Request: Setting a threshold for frame interpolation

Recently I was editing a project for a friend that was shot mostly on the A7S Mark II with a small sequence shot by me with my BMPCC. While color grading though, I noticed that playback performance was abysmal for the BMPCC footage. I had never had problems with BMPCC footage before and disabling grades wasn't helping at all. I had no idea what was happening and it wasn't a disk I/O issue.

Then I noticed that the cars passing in one shot looked really distorted. My first thought was that this happened without my knowledge when I converted the footage to 4:1 compressed in SlimRAW but the footage played back and looked fine in the Media tab. Then I realized that the issue was temporal. I realized that the footage I shot was 24 fps and was placed in a 23.976 timeline and it was being interpolated with optical flow. Changing the retime process to Nearest fixed all playback issues.

This took me hours to figure out and I can imagine a similar issue happening to others so it would probably be wise to either limit optical flow so it doesn't deal with frame rate changes that are far less than one frame difference or to allow people to set a threshold for when optical flow turns on.

This will come out snarky, but, I do think the best solution is for editors to know what they're doing and do it right, rather than BMD spending limited resources trying to cover for editors who do it wrong.

There's no need to convert BMPCC footage. Even my older i7 920 could handle it in real time.

Recently I was editing a project for a friend that was shot mostly on the A7S Mark II with a small sequence shot by me with my BMPCC. While color grading though, I noticed that playback performance was abysmal for the BMPCC footage. I had never had problems with BMPCC footage before and disabling grades wasn't helping at all. I had no idea what was happening and it wasn't a disk I/O issue.

Then I noticed that the cars passing in one shot looked really distorted. My first thought was that this happened without my knowledge when I converted the footage to 4:1 compressed in SlimRAW but the footage played back and looked fine in the Media tab. Then I realized that the issue was temporal. I realized that the footage I shot was 24 fps and was placed in a 23.976 timeline and it was being interpolated with optical flow. Changing the retime process to Nearest fixed all playback issues.

This took me hours to figure out and I can imagine a similar issue happening to others so it would probably be wise to either limit optical flow so it doesn't deal with frame rate changes that are far less than one frame difference or to allow people to set a threshold for when optical flow turns on.

First of all you have done biggest error putting 24p assets into 23.976p project.
2nd your "fix" will now produce master which will have at some places dropped frames and will look jerky when played through proper monitoring: broadcast monitor or TV.

There are frame rate conversion tools which analyse motion vectors "quality" and if to low then they swap to blended interpolation, but this has its own problems.

In your case solution is very simple- use 24p project or if you really need 23.976p master then set in clip properties 23.976p for your 24p sources (or shoot 23.976p next time).

First of all you have done biggest error putting 24p assets into 23.976p project.
2nd your "fix" will now produce master which will have at some places dropped frames and will look jerky when played through proper monitoring: broadcast monitor or TV.

This will come out snarky, but, I do think the best solution is for editors to know what they're doing and do it right

Both of you assumed this was information given to me ahead of time. The movie in question had 99% of it filmed and edited before I had even been associated with the project. The footage that I shot accounted for less than a minute of it. It was shot to replace a minute of wildly overexposed footage during principal photography and was added to the original edit which was done completely in Premiere Pro and didn't exhibit a slowdown. When I transferred the footage to Resolve to color grade a few month later, that's when I noticed slowdown.

rather than BMD spending limited resources trying to cover for editors who do it wrong.

This would likely be just a few lines of code. It would just require it to divide the source framerate by timeline framerate to determine a threshold. If it doesn't meet that threshold then use Nearest as a fallback. We're talking about at a 0.001 % difference in frame rate which won't result in dropped frames.

Or perhaps it would be better to have some icon on the footage that informs the editor that a particular clip is being re-timed? That way it wouldn't have to fix the mistakes made in production or assume anything in the edit.

There's no need to convert BMPCC footage. Even my older i7 920 could handle it in real time.

I assume this is in reference to me converting the footage to 4:1. I never said I did that for playback reasons. I did that because I was running low on hard drive space and converting it saved me a little over 200 GB of space.

I really don't understand this take of acting like you're all perfect editors who don't make mistakes. In my case I just figure that shouldn't have been so much of a hassle to troubleshoot and was suggesting that something small be put in-place to help people out in the future. Especially in instances where someone is being handed off an edit from somebody else or transferring them to another program, this sort of stuff helps.

I think what is important is for Resolve to have a solid and reliable toolset and not to implement features that are fixes for user error. Checking that project framerates match is a fairly basic editing operation. I understand your frustration, but implementing features that only address individual operator error is going to bloat Resolve with 'fixes' rather than tools and workflow improvements. BTW Optical flow can be turned off from being the default in Project preferences. That's the default setting for a new Resolve install.

I second that.

can you select the clip and change framerate?

shot was 24 fps and was placed in a 23.976

also, i have a smart bin that is set as [show clips that framerate IS NOT 23.98] and I check there every once in a while: you will see the clips that does not match.