Problems with 20 Frames/Second

[Keybored]

I have several movies in avi format that are 20 frames/second instead of 25 frames/second. I have never had problems encoding the ones which are 25 but neither TMPG Encoder, Panasonic Mpeg1, or LSX MPEG Encoder will encode these. Is there a program that will encode these or is there a way to change an avi from 20 to 25 frames/second? Any help would be appreciated.

[VidGuy]

The only way to change 20 frames to 25 is to add 5 extra frames every 20 frames. I suspect that no matter how you cut it - the resulting video will look choppy. Basically, every 4th frame, you have to duplicate a frame. You can try VirtualDub or AviSynth to do the rate translation, but I've never had any luck with getting good results.

[tacosalad]

If I recall correctly mpeg-1 can use only pre-defined frame rates, and 20 FPS isn't one of them.

But I though TMPG would automatically change the frame rate. What does it do when you try to encode this avi at 25 fps? Maybe there's something else wrong besides the frame rate...?

[Keybored]

Well, the video portion turns out fine but the voices don't match up with the movement of the mouths. It's like watching a bad King Kong movie. Any idea what speed or setting I need to encode the audio at through virtual dub and then I will mesh the two together with TMPG. Thanks for the responses by the way.

[tacosalad]

Ick!

Does the sound track drift farther out of sync during playback, or is it always off by the same amount of time? You may have to check at several points in the video.

It the sound track is simply out of sync by a constant amount, this can be adjusted fairly easily. VirtualDub, for example, has an Audio Skew setting in the Audio Interleave dialog box. TMPG has an Audio Skew setting oddly buried in the "Source frame range" settings.

It plays correctly in the original AVI file, doesn't it?

[Keybored]

Correct, the avi is fine. How do you do the skewing in the two programs mentioned?

[BlackAdder]

Please check out this post http://www.vcdhelp.com/phpBB/viewtopic.php?topic=49045&forum=3

My mpeg's come out perfectly synched every time and jerkiness is kept to a minimum

I encode to 23.976 from 20 fps with the described method and the results are much better then letting TMPGenc do the frame rate conversion. It's not perfect, but it's watchable. I've also updated the AVISynth script:

#PULLDOWN
AVISource("e:\test.avi")
BicubicResize(352,576)
AssumeFrameBased
SeparateFields
SelectEvery(8, 0,1, 2,3,2, 5,4, 7,6,7)
Weave
#At this point your AVI will be 25fps.
#Uncomment the next line to slow the avi down to 23.976
#AssumeFPS(23.976)
# END of script

Open the script in Virtual Dub and add a 2:1 Verticle reduction filter. This will bring the video back down to 352x288. Believe it or not this helps to reduce interlace lines in the final mpeg. Basically, just double the height of your source avi for the BicubicResize in the script, do the 2:1 V-reduction in Vdub, and then crop if needed. Then frameserve out to TMPGenc.



I then use Sefy's SxVCD template fro TMPGenc. I set motion search precision to "High Quality" on the video tab, uncheck "Detect Scene change" on the GOP Structure tab, uncheck "No motion search..." and check "Soften block noise" on the Quantize matrix tab. I also set the audio to 128K. Enable noise reduction if you like, though it takes along time to encode with this on.

Follow the rest of my method as described. Good luck, and please let me know how it turns out.

Also, if anybody can improve this method, plese post a reply.

[Keybored]

I apologize but all this seems like too many hoops to jump through. Im gonna have to re-evaluate how important this all is to me, lol. However, I appreciate the replies guys. There are just too many programs I'm not familiar with. Thanks

[BlackAdder]

It just seams daunting at first, but it's very simple once you get the hang of it. Actually, I have to admit that I enjoy the challenge of encoding a movie, of making it the best I can. I don't think I would be here if I didn't.

Anyway, here's the steps:

1. Extract the audio with Virtual Dub - 5 minutes.

2. Put the name of your source in the avisynth script.
Don't worry about the bicubicresize stuff - 1 minute.

3. Load the avs file (avisynth script) into Virtual Dub and
start the frameserver. - 30 SECONDS.

4. Start TMPGenc, load the vdr file as your video source
and the wave as your audio source. - 1 minute.

5. Hit Encode.

Very easy, 7 1/2 minutes to setup including extracting the audio, actually less, but who's counting.

Worry about the other stuff later.