Re: YUV Framebuffer

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:

quoted

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 */

quoted

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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