audio_track_set_format
static int audio_track_set_format(audio_track_t *, audio_format2_t *);
error = audio_track_set_format(ptrack, &pfmt);
error = audio_track_set_format(rtrack, &rfmt);
audio_track_set_format(rtrack, &saved_rfmt);
audio_track_set_format(ptrack, &saved_pfmt);