On Thu, 2 Jun 2011, Soho Soho123 wrote: > >> Soho: in our platform the time precision is 10ms per tick . > > > > In a PC, the time precision is between 1 and 10 ms per tick. But PCs > > also have high-precision timers available; apparently your platform > > does not. Without high-precision timestamps, there's no way to tell > > what's causing your latencies to be so large. > > > soho:???? If your usbmon timestamps were accurate down to microseconds, I could tell whether the latency was caused by ehci-hcd, by uvcvideo, or by something else. > > One other thing you can try: Increase UVC_MAX_PACKETS to 100. > > soho: we will try it later. Could you explation the consideration > about increase uvc max packet? With UCV_MAX_PACKETS set to 32, you get an interrupt and have to submit a new URB every 4 us. That's a pretty high rate. With UVC_MAX_PACKETS set to 100, an interrupt will occur every 12.5 us. The timing requirements will be less strict and the overhead of interrupt handling will be reduced. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
