60fps to 24fps

HotConductor

HotConductor

Well-known member
Do you all see any drawbacks to this? Ideally I would just shoot everything is 720p 60fps, and drop it to 24 in post. That way if I WANT slo-mo, its there, and if I don't, I can just render it out 24fps anyways.

Please let me know your thoughts. I've had mixed results but I'm wondering if its just a 'feeling' I'm having and not real results.
 
Search through my some of recent posts, I have written extensively on multi format conversion, and considerations on frame rates... I also have blog @ www.hingsberg.com with an article on it.

Basically, 60fps will not go to 24fps very well and you should avoid that plan. If anything, shooting 60i will give you the most flexibility in post if you are not sure where you will end up. ie. 60p, 30p, 24p.
 
I just read your article but you don't mention any reasons behind your observations. I also didn't see any of the math. To my simple calculations 60 fps translated to 24 fps is a 2.5:1 conversion. Seems like 24p would be an easy conversion from 60p. Why doesn't it 'work' in reality?


Why would 60i give more 'flexibility' than 60p? Whats more flexible about dealing with a non-progressive format, when your output ultimately is progressive. (Thats a major gripe of mine about ALL digital formats. Interlacing should have died a long time ago.)

Thanks for your feedback!
 
HotConductor said:
I just read your article but you don't mention any reasons behind your observations. I also didn't see any of the math. To my simple calculations 60 fps translated to 24 fps is a 2.5:1 conversion. Seems like 24p would be an easy conversion from 60p. Why doesn't it 'work' in reality?
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Because it's not evenly divisible. e.g. How you represent 0.5 of a frame ?

He's not referring to slo motion, where the same number of frames are used, just the frames per second are reduced

He's referring to a standards conversion, which requires decimation +/- new frames being generated by blends/dupes or interpolation



Why would 60i give more 'flexibility' than 60p? Whats more flexible about dealing with a non-progressive format, when your output ultimately is progressive. (Thats a major gripe of mine about ALL digital formats. Interlacing should have died a long time ago.)
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It doesn't. 60i => 24p is just as bad as 60p => 24p, assuming it's not slo mo being referred to. The article says "You can even create good looking 24p from 60i using post production plugins." I'm assuming he means interpolation. This is far from clean. Motion interploated frames can sometimes be great but other times suffer from morphing artifacts


The reason why you wouldn't shoot 60p all the time is your resolution is decreased. 1920x1080 vs. 1280x720. HMC150 can't shoot 1920x1080p60 (even though some consumer cams can)
 
Shooting 60fps and putting it on a 24fps timeline will simply give you 2.5 times slow motion.

Coverting from 60fps to 24fps and keeing time the same would require a combination of frame dropping and blending which will result in jerky looking playback (like the girl from the RING coming out of the well...). ie. If you drop every 2nd frame you go from 60p to 30p and the motion of the footage looks fine, but drop every 2nd frame and then the 3rd frame and that extra frame is enough to make the footage look jerky on playback.

I say 60i is flexible because it will in fact allow you to go different frame rates and create progressive looking frames but as PDR pointed out it all uses interpolation and/or frame blending techniques so the result can be some visible artifacts on your image but I disagree that 60i -> 24p is just as bad as 60p -> 24p because with interlaced footage you have more information to work with and blend fields to make new frames.

Have a look for Magic Bullet plugins, Cinemotion, Cinelook, or DVfilm. Some plugins will simulate the look of 24p in 60i, while some will actually result in 24p footage.

I'm definitely not saying this is perfect... I'm just saying technically it's possible and therefore quite flexible.
 
starcentral said:
but I disagree that 60i -> 24p is just as bad as 60p -> 24p because with interlaced footage you have more information to work with and blend fields to make new frames..
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Do you mean more spatial information? Because the temporal samples are the same. I was referring to cadence. 60p is just as bad as 60i. Both represent 60 moments in time per second. Both convert poorly to 24p for that reason

If you meant spatial information 1920x540 fields vs. 1280x720 frames, then it's debatable.

By the time you deinterlace it and apply post processing, the actual resolution is not very high. It depends on the deinterlacing algorithm used, and if this is a static shot vs. a motion shot. If you use a simple bicubic resize of fields (what all NLE's do), you end up with jaggy aliasing artifacts when bob deinterlace to 1920x1080p60. If you use 3rd party deinterlacers, then you can significantly increase the quality over the simple deinterlace scenario
 
I suppose that taking fields from 60p frames to combine/interpolate into making new 24p frames would be no different than if taken from 60i to begin with, but I have never tried it and thus far only done countless conversions using 60i and 50i sources.

