Having framerate issues converting to DVD

[MikeCouves]

I have been trying to find a working program that will convert my .avi, .mpg, etc. type moves to DVD for a long time. I used several programs, and ffmpegx seemed like one of the better ones. Everything converted fine, and I could open it up with the DVD Player that comes standard with my Mac. The problem was, when viewing the converted movie, it's really "choppy." I am quite inexperienced with converting movie files, and that's the only word I could think of to describe it. Right from the start, it is unpredictably choppy and off sync with the sound. I honestly have no idea what to do. Any help would be greatly appreciated. I can provide further information if needed, because I don't know what you need to help me. Thanks ALOT!

-Mike

[Case]

One of the reasons why DVD video might seem choppy in Apple DVD Player, is when the framerate is 23.976 fps and there is no 3:2 pulldown on the video.
- What is the framerate of your source video?
- What is the framerate of your target video?
- Did you use the DVD mpeg2enc or DVD ffmpeg engine?
- Did you apply a pulldown, if applicable?

See also topic 326567, amongst others.

[MikeCouves]

- What is the framerate of your source video? 23.976

- What is the framerate of your target video? NTSC 23.976

- Did you use the DVD mpeg2enc or DVD ffmpeg engine? ffmpeg mpeg2

- Did you apply a pulldown, if applicable? Please elaborate on the pulldown, never heard of it.

Thanks again,

Mike[/b][/quote]

[Case]

The 3:2 pulldown is the process of converting 24-frame-per-second film to video by repeating one film frame as three fields, then the next film frame as two fields. Essentially the smoothest way of turning each 4 film frames into 5 video frames (10 interlaced video fields). For MPEG-2, this process can be done at playback time, when a pulldown command is inserted as an instruction to the video. The movie itself stays 23.976 fps progressive, but with an instruction for smooth playback on 29.97 fps interlaced devices (like tvs). This saves 20% bandwidth and is the de facto standard for NTSC FILM material on DVD, as theater movies are 24 fps, and NTSC tv broadcast is based on 29.97 fps.

The lack of a pulldown makes Apple DVD Player stutter, as well as many DVD set top players. I think it repeats each 12th frame a couple of times until it syncs up again with the audio and/or timecode.

Links for more in-depth information, with nice diagrams and all:
• Pulldown explained
• 3:2 Pulldown Explained

As far as I know, this applies only to MPEG-2. I don't think this technique is used with other codecs.

------------------------

The MPEG-2 (mpeg2enc) setting does have a "Set 3:2" checkbox for a 3:2 pulldown in the Options tab.
Unfortunately, the MPEG-2 (ffmpeg) setting doesn't have such an option for a pulldown (yet).
To add a pulldown to your MPG file created with the ffmpeg engine, you'll need to demux the file to a separate video-only file and an audio-only file. Next, apply a pulldown to the video-only file using the Pull tool in the Tools tab. Next, mux the video and audio back together again using the Mux tool in the Tools tab (which also allows for authoring as DVD, i.e. making a VIDEO_TS folder).
Because of all the extra steps, the mpeg2enc engine may be easier next time (for 23.976 fps material)?

[MikeCouves]

It works! The movie I have been working with is now viewable with DVD Player on my Mac. All I needed to do was check 3:2 pulldown ...

All I need to learn now is how to join multiple movies into one DVD, I should be able to find that on this forum.

Thanks a lot for your help! I have been trying to get this for a while.

[tiny-e]

I had this same problem with a video that I was trying to convert to a DVD... What I did was set the frame-rate to NTSC (29.97) in the Video Options section of the Video tab -- and it worked, no more stuttering.

Maybe that would work for you and save the time of demux / remux.

[MikeCouves]

I was wondering if that would work as well. I will give it a try.

I converted a movie using 3:2 pulldown yesterday, and although it was a lot better, there was a still a little stutter in it. I'm still trying to master this encoding business, it's rather complicated and I find it varies from movie to movie.

[tomlee59]

Understand that pulldown is a hack. It's clever -- even brilliant -- but it's a hack nonetheless. Setting the pulldown flag greatly improves playback over what you previously had, but pulldown in and of itself produces unavoidable motion artifacts known collectively as "judder" (a combination of jitter and shudder). It is a fundamental consequence of conversion from 24fps to 30fps using this method. You will never completely eliminate it when attempting to go from film to NTSC using pulldown. You can fiddle with settings all you want, but there will always be a residual judder (particularly noticeable in panning shots, for example).

Maybe in the future, they'll fix this by upsampling to, say, 120fps, and swapping each 4 frames of the source for 5 frames of the target. But that day is not here.

