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x264_quality [2014/08/17 21:44] – beandogx264_quality [2014/08/17 21:47] (current) – beandog
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 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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