Re: YUV Framebuffer

[Geert Uytterhoeven <geert@linux-m68k.org>]

On Wed, 17 Oct 2007, Rhee, C. Joon wrote:
> Interleaved means YCBCR is on the same plane in this order.
> Y CB Y CR Y CB Y CR.... (TV-Out)

So it's still FB_TYPE_PACKED_PIXELS.

> The problem of matching Y=G, CB=B and CR=R for RGB offset is that the
> pixel cannot be represented directly since CB/CR gets shared between Ys.
> 
> So, bitsperpixel would be 16 bit and both B and R offset will be 8.

Doesn't sound that bad to me, if you introduce a FB_VISUAL_YCBYCR
visual. Even pixels have a Cb, odd have a Cr component.

The alternative is to sets bits_per_pixel = 32, but then you get more
illogical component offsets.

Anyone with a better suggestion?

> -----Original Message-----
> From: geert@linux-m68k.org [mailto:geert@linux-m68k.org] 
> Sent: Tuesday, October 16, 2007 11:58 PM
> To: Rhee, C. Joon
> Cc: Linux Frame Buffer Device Development
> Subject: Re: [Linux-fbdev-devel] YUV Framebuffer
> 
> On Tue, 16 Oct 2007, Rhee, C. Joon wrote:
> > Is it possible to create framebuffer color format in YUV (eg. YUV422
> > interleaved) and expose it through /dev/fb?
> > 
> > What would be fb_info type?  
> 
> What do you mean with `interleaved'?
> Even and odd frames are separate (interlace)?
> 
> For YUV422, you have to add a new visual type.
> 
> A long time ago, I used this for a non-public test project:
> 
> #define FB_TYPE_PACKED_PIXELS_LACED     5       /* Interlaced Packed
> Pixels */
> #define FB_TYPE_PACKED_PIXELS_4AREAS    6       /* 4 areas of Packed
> Pixels */
> 
> #define FB_VISUAL_YCBCR422              6       /* YCbCr 4:2:2 */
> #define FB_VISUAL_YCBCR420              7       /* YCbCr 4:2:0 */
> 
> > And how about about fb_var_screeninfo.green/blue/red offset? 
> 
> Just assume red, green, and blue mean Y, U, and V?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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