Optical Flow Speed Warp advice please

I have been using Resolve for grading for some time. I have generally been using Avid Media Composer for most of my editing though - I have high familiarity with it since I have used it since the early 90s. However I am starting to migrate more and more to Resolve because I like it. I have often done slo mos in MC using Fluidmotion but I am not always happy due to the creation of ugly artifacts on some abstract material (an. area I work a lot in) so I thought I'd evaluate Speed Warp.

I am slowing down one Red shot and my timeline is around 2 mins long. I started exporting this test slow motion last night and then went to bed. It had said 13 hours to export!. This morning it is still saying over 4 hours to go. Is this normal? I am exporting at ProRes 4444 which I admit is rather high.

Ultimately I want the best quality slow motion I can get. I am happy to wait for renders but didn't think it would be this long.

Any advice here?

Thanks, Phil

You'll need a very strong GPU for SpeedWarp. Which one do you have?

You'll need a very strong GPU for SpeedWarp. Which one do you have?

Thanks

Mac Pro (Late 2013) - 3.7 GHz Quad-Core Intel Xeon E5, 64GB RAM

This process appears to have taken over my computer and I can't use it for anything else!

When you're using an unsupported GPU, SpeedWarp falls back on the CPU, which will take exponentially longer. I deal with it a lot. My advice would be to use a different interpolation method while you're finessing the edit. Then, once your edit's locked, try OpticalFlow+Enhanced Better first. If the motion in the shot is continuous enough to begin with, it's as good as SpeedWarp. What you'll notice when it's not continuous enough, is a rhythmic, pulsing fast-slow-fast-slow behavior. If that happens, THEN try SpeedWarp, but you might want to blade up the segment, and test a short piece first, because SpeedWarp sometimes has a hard time with repeating patterns, like pinstripes in clothes, chainlink fences, bricks, etc, and the sort of artifact it produces in those cases is far uglier and more distracting than OpFlo+Better.

Another Fun trick I've found is that Fusion gives you more control over how OpFlow data is applied, although I don't often use it to slow down footage. More often, I'll use it to add motion blur to something like a time lapse, where you want the blur to extend beyond the 360º shutter angle that the color page limits you to (which it calls 100%, not 360º).

The trick with doing optical flow in Fusion is that you have to first analyze the footage for OpFlow, and export an .EXR to disk via a Saver Node. Once you've done the analysis, you can replace that part of the node tree with a loader, and read the vector data back into wherever you want it applied, such as vector motion blur. The advantage of doing it this way, is that the computationally expensive analysis only gets done once, and then you're free to design iteratively.

*Edit*
and yes, a Mac with those specs is falling back on the CPU.

I was asking about the GPU, not the CPU.
But Jason has already explained the problem in detail. My iMac is not falling back on the CPU, its 580 is working at the limit and the CPU cores are next to idle. The process scales pretty well: if I connect my eGPU, the rendering time for a sample goes down from 4:20 to 2:35.

I was asking about the GPU, not the CPU.
But Jason has already explained the problem in detail. My iMac is not falling back on the CPU, its 580 is working at the limit and the CPU cores are next to idle. The process scales pretty well: if I connect my eGPU, the rendering time for a sample goes down from 4:20 to 2:35.

Ah yes, sorry - the answer is 'AMD FirePro D300 2 GB'

As you say, Jason has explained the situation well - thank you Jason.

The export finally finished and the reults are very good - definitely better than Avid's Fluidmotion. I'll be doing more Speed Warp slo-mos when I can cope with locking up my Mac Pro for half a day. Is there a way of compartmentalising the use of the CPU so that Resolve doesn't take up all power of the machine to export a file? When it was exporting this slo-mo I couldn't even send an email or navigate in the Finder.

Under File in the left side of Deliver you can reduce the render speed.

Under File in the left side of Deliver you can reduce the render speed.

So would that up the time but reduce the amount of CPU used?

I can't tell, since my GPU is doing the job, but I'd expect it, yes.

Thank you for your help. I am about to embark on another Speed Warp render. One thing that would be good to understand before I do:

I want to scale this 8K Red image to only use around 1/4 of the original image. I guess I should do that re-scaling before I do the Speed Warp - then it is using the new image to create interpolated frames from. If I Speed Warp the 8K image first then I'll have to export it at max 4K (since working in a 4K project) so losing 3/4 of the data prior to my later significant scaling. Does this approach make sense? In a 4K project am I actually accessing the full 8K image?

