[x264-devel] x264 SSIM analysis

[Niccolò Belli]

Hi, I did analyse SSIM from two videos compressed with x264 using 
CRF=18 and different presets. I expected to get a similar SSIM 
considering x264 tunes for SSIM by default and not for PSNR. 
Unfortunately SSIM differs quite a lot (see attached image).

I did calculate the SSIM using qpsnr (http://qpsnr.youlink.org/):
./qpsnr -a avg_ssim -o blocksize=16:fpa=24 -r ~/placebo-lossless.mkv 
~/placebo-cfr18.mkv ~/veryfast-cfr18.mkv > output.csv

Why did I get such a strange result?

Niccolò
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