[MEncoder-users] Skipped (dropped) frames result in shorter video (only 69% of what should be)

[Tomasz Ksiezyk]

Hi,

I have been using mencoder to rip DVDs quite successfully for some time. 
Recently, while ripping titles from several DVDs (all of them from the 
same series) I have encountered the following problem:

the produced AVI files, when played back, proved to be shorter that 
intended.

I have experimented with several different durations and determined that 
the produced AVI files ran only 69% of the time I set with the -endpos 
parameter. This 69% was consistent across a wide range of duration 
times. Because the video at the end points (as set for the ripping) of 
the original DVD and the ripped file looked the same, I have concluded 
that some frames must have been skippd. Because of this problem the 
audio (which seems to be ripped correctly) was out of sync with the video.

When I ran:

mplayer dvd://1 -dvd-device /media/cdrom -nosound -vo null -benchmark

to determine the type of the video, I got just:

Starting playback...
V: 174.0 5214/10428  0%  0%  0.0% 0 0

There were no messages about '24000/1001fps progressive NTSC' or about 
switching frames.

When playing the DVD with:

mplayer dvd://1 -dvd-device /media/cdrom

I saw among others:

VIDEO:  MPEG2  720x480  (aspect 3)  29.970 fps  7400.0 kbps (925.0 kbyte/s)

The DVD played just fine.

The script for the 2-pass ripping which I used was:

---

mencoder dvd://<title-number> -dvd-device <video-ts-dir> -ovc frameno -o 
frameno.avi -oac mp3lame -aid 128

mencoder dvd://<title-number> -dvd-device <video-ts-dir> -oac copy -vf 
crop=720:480:0:0,scale=576:272 -ovc lavc -lavcopts 
vcodec=mpeg4:vbitrate=1000:v4mv:mbd=2:trell:cmp=3:subcmp=3:mbcmp=3:autoaspect:vpass=1 
-o /dev/null

mencoder dvd://<title-number> -dvd-device <video-ts-dir> -oac copy -vf 
crop=720:480:0:0,scale=576:272 -ovc lavc -lavcopts 
vcodec=mpeg4:vbitrate=1000:v4mv:mbd=2:trell:cmp=3:subcmp=3:mbcmp=3:autoaspect:vpass=2 
-o <film-name>.avi

---

I would appreciate any suggestions explaining the nature of the problem 
and the way I could fix it.

Thanks,

Tomasz Ksiezyk