[MEncoder-users] Tuning hqdn3d

[Nicolas George]

Le quintidi 25 floréal, an CCXVII, RC a écrit :
> Both CRF and 2-pass will do everything they can to acheive consistent
> quality, from beginning to end.  You're making no distinction.

I am not trying to make a distinction, I am trying to establish a
prerequisite for my arguments.

So I take it you agree to the basics: quality should be as constant as
possible?

> That only applies to the relative distribution.  Not the absolute
> quality level, which will be determined as "as high as possible with the
> given number of bits".  

I do not see the point of the distinction you are trying to make.

> It does, but given enough of a fudge factor, thanks to a bitrate, modest
> errors will not be visible.

So basically, what you are saying is that if we give target-bitrate encoding
more than enough bits to work with, we will note notice that it's not
perfect?

> > - The best overall encoding should have a roughly constant subjective
> >   quality.
> There's no basis for this.  Consistently low quality is certainly not
> better than alternating between low and high quality.

And consistent high quality is better than both.

Don't you notice you forgot a variable?

> Bitrate encoding tries to provide the best quality for a given bitrate. 
> It does not try to acheive a certain quality level, and throw away
> available bits if it thinks it has.

Nor does it take the bits it needs to achieve it if that is beyond the
target bitrate.

> In theory, yes, but CRF is simply a different equation.  It is not
> "quality". 

Do you have any arguments to presume that what target-bitrate encoding is
trying to optimize is a better approximation of "quality" than CRF?

> > Finding the bitrate to achieve the desired quality is hard.
> No.

Yes it is. It requires to know the whole video.

> > - Multi-pass encoding could be beneficial for global optimizations of
> > the encoding, but current implementations of the codecs only use the
> >   global information for rate control.
> Not true.

Well, that would be new information. Care to be more specific and technical?
What codec implements such global optimizations, and what exactly do they.

I looked in the code of x264 at least, and it did not seem it did.

> Repeating it won't make it any more true.

Repeating it in different words may help you understand the arguments I am
stating, so that you can either accept or give them a valid refutation.

Regards,

-- 
  Nicolas George
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