Hey, sorry about so many emails, I finally decided to join this list, With my bttv card (BT878) and driver from Linux 2.4.5, when I read a 720x480-sized frame (525/59.94) using 4:2:0 sampling, I've found that the chroma I get is only for the top field !! You can see how this may make sense if you think about the spacial positions of the samples, but it goes totally against MPEG's standard of 4:2:0, where every second chroma scanline comes from a different field. As a workaround, my recorder application has been reading as 4:2:2 and then doing a crappy interpolation the way I want before compressing and writing to disk. Ugh. Looking at the datasheet, I'm unclear as to whether we can change the behavior of the bttv driver to output correct chroma. If we can, I think we should, as I bet other capture cards do the MPEG-style thing. At least, I'd _hope_ they would. Can anyone confirm/deny this? Regardless, I think that video4linux should specify per image format type what style the chroma is, and create new data types or whatever when cards support things differently, since otherwise my app has to kinda 'guess' whether it needs to do its own scaling, which could be worse than the hardware is capable of. Thoughts? -- Billy Biggs bbiggs@xxxxxxxxxxxx http://www.billybiggs.com/ wbiggs@xxxxxxxxxxxx
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