Ben Bridgwater wrote: > > 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 Alan, would you accept this as a patch for videodev.h ? --- videodev.h Sat May 12 21:57:26 2001 +++ videodev-new.h Sat May 26 10:49:06 2001 @@ -126,6 +126,8 @@ #define VIDEO_PALETTE_RGB32 5 /* 32bit RGB */ #define VIDEO_PALETTE_RGB555 6 /* 555 15bit RGB */ -#define VIDEO_PALETTE_YUV422 7 /* YUV422 capture */ -#define VIDEO_PALETTE_YUYV 8 +#define VIDEO_PALETTE_YUY2 7 /* 4:2:2 YUYV */ +#define VIDEO_PALETTE_YUV422 VIDEO_PALETTE_YUY2 /* deprecated */ +#define VIDEO_PALETTE_Y41P 8 /* 4:1:1 UYVYUYVYYYYY */ +#define VIDEO_PALETTE_YUYV VIDEO_PALETTE_Y41P /* deprecated */ #define VIDEO_PALETTE_UYVY 9 /* The great thing about standards is ... */ #define VIDEO_PALETTE_YUV420 10 Ben
