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#1 | Link |
phjbdpcrjlj2sb3h
Join Date: Sep 2005
Location: Western Australia
Posts: 1,692
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Temporal blurring of quantizer
Hi all, I was wondering if someone could take the time to explain why x264 temporally blurs the quantizer curve, why blurring is applied twice, and what units (or scale) the two settings are in.
On a somewhat related note, as I understand it, the default --qcomp setting moves the bitrate distribution from what the encoder feels is optimal to a more constant distribution. How does it do this, and why is this not set to 1.? |
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#2 | Link | |||
x264 developer
Join Date: Sep 2004
Posts: 2,392
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[QUOTE=check;986387]Hi all, I was wondering if someone could take the time to explain why x264 temporally blurs the quantizer curve[QUOTE]
It makes quality more stable. Especially in anime, where the framerate of the content is often less than the nominal framerate of the video, so in two consecutive frames one has motion and the next doesn't. Without any temporal blur they'd have very different qp, but the optimal encode is to make them the same. Quote:
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qcomp=1 would be identical to cqp. |
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#3 | Link |
phjbdpcrjlj2sb3h
Join Date: Sep 2005
Location: Western Australia
Posts: 1,692
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Thanks for the info. A few more questions from your answers:
o if the normalised t.blur setting is 1, will that average all frames, or just everything within IDR range or similar. o do either of the blurs take into account (presumeably by ignoring) scene changes? o with --qcomp, was 'optimal' something that you could measure, or is it by a large part perceptual? Thanks again. |
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#4 | Link | |||
x264 developer
Join Date: Sep 2004
Posts: 2,392
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