[exekutive]

I converted a 24 fps video to 30 by re-encoding (not pulldown) and still experience mild 'jutter' (My own word for jitter and stutter)

[tomlee59]

You got judder because the framerate conversion algorithm still uses pulldown (!), and merely hard-burns the result. You could've saved the 20% bitrate, avoided quality loss, and avoided the transcoding time by just leaving it at its original framerate and simply setting the pulldown flag, letting the player handle the framerate conversion on the fly.

[exekutive]

Wow that sucks. But aren't most commercial DVD's encoded at 24 fps? Surely everyone isn't watching juddery movies at home with their household DVD players & TVs. (I don't know because I use a computer)

[tomlee59]

Yes, it doth suck!

And judder is an unfortunate fact of life for viewing films on an NTSC device. It's quite annoying to me, but not everyone notices or is bothered by it. It's one reason that I prefer DVD playback on the computer, as do you, apparently.

[exekutive]

By NTSC device, I assume you mean your standard CRT television.

OK, so given that most films are released on 24fps DVDs and most televisions in North America display @ 30fps, why don't DVD players automatically pulldown? Why do we have to explicitly set flags?
OR
Why aren't DVD mastered in 30fps? The higher framerate should look smoother anyways.

None of this makes any practical sense.

[tomlee59]

DVD players *do* automatically pulldown. *How* they pulldown depends on whether or not the flag is set. If it's set, it does the "normal" pulldown sequence. If not set, it makes an ad hoc stab at things when it notices that "something is wrong." That leads to extremely craptacular judder, instead of the ordinary annoying judder.

A flag is needed because the DVD player needs help in determining whether the DVD contains material mastered at 24fps, or at 30fps (I'm using round numbers). That is, the source material could have originated from film or TV, for example. The different framerate standards used for those two sources is why a flag is necessary.

And why isn't everything a single framerate? It's because film and TV evolved along different trajectories, driven by different practical considerations. Film isn't 30fps, despite the greater smoothness you cite, because it would require 25% more film. That means less time per reel, more reels per movie, more reel changes per movie, more weight, etc.. Visual quality is only one of several factors that trade off against one another to produce the final result.

Btw, film framerates used to be much lower (again for lower cost/weight of film stock), but crept upward until they got to a high enough value to get acceptably low flicker at 24fps. The Europeans ended up at 25fps for TV, following a similar set of experiments. Engineers like round numbers, so they ended up with 25, instead of 24 (drat!). The US chose 30fps, for even lower flicker. They didn't think of the trouble they would be creating for film playback on TV, because everything was live initially. Only later did they do a Homer Simpson forehead slap "Doh!" And so we're living with those choices, a good part of a century later...

Once a film has been shot at 24fps, you can convert to 30fps, but the question remains: How? Pulldown is the standard answer. To fully appreciate the problems, study the links that Case highlighted. Once you understand the nature of the challenge, you'll understand why simply saying "DVDs should all be authored at 30fps" misses a lot.

[exekutive]

You mean DVD playes are too stupid to be able to detect the source framerate and choose the right display method? Talk about user friendly technology.

In regards to the DVD's. Do they still use film stock? I would have though they had gone digital by now, eliminating the need for these archaic methods. And even if they are shot on cellulose, there is SO much post-production, with the MOST expensive equipment in the industry, that goes on before the film ever touches DVD. WHY can't they use all this fabulous gadgetry to master these films as NTSC for all the nice folks out there? Perhaps by upsampling to 120fps as you mentioned earlier, though I'm sure more sophisticated approaches exist. Wouldn't that make sense?

I think if they can spend the money to make movies in HD, 3D, 3-way copy-protected, anti-aliased, blueray, surround-sound, director's cut with special features, they can make it friggin JUDDER FREE! *throws up hands*
OK I'm done.

[tomlee59]

It's happening now, but it'll take time and $$ to convert the many, many films made in the last century. And only a small fraction of those would generate revenue sufficient to justify the expense. But the costs will come down over time, and more and more of these older films will get the full digital treatment. Until then, we'll be living in the Age of Transition, where we'll have to tolerate some irritating artifacts that result from legacy technologies. You'll be able to tell your grandchildren all about it.

[exekutive]

Of course it would be a lot to ask to convert all EXISTING films. I was actually referring to stuff currently being released. I understand there's probably time and money involved, but man this is one annoying and noticeable artifact!

[tomlee59]

Remember, theaters are still mainly film-based, so until $$$ get spent to convert enough of them to all-electronic projection, this legacy problem will be with us.

Be patient. Revolutions take time.

{"Give me patience, and give it to me now!")