Hi Paulo, On Tuesday 02 June 2009 17:35:17 Paulo Assis wrote: > Hi, > I think I can add this to guvcview and run some tests, but I would like > some info on the v4l2_jpegcompression struct, especially on the > **jpeg_markers flag, I believe for mjpeg I should set all flags, except > V4l2_JPEG_MARKER_DHT, since huffman tables are not included in the video > stream, is this correct, or it just doesn't make any difference?
It won't make any difference with the uvcvideo driver. The driver ignores the flags on VIDIOC_S_JPEGCOMP and returns V4L2_JPEG_MARKER_DQT only on VIDIOC_G_JPEGCOMP. The DHT, DRI and COM segments are not included in the MJPEG stream, and the APP0 segment is not user-configurable. > Also is the correct aproach a call to VIDIOC_G_JPEGCOMP for filling the > struct and then just change the quality entry and call VIDIOC_S_JPEGCOMP? This is still unclear in the specification. I would assume that drivers will fix the flags if the requested value is unsupported. If you want to make sure you don't modify them, calling G_JPEGCOMP prior to S_JPEGCOMP sounds good. Best regards, Laurent Pinchart _______________________________________________ Linux-uvc-devel mailing list [email protected] https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
