Blackmagic Forum

In my experience with several different NLEs and other video creative software, usually throwing 24 fps footage on a 30p timeline will look a lot better than the other way around, which usually ends up in extremely jerky motion, especially if it's a camera travel sideways or similar.

Now I'm working on a 30p timeline (just to clarify, real 30p, not 29.97p) and I'm throwing different clips, some of which are real 24p and others 23.98p. The motion is not terrible, but I'm one of those annoying perfectionists that catches those details, and I was wondering if Resolve has a way to make that better.

I tried the different motion estimation methods in the project settings, but I didn't change the retime process because the other two choices are always bad. Frame blending will create ghost frames that are very noticeable, and Optical Flow will always make a mess unless the footage is very slow or static. Since this video has cuts every second and it's full of clips with a lot going on in the screen.... Well, thinking about it I will try it just for laughs because it's going to make a mess.

But regardless, if anyone has any tips on this I would appreciate it.

Why deliver in 30fps? Why not go 29.97fps?

If it were me, I'd compare the number of 23.98 and 24 clips, decide which is more, and then convert them using Clip Attributes. This will allow you to change 23.98 to 24.00 without any artifacts.

On one archival project we had some years ago, the post supervisor had us prep the 23.98fps film clips and convert them to 29.97 with 2:3 pulldown, and then the subsequent 29.97 transcodes were inserted into the show (same exact run time, plus or minus 1 frame). In general, this worked very well.

Marc Wielage wrote:Why deliver in 30fps? Why not go 29.97fps?

This is one is just for me, and most people will watch it on YouTube in a computer screen, therefore 30fps is better.

Marc Wielage wrote:If it were me, I'd compare the number of 23.98 and 24 clips, decide which is more, and then convert them using Clip Attributes. This will allow you to change 23.98 to 24.00 without any artifacts.

I did that on the ones that were 23.98, but I can barely tell the difference. In most cases it's not a big deal, but there's a camera traveling sideways that seems really jerky, and it was shot on a slider very smoothly.

It depends on how important it is to maintain speed/sync. If the clip is not being used in sync with any sound and you don't mind rolling the clip at your timeline rate, just change the clip fps to your timeline fps in clip attributes. Obviously the speed will differ slightly than at its native rate, but it will very smooth because it's 1:1 frame for frame.

If you need to keep the true speed of the original clip because it is in sync with sound or you simply want it to be the correct speed, then you will either need to:

• do a hardware conversion
• use optical flow
• deal with the jerky playback from duplicate frames

Have you actually tried Optical Flow in Resolve set to 'Speed Warp Better'?

I consistently find Resolve's optical flow to be far superior to both Avid and Premiere's and it is very rare that I ever encounter artifacts when Motion Estimation is set to Speed Warp Better. On the very rare occasion that there are artifacts, they're easy enough to paint out with a clean render.

I do heaps of docos with A cam and mastering happening at 25 alongside archive material and stock footage with source frame rates all over the place. Just today I had 23.98, 24, 29.97, and 30 in a single 25fps show. I used Optical Flow/Speed Warp Better for all of them and didn't have a single artifact — just buttery smooth motion.

Networks do still often insist that any frame rate conversions be hardware based, but I've been using Resolve's optical flow to do this for the last five years at least and have never once had a single push back from anyone.

tyesamson wrote:Have you actually tried Optical Flow in Resolve set to 'Speed Warp Better'?

The new AI Speed Warp Faster in Resolve 20 is pretty amazing.

Mixolydian wrote:most people will watch it on YouTube in a computer screen, therefore 30fps is better.

I have to disagree with that. 24 fps looks just fine on YouTube. I watch videos that use it all the time.

If all your material is 24 and 23.976, edit in a 24 fps timeline and change the speed of the 23.976 to match.

Jim Simon wrote:

Mixolydian wrote:most people will watch it on YouTube in a computer screen, therefore 30fps is better.

I have to disagree with that. 24 fps looks just fine on YouTube. I watch videos that use it all the time.

If all your material is 24 and 23.976, edit in a 24 fps timeline and change the speed of the 23.976 to match.

I said that because I was replying to Marc’s post asking why not deliver in 29.97 instead of 30 fps.

Yes, 24p looks fine on YouTube. If I only had clips that are 23.98 and 24, 24 would be my first choice; but I also have many 30p clips with motion graphics, therefore 30p is the best choice for this.

Mixolydian wrote:Yes, 24p looks fine on YouTube. If I only had clips that are 23.98 and 24, 24 would be my first choice; but I also have many 30p clips with motion graphics, therefore 30p is the best choice for this.

We routinely take all 30fps clips and convert them (with Clip Attributes) to 29.97fps, because we're always concerned about how they're going to be played on streaming or other services that expect 29.97. There is zero effective difference between 29.97 and 30fps, assuming they're both progressive. (I would avoid mixing the two if possible.)

Mixolydian wrote:I also have many 30p clips with motion graphics

Got it.

