[MEncoder-users] NTSC DVD to 25 fps MPEG

[The Wanderer]

Richard Bromley wrote:

> Hi. I would like to copy an NTSC DVD title to a single .mpg file,
> preserving the original video and audio streams but changing the
> framerate to 25. It goes without saying the audio rate needs to
> change as well so that the audio stays in sync with the video.

Since frame rate is a characteristic of video streams, how do you
propose to change the frame rate without modifying the video stream?

The only way this could even potentially be possible is by setting a
frame-rate field in the container somewhere, and that would likely just
produce broken playback unless the player did the necessary filtering to
change the effective frame rate at playback time - which would be very
complicated and highly computationally intensive.

> The DVD video is film encoded in the standard way at, that is, the
> majority is soft-telecined at 24000/1001 fps, with small 
> hard-telecined segments mostly at scene boundaries.
> 
> I have already tried the following:
> 
> $ mencoder -oac copy -ovc copy -of mpeg -ofps 25 -speed 25025/24000 
> -vf softpulldown,filmdint,harddup dvd:// -o dvd.mpg

The video filters here are ignored, because you've told MEncoder to copy
the video stream without modifying it; video filters inherently modify
the video stream. I strongly suspect that the -ofps is also ignored for
the same reason. (I'm not sure about the -speed option.)

In order to apply such filters, you definitely have to transcode the
video. I'm about 99% sure that the same applies to changing the frame
rate.

-- 
       The Wanderer

Warning: Simply because I argue an issue does not mean I agree with any
side of it.

Secrecy is the beginning of tyranny.