FUKUCHI Kentarou wrote: > > Hi all, > > V4L Kernel API reference (/usr/src/linux/Documentation/video4linux/API.html) > claims that VIDEO_PALETTE_YUV422 is a format that packs YUV values into 8 bits. > But bttv-driver maps YUV422 to BT848_COLOR_FMT_YUY2, and thats format is > different from the description of API reference. > > Why? In which way should I implement v4l driver? IMO you should follow bttv to avoid breaking applications, but we should deprecate the bad V4L_PALETTE names (the two below) and replace them with correct ones. There are two packed YUV formats whose V4L names are wrong: VIDEO_PALETTE_YUV422 --> bttv YUY2 VIDEO_PALETTE_YUYV --> bttv Y41P VIDEO_PALETTE_YUV422 as a name is ambiguous as there are many possible 4:2:2 planar Y,U.V component orderings (and of course they're all 16 bpp, as 4:2:2 implies). YUY2 is only one of the possible 4:2:2 formats (which, adding to the confusion, has component order Y,U,Y,V!), VIDEO_PALETTE_YUYV as a mapping to Y41P is obviously wrong, but that's the way bttv has always been, and AFAIK this is a Bt848 only mode anyway (although other drivers could create it in software, I guess). So... I'd recomment you follow bttv, but that we should also introduce synonyms VIDEO_PALETTE_YUY2 and VIDEO_PALETTE_Y41P and deprecate the old names. I believe V4L2 already uses these names (or at least non-ambiguous ones that make sense). Ben
