[MEncoder-users] filesize become very big after convertion

[Corey Hickey]

Achilles Xu wrote:
> Hello mencoder-users,
> 
> I use the following command to convert some video to flv file format.
> 		mencoder aaa.mov -o aaa.flv -of lavf -oac mp3lame -lameopts abr:br=56 -ovc lavc -lavcopts 				vcodec=flv:vbitrate=16000:mbd=2:mv0:trell:v4mv:cbp:last_pred=3 -srate 22050 -lavfopts 				i_certify_that_my_video_stream_does_not_use_b_frames
> The 16000 vbitrate is for get best quality, but the filesize become twice or three times.
> What can I do to decrease the filesize without losing quality?

Unless you absolutely have to convert, the best solution is to leave the 
original file alone. Except when encoding with a lossless codec (which 
results in a very large output file), there is no way to re-encode 
without losing quality. Specifiying a high bitrate only minimizes the 
quality loss.

There are a few other ways to reduce the loss in quality.

1. Use two pass encoding. Read the manual for the vpass option.

2. Use a better format. FLV isn't that great. H.264 (with the x264 
codec) and MPEG-4 (with XviD or lavc codecs) can each do much better.

3. Scale the video down somewhat (-vf scale=xxx:yyy). This will make the 
video smaller, of course, and lose some detail, but to a certain point 
this usually looks better than blocky artifacts.

4. Use different lavcopts. The ones you have look pretty good, though, 
so I wouldn't expect too much improvement there. These are the ones I 
used for some flv stuff a while ago. Add your own vbitrate and vpass.
---
vcodec=flv:mbd=2:mv0:trell:cbp:precmp=2:cmp=2:subcmp=2:\
sc_factor=6:vrc_eq=(tex+10^8*mcVar)^0.6:predia=2:dia=2:preme=2
---
You may get a slight improvement there. Maybe not. I didn't test them 
thoroughly.

-Corey