Hi, I'm writing an USB Video Class Driver (UVC) to use the DaVinci EVM as a video class device.
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? Section 5.6.4 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? Any help or direction are much appreciated. Thanks in advance! Patrik [1] -YUY2 (4:2:2) at 30fps -video frame size: 320*240*2 (uncompressed) = 153600 bytes -bInterval (sampling rate): 125us -> 8000 uframes per second -8000/30fps = 266 uframes/video frame => 240 uframes per video frame with payload of 640 byte + 2 byte UVC header (the video frame size isn't divisible by 266) => 26 zero-length packets!? ------------------------------------------------------------------------- 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 _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
