24fps and 23.97fps

[scottrwn98]

Ok, I have an old movie that I made that is 640x360 24fps and I want to convert it to DVD MPEG. But In TMPGen I can make it either Video mode or Film mode. Video mode (29.97) makes the video a little jumpy here and there. Film mode (23.97) skips every 1-2 seconds like it has trouble loading. What is the good idea for converting a 24fps AVI to DVD MPEG as far as frames per second?

[chazzie]

Use VirtualDub to convert the framerate to your desired format. If you have audio in that movie too, you must transcode it to fit properly into the video after you've converted it. Check for a NTSC to PAL guide on the site or on the net, that'll explain it to you.

[scottrwn98]

So convert the film to 23.976 in VirtualDub and save it as another AVI? Now what is transcode? The movie is 26minutes with 41kH audio at 24fps ... I want to convert it to DVD MPEG with out it skipping but I'm not familar with this process

Thanks,

[adam]

If you live in a PAL region than go ahead and convert to PAL. TMPGenc will work fine. Load the PAL DVD template, and on the advanced tab check the "do not framerate conversion" filter. This tells TMPGenc to simply speed up your movie rather than duplicate frames to increase the fps. You will have to process your audio separately, regardless of how you convert your movie. You should use BeSweet. It has built in options for converting between regional formats.

You should not convert to PAL unless you actually live in a PAL region. Depending on your playback device, a PAL DVD may be completely useless to you.

So, if you live in an NTSC region you need to convert to NTSCfilm. Again, set the "do not framerate conversion" filter on and set the fps to 23.976fps. I think your mistake was that you did not set the encode mode to 3:2 pulldown while playback. The NTSC standard requires 29.97fps playback. It is extremely common, in fact it is the industry standard, to encode NTSC material at 23.976fps (NTSCfilm) and use pulldown flags to instruct the DVD player to telecine the movie to 29.97fps while the movie plays. Without the flags, the movie will skip badly. With the flags you will get perfectly smooth playback. NEVER just convert a 24fps or 23.976fps source to 29.97fps. You will get horribly choppyness.

Your audio does need to be slowed down slightly to match the newly encoded video, but the difference between 24 and 23.976fps is so slight that you can probably skip this. I doubt its humanly possible to notice this difference.

[scottrwn98]

So if I was to render something in 3D Studio Max that I wanted at 24 fps, I would render it at 24fps and then convert the AVI file to 23.97 (since there is no audio or whatever) and then import it in to premiere?

[scottrwn98]

If I set the frame rate to FilmMode (23.976) and check the do not convert frame rate, the encode mode is on 3:2 ... it will play smooth for 12 frames, pause , play 12 frames, pause...what causes this?

[chazzie]

To avoid complicating this further, if you set TMPGEnc as written above, and the source AVI has no sound, playback on a DVD player will be as smooth as the latest Hollywood DVD you bought. The 3:2 pulldown works like a charm and will not cause the video to skip. Should it skip and/or freeze, there's something else that is afoot, no the telecline. I've converted a few of my self produced films from PAL 25 fps to NTSCfilm with the 3:2 pulldown and I can't tell the difference from the original. Just observe that the 3:2 pulldown at runtime only works with MPEG-2 video, not MPEG-1.

This seems to explain the 3:2 pulldown quite well. Plasma.com

An NTSCfilm clip will be 4% longer than the exact same PAL clip. This is logical considering you don't convert the framerate, you just slow the video down by roughly a frame per second (24 / 25=0,96=96%). This means that if you have an audio file that is supposed to play along with the video (like speech in a movie), you must also change the length of the audio file. Makes sense, right? The audio file should now also be "teleclined", but the term for "audio teleclining" is "transcoding". Download BeSweet (Freeware) and read the guide on dvdrhelp.com. BeSweet have preset switches for audio conversion. But if the clip you have converted doens't have audio, you won't need to bother with this.

Good luck!
Chazzie[/url]

[scottrwn98]

Ok, I did it and it works (24fps is the original and I converted it to 23.976(actually it outputs at 29.97) and it is smooth motion ! Yay! But the audio is off by like 3 seconds at the end (original 53:26 ... new file is 53:29) Does anyone know the percentage of the conversion that I can set my audio? I think its like .999% or .996% or do I just have to do the math on whatever I'm saving?

Thanks for all of your help !

[chazzie]

Ok, I did it and it works (24fps is the original and I converted it to 23.976(actually it outputs at 29.97) and it is smooth motion ! Yay! But the audio is off by like 3 seconds at the end (original 53:26 ... new file is 53:29) Does anyone know the percentage of the conversion that I can set my audio? I think its like .999% or .996% or do I just have to do the math on whatever I'm saving?

Thanks for all of your help !

Let's see, I've brought out my trusty graph-calculator...

You've got A: 24 fps = 53:26 = 3206 seconds = 76944 frames
And also B: 23,976 fps = 53:29 = 3209 seconds = 76939 frames (almost)

The number of frames should be the same, but I guess you've rounded of the playing time values. What's interesting in the audio part is the small difference in speed: 3206 / 3209 = 0.9990651293. This is the rate the audio should be playing. Since BeSweet doesn't support 24 fps to 23.976 conversion by default, I suggest you use an audio editing software and "Time Stretch" the audio part. Import the converted (23.976 fps) video file in a suitable video editing program and write down the EXACT length of the clip, (i.e. 53:29,540). Now, open the old (24 fps) audio file in the audio editing program and select "Time Strech". Enter the new time (length) of the audio into the one that corresponds to your new (23.976 fps) video file.

You should now have successfully slowed down the audio to the NTSCfilm rate, without it being noticed in pitch at playback.

You mentioned that the actual framerate is 29.97 fps. This is exactly how the 3:2 pulldown works. It takes 23,976 fps video and at the discretion of the MPEG decoder, it adds frames to recive the 29.97 fps. If you read the link I provided earlier, you should get the hang of it.

Happy encoding!
Chazzie

[scottrwn98]

So basically to sum all of this up ... all of my old movies in AVI format (30 fps and 24 fps) all I need to do is take them and change their frame rate in VirtualDub (30 to 29.97 .. and .. 24 to 23.976) and then slow the audio down to synch up to the video ... save as a new AVI (DivX) and then bring into TMPGen and output MPEG (DVD) with 100% smooth motion movie ... or import into Premiere and save as Digital Video with 100% smooth motion.

So if you were play a movie on VHS and DVD together synched up, one would eventually go faster than the other (or slower than the other)

All of you have been a big help .. thank you very much!

[chazzie]

... save as a new AVI (DivX)

DON'T USE DivX!!! The DivX format is designed as a "final" compression, so unless you plan to convert the movies to DivX ONLY, use another CoDec. I use DV codecs or HuffYUV.

Chazzie