In lists.linux.v4l, you wrote: > On 26 Jan 2001, Gerd Knorr wrote: > > (VIDIOC_S_FMT). Then ask the driver using REQBUFS for buffers, > > indicating whenever you want to use your own userspace memory buffers > > or mmap() the memory from the driver. For the second case you'll > > have to mmap() the buffers here. The you can queue the number of > > buffers VIDIOC_QBUF which you aquired using REQBUFS, start capture > > with VIDIOC_STREAMON, get/requeue buffers using VIDIOC_DQBUF/VIDIOC_QBUF > > until you are done, and finally call VIDIOC_STREAMOFF and REQBUFS(0). > > munmap() the driver memory if needed. > > For a bt848, when are the risc program(s) generated? When REQBUFS is called, > or when VIDIOC_QBUF is called? QBUF. > > Packed pixel formats can use the v4l2_pix_format.bytesperline to > > specify any padding they want. Planar formats can't have padding > > (any objections on this? If so: why? I can't think of any useful > > application for this...). > > What if you want to overlay the video into a larger image, except you're > using planar mode? Any reason to do that with a planar video format? The main reason I see to have some padding is that you provide video data for some other piece of hardware (vga for ewample) where you might have some constrains on what the hardware allows you / you want to put that into a window / whatever. But Hardware prefeares packed video formats because it's easier to handle. My Matrox G200 for example can do packed video formats only (only G400 + later can do planar modes too). Common applications which do better with planar formats are video compression. I can't see any need for padding here... > What about clipping? ??? We are talking about capture here, not screen overlay... Gerd -- Get back there in front of the computer NOW. Christmas can wait. -- Linus "the Grinch" Torvalds, 24 Dec 2000 on linux-kernel
