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x264_quality [2014/08/17 15:44]
beandog
x264_quality [2014/08/17 15:47] (current)
beandog
Line 53: Line 53:
  
 Rounding it out to an integer, would be 55, for a result of 55%.  So when encoding this particular video at double the bitrate, the SSIM increases by 55%.  Not bad! Rounding it out to an integer, would be 55, for a result of 55%.  So when encoding this particular video at double the bitrate, the SSIM increases by 55%.  Not bad!
 +
 +Here's a PHP function to do the same thing:
 +
 +<​code>​
 +function ssim_improvement($old_ssim,​ $new_ssim) {
 +
 +        $a = 1 - $old_ssim;
 +        $b = 1 - $new_ssim;
 +
 +        $c = $a / $b;
 +
 +        $d = $c - 1;
 +
 +        $e = $d * 100;
 +
 +        return $e;
 +
 +}
 +</​code>​
 +
 +=== PSNR ===
 +
 +Using the doom9 forum post as a reference, the equation is:
 +
 +<​code>​
 +(new - old) / 0.05 = % improvement
 +</​code>​

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