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Old November 27th, 2015, 06:16 PM   #1
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Adjusting Velocity & Smooth Slow Motion

Question:

It seems like whenever I use the "velocity" band to slow the footage down, it always looks a bit "studdery" once I render the file for youtube or vimeo. Is there a way to ensure smooth looking slow motion once the file is rendered? Any settings that you recommend?

Thanks!
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Old November 28th, 2015, 01:55 AM   #2
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Re: Adjusting Velocity & Smooth Slow Motion

How much are you slowing it down, Jerry, in terms of %?

In my experience, regular footage shot at 24/25/30 etc frames per second (especially footage with lots of rapid movement) doesn't do too well with extreme velocity decreases because there is too much difference from frame to frame and not enough frames in each second to make the transition from frame 1 to 2 to 3 etc nice and smooth. When planning for slow motion it's worth cranking your camera's frame rate up to give you the 'missing' frames.

Some cameras have the ability to shoot at very high frame rates thereby giving you four or five times as many frames. When you slow it down, the jump between frame 1 and 2 and 3 etc is barely noticeable. My GH4 allows 96fps giving me four times as many frames. Others go up to 200 - that's EIGHT times - allowing for super slow motion. There are some caveats, namely that you might find the camera only records high frame rates at lower bitrates, therefore your image might not be quite as good looking as if you shot at normal frame rates, or it might break up if you push it with colour corrections - but it will be smooth! I only have experience with the GH4 (and have been very happy with it) and can't comment on other cameras.

There is a third party plugin - Twixtor - which does a pretty good job of interpolating the movement between frames. In other words it synthesizes the missing frames. This gives a much better result than you could achieve just using Vegas velocity curves. Even so, I think there is only so far you can push regular footage before it starts juddering. Twixtor ain't cheap ($300+) but there's a demo version if you want to try it out. RE:Vision Effects, Inc. : Products: Twixtor

Hope that helps.
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Old November 28th, 2015, 03:19 AM   #3
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Re: Adjusting Velocity & Smooth Slow Motion

Quote:
Originally Posted by Jerry Neal View Post
Is there a way to ensure smooth looking slow motion once the file is rendered?
Mostly no. It all has to happen prior to render with the proviso on the type of render you produce.

Quote:
Originally Posted by Jerry Neal View Post
Any settings that you recommend?
I'd need to know more about your source footage and the render work-flow you have used. And then there is the compromise: good enough.

To ensure - if you DO mean "ensure"? - then you'd require the kit that would do it and planning, which would also include lighting. But, if you are open to compromise - that word "ensure" has me severely worried - then there is "something" that can be done.

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Old November 28th, 2015, 03:45 AM   #4
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Re: Adjusting Velocity & Smooth Slow Motion

Further to Ian's mention of Twixtor, there is a demo video here :


which shows the type of difference you might expect from that kind of software, which uses 'optical flow' to create new frames.

That clip actually uses MV Tools, which is a freeware alternative to Twixtor.

The downside is that using MV Tools is not very 'friendly' to start with

I did post some notes on using MVTools, linked to from post #5 this thread:

How Slow Can I Go....
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Old November 28th, 2015, 05:39 AM   #5
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Re: Adjusting Velocity & Smooth Slow Motion

The other thing you can try (no guarantees though) is to "Disable Resample" on the specific clip. I've done this a few times and the results have been acceptable. Not perfect but acceptable for my needs.
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Old November 29th, 2015, 12:35 AM   #6
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Re: Adjusting Velocity & Smooth Slow Motion

As Mike's suggestion. I use TWIXTOR and this is an absolute must, so try it and compare the outcome.

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Old December 2nd, 2015, 01:08 AM   #7
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Re: Adjusting Velocity & Smooth Slow Motion

Quote:
Originally Posted by Jerry Neal View Post
Question:

It seems like whenever I use the "velocity" band to slow the footage down, it always looks a bit "studdery" once I render the file for youtube or vimeo. Is there a way to ensure smooth looking slow motion once the file is rendered? Any settings that you recommend?

Thanks!
Sometimes a little added 'motion blur' can help.
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Old December 2nd, 2015, 07:25 AM   #8
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Re: Adjusting Velocity & Smooth Slow Motion

A lot will depend on how much you are expecting to slow down your clip.... if only by a factor of 2 or 3 then I think motion blur may well help to reduce any 'stutturing'.

For more extreme 'slow down' ratios it's probably only optical flow processing that can give really satisfactory results
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