Converting 25fps XVID to 29.97 MPEG2

[dkrajisnik]

Hello all,

I was hoping to get some guidance converting a video file which I had downloaded. I am operating on a Linux computer and would prefer to continue doing so. The file is in an AVI container and has the following properties:

Video:
Resolution: 608x336
Aspect ratio: 1.8095
Format: XVID
Bitrate: 726
FPS: 25.000

Audio:
Format: AC3
Bitrate: 192kbps
Rate: 48kHz
Channels: 2

What I want as an output is an MPEG2 file that conforms to NTSC DVD specifications and can be used as input to DVD authoring utilities (without further re-encoding).

I have tried using mencoder as follows:

$ mencoder -oac copy -ovc lavc -of mpeg -mpegopts format=dvd:tsaf -vf scale=720:480,harddup -lavcopts threads=3:vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=5000:keyint=15:vstrict=0:aspect=16/9 -ofps 30000/1001 -o mr.mpg mr.avi

The output gives me thousands of lines like this:

1 duplicate frame(s)!
Pos:   9.0s    226f ( 0%)  0.00fps Trem:   0min   0mb  A-V:0.007 [1376:192]

1 duplicate frame(s)!
Pos:   9.2s    231f ( 0%)  0.00fps Trem:   0min   0mb  A-V:0.007 [1457:192]

1 duplicate frame(s)!
Pos:   9.4s    236f ( 0%)  0.00fps Trem:   0min   0mb  A-V:0.007 [1502:192]

The output file DOES conform BUT the video is slightly jerky. This is barely noticeable on my Quad Core PC but once the DVD is authored, it is so jerky that it is impossible to watch on a hardware DVD player.

I have looked through the man pages, the web pages, etc. but to no avail. I cannot seem to see where I have gone wrong though I have a suspicion that the "duplicate frame" warnings have something to do with it. If I drop the -ofps option, the warnings will disappear and the video will play smoothly but the output framerate will be 25fps (i.e. not NTSC).

I have also tried using ffmpeg as follows:

ffmpeg -threads 3 -i mr.avi -target ntsc-dvd -r '30000/1001' -aspect 16:9 -acodec copy mr.mpg

The result is absolutely the same.

Any help?

[guns1inger]

I don't know of a simple and neat way to do this on a linux box.

If the source video was originally a film then you may be able to IVTC the file to get back to a 23.976 progressive master. From there you can resize to NTSC D1, re-encode with 3:2 pulldown, and author.

If the source was 25 fps originally then there is no nice way to get to 29.976 fps without creating the missing frames. In software this rarely goes well, as you will end up with blended frames or jerkiness or both. On a windows PC I would resize to NTSC D1, then encode at 25 fps. I would then apply a custom pulldown to get from 25 fps to 29.976 fps during playback using DGPulldown (a windows only app - although it might run under WINE or similar).

Actually, to be honest, I would never do the conversion. It is far simpler just to use playback equipment that supports multi-format playback.

[dkrajisnik]

Thank you for the reply.

I don't know of a simple and neat way to do this on a linux box.

If the source video was originally a film then you may be able to IVTC the file to get back to a 23.976 progressive master. From there you can resize to NTSC D1, re-encode with 3:2 pulldown, and author.

If the source was 25 fps originally then there is no nice way to get to 29.976 fps without creating the missing frames. In software this rarely goes well, as you will end up with blended frames or jerkiness or both. On a windows PC I would resize to NTSC D1, then encode at 25 fps. I would then apply a custom pulldown to get from 25 fps to 29.976 fps during playback using DGPulldown (a windows only app - although it might run under WINE or similar).

Indeed, this was a film so the procedure you describe may be possible. Could you go into a bit more depth? Obviously, you don't have to write out the command line parameters but perhaps a step by step list of what should be done. Reading your reply, it seems like that is exactly what I have done, just with a single step with mencoder. I don't have any problem transferring the file to a Windows PC for the pulldown step but I would prefer to complete the process on the Linux computer if at all feasible.

Actually, to be honest, I would never do the conversion. It is far simpler just to use playback equipment that supports multi-format playback.

This is also a good point. Do you think that most NTSC hardware DVD players would play a PAL-encoded disc, if the region code is not present? I'll give it a try anyway.

[guns1inger]

Again, on a windows host (which is what I work on), it would normally done using avisynth. If you search the forums for IVTC and avisynth you will find various samples and example scripts.

Unfortunately most NTSC players do not play PAL as well, although a growing number of unbranded players are starting to support it.

[Calidore]

I would think regardless of whether the source was 25 fps, the movie in question could still be slowed non-destructively to 23.976 fps and then converted more cleanly to 29.976. Is this not feasible?

Best,

Calidore

[guns1inger]

If it was a simple speed up for PAL then it could be as simple as slowing down the framerate, then using Audacity to slow down the audio to match. Once the video is running at 23.976 fps progressive, the rest is easy

[dkrajisnik]

Thank you for the replies. It turns out that not only will my DVD player accept PAL format DVD's (provided the region code is not in place) but it will actually play the MPEG4 file as-is, simply burned onto a DVD! No encoding is actually necessary.

I would still like to learn how to do this but perhaps starting with a more theoretical background. Learning to click on some program to run an IVTC doesn't mean much to me when I don't even know what IVTC truly does. I'll look into some books; any recommendations are welcome.