Dne 16.8.2011 22:41, Torsten Schenk napsal(a):
Hi Pierre,
- The device/driver sends per urb a constant number of packets (as
you already also discovered). The number of samples per packet differ however (+- 1 sample per packet). I accuse the asynchronousity between the urb interval and the sound card's internal clock for this fact. The device expects the driver to send back an urb with exactly the same structure. The device produced crackling noise if the samples per packet were not equal. I cannot say to what extend this is true (i.e. if you could wait some packets until catching up the difference without producing crackles)
Could we attribute this to the adaptive mode and PLL striving to produce steady stream of well-timed samples to the DAC? IMHO the lower variation in samples per packet, the lower jitter of the PLL-recovered clock.
Pavel.