> >16 frames per cycle! yow! this h/w can really do that? > > > you can even go down to 2 frames/cycle but obviously everything below 64 > is not really practical with my single-cpu 450 MHz system. 16 can run > in perfect sync for a few seconds until the kernel in one of its ignorant > moods decides to block the audio thread for a while :(
Since the number of frames/cycle directly determines the amount of time the computer has for performing rt dsp, there is probably no reason to want to go below 64 frames. However, if you are simply interested in recording without performing dsp, the lower the better. I have just begun using a fostex D1624 hard disk recorder. It has 2 adat ins, 2 adat outs, 8 analog ins, and 16 analog outs (similar to the original design of ardour). By pre-recording to track 1 then routing analog out 1 to analog in 2, and adat out 1 to adat in 2, then playing back track 1 while recording track 2 from the analog input and track 9 from the digital input, then transferring the whole thing into my daw, I measured 87 samples of latency on track 2 and *20* samples of latency on track 9. This is a true full duplex experiment. Either fostex has implemented capture offset or they use 10 frames/cycle. The fact that latency on the digital ports was >0 suggests that they don't perform capture offset. Tom
