Re: Re: YUV to RGB

Hi,

If you're looking for some pretty fast, portable C code, here's  
another version that uses pre-calculated lookup tables (starts around  
line 665):

http://iaxclient.svn.sourceforge.net/viewvc/iaxclient/branches/2.0/ 
lib/video.c?revision=1199&view=markup

This is part of the iaxclient project, which is licensed under LGPL,  
so if LGPL works for you, you can re-use the code.  If LGPL is not  
acceptable, you can probably re-implement the idea.

Mihai

On Jan 15, 2008, at 5:52 AM, Shane Stephens wrote:

> Hi,
>
> Be aware that the SSE implementation in oggplay is not perfect - in  
> particular it does not correctly do linear interpolation of 4 pixel  
> values for chrominance (instead it uses 2 values per pixel).   
> Actually, strictly speaking I think it's MMX from memory (using  
> fixed-point integer arithmetic instead of floating-point arithmetic).
>
> Fragment shaders vs. vector-based CPU instructions is an  
> interesting trade off - on the one hand fragment shaders free up  
> CPU cycles; on the other the vector-based routine is a fraction of  
> the cost of Theora decoding (I measure about 11%) and I bet more  
> existing Intel-based machines support MMX than fragment shading.
>
> Cheers,
>     -Shane
>
> On Jan 15, 2008 6:48 PM, Ralph Giles <[email protected]> wrote:
> On Mon, Jan 14, 2008 at 10:59:39PM -0800, wesley kiriinya wrote:
>
> >  I'm trying to write an OpenGL application that plays theora  
> frames. SDL is not an option. Is there a function/routine that can  
> do this for me efficiently or do I have to write my own with a bit  
> of SSE so that the YUV to RGB conversion is fast enough. Also  
> wouldn't it be OK if a Theora stream could be encoded in RGB  
> instead of YUV or is there already something like this? I'm writing  
> a decoder not an encoder.
>
> If you're doing OpenGL, the best thing is to write a fragment  
> shader to
> do the conversion. In most applications the GPU can more easily spare
> the cycles.
>
> For one implementation on the host side, see:
>
>  http://svn.annodex.net/liboggplay/trunk/src/liboggplay/ 
> oggplay_yuv2rgb.c
>
> There are many others, of various speed and quality.
>
> I'd eventually like to add to-from RGB routines to the reference
> implementation, but that's post-1.0.
>
> HTH,
>  -r
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