[MEncoder-users] Tuning hqdn3d

[RC]

On Tue, 12 May 2009 12:43:48 +0200
Nicolas George <nicolas.george at normalesup.org> wrote:

> What do you prefer: the first half of the movie almost perfect and the
> second half very poor, the first half very poor and the second half
> almost perfect, or the whole movie in medium quality?

This is a pretty pointless question.  2-pass and CRF will both give you
the latter.  The only difference being that CRF will only consider it's
best-guess for quality, while 2-pass mode will chose the best possible
quality for a given bitrate distributed over the length of the file,
within specified min/max instantaneous bitrates.

> Is the evaluation function for crf significantly worst than the one
> for the multi-pass rate control system?

With CRF, you are dependant upon the equation correctly
estimating visual quality.  With 2-pass, you are merely depending on it
for an approximately appropriate distribution of bits.  ie. Even if
the ratecontrol equation guesses that an extremely low bitrate will work
for a particular video, as long as it is inaccurate in the same
direction over both comlpex and simple scenes, it would still work fine
with 2-pass.

But more importantly, and less controvercially, some options just
require look-ahead, which x264 in single-pass/CRF mode simply can't do.

-- 
Don't trust me! I'm wrong!