[MPlayer-users] mencoder dvd -> avi question

[Matthias Wieser]

Am Montag, 15. März 2004 07:34 schrieb Aaron Peterson:

> okay, nevermind that.  i see i must do 3 pass encoding for mplayer to
> estimate the vbitrate needed after encoding audio on the first pass. 

Read the manual but don't believe what's written there. Some people say 
that 3-pass encoding may introduce a-v desync.

> and splitting on chapter boundaries is as simple as using -chapter 1-21
> as you noted earlier.
>
> So...  here is the revised process that I'm considering:
>
> #encode audio - output gives estimated target video bitrate for
> different cd sizes at end
> mencoder -dvd 1 -aid 128 -chapter 1-21 -dvd-device /dev/dvd -o
> frameno.avi -ovc frameno -oac mp3lame -lameopts preset=standard

-lameopts preset=130 will produce average bitrate of 130bit/s. So you 
don't need 3-pass.


> #get info for determining vbitrate for proper filesize
> mencoder -dvd 1 -aid 128 -chapter 1-21 -vop crop=720:362:0:56 -o
> movie.avi -ovc lavc -lavcopts
> vcodec=mpeg4:vhq:vbitrate=1471:v4mv:keyint=128:vpass=1 -oac copy

"vhq" gives bad quality (I know that encoding-tips.txt suggests that 
option), better use "mbd=2"

> 1) should i scale down the screen size of the new avi to encode a
> higher bitrate with the same filesize, or will i get better quality
> leaving the original size and taking the lower bitrate?

MPlayer/TOOLS/calcbpp.pl may help. For slow films a bit/pixel number of 
0.15 should produce good quality, for action films you should use a 
higher bitrate.

Matthias