Render & Replace not frame accurate

[PeterVerhoeven]

When I use Render and Replace to reduce the load of heavy effects on my clips in the timeline, I encounter some issues. The transcoding completes without any error messages, but the resulting rendered clip is no longer frame-accurate. The clip "block" remains in the same position, but the footage itself is shifted, sometimes by multiple frames.

This occurs when I select "Sequence" as the source. Enabling "Include Handles" doesn't make any difference. When I choose "Individual Clips" as the source, the option to render clips with video effects is greyed out.

To be fair, some of my clips are interpreted footage (59.97 fps interpreted as 29.97 fps), but I can't redo my entire timeline edit for that. Nesting is not a solution either, since you can't render and replace a nested clip that has effects applied.

My current workaround is to render the entire timeline to a high-quality codec, and then use Scene Edit Detection to automatically slice up the video, but this process is very time-consuming.

Does anyone have a better workaround or a real solution?

[R Neil Haugen]

Did you use the Speed/Duration controls, or the Interpret Footage controls? They aren't the same thing, and for most purposes, S/D is oft considered better.

BUT ... if there's some cadence change or something like that, then I-F might be the better choice, if I recall correctly.

[PeterVerhoeven]

I used the Interpret Footage for most clips. No Speed/Duration was used.

[R Neil Haugen]

Could you try the Speed/Duration for a clip or two, just to see if it gets a correct behavior? That would be useful information.

[Dani_V.]

Hi @PeterVerhoeven,

Sorry you're experiencing issues. What camera and file type is your source media, and what kind of effects are being applied to these clips? Are you working with Variable Frame Rate (VFR) footage at all?

Confirming this is only happening with the clips that have had their frame rate modified with 'Interpret Footage' and not others?

Sorry for the frustration,

Dani

[PeterVerhoeven]

It behaves the same way. Strangely, the frame shift is less noticeable on clips with heavy effects applied. For example, clips with NeatVideo Noise Reduction show less frame shift than clips without any effects.

[PeterVerhoeven]

The cameras used were the Sony A7III and A7SIII, and footage was originally recorded in ProRes 422 LT. The clips are second-generation renders from a selection pool, also in ProRes 422 LT, to minimize quality loss. No variable frame rate (VFR) was used within the same clip. And it happens only with clips that are interpreted as a different framerate.

[Dani_V.]

Thanks for the additional information @PeterVerhoeven. Interesting this is happening with Speed/Duration as well.

Couple of follow-up questions: Is the original footage 59.97 or 59.94 fps? And is your sequence frame rate at 29.97? When you right-click clip Modify > Interpret Footage, what number/decimal is showing up for 'Use Frame Rate from File'?

Also, you mentioned the frame shift is sometimes by a few frames, but can you tell if the speed of the footage itself is changing as well after Render and Replace, or is the speed the same but frames are just off? I know you want effects included, but if you choose 'Individual Clips' as the Source for Render and Replace, is the same frame shift happening?

[PeterVerhoeven]

My mistake, the orginal footage was 59.94 fps of course (not 59.97 fps like I mentioned before).

"I know you want effects included, but if you choose 'Individual Clips' as the Source for Render and Replace, is the same frame shift happening?"
Sorry, I deleted all the 'render and replace' footage and went another way. I will try to replicate when I finish this project and have time to do so.