From: Serguei Miridonov > A user of your driver and I were trying to figure out why > tvtime wasn't working. tvtime operates by grabbing interlaced > frames at full rate (29.97/25fps), 4:2:2 Y'CbCr sampling, and > deinterlacing them to give an output at field rate (but increased > to frame size) of 59.94fps/50fps progressive. The zoran driver, > when capturing at 640x480 4:2:2, was providing nasty green > frames/colourbars instead of providing any reasonable video > content. > > The user determined that this is because of some memory > limitations of the card, it can't handle this data rate, It depends on the Zoran PCI controller (new versions work better than the old one), and on the motherboard. Intel is much better than VIA, for example... > and so only lower resolutions like 320x240 or something can be > provided when asking for raw 4:2:2 images, and that some sort of > bigphysmem thing is required to get it to work, if at all. > > This restriction seems pretty reasonable given the hardware > involved, so that is not my concern. My concern is simply that > the driver did not fail or anything, but fooled tvtime into > thinking everything was 'ok'. I would very much appreciate it if > the driver could return some error when it is set in a mode that > will not work. Is this at all possible? It's not so simple. I can only guess which hardware combination will work and which will not (see above). And the hardware provides no means to detect any buffer overflow for uncompressed video capture. Perhaps, this is because the card was primarily designed for MJPEG capture (low bandwidth) and to provide video monitoring on the computer display (no RAM access, just the PCI-PCI transfer from Zoran to any graphics adapter. It can capture uncompressed video into memory even at full frame rate but not on every system. My old system with Pentium MMX 266MHz with Intel 430TX works better than newer Athlon XP 1800+ at VIA KT266A and DDR memory. Pentium MMX system can capture uncompressed video to memory but can do nothing with it due to CPU and disk I/O limitations. Athlon system can do anything (even encode into MPEG-4 in real time) but some uncompressed frames are dropped due to PCI limitations on VIA chipset... Marcel Birthelmer wrote: > Sorry for the misunderstanding, i wasn't complaining about a bug. > I looked through zoran.c and i realized that the reason for > grabdisplay not working was the 128 limit, This is a limit from Linux kernel: it will not give you contiguous memory longer than 128Kbytes without some special tricks: bigphysmem patch or reserving memory at system boot using mem=XXX line in LILO or GRUB configs. > so i tested it, and grabdisplay does work with very small picture > sizes. So my question is, what are my options for increasing this > memory amount? Bigphysmem patch or reserving memory at boot time. I suggest you to read README file: it has notes about this. > just changing 128 to 1024 doesn't seem to work, but also i don't > really want to patch my kernel unless i have to. Any > suggestions? If you need help, please, describe your system: motherboard chipset, processor, memory size and type, etc. Also please note that older ZR36057 chip may not work properly on some motherboards. Newer ZR36067 is better but it also may have problems with VIA chipsets.