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Old 13th August 2020, 19:39   #5  |  Link
benwaggoner
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Join Date: Jan 2006
Location: Portland, OR
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Note that --tune ssim is a tuning for a particular objective metric. IIRC, --tune psnr and ssim were added by Dark Shakiri years ago because x264 kept losing to encoders tuned for objective metrics in tests for objective metrics. It was sort of a middle finger at people who were hyperfocused on an objective metric instead of actually looking at the video to determine "quality" and to demonstrate that x264 could win any psnr or ssim based evaluation by providing a tuning for that. And also demonstrating that tuning for the standard objective metrics actually hurt subjective quality.

In general, not using --tune ssim is going to deliver better subjective quality at a given bitrate. So, the reducing in bitrate will generally reduce quality more than it reduces bitrate.

The best way to compare this would be a 2-pass encode, so quality at a fixed ABR can be compared head to head.
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