Converting Canon C300 footage shot at 30fps, 48fps, and 60fps to play at 23.98fps in Final Cut 7

Posted by leopardt 
We shot a lot of slow motion at 30, 48, and 60fps with the intention of having the option of regular speed (23.98) or slow motion for each of the shots.

The MXF files were converted to Pro-Res using log and transfer in Final Cut 7 with the Canon Plug-In. There are no options in log and transfer to adjust the speed, so I used the change speed function within Final Cut to convert the slow motion clips to play back at normal speed and to sync the sound.

However, there is a distinct motion blur with the speed change. With the frame blending option it almost looks dream-like, without it the dropped frames are really noticeable, especially the stuff shot at 30fps. Is there a better way to do this that will look right?
Re: Converting Canon C300 footage shot at 30fps, 48fps, and 60fps to play at 23.98fps in Final Cut 7
September 27, 2012 08:35PM
Nope, you're not doing it the right way. Capture those clips at their current FPS (which is usually what it defaults to), make copies of the clips, change their name (eg. add a suffix like "23_98fps"winking smiley, then use Cinema Tools to conform them to 23.98fps.
Thanks for the response. I'm not sure my question was completely clear though. The footage comes in from log and transfer at 23.98. So without me doing anything, the footage that was recorded at 30, 48, and 60fps is already playing back in slow motion at 23.98. I believe the C300 does an in-camera conversion (see article below).

Is there a setting I can use in Cinema Tools to make it play as if it were shot at 23.98, in essence changing the speed by 125%, 200%, or 250%?


Normally I wold convert 60 fps footage with Cinema Tools on the Mac. However, the C300 has a “Slow and Fast Motion” feature where the conversion in essence is done in camera.

Access the menu and go down to the wrench icon (“Other Function”). Select bi-rate resolution to switch to one of the 720p modess.
Then back out of bit rate/resolution and scroll down to access the Slow & Fast Motion setting. Select 60 (it increments from 1-60. Note, the menu simulator may not change to show you all the increments).
Then back out of Slow & Fast Motion and scroll up to “Special Rec”. This will allow you to activate the “Slow and Fast Motion” feature.
Once activated, you’ll see an “S & F” at the top of the viewfinder. Where the frame rate shows you’ll see 60/23.98. This represents the shooting rate and playback rate. Any clips you shoot now will be at 40% slow motion in camera. No need to convert on the computer.
If your camera really shot 60p then when it output 24p from this it would have done exactly what Cinema Tools does. Conforming changes just the video header and introduces none of the dreamy slime you saw.

But your camera does not shoot 1080/60p. It is only capable of 1080/60i, 1080/30p or 720/60p. If you asked it for 1080/24p as if shot at 60 fps, then who knows what it actually sampled at the sensor? Maybe 1080/60i, maybe 1080/30p, maybe 720/60p, or maybe something special. Apparently it did a bad job of making the 2.5× slow motion 1080/24p from what it sampled.

You'd be better off shooting 720/60p, uprezzing to 1080/60p, and then conforming to 1080/24p. Alternatively, shoot 1080/60i, double deinterlace to 1080/60p, and then conform to 1080/24p.

Note: all frame and field rates have been rounded to whole numbers.

Dennis Couzin
Berlin, Germany
Your problem seems to be the only one I've come across that is like mine. I saw your post here and wanted to try contacting you to see if you ever got this figured out.
We just used the c300 for the first time last week after using 1D's and 7D's previously in the past. We would shoot stuff with the D series cameras at 60 frames and we could pick and choose which shots we actually conformed in Cinema Tools to slo mo. I've now read that is not the case with the c300. Well, I'm stuck with a bunch of footage at 23.98 slomo that I need to speed up to regular or normal 23.98. Were you ever able to work something out? Are there any programs out there that will do the conversion for you? If not, do you just have to "Change Speed" in your sequence timeline? What speed did you change it too? Any insight that you could give me would be greatly appreciated. A few of the shots are integral to our story edit and they have people talking in them and I need the smoothest speed up possible so that I can hope to at least visually sync up the audio.

Thank you!
Your camera shot at 60 fps and made a 24 fps clip from this so it's 60/24 =2.5× slomo in your 24 fps sequence. To make it natural speed again you just need to discard 36/60 = 3/5 of its frames. Trouble is, you can't drop 3/5 of the frames in a perfectly regular way. You will wind up doing something like converting ABCDEFGHIJK... to ADFI... where the time between A and D in the world was 3/60 of a second, while the time between D and F in the world was 2/60 of a second. Now they're all displayed 1/24 second apart causing a small irregularity in the perceived motion. Whether it's a serious defect depends on the nature of the motion and on the accuracy of the 24 fps display.

Setting "speed %" to 250 in the FCP7 motion tab converts ABCDEFGHIJK... to ADFI... . It's clean and simple if you can live with the resulting motion.

The alternative is to not discard 3/5 of the original frames but to instead discard 4/5 of them and create new frames totalling 1/5 of them. Instead of converting ABCDEFGHIJK... to ADFI... you'd convert it to A[CD]F[HI]... where [CD] denotes a frame midway between C and D; [HI] denotes a frame midway between H and I; etc. Don't do this by cheesy frame blending, for that's too obvious at 24 fps display. Use optical flow software (or hardware) to create new frames [CD], [HI], etc. You already have fairly good optical flow in Compressor. In the Compressor's Frame Controls tab "Set Duration to" 40%. For the "Rate Conversion" method choose Best (Motion compensated). Cross-your-fingers.

Compressor's optical flow speedup will look nice and smooth, but it may or may not be weirdly artefacted. Other speed changing optical flow software like Twixtor provide user controls which can reduce artefacting. (Andreas Kiel post.) But for some subjects you can't get the desired new frames [CD], [HI], etc. Then you must reconsider the FCP7 motion tab way.

Dennis Couzin
Berlin, Germany
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