Thanks for taking the time :) On 17 Oct 2001, Gerd Knorr wrote: > volodya@xxxxxxxxxxxxxx wrote: > > > > Hi all :) > > > > I am from GATOS project (http://www.linuxvideo.org/gatos ). We now have a > > small v4l capture module that works with Radeon All-in-Wonders. > > > > It's a first cut so, naturally, I have some questions: > > > > * in the card the alternating TV fields (odd and even) are captured > > in two separate buffers. Right now the module presents them as > > consequetive frames (so that NTSC stream 640x480@30hz interlaced > > becomes 640x240@60hz), which is wrong. How do I tell through v4l > > interface that every other frame is odd one ? > > v4l2 has buffer flags for even/odd field, v4l has not. Is there any way Does it make sense to do v4l2 ? When is it going to make it into the kernel ? (I don't want to require people to patch the kernel in addition to everything else..) > to capture both fields interleaved into one buffer? Using pitch = > 2*scanlinelength or something like that? Applications expect the image > interleaved in one buffer ... Not really. (As DMA granularity is 4096 bytes, but pitch is 640*2). I could make it fake this during read but this requires doubling buffers. (4 instead of 2, 1.2meg ram instead of 600k) > > > * what are the features most desired in a v4l driver ? > > capture / overlay? For the Radeon probably capture is more important, > as overlay is available throught Xvideo, right? Yes. This is just an "auxiliary" module, it requies X with xawtv running to be able to capture anything. > > > * if someone can give some links to capture tools/encoders etc > > for compatibility testing this would be much appreciated > > Any v4l app should work (in theory ...). > There is no test suite (at least I don't know any ...). Well, I just wanted to take the easy way and get this to work with some existing apps instead of implementing ioctl's one by one ;) > > > * do we need to get a define in videodev.h ? how many ? > > (there are different All-in-Wonder cards: mach64, Rage128, Radeon > > and they come with different decoder chips). > > Just mail a diff with the new #defines to Alan ... OK > > > * is there an issue of latency versus number of buffers versus > > reserved space ? Any comments from people who care about such > > stuff ? > > Using more (than two) capture buffers basically reduces the risc that > you lose frames on temporary CPU load peaks. Do you know of any apps that actually care about latency issues ? thanks Vladimir Dergachev > > Gerd > > -- > Netscape is unable to locate the server localhost:8000. > Please check the server name and try again. > > > > _______________________________________________ > Video4linux-list mailing list > Video4linux-list@xxxxxxxxxx > https://listman.redhat.com/mailman/listinfo/video4linux-list >
