[MPlayer-users] mencoder dvd -> avi question

Aaron Peterson aaron at alpete.com
Mon Mar 15 07:34:06 CET 2004


>> Actually if you follow the directions and rtfm, you'll see that you
>> can get better quality on ONE cd than you were getting on two before.
>> So if you were happy with the quality you got before, you should just
>> do 1disc encodes, but for goodness sake, do them RIGHT...
>
> Heh, glad i asked if i was doing something stupid :)  Could you link me to
> the parts of the manual you speak of that explains calculating bitrate to
> get desired filesize, and encoding movies in parts split on chapter
> boundaries?  I've been reading and haven't seen either of those two things
> yet.

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.  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

#get crop values
mencoder -dvd 1 -oac copy -ovc lavc -vop cropdetect -o /dev/null

#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

#encoding final
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=2
 -oac copy

my two questions now, are

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?

2) do i need -ofps here somewhere?  the two values for -ofps I see most
often are 29.969999 and 23.976.  how do i know which one i need when? 
okay, that was like question 2 and a half :)

aaron




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