How does 3:2 pullback work

[Wolverine_Ecks]

I have some 23 fps movies I want to burn but DVD's require 29 fps, could anyone explain what I have to do?

[Meteor]

If you search for telecining, you will find what you seek.

[adam]

Just run the video stream through pulldown.exe. Its self explanatory with the gui. This is covered in all of the guides too.

[Vejita-sama]

Several guides here and at http://www.doom9.org You can d/load pulldown.exe and a good GUI for it from doom9.org too. Do a forum search for more background info but basically:

"pulldown source.m2v output.m2v"

that's pretty much it Pulldown ONLY works on elementary streams, so if you've got a muxed MPEG file de-mux it first. You can then use the pulldown generated video and the source audio to author your DVD.

[Wolverine_Ecks]

Practically all of the movies are AVI, but in doing this 3:2 pulldown will quality be altered if so, would it be better to convert it to 29 fps and resync the audio?

[FOO]

Pulldown only works on MPEG files. Encode the avi to
MPEG2 first (without changing frame rate) and then run
pulldown. TMPGenc will do both at once .

[Wolverine_Ecks]

I understand that part, but will I lose quality in the video?

And, would the results be better if I converted the file into 29 fps with Vdub and resynced the audio with the interleaving?

[FOO]

I understand that part, but will I lose quality in the video?

I don't think you do understand.
Define "quality"
3:2 pulldown converts 23.976 into 29.97
it actually creates 1 new frame for every 4 originals
You don't need to modify the audio at all .

Ask yourself if you think you know what exactly happens when you
"convert to 29.97 fps with Vdub"
I'll tell you ,--- Nothing -- it just plays faster and the audio will be out of sync.

[Wolverine_Ecks]

No need to get snippy, I was talking about I understand I can do both processes with TMPEnc ... ask a question and get griped at ...

[FOO]

Didn't mean to gripe .
Drives me nuts when somebody sez "will I lose quality"

[adam]

Its higher quality to encode the video at 23.976fps and allow the decoder (DVD player) to telecine it as it plays to 29.97fps, than to physically code it to 29.97fps. The main reason is that a 29.97fps has ALOT of additional overhead. There are 20% more frames every second, and it is now coded interlaced (you have to interlace it to do the conversion to 29.97fps.) These things require additional bitrate.

If you instead let the player deal with the conversion you get the same output, ie:29.97fps but you don't have to worry about physically storing that additional overhead.

Almost all commercial NTSC DVDs are encoded at 23.976fps and use 3:2 pulldown flags.

[leera2]

Funny I never use 3:2 Pulldown, if I have an avi file at 23fps I convert it to mpeg2 using TMPGEnc and just set it to 29fps. works ok for me every time. 8)

[adam]

Yes it will work. I think if you do that TMPGenc automatically uses its 3:2 pulldown filter which hard telecines it to 29.97fps. Basically it does what the 3:2 pulldown flag does during playback. I can assure you that you are losing substantial quality doing it this way. Try setting output to 23.976fps and enabling the 3:2 pulldown durin playback option on the video tab instead. You will find that this also works, and you should see a substantial increase in quality as well.

When Foo mentioned that using Vdub to convert to 29.97fps would not work, that is because it will not use a 3:2 pulldown filter by default, and so it will simply speed it up which will make it unwatchable. You could load such a filter manually, and again it would work, but you lose too much quality this way for no good reason.

progressive 23.976fps material should be kept that way.

[p_l]

So isn't that what the Wizard sets as its default settings when you load a 23.976 fps source in TMPGEnc, anyway?

When I load a 23.976 fps source in TMPGEnc, on the Video Tab I get:

Frame rate: 23.976 fps (internally 29.97 fps)

Encode mode: 3:2 when playback

Would there be any reason to change these default settings? Are these settings right for a 23.976 fps source?

[adam]

For a 23.976fps source, yes those are the correct settings. The only reason you wouldn't keep an 23.976fps source at that framerate is if you were outputting to an analogue format or if you needed to make an mpeg1 DVD, which only supports 29.97fps for NTSC. But in that case you'd be better off just encoding to mpeg2 instead.

[p_l]

Thanks for the clarification.

[thor300]

Ask yourself if you think you know what exactly happens when you
"convert to 29.97 fps with Vdub"
I'll tell you ,--- Nothing -- it just plays faster and the audio will be out of sync.

It works well, you are talking about framerate adjustment, he asked about framerate conversion. You can even do framerate conversions in vdub with direct stream copy for the video, but that would probably not be possible with the files he is talking about unless he save to uncompressed AVI, and pulldown is the best in this case anyway... Still, it CAN be done with vdub without squeezing or stretching. Just one thing with framerate conversion in vdub, it will adjust it at the key-frames (when using direct stream copy), so if the keyframes are for ex 10 seconds intervall and converting from lets say 29.97 to 25 the video will jump badly and the sound will be in sync only at and immediately after a keyframe. The practical use of it is very limited, for ex 30fps to 29.97 when the keyframes are one sec interval or less. I guess it can give good results when saving to uncompressed AVI, but i didnt try that so cant say.