On Tue, 31 May 2011, Soho Soho123 wrote: > Dear Laurent, > ====================================================================================== > Let me explain my problem again. > We use MJPG-streamser to test IP Cam function. the network interface > is WiFi. WebCam is using UVC driver. > We have the issue is the stream will disconnect in a few minutes on > our embedded system. > the reason is : the call back function of uvc urb complete can not > re-submit urb successfully. The error code is "-EFBIG". EHCI driver > think the urb submit is too late. > the ip cam test condition is 1280x720 30 fps via WiFi(802.11n). > the call back function seems take more cpu cycles when itd_complete, > because it decode data and re-submit urb . the call back function is > included in ehci irq path. it may increase irq latency. > Do you have idea about : > is it "must" decode data in uvcvideo complete call back function? > is it "must" re-submit urb in uvcvideo complete call back function? The callback routine must resubmit the URB. In theory the decoding could be delayed. But it would still require the same amount of time. Although the latency might remain low, you would probably find that uvcvideo has to drop some frames every now and then. It's possible that your CPU simply isn't fast enough to keep up with the video stream at this resolution. 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