Regarding resolution, it would only be affected where motion is present so it is hard to say the "entire" resolution is lowered when technically it is only lowered for certain parts of the footage.. Amongst my conversion methods were several 3rd party script based video processing programs where I could chose from a variety of filter modes, ie. bicubic, bilinear, lanczos, nearest neighbour, etc.... allowing me to experiment and try different settings for optimal results.
 
Eh, I've mixed 60p in a 24p timeline before - yeah it's a little jerky, but as long as frame blending is off I think it's okay as long as you're not dealing with a lot of motion in the shots.
 
starcentral said:
I suppose that taking fields from 60p frames to combine/interpolate into making new 24p frames would be no different than if taken from 60i to begin with, but I have never tried it and thus far only done countless conversions using 60i and 50i sources.
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Yes, in terms of cadence, it's the same, but the other differences mentioned make a blanketed statement hard to justify. I don't think it's such a clear cut answer. There are so many variables, and there is a continnuum of quality between the different deinterlacing algorithms. If you use a crappy or regular algorithm, the aliasing artifacts are propagated when you interpolate new frames. The resize method of the deinterlace (e.g. spline vs. lanczos etc...) makes less of a difference in quality than the post processing applied in terms of deinterlacing. If you use a good algorithm, the end result can be fantastic, and the interpolated frames much cleaner

There are other variables to consider - for example, interlaced encoding is less efficient than progressive encoding. Motion vectors get truncated and do not cross odd/even field pairs. For a given scenario under the same bitrates, DCT ringing and compression artifacts will be greater for interlaced encoding. These artifacts can reduce the quality of the motion interpolation.
 
Thank you all for weighing in. A few notes...

1. I am not talking about slow-mo. I love taking 60fps and slowing it to 24fps. I use it frequently, and love the technique. No questions there.

2. Resolution. I am aware of the fact that 1080p cannot be shot at 60p but rather 60i. I am not interested in interlaced footage AT ALL. I will NEVER shoot interlaced ever again.

My general technique has been to shoot everything 1080p 24fps and only use 720p 60fps for instances where I KNOW I will need slow motion at a later point. My main purpose in asking this question is whether 60fps can successfully transfered to 24fps without juggery looking footage. I will have to try it without frame blending.

An example: Shooting a wedding. Not my favorite gig, but they're there. Ideally I would shoot 720p 60fps and be able to drop into slow motion during any part of the footage, and render out to 24fps with the final product. As it is, I am just shooting everything 1080p 24fps and not using slow motion except at certain points during the reception.

Are there any plugins you'd recommend? I edit within Vegas 10 and the CS5 suite (learning AE and Premiere, just not there completely yet).

Thank you all for your feedback. This has been a very helpful discussion for me! I love this forum.
 
HotConductor said:
Thank you all for weighing in. A few notes...

1. I am not talking about slow-mo. I love taking 60fps and slowing it to 24fps. I use it frequently, and love the technique. No questions there.

2. Resolution. I am aware of the fact that 1080p cannot be shot at 60p but rather 60i. I am not interested in interlaced footage AT ALL. I will NEVER shoot interlaced ever again.

My general technique has been to shoot everything 1080p 24fps and only use 720p 60fps for instances where I KNOW I will need slow motion at a later point. My main purpose in asking this question is whether 60fps can successfully transfered to 24fps without juggery looking footage. I will have to try it without frame blending.

An example: Shooting a wedding. Not my favorite gig, but they're there. Ideally I would shoot 720p 60fps and be able to drop into slow motion during any part of the footage, and render out to 24fps with the final product. As it is, I am just shooting everything 1080p 24fps and not using slow motion except at certain points during the reception.

Are there any plugins you'd recommend? I edit within Vegas 10 and the CS5 suite (learning AE and Premiere, just not there completely yet).

Thank you all for your feedback. This has been a very helpful discussion for me! I love this forum.
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Yes you can, but the negatives are slow processing times, morphing frames (edge artifacts) if you decide to interpolate.

