Mending flash frame errors in Resolve.

[Kevin Cannon]

Hi Ian,

We’ve had this on three features I can recall – twice on Red and once on an external recorder taking a signal from an f3. The former had corrupt frames regions in the frame and the latter had completely missing frames (the editors didn’t notice because their dailies had a doubled frame instead of showing a black frame.)

Anyway we took three separate approaches:

If the corrupt region of the shot was pretty still we would render the shot out as DPX (2K for these particular projects, we do red log film and cameraRGB or red color 3 depending on the colorist’s preferences). Then load the shot back in on the track above and use the resolve dust/dirt tool set to auto/temporal +1/-1 to drag rectangles and “paint” away the corrupt frames with the previous and next frame. Resolve fixes the DPX source files “destructively” with this tool so there’s not unlimited undo with this approach so we would proceed slowly and keep a copy of the DPX in case we needed to start over.

If the region of the shot was moving, the first approach might have failed. Then we would go into the edit window, copy the shot to the track above, trim it so the top track clip starts on the frame before and is three frames long: good frame bad frame, good frame. Then set it to double speed, (good frame, good frame) and render it (you can add extra frames if it helps, we used DPX). Then drop that clip in on a track above and make it half speed with whatever blending mode works best, and it will interpolate frames in between and line them up again so you have good frame, new frame, good frame. Also you can add an alpha output and use it to limit the interpolated layer to the bad part of the frame.

In one of the cases (the external recorder) we had driving scenes and dance scenes with missing frames, so the interpolation was sometimes a failure anyway. In those cases we output DPX to after effects, did the same type of interpolation, and painted out the artifacts it created.

It took a while but hopefully the specifics of your footage makes it as easy as possible.

KC

Prehistoric Digital

[Ian Bloom]

Thanks, for the great reply.

I did a test on a few shots using Resolve and essentially the process is:

1. Identify each flash frame by razor-blading the before frame, flash frame and after frame, to create a trio of three small clips for each flash frame.
2. Select and shift all of these frame trios up to a new track.
3. Copy and past all of the sets of three frames into a new timeline.
4. Make a one frame solid black clip, copy and paste this clip between every set of three frames and delete the empty spaces between sets.
5. Ripple delete flash frames from the center of each trio.
The timeline is now a pattern Before Flash-frame, After Flash-frame, Black Frame, Before Flash-frame, After Flash-frame, Black Frame….
6. Export the sequence as a single EXR sequence
7. Import the sequence as a clip into a new timeline, change the speed to 50% with optical flow and ripple sequence turned on.
8. Export the sequence as single EXR sequence
9. Import the sequence into a new timeline.
The sequence will now be Black Frame, Half Black Frame, Before Flash-frame, Intermediate Frame, After Flash-frame, Half Black Frame …
10. Razor blade out the intermediate frames. Shift them up to a new track. Copy and paste them into the original timeline. Move each intermediate frame over it’s corresponding flash frame.

The results of just that process have been pretty impressive. We’ve been playing “spot the flash frame” to see if we could tell where the new intermediate frames are without knowing! Looking like about 10 minutes of labor for a 10 second shot depending on the frequency of the errors, but the process can definitely be batched over a whole reel.

Cheers,
Ian

Ian Bloom
https://www.dungeonbeach.com