[MPlayer-users] best parameters to encode for 200kbps?

Loren Merritt lorenm at u.washington.edu
Wed Sep 29 07:50:56 CEST 2004

On Tue, 28 Sep 2004, Ricardo Kleemann wrote:

> I'm trying to find the best combination of options, to encode with lavc
> for 200kbps, at 352x240 (quarter ntsc).
> I've tried several combinations, but still get very blocky output. I
> imagined that lavc with mpeg4 would produce very good quality at 200k.

What gave you that idea? Bitrate doesn't just scale with resolution.
The actual relation depends on how much detail is in the original, but in 
my experience, bitrate (at a given quality) is approximately proportional 
to sqrt(pixels).
I wouldn't consider encoding a 720x480 MPEG-4 at less than about 1000kbps, 
unless it's very low motion. So HQ 352x240 might be around 500kbps.

> My current settings are (please correct me if I'm misusing anything)
> mencoder -oac copy -ovc lavc -lavcopts
> abitrate=32:vcodec=mpeg4:vbitrate=200:vhq:v4mv:mbd=2:trell:cmp=3:subcmp=3:mbcmp=3:
> autoaspect:vpass=1

vhq, mbd, and mbcmp all control the same parameter. Keep mbd=2 and drop 
vhq and mbcmp.

> -vf hqdn3d,decimate,scale=352:240,pp=de/fq/tn:1:2:3

(In addition to Richard Felker's comments)
hqdn3d can be useful, but make sure you set it to an appropriate strength. 
That depends on how much noise is in the video, and I can't tell you what 
numbers to use.
Also (since I don't see any cropping in your -vf), make sure there are no 
black borders or other edge noise. Those will have an even bigger quality 
penalty than at full resolution.

--Loren Merritt

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