[MEncoder-users] Backup policies

[Reimar Döffinger]

Hello,
On Sat, Nov 17, 2007 at 08:26:11PM +0000, Michael Rozdoba wrote:
[...]
> My immediate intuitive reaction is to say what if one has a video with 
> 30 minutes of a static scene followed by 30 minutes of noise? 2pass 
> surely allocates most bits to the 2nd half while CRF, whatever it does, 
> can't allocate different bit distributions in awareness of the 
> distinction between 1st & 2nd halves (*).

Of course it does "allocate different bit distributions", it since it
trivially reaches the desired quality in the first part so it uses very
few bits, whereas in the second part it must use lots to get the desired
quality.
Actually I don't know why 2pass should provide better quality than CRF
(except that it can be a pain, if not almost impossible to get the desired
file size with CRF).
Well, actually there is one case I can think of: If you know that e.g. the next frame
will be a keyframe due to its immense complexity, then you can encode
the current frame with less bits with hardly a _visible_ loss of quality
- which is one information you don't know with one-pass CRF.

Greetings,
Reimar Döffinger