I was asking this on reddit, but it's probably better to ask here:
Note: This feature IS NOT for capturing real-time footage. Use something like OBS, SimpleScreenRecorder or FRAPS to achieve that, as they do a much better job at intercepting the compositor than Godot can probably do using Vulkan or OpenGL natively. If your game runs near real-time when capturing, you can still use this feature (but it will lack audible sound playback, as sound is saved directly to the video file).
Hm, I'm still not sure I understand.
What I would expect from this play mode is guaranteed rendering at a certain frame rate. So if I set it to 60 fps, I would expect the resulting avi file would contain exactly 60 frames every second, rendered gameplay at regular 0.016 intervals. But I would not expect this mode to have 60 fps while playing/recording: If one frame for example would take 0.5 seconds to render while the other frames only take 0.016 seconds, I would expect to see this one frame for 0.5 seconds on screen while playing/recording in this mode, but during playback of the video file, I would not see any hickup, just smooth 60fps and no pauses in gameplay.
This means, provided the playing/recording framerate is stable because my hardware can handle it, it should be totally fine record gameplay with it. Even recommendable and advantageous over FRAPS or OBS who will also records any frame rate dips.
Even if my hardware can't cope and I therefore get freezing frames while playing/recording in this mode. If these dips are within the millisecond spectrum, and Inputs don't change radically, I don't see any negative consequence recording gameplay. The recorded video should almost always look better (while of course playing with hickup ain't as much fun). But when you are recording video footage of your project, you having fun with gameplay while doing so is not the top most priority anyway. You are creating assets to reuse in your project or for marketing.
Am I wrong here? Did I miss something obvious?
Recording interactive project footage would be my main use of this thing. If this is not what this does, why would you want to have this? Blender is a thousand times more suitable for linear movie 3D rendering and production, any Animation Software for 2D animation and rendering.