wrong colors with Xv extension and image format id: 0x59565955 (UYVY) from an rgb mapping

[Amos Tibaldi]

2009/1/22 Tomas Carnecky <tom at dbservice.com>

> On 01/22/2009 06:15 AM, Amos Tibaldi wrote:
>
>>
>> Hello,
>> I am trying to use the Xv extension in order to display images on
>> windows. I have obtained the image formats with
>> xvc.fo <http://xvc.fo> = XvListImageFormats( xvc.display, xvc.port, (int
>> *)&formats );
>> and I have chosen the format
>> id: 0x59565955 (UYVY)
>> guid: 55595659-0000-0010-8000-00aa00389b71
>> bits per pixel: 16
>> number of planes: 1
>> type: YUV (packed)
>>
>
> [snip]
>
>  and to display the image with
>> void XVWindow::Redraw()
>> {
>> unsigned short int u, y, v;
>> RGBToUYVY(255,255,0,&u,&y,&v);
>> unsigned short int thecolor = u << 12 | y << 8 | v << 4 | y;
>>
>> for ( int y=0; y<ImageHeight; y++ )
>> for ( int x=0; x<ImageWidth; x++ )
>> ((unsigned short int *)BGimage->data)[ y * ImageWidth + x ] = thecolor;
>>
>> counter++;
>> XvPutImage( xvc.display, xvc.port, window, gc,
>> BGimage, 0, 0, ImageWidth, ImageHeight,
>> 0, 0, WindowWidth, WindowHeight );
>> }
>>
>
> I think you are confused by 'bits per pixel: 16' in the Xv format list.
> Your code in :Redraw() that composes the pixel is wrong. I know I couldn't
> explain it better, so I'm including a link to a website that explains it
> pretty well:
> http://www.fourcc.org/yuv.php#YUY2
> (Each macropixel is 32 bits, so each of the YUV components is 8 bit and not
> 4 like you used in your code)
>
> tom
>
>
> Hello, BGImage->data_size is equal to w x h x 2 bytes (2B per pixel in the
data allocated), and X has calculated it. Moreover I have tried even with
<<24 |<<16|<<8 and the thing is the same. Are you sure of that?

Thanks,


-- 
Amos Tibaldi
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