Justin Schoeman wrote: > > Justin Schoeman wrote: > > > > "Gleicon S. Moraes" wrote: > > > > > > Edgard Alexander Sotter wrote: > > > > > > [snip] > > > > > > > someone told me that I have to work with video_buffer struct, > > > > anyone has experience in work with this struct???... anyone has a example of > > > > grabbing image in real time (video)??? using more than one buffer. > > > > > > > > > > I uploaded an attempt to use the double buffers to grab. > > > My primary source of information were the Programming txt found in xawtv > > > tarball. > > > The link is the same: > > > > > > http://planeta.terra.com.br/informatica/gleicon/videodog.html > > > > > > The process looks is: sync buffer one, grab buffer 2, sync buffer 2, > > > grab buffer 1. > > > I hope it helps, sorry but I did it in a hurry, its not the nicest code > > > overthere ... BTW if somebody got some clue to help improve this double > > > buffer grab code, I would thank a lot. Probably I will do a presentation > > > about video processing using linux, and would be very cool if I got some > > > almost-real time processing :-D > > > > > > Regards. > > > > Here is a non-bttv specific example. I no longer use v4l, so I can't > > ... > > > > > Also, please note that to be formally correct, the app must first test > > for streaming capabilities with VIDIOCGCAP, and set the picture format > > with VIDIOCSPICT (before any call to VIDIOCGMBUF is made). > > Sorry - there should also be a VIDIOCSWIN ioctl (I think) to set the > image size. Quoting the v4l API document: > > "To use the mmap interface a user first sets the desired image size and > depth properties. Next > the VIDIOCGMBUF ioctl is issued." The only way I know of to set the > size and depth parameters is the SWIN call??? VIDIOCSPICT and VIDIOCSWIN are only used for setting up an overlay window, not for memory capture. For doing memory capture the size/format are passed to each VIDIOMCAPTURE call. If anyone is wiling to host it, I have a thin C wrapper for V4L and some simple examples showing how to to streaming mmap capture displayed in an X window, that might be useful to people starting out. Ben
