[FFmpeg-devel] [PATCH] make tiny_psnr work with 32-bit audio

[Michael Niedermayer]

On Sun, Nov 08, 2009 at 03:29:47PM -0500, Justin Ruggles wrote:
> Justin Ruggles wrote:
> 
> > Hi,
> > 
> > I was trying to do some comparisons with 32-bit audio, but tiny_psnr
> > kept crashing with a float exception.  Then I noticed it does not really
> > support 32-bit integer comparisons.  The attached patch seems to work.
> > 
> > -Justin
> 
> Hmmm...  Most of the regression tests fail with this patch because of:
> 
> -        psnr= ((2*log16(max<<16) + log16(i) - log16(sse))*284619LL*F +
> (1<<31)) / (1LL<<32);
> +        psnr= ((2*log16(max<<16) + log16(i) - log16(sse))*284619LL*F +
> (1LL<<31)) / (1LL<<32);
> 
> Looking at an objdump of tiny_psnr.o, it appears that the compiler is
> treating (1 << 31) as a 32-bit integer (with a negative value), then
> sign extending it to 64-bit.  Is that what is meant to happen?

i think your LL addition fixes a rounding bug

[...]
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