The math is like this: you're going from 60p => 120p so every 2nd frame is fake. Then you're taking 120/5 = 24. That's the only way you get evenly spaced frames and decimation because 120 is the lowest common multiple between 24 and 60.

Vegas can only do blends or duplicates. Usually blends are preferrable to duplicates (less jerky), but more blurry.

The 3rd method to generate the new "in-between" frames is motion interpolation. Options on a PC include AE (pixel motion, timewarp), twixtor pro, avisynth mvtools2, kronos (timewarp is based on this), there are a few others. They all give simlar quality results and side effects. mvtools2 is fastest processing wise. The "pro" aspects of the plugins allow you to use foreground/background edge mattes to limit the morphing, these are meant for VFX shots, but it sounds like you want a push button solution and won't be fiddling with mattes

On some types of footage, interpolated frames can look very good, but on others you can get disasterous results. Those with predictable, linear motion usually yield better results, because motion vectors are more easily tracked. So something like a slow pan at a wedding will give better results than a run and gun action shot.

I honestly can't recommend doing this for the main 24p footage. IMO there are more negatives than positives, but feel free to experiment. Make sure you do your experiments with plenty of time before doing something for a client :)
 
Yes anything you do to go from 60p to 24p can not be done without some level of frame related manipulation. If you want a way to do it without frame blending manipulation, you will not like my solution which is to shoot PAL at 50p, since it can go to slow motion at 2 times slower speed, or easily create 25p by skipping frames, and then finaly to 24p by mapping one progressive frame to another resulting in a 4% longer clip, and audio whuich needs to be time stretched/pitch corrected to match the new length.

Complicated? Yes and no depending what you want to sacrifice.
 
You can also shoot 48frames with a 220degree shutter.

This way, your normal speed, 24p will be protected by simply skipping everyother frame, and if you need it, you can slow the 48 down by50% to get slowmotion. Record your sound seperatly. I wouldn't shoot the whole film this way, but for scenes where you need speed ramping, its useful, and you don't get exposure ramping issues.
 
TimurCivan said:
You can also shoot 48frames with a 220degree shutter.

This way, your normal speed, 24p will be protected by simply skipping everyother frame, and if you need it, you can slow the 48 down by50% to get slowmotion. Record your sound seperatly. I wouldn't shoot the whole film this way, but for scenes where you need speed ramping, its useful, and you don't get exposure ramping issues.
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The HMC150 doesn't shoot 48fps. How are you suggesting i do that? If the camera offered that option, I would have used it ages ago.
 
HotConductor said:
The HMC150 doesn't shoot 48fps. How are you suggesting i do that? If the camera offered that option, I would have used it ages ago.
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You can get a PAL version of the HMC150 and shoot 50fps giving you the flexibility of going to 25p, 24p or even 48p with some simple frame mapping on your timeline. No field blending either or weird things like that. Again, not the answer you want, but of course the possibilities exist depending how important it is to you. For years I shot on 50i PAL and converted to 24p way before it existed as an option on camcorders. Needless to say I was quite desperate and HATED the interlaced look.
 
Please explain what you mean. I would love to be enlightened! How can you film at 48p. I thought it only shot 25p or 50p, which would be ideal if I were going to be doing slomo with the goal of a 25p timeline. How would shooting 50p be any better for frame mapping than 60p?

I am not being sarcastic or anything, I would really like to know.
 
I like sarcasm anyway, so no worries either way :D

I think I wrote in a previous post already that from 25fps you can skip every last frame (25th frame) and end up with 24fps. This was one method of converting 25fps to 24fps for film conversion, the same can be done for video. If you shoot 50fps, you can still skip every 25th frame and will have 48fps. WOW - 48fps is the latest craze and now everyone including YOU and James Cameron can do it too!!!

The other method which is what I use to use to go from a 25frame based timeline to a 24frame based one, was to map each frame of 25fps to 24fps. When you do that however, you have 1 extra frame where ever there is 24, so effectively you add 4% in time to your overall timeline. 4% is NOTHING to notice, and I've shot dozens of films this way that have played at major film festivals. It really does work but don't get me wrong it is a pain in the arse. Your sound which is not stretched now ends sooner than your video --- so what you do is stretch it back out by 4% using time/pitch correction and marry it up with your video clip again. Again, no body will notice. Only you will know!
 
Ahhh this is hmc150 forum..... stupid dvxuser mobile doesn't tell you what forum you're in.....
 
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