The 3 ways of converting 30p to 24p

There are 3 ways to convert 60i/30p to 24p. Each one has its ups and downs. None is really ideal for all cases, so if you really need real 24p, get a real 24p camera. In detail:

1. Resampling (or motion estimation)
This is the default Sony Vegas mode when your project properties has a specific source frame rate and you export in another, or when you slow-down footage. There is a huge amount of ghosting introduced when resampling is ON. I personally always make sure that all the clips in my timeline are set to “disable resample” before I export. I suggest you do too. Vegas’ resampling is one ugly algorithm, avoid. Ghosting:

2. Drop frames
This method will drop 6 frames per second in order to convert from 30 to 24 fps. On Sony Vegas you do that with the “disable resample” option mentioned above. Other editors, use this method by default (it’s the simplest to implement). The problem of this method is that the video it produces is jerky. You see, the camera didn’t record 24 frames at 24 even times a second, but 30, and so there will be “gaps” in the motion of the video. These gaps will show up as jerky video. The good news is that many viewers never notice, the bad news is that this will still not visually feel like real 24p.

3. 25% slow down
This is my preferred method. Basically, by slowing down the playback rate by 0.800, we essentially emulate the 24p capturing process perfectly. There is no jerkiness, everything gets a smooth, dreamy look, which is very cinematic. And no, the vast majority of the viewers will never realize that the footage was slow-motion’ed! It is the perfect way to shoot music videos (using this trick), artistic/abstract pieces, and anything else that doesn’t require synchronized speech. See, this method has a drawback: you can’t resample audio with the same effectiveness as you do for video, it will sound real slow and bad (even after correcting the pitch). So basically, this method is out from the moment you want to use the audio captured along the video. You can only add music/narration during post processing, but no sync’ed speech. This method takes out the ability of shooting short movies where people have to talk on camera, but it’s good for everything else.

Showing all 3 methods visually:

My model is Emily Palen, from the band Dolorata

Here are the playback rates you need to use for the 3rd method:
60i (via interpolated de-interlacing), or 29.97 fps to 23.976 fps: 0.800
60i (via interpolated de-interlacing), or 29.97 fps to 24.00 fps: 0.801
30.00 fps to 23.976 fps: 0.799
30.00 fps to 24.00 fps: 0.800
Of course, always disable resample just before you export, on all your clips in the timeline.

10 Comments »

Nekoneko wrote on August 5th, 2009 at 5:13 AM PST:

While the listed examples should work ok for converting native 60i/30p material to 24p, I’m not sure I understand why you’d want to do that.
Why not work with the native speed?


This is the admin speaking...
Eugenia wrote on August 5th, 2009 at 11:02 AM PST:

Because a lot of people don’t like the 60i/30p motion look for short movies or other special purpose videos. I am one of these people, and there are thousands with the same gripe in the Canon 5D Mark-II market too.


Stephen James wrote on August 5th, 2009 at 12:34 PM PST:

Thanks for this Eugenia… 🙂
One question though, after choosing a method, do you have to then change the Video properties to 24 or 23.976fps and then render.. or render it out first then create a new project with a 24 or 23.976fps and bring in the previously rendered file? Thanks for any help on this.. appreciate it much.

Steve


This is the admin speaking...
Eugenia wrote on August 5th, 2009 at 1:29 PM PST:

You can use a 30p timeline, and then apply any of the 3 methods and export at 24p at the end. If you have mixed 30p and real-24p files, then export them to 24p individually first and then put them in a real 24p timeline. For the first and second method you can use them in a real 24p timeline directly, but for the slow-down method better make sure it uses all the frames, so use it in 30p and export to 24p later.


Stephen James wrote on August 6th, 2009 at 12:02 PM PST:

Thanks so much Eugenia… I appreciate the quick response.


Mike the Noob wrote on August 10th, 2009 at 10:29 PM PST:

Does the slowdown method produce a better quality result than shooting in PF24 and removing the pulldown? Also, how does the slowdown method compare to using a 3rd party app to do the conversion such as Magic Bullet Frames or TMPGEnc Xpress. Thanks in advance.


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Eugenia wrote on August 10th, 2009 at 10:41 PM PST:

It’s just different. It’s the motion that’s different, not the quality of the pixels. Plus, as I wrote above, you can’t use speech with that method, while the apps you mention can.


Raphael wrote on August 14th, 2009 at 5:03 AM PST:

Where did you get the sample material from? 🙂


Caner wrote on August 14th, 2009 at 10:45 AM PST:

Is there a value you can give for converting from 30fps to 25fps?


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Eugenia wrote on August 14th, 2009 at 10:59 AM PST:

Not really, unless you want to create PAL DVDs. And this post is for 24 fps btw, not 25 fps. 24p is the cinema frame rate.


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