On Tue, 11 Sep 2007 03:22:37 +0200, David McNab <[EMAIL PROTECTED]>
wrote:
Hi,
Does anyone know of any nix-compatible tools which can objectively
measure the quality loss of video caused by various types of
compression/manipulation?
One way I can think of is sum of squares of pixel YUV or RGB
differences. How effective would this really be? Are there better ways?
For example, to limit the sum of squares calculation to i*j-sized pixel
groups?
This only adresses half of the "quality" aspect of lossy codecs: How
small the absolute errors are. It is much harder to compute how
perceptible
those errors are to a human, and that's what really counts.
Sure, if you want _almost_ lossless codecs for capturing, archiving,
proxies and intermediate renders, then absoulute errors matter. Errors
that are imperceptible may become obvious after colour grading and various
enhancements.
Another aspect to consider: Does the lossy codec raise or lower overall
noise? I.e. is it harder or easier to compress gracefully with another
codec.
--
Herman Robak
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