Michel Pelletier wrote:I do know USB and libusb and the key in this case is how bulk
> I'm expecting that there will be no reliable correlation.
transfers are scheduled on the bus - namely optimized for throughput.
Bulk transfers fill whatever bus time is free up to the maximum
throughput the device can handle.
And even if we imagine that you could have two host controllers with
a synchronized schedule (not possible without rewriting the kernel
USB stack) you still don't know what happens inside the USB device,
there is no guarantee that it doesn't introduce jitter too.
USB is not a low latency synchronized interconnect, it is optimized
for throughput.
Reliable scheduling over USB *is* possible, but not using bulk and
not with too high throughput.