On Fri, 19 Jan 2007, Patrik Nagel wrote: > Hi, > > I'm writing an USB Video Class Driver (UVC) to use the DaVinci EVM as a > video class device.
This sounds like you're writing a driver for the host, not the camera. But what you write below contradicts that. > I want to stream with 30fps, so the maximum number of uframes per video > frame is 266. But I do only fill 240 uframes [1] with payload data to > transmit one video frame over the isochronous in-endpoint. What needs > to be done with the remaining 26 requested uframes until the > transmission of the next video frame can start again? In principle the camera can put anything it wants into those packets. But you are constrained by the video class specification. I haven't read that spec, but so long as you conform to it you should be okay. > Section 5.6.4 Of what document? The USB 2.0 spec? > Isochronous Transfer Bus Access Constraints says: > "An isochronous IN endpoint must return a zero-length packet whenever > data is requested at a faster interval than the specified interval and > data is not available." > > So, do I only need to set the payload length of the remaining (but > "unused") packets to zero to keep the frame rate? Must I also omit the > two-byte UVC header? > > Or is there an other way to accomplish the illustrated problem? Provided you remain consistent with the class specification, so that hosts will understand your data format, you can do anything at all. Alan Stern ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
