#8529: the ssim_c1 has bug in vf_ssim.c
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Reporter: wangwei1237 | Type: defect
Status: new | Priority: important
Component: avfilter | Version: git-
| master
Keywords: ssim_c1 | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Summary of the bug:
I'm learning the SSIM, and I find FFMpeg provides this capability in the
vf_ssim.c and tiny_ssim.c. I analyzed the code of the tiny_ssim.c and find
a bug for the define of the '''ssim_c1''' variable in the
ssim_end1() function.
I recalculate the mathematical formula of SSIM according to the algorithm
of tiny_ssim, and get the following formula:
SSIM(x,y)=((2*s1*s2+64*64*C1)(2*(64*s12-s1*s2)+64*63*C2))/((s1*s1+s2*s2+64*64*C1)(64*ss-s1*s1-s2*s2+64*63*C2))
Thus the ssim_c1 shoule be (.01*.01*PIXEL_MAX*PIXEL_MAX*64'''*64''' + .5)
instead of ssim_c1 = (int)(.01*.01*PIXEL_MAX*PIXEL_MAX*64 + .5).
How to reproduce:
{{{
static const int ssim_c1 = (int)(.01*.01*PIXEL_MAX*PIXEL_MAX*64*64 + .5);
}}}
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Ticket URL: <https://trac.ffmpeg.org/ticket/8529>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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