High frame rate playback option in iOS/iPadOS 18

iOS/iPadOS 18 introduced QuickTime FullFrameRatePlaybackIntent tag:

"key that represents whether this movie should play at full frame rate

Some apps play movies recorded at frame rates of 120fps or higher in slow motion. If your app records high-frame-rate movies, you can add this movie-level metadata to indicate whether the movie intends to play at the full frame rate (1) or at a slow motion rate (0). Apps that play movies may use this metadata, when present, to guide their behavior."

quickTimeMetadataKeyFullFrameRatePlaybackIntent | Apple Developer Documentation

macOS 15 Sequoia QuickTime Player plays middle part of high frame rate movies (seems to be ≈85 fps or more) in slow-motion without that tag (earlier macOS like Ventura seem to behave the same).

For example, losslessly convert an existing 25 fps .mov video to 250 fps (25/250=0.1) and delete audio:

ffmpeg -itsscale 0.1 -i input.mov -c copy -an output.mov

The whole movie plays at 250 fps in Sequoia after adding or editing (exiftool 13.09 and later):

exiftool -m -P -overwrite_original '-Keys:FullFrameRatePlaybackIntent=1' output.mov

Back to the default slow-motion behavior:

exiftool -m -P -overwrite_original '-Keys:FullFrameRatePlaybackIntent=0' output.mov

Or just delete FullFrameRatePlaybackIntent tag:

exiftool -m -P -overwrite_original '-Keys:FullFrameRatePlaybackIntent=' output.mov

BTW it seems currently Windows might be incompatible. If that tag is present, Windows might fail to display thumbnails and most metadata items in its Details panel (Media created, resolution, frame rate, audio details etc).