[x264-devel] Re: patch: visualization for X11

[Loren Merritt]

On Tue, 17 May 2005, [iso-8859-1] Måns Rullgård wrote:
> Loren Merritt <lorenm at u.washington.edu> writes:
>>> Another thing that could be visualized is the QP value. Any ideas?
>>> I'm not sure if it varies between partitions/MBs yet in x264, but it could.
>>
>> It used to vary as part of the CBR ratecontrol. I removed that when I
>> added ABR, because it was unnecessary at sane buffer sizes. But yes,
>> there are other forms of adaptive quant that could be useful.
>
> I guess I could read the code and find out, but what is this ABR
> anyway?

Average bitrate. As close as possible to the 2pass quantizer distribution 
as you can get in 1 pass. Gracefully degrades to near constant bitrate if 
you restrict VBV.
It's the algorithm I was saying was about 4dB better than CBR (when 
unrestricted). At small VBV sizes I see around .5 dB gain.

--Loren Merritt