Why is this reversed footage stuttering?

[unknownsailor]

On a 30fps 1080 timeline I have placed 4K footage from the Mavic Pro 2 (10bit, 30fps), reduced to 50% dimensions to fit. Shot in log it has a LUT applied.

In every instance where I have reversed the clips playback is stuttering badly. Here is an example:

Sequence 13 - YouTube

Funnily enough when it plays in youtube it doesn't look as bad as the playback on my computer (powerful Ryzen 7) but you can still see how the footage looks a little blurred. On my computer it plays like an old-school badly interlaced clip with horizontal lines.

I have tried Optical Flow on each clip but this doesn't make any difference.

Why should a clip play back like this when all that's happened is that it has been reversed?

[rodneyb56060189]

I wouldn't mind seeing the same footage sample(s) you have on that youtube site now playing on your link, to one using forward and put on youtube so I could compare them...

I don't see stutter, but does look a bit blurry (especially on full screen). Without comparing I'd be tempted to say try 60 fps (probably have to go down to 1080p to shoot that high frame rate ), and turn off image stabilization maybe .. who knows. Got nothin to compare it with.

It's not HORRIBLE the way it is... but is a bit on the 'not sharp' end... like a not so great lens kinda thing...

[unknownsailor]

Yes, I figured I should have put this up too for comparison. Unfortunately I'm about to go offline for two days so I'll give you a shout when I can post up the original footage. For the time being I've removed the reverse effect and gone with the originally shot forward motion and it is all fine. I often reverse my drone footage and I've not come across this issue before, it's odd.

[Ann Bens]

Drone footage is heavily compressed. Also 30p is not very suited to be slowed down 60p would have been a better framerate.

Slowed down and reverse needs optical flow and Rendering (green).

Best is to use proxies with this kind of footage.

[unknownsailor]

It is neither compressed nor slowed down. The Mavic Pro 2 shoots at 100mbps in 10bit with a 1" sensor, and footage is rendered at 100% speed. Using proxies has nothing to do with it, I am referring to choppy playback after it has been rendered. All other footage is crystal clear, only the reversed clips have this issue.

[Ann Bens]

Sorry misread: not slowed down.

But drone footage is still heavily compressed.

Reversing footage takes horse power.

You are flying to fast for 30p footage.

[unknownsailor]

I appreciate you trying to help, Ann, but none of what you say makes sense. In this instance the frame rate has little to do with drone speed. It is the shutter speed, or shutter angle, that creates the 'correct' motion blur. Since this is shot at 30p the shutter speed was set to 1/60, the equivalent of 180° shutter angle. Irrespective of this, the forward version has no problems playing correctly. What do you mean 'reversing footage takes horsepower'? And I still don't understand what you mean about drone footage being compressed. It is 10bit, 422. Can you explain further?

[rodneyb56060189]

Since you understand the shutter speed ( at 180 equiv.) if you shoot at 60fps, it will be 120th / sec.

That would give you less blur per frame.  But you need twice as much light, or open up a full stop ( from 1/60th / sec. ).

H264 was fundamentally designed to 'watch' ( not edit ). It is heavily compressed footage. It looks nice. But it's not the best for editing. Luckily computers got really fast and powerful and now you can actually edit the stuff way better than say 10 years ago.

To keep down the weight of camera and internal electronics and using light weight SD cards, drone cameras typically use H264 for compression. The quality of the footage is pretty amazingly good, in my opinion. But it is still ( the H264) not the ideal editing codec.  No big deal.

When applying effects in the editor ( including reversing footage ) it requires the editor to take the frames and render them from the last frame (first) to the first frame ( last ), and that takes what Ann referred to as horsepower. Luckily you have a powerful computer and can do it. Apparently something is not working too great and it's related to the combination of your computer, the editing program, your source footage, and the effect(s) applied ( and to some extent how you shot it (frame rate / shutter speed )).

You might be able to set your render to something like I-frame only something or other … render it after applying effect, and when you export check 'use rendered cache if available' … see if that works.

It's kinda a crap shoot, how to fix things.

Good luck !

P.S. don't fly too far away !

[Ann Bens]

Exporting to I frame only mpeg only is not an good choice as its a lesser (preview) codec.

[rodneyb56060189]

Is there any other thing it can be rendered to that will be a decent export from cache, Ann ?