[x264-devel] Global optimization of keyframes

[Nicolas George]

Hi.

I am wondering if you considered implementing a global optimization of
keyframes using two-pass encoding, even in CRF mode.

The way I see it, allocating keyframes with regard to the GOP size is a lot
like allocating line breaks in a paragraph with regard to the page width.
And we know since TeX that this can be optimized globally in an efficient
way and greatly increase the quality. Keyframes have even more freedom than
line breaks, the benefit could be even bigger¹.

I tried to encode something to have figures to illustrate this mail;
unfortunately, it seems that forcing the frame type, even to what it would
have been anyway, greatly decreases the quality of the encoding.

Anyway, I believe this idea may be worth some thought.

Regards,

-- 
  Nicolas George



1: Example: the camera is looking through the window of a moving vehicle,
every five seconds, there is a tree, every odd tree being somewhat bigger.
The tees are a good place for a keyframe, the bigger ones are a better
place. Catching a big tree early in the scene allows to catch all big trees.
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