[MEncoder-users] Limiting peak bitrate with CRF - vbv_maxrate?

[Andrew Berg]

There are some videos I'd like to encode without having the bitrate peak
above 20Mbps while using CRF. I have 2 reasons for this: first, the
original videos don't peak above 20Mbps (they appear to be 1-pass ABR
with a max peak BR of 20-21Mbps), and my encoding settings are more
efficient, so it won't take more than that to achieve the same quality
(this is in areas where there is artifacting, so even if there is
quality loss, only a significant amount would be noticeable), second, it
keeps the AVC level to 4.0 (if it the BR doesn't need to go over the 4.0
limit of 25Mbps, why use 4.1?). The only option I've found that might do
this is vbv_maxrate, but I don't quite understand exactly what it does.
There's not much information out there on how this affects a CRF encode
and I don't have much experience with CBR or ABR modes.

In case it's relevant the command line I use for the video step is this:
mencoder 2010.02.02.m2ts -msglevel all=1:statusline=5 -fps 50 -ofps 25
-demuxer lavf -of avi -oac copy -ovc x264 -x264encopts
crf=19:keyint=300:keyint_min=30:frameref=4:mixed_refs:weightp=2:b_pyramid=normal:weight_b:bframes=4:b_adapt=2:me_range=24:direct_pred=auto:cabac:8x8dct:me=umh:trellis=1:subq=7:threads=auto:nointerlaced:nopsnr:nossim:deblock=-1,-1
-vf yadif=1,filmdint=io=50:25,hqdn3d=0:0:8:8,harddup -o 2010.02.02.avi

I get a peak BR of 57.4Mbps, which is quite a bit higher than the
20-21Mbps peak in the original. Certain parts require a very high BR to
get decent quality, but since the quality is already lost in the
original, there's no point in trying to preserve it.