[Ffmpeg-devel] Optimised yuvj420p_to_rgba32

Michel Bardiaux mbardiaux
Thu Mar 23 14:03:34 CET 2006

Luca Abeni wrote:
> Hi Michel,
> On Wed, 2006-03-22 at 19:30 +0100, Michel Bardiaux wrote:
>>I succeeded in decoding from my application a simple JPEG file using 
>>lavc (details on request). Its 40% faster than using the generic libjpeg 
>>(IJPEG6b), which is great. But -pg profiles show that 40% of the time is 
>>spent not in decoding the image, but in converting to B/G/R/X which is 
>>mandated by the rest of my application since the image has to be sent to 
>>an X server on Ix86/Linux.
> I saw similar results in the past: it seems that ffmpeg codecs are much
> more optimized than the ffmpeg code doing rescaling / color space
> conversion.
>>Is there a hope of SSE-fying that function? I mean, I dont ask that 
>>anyone do it, just that someone expert in MMX and SSE tells me if it is 
>>*doable* (and worth it).
> Try to use swscaler with the patches I posted some time ago...
> I did not test the jpeg colorspace, but some tests converting rescaling
> and converting between common colorspaces showed that you get a very
> good speed improvement.

Cant. Guess why? GPL.

> (so, it is certainly doable :)

Then I will have to be careful *not* to look at any swscaler code!

> 			Luca

Michel Bardiaux
R&D Director
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