Ralf Mardorf wrote: > I never tested it myself, however, I remember that it often is mentioned > not to use -n >2. Is there a reason to avoid -n >2 or is t juts a myth? The buffer size is the product of the period size (-p) and the number of periods (-n). A larger buffer size increases latency, but reduces the risk of underruns. A smaller period size _slightly_ increases CPU usage because of the overhead needed for handling a period. Therefore, when optimizing for low latency, one typcially uses two periods and makes -p as small as possible. With USB devices, the period boundaries (where interrupts are supposed to happen) are not necessarily coincident with the USB frame boundaries (where interrupts actually happen). This results in delays (jitter) of up to 1 ms in the timing of period interrupts; with very small buffer sizes, this increases the risk of underruns greatly. So if, e.g., the machine is not able to handle "-p 64 -n 2" reliably, increasing the number of periods to 3 results in lower latency (3*64=192) than increasing the period size (2*128=256). (Using "-p 96 -n 2" would have the same latency, but works only if that particular Jack version allows period sizes that are not a power of two.) Regards, Clemens _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