Marc Wielage wrote:

Mixolydian wrote: There is zero effective difference between 29.97 and 30fps, assuming they're both progressive. (I would avoid mixing the two if possible.)

There is a difference in speed, which means you need to process audio as well. Otherwise 29.97<->30 change is seamless.

You need to convert 23/24 clips with AI fps converter. There is really no other way.

Marc Wielage wrote:

tyesamson wrote:Have you actually tried Optical Flow in Resolve set to 'Speed Warp Better'?

The new AI Speed Warp Faster in Resolve 20 is pretty amazing.

I just tested it, and you're absolutely right. It's impressive. One thing I don't like, but I don't think it's bad because of it, is that it makes 24 fps clips look like they are 30 fps natively. I would prefer a way to have 24 smooth playback inside 30 fps that still looks like 24 fps. You know, kind of like the olden times when all movies on TV sets were 24 inside a 29.97i wrapper.

But it does a remarkable job nevertheless.

24p can be inserted only into 60i with 32 pulldown. Then you are getting interlaced ( actually mixed interlaced and progressive) video and this is only good for broadcast. You don’t want to do this for web. It’s bad.

There are fps convertes which can preserve shutter speed, so it would look more like film even at 30fps, but Resolve doesn’t offer such an option. You have to use open source tools for this or rather expensive enterprise solutions.

Marc Wielage wrote:

tyesamson wrote:Have you actually tried Optical Flow in Resolve set to 'Speed Warp Better'?

The new AI Speed Warp Faster in Resolve 20 is pretty amazing.

I'm still in 19, but just had a shot producing optical flow artifacts when using Speed Warp Better. Switching to Speed Warp Faster, all artifacts are instantly gone!

It's interesting that they're given labels assigning judgement as to which is 'better.' I totally get that 'Faster' is probably just shorthand for 'less computationally expensive,' and 'better' will take longer to render! However, it does quite often seem that they can each sometimes be more effective than the other depending on the context of the shot!

This is 'normal'. In some cases faster can look better, but if you take 1000 masters better will most likely have less artefacts by average. Fps conversion is difficult.

Yes. It's all an illusion, really. Interpolation process. Inventing that which is not there. And some illusions can be more effective depending on the type of shot. Optical flow, specifically, can look fantastic and run smoothly if the motion vectors move linearly in one direction without interruption. However, when something crosses its path and new motion vectors are created, they conflict with the original vectors, causing what we call artifacts.

The "warp speed" algorithm may attempt to compensate for this, but it can over-compensate or encounter scenarios it wasn't trained on, depending on its training model. The "speed faster" model is newer, so it's possible it was trained more efficiently to be faster and produce similar quality, especially in certain shots. Either way, at least we have options.

For very difficult shots, you can use depth maps, magic masks, or manual rotoscoping to isolate parts and process them in multiple passes with appropriate algorithms. However, this is more like VFX work than something an editor or colorist would typically do.

Fusion tools also use forward and backward motion vectors from optical flow and can be powerful in stereoscopic workflows, for which they were originally designed. In stereoscopic workflows, there can be two images and two virtual cameras, each with its own set of motion vectors, generated by otpical flow. Allowing you to choose how to layer them and create conflicts. All of this can involve a lot of manual work, so it's great that we have AI tools to speed up many scenarios. But when they fail, or when an specific VFX effect is needed, or during the integration of VFX effects into existing slow-motion or variable-speed shots, it's good to have other tools available.

The main problem with Optical Flow, and this is the same in Resolve, Final Cut Pro, Premiere, etc, is that the developers don't offer the user any tweaking. At least Resolve has all those options like SpeedWarp faster or better, etc.

I think Optical Flow is another name for what the plugin Twixtor uses, which was super impressive even ten years ago or more, but the good thing about Twixtor is that it offers several parameters to correct the optical flow if there was anything that didn't look right. I mean parameters with sliders, I don't remember exactly what they were because last time I tried the demo it was several years ago. But I remember those parameters could save the clip in many cases.

I'm just saying it would be a good idea if Resolve had more parameters to tweak for that, even if it's just a Studio capability.

Blackmagic just gave use three new tools that leverage optical flow. (Vector Warping Toolset) On top of at least half a dozen previous tools. Re Vision, the company behind Twixtor also has their own version of motion vectors that is similar to optical flow nodes in resolve. They even offer a converter tool. But optical flow is just a method to make motion vectors, or almost anything. What you do later with them is up to you. Smooth cut, repair frame and many tools in revival catergory or resolve FX also leverage optical flow. etc, etc, etc. Speed war type tools only use compensate, but don't generate the vectors. And that is really what optical flow does, it simply generates the motion vectors and than many tools leverage them.

De-noising, stabilization, adding motion blur, warping, repair and distortions, interpolation etc. Most of the tools that do that rely on motion vectors, and in resolve that is done with optical flow. Most companies have their flavor of it. So does Re-vision effects. I use their tools all the time.