Also, when should I grade + sharpen this image etc. - on the re-imported Speed Warped 4K image or should I grade and change the speed at the same time on the 8K image and then export complete?

Thanks, Phil

If your final delivery is 4K, there is nothing wrong with using a timeline in 4K. If you zoom into it, Resolve will use the original resolution. But I'd treat the footage with any sharpening or significant grading after the speed change only.

If your final delivery is 4K, there is nothing wrong with using a timeline in 4K. If you zoom into it, Resolve will use the original resolution. But I'd treat the footage with any sharpening or significant grading after the speed change only.

So do the scaling before the speed change but leave the grading until later?

Thanks

Yes, since doin the speed change on the full resolution would take much longer.

Another thought - is there any way I can speed this process up other than buying a new Mac? I have two pretty high spec 2017 Macbook Pros - could I use them as slave computers with the Mac Pro? Or could I buy some external hardware to boost my Mac Pro's capabilities?

If I may cite myself from above:
"The process scales pretty well: if I connect my eGPU, the rendering time for a sample goes down from 4:20 to 2:35."

I doubt your laptops will be even able to handle this process. Which GPU do they have?
Anyway, to get any help from those you'd need to do it manually by sending single clips over for processing.

If I may cite myself from above:
"The process scales pretty well: if I connect my eGPU, the rendering time for a sample goes down from 4:20 to 2:35."

I doubt your laptops will be even able to handle this process. Which GPU do they have?
Anyway, to get any help from those you'd need to do it manually by sending single clips over for processing.

Ah, now I understand - I didn't know about eGPUs. I can see that that might be a good addition to my Mac Pro and would be much more cost effective than buying a new Mac Pro.

Wait a moment: your Mac Pro is the so-called 'ashtray', right? It has only Thunderbolt 2, which might be a bottleneck.

Wait a moment: your Mac Pro is the so-called 'ashtray', right? It has only Thunderbolt 2, which might be a bottleneck.

That's the one - nappy (diaper) bucket as we affectionately have known it in the UK. Yes Thunderbolt 2 will be a bottleneck. Does that mean that eGPU won't really help me? Both my MBP's are Thunderbolt 3.

In German we call it the "Urne" (cinerary urn)

I'm not sure, I never tested it with TB3. Can you give me the details of those laptops? They might work.

In German we call it the "Urne" (cinerary urn)

I'm not sure, I never tested it with TB3. Can you give me the details of those laptops? They might work.

Ha, ha - everyone has their name for it! I use it with TB3 hardware all the time, via TB3-TB2 adapters but I accept that it will only then work at TB2 speeds.

The highest spec of my two MBPs is 3.1 GHz Quad-Core Intel Core i7, 16GB RAM, Graphics - Intel HD Graphics 630 1536 MB. The other one is a bit lower spec but same generation - 15 inch 2017, both with TB3.

By the way, I've done two Speed Warps so far and one looked good but not the other. It had artifacts and Enhanced Better didn't do much better. Both shots are difficult material - rippling water reflections. Between Avid's Fluidmotion & Blended Interpolated and Resolve's Speed Warp & Enhanced Better I am choosing the best results.

Phil

Those laptops are not too different from my Mac Mini, they should work pretty well with an eGPU. I found both components of mine second-hand, BTW. It would be quite interesting to find out if they work better or if the MP is faster with the eGPU via TB2.

Those laptops are not too different from my Mac Mini, they should work pretty well with an eGPU. I found both components of mine second-hand, BTW. It would be quite interesting to find out if they work better or if the MP is faster with the eGPU via TB2.

Thanks. Do you have any recommendations re. eGPUs?

See my sig.

See my sig.

Thanks

Resolve 16.2.8
MacBookPro. 2.4 GHz 8-Core Intel i9. 32GB 2400HZ DDR4
eGPUPro
Get Info for Resolve is set to "prefer external GPU. The preferences are set to Metal.

As soon as Optical Flow Speed Warp is used the Mac is locked until it finishes - 30 minutes for a 5sec clip.....
Checking the Activity Monitor and GPU History windows, it is clear that Resolve is only using the internal GPU, the external is being ignored. The only way I can get the eGPU to work is to uncheck the internal GPU within preferences - which sort of implies the 'Auto" setting does not work. When the eGPU works the computer is not locked but Resolve only uses the eGPU. I had assumed that Auto would use both GPUs.

Matt