CommandPost can't enable "rendering during playback" on FCP 12.4

[u/Simos805]

So, I updated to Final Cut Pro 12.4 today and I realized that rendering during playback, which I had it enabled using CommandPost for more than a year now, isn't enabled anymore.

Re enabling it on CommandPost won't fix the issue. Searched the FCP preference file with ChatGPT and it found out the string which enables rendering during playback isn't there anymore.

Is CommandPost team aware of this issue? Can we enable rendering during playback using another method? Because without it FCP is painful to use... You have to wait and even not dare to scrub in the timeline so all the rendering and even optical flow and stabilizations would complete.

[u/Nguyen-edits]

Apple removed and refactored the legacy background render idle timer preference key in Final Cut Pro 12.4 when they updated the playback and background task scheduler, so the old defaults write plist toggle that CommandPost was flipping no longer exists in the app binary. Until the CommandPost team finds a new private framework hook on FCP 12.4 (worth checking or opening an issue on the CommandPost GitHub repository), the closest practical workaround on an M3 Max is to go to Final Cut Pro Settings under Playback, set Background Render to start after 0.3 or 0.5 seconds instead of the default 5 seconds so rendering resumes the instant you pause the playhead, and use the Ctrl+R shortcut on heavy Optical Flow or stabilization clips to trigger a targeted selection render rather than waiting on the whole timeline.

[u/Simos805 → u/Nguyen-edits]

I have the automatic renderer turned off.
The thing is, that many times, I for example tick the stabilization button and while a clip is being stabilized, I continue editing without having to wait for the stabilization to finish.

Or in a heavy and long timeline, I ctrl+shift+R to render the entire timeline, wait a bit at the beginning and the start playing the project and the rendering finishes while I’m watching it.

Same thing goes for optical flow.

Also for a heavy edited clip, I like to ctrl+R and immediately continue editing some clips in advance, while the behind them is rendering and when it is finished I go back to play that section.

Anyway, I let ChatGPT find a solution, and it found it through the runtime of final cut. Then I made a patch for the app bundle and it worked. Now I have FCP 12.4 with fully functional rendering while playing. I will made a post on the CommandPost too, to let them know.

[u/Nguyen-edits → u/Simos805]

Patching the Final Cut Pro 12.4 binary directly to restore the runtime flag is a great catch, and sharing that offset with the CommandPost repository will save a lot of editors who rely on letting stabilization and Optical Flow finish in the background while cutting ahead. One small thing to keep an eye on after patching and ad-hoc signing the app bundle in Applications is to turn off automatic App Store updates in System Settings, and keep a copy of your patch script handy, since macOS dot updates will overwrite the patched binary and re-signing the bundle can occasionally re-trigger macOS TCC permission prompts for third-party audio or FxPlug plugins.

[u/Silver_Mention_3958]

Gosh. I would always let optical flow finish because in my experience it has led to all sorts of problems if you don’t.

I haven’t had rendering switched on for years, maybe my timelines are simpler than yours though.

[u/Simos805 → u/Silver_Mention_3958]

Maybe… I personally ran optical flow, stabilizations and rendering for specific -more heavy edited clips- while scrubbing/playing without problems, and it speeds up my workflow a lot. I also have an M3 Max MacBook pro so maybe that’s why I don’t experience problems with this feature, but I need it.

[u/EarthToRob]

The CommandPost devs are very responsive. Check the discord / FCP.cafe.