[NUT-devel] [RFC] FourCCs for rawvideo rgb4_byte / bgr4_byte

[Michael Niedermayer]

On Thu, May 27, 2010 at 12:14:24PM +0200, Stefano Sabatini wrote:
> On date Thursday 2010-05-27 00:59:21 +0200, Stefano Sabatini wrote:
> > On date Wednesday 2010-05-26 00:49:54 +0200, Stefano Sabatini wrote:
> > > On date Sunday 2010-05-23 04:30:44 +0200, Michael Niedermayer wrote:
> > > > On Fri, May 21, 2010 at 12:19:10AM +0200, Stefano Sabatini wrote:
> > > > > Hi all, this follows a thread from ffmpeg-devel:
> > > > > http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/109054/focus=109394
> > > > > 
> > > > > I proposed these names:
> > > > > B4BY (bgr4_byte) Packed BGR 1:2:1,  8bpp, (msb)1B 2G 1R(lsb)
> > > > > R4BY (rgb4_byte) Packed RGB 1:2:1,  8bpp, (msb)1R 2G 1B(lsb)
> > > > > 
> > > > > Other idea:
> > > > > bgr4_byte => B[1][2][1]
> > > > > rgb4_byte => R[1][2][1]
> > > > > 
> > > > 
> > > > > Note that I'm very satisfied with these names, maybe someone can find
> > > > > a better scheme.
> > > > > 
> > > > > What do you think?
> > > > 
> > > > i think you are missin a "not" in your sentance
> > > 
> > > Yes indeed.
> > >  
> > > > and iam not sure abut the fourccs here, this format is simply inefficient
> > > > to store 4bit rgb, is it used in the wild?
> > > 
> > > I have not the faintest idea, and I couldn't even manage to understand
> > > who introduced it, since it exists since the night of time of FFmpeg.
> > > 
> > > > if not (its just for ffmpegs test lavfi test system we can just pick any
> > > > random fourcc and treat it like some ffmpeg internal thing)
> > > > either of your choices would do for that
> > > 
> > > My problem is that I need to *write* such a format in NUT, so I need a
> > > codec for that. Also to add such a tag shouldn't hurt anyway. If you
> > > have an idea for avoiding to define a tag for it and still be able to
> > > store such a format in NUT please tell (well an idea would be to make
> > > possible to define the codec tag), as for me I prefer to add these two
> > > rather than add exceptions/special cases to the FFmpeg code.
> > > 
> > > Patch updated, regards.
> > 
> > > Index: docs/nut4cc.txt
> > > ===================================================================
> > > --- docs/nut4cc.txt	(revision 669)
> > > +++ docs/nut4cc.txt	(working copy)
> > > @@ -96,6 +96,8 @@
> > >  B0W1    black/white bitstream, 1bpp, 1 is white, 0 is black, in each byte pixels are ordered from the msb to the lsb [NOT in AVI]
> > >  BGR[4]  Packed BGR 1:2:1 bitstream,  4bpp, (msb)1B 2G 1R(lsb), a byte contains two pixels, the first pixel in the byte is the one composed by the 4 msb bits [NOT in AVI]
> > >  RGB[4]  Packed RGB 1:2:1 bitstream,  4bpp, (msb)1R 2G 1B(lsb), a byte contains two pixels, the first pixel in the byte is the one composed by the 4 msb bits [NOT in AVI]
> > > +B4BY    Packed BGR 1:2:1,  8bpp, (msb)4X 1B 2G 1R(lsb), one pixel per byte, the 4 most significant bits are ignored
> > > +R4BY    Packed RGB 1:2:1,  8bpp, (msb)4X 1R 2G 1B(lsb), one pixel per byte, the 4 most significant bits are ignored
> > >  BGR[8]  Packed RGB 3:3:2,  8bpp, (msb)2B 3G 3R(lsb) [NOT in AVI]
> > >  RGB[8]  Packed RGB 3:3:2,  8bpp, (msb)2R 3G 3B(lsb) [NOT in AVI]
> > >  RGB[48] Packed RGB 16:16:16, 48bpp, 16R, 16G, 16B, the 2-byte value for each R/G/B component is stored as little-endian [NOT in AVI]
> > 
> > I was almost committing, but since there are other formats I want to
> > add support for, maybe someone can find out a scheme for all of them.
> > 
> > These are the format I want to add support for:
> > bgr4_byte ->none
> > rgb4_byte ->none
> > rgb444be ->none
> > rgb444le ->none
> > bgr444be ->none
> > bgr444le ->none
> > 
> > I propose this scheme.
> > 
> > First byte:
> > b = BGR
> > B = BGR+A
> > r = RGB
> > R = RGB+A
> > a = ABGR
> > A = ARGB

i dont like this at all, using upper/lower case to distinguish formats

following is much closer to the existing system:
RGBA -> RBA[bits]
ARGB -> ARB[bits]
ABGR -> ABR[bits]
BGRA -> BRA[bits]

[...]
-- 
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