Finally, I try to understand the RISC program and INT_STAT register. So, I patch the bttv driver 0.7.91 and make temporal decimation successfull. I made 3 major modifications: - I re-order the RISC program to capture EVEN field first (since ONE IMAGE is EVEN field first (at least for my PAL camera)). - I added FDSR in the INT_MASK. If you don't do that you can't distinguish between RISCI (IRQ requested by the RISC program) and FDSR (IRQ set when there is no image at all). - I change the position of RISC status used to synchronize the bttv driver (bit 1 saying: end of image and bit 3 saying: start capturing). For those interested, I only use "frame" decimation, meaning that EVEN and following ODD field are suppressed at the same time. Other register flags (DEC_FIELD & FLDALIGN, documented page 107 of the bt878/879 datasheet) does not seem to work. What diff option should I use to post a patch on the list? Benoit PS: BTW, my next option will be to add 16 cards in a PC, so I'll be interested in patching the driver for more than 4 cards. > > Hi there, > > I'm using the bttv driver version 0.7.91 with a 2.4.18 kernel. > I compiled the bttv driver separately from the kernel using > http://bytesex.org/bttv/ and apply the patch > "pending/bttv-0.7.72.subcap.patch" found in the tar.gz with minor > corrections. > > I try to use temporal decimation (ie, I only want 3 frames out of 25 > transfered on the PCI bus) since I have dozen of bttv based PCI cards > and grabbing 25 frames per second at 640x480 is too much for the PCI > bus bandwidth. > > So, using v4l API and the temporal decimation patch, I start grabbing. > However, the ouput images are either black, or with a missing fields > (only odd or even lines contains an image). Moreover, the v4l API > returns the same image several time!!! > > I'd like to know if some other people out there have succeeded in > using temporal decimation and HOW :-). > > I already read the bttv driver source code (which is not totally clear > to me) and the bt788 datasheet (pdf). > > Thanks in advance. > Benoit > > > > _______________________________________________ > Video4linux-list mailing list > Video4linux-list@xxxxxxxxxx > https://listman.redhat.com/mailman/listinfo/video4linux-list >
