI is no longer required for using the
MeetMe application. Unfortunately, this is not the case. In addition to
providing timing, DAHDI also provides a conferencing engine which the MeetMe
application requires.