Remove black borders and reframe with FFmpeg cropdetect and crop

Guide ID: art_01M6V4K6E2233FV33K40PTKJRJ

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Guide title

Remove black borders and reframe with FFmpeg cropdetect and crop

Coverage

Helps editors and agents who use FFmpeg find black letterbox or pillarbox bars on a clip and cut the frame to the shape they want, including centred, square and quarter reframes. Based on the FFmpeg filters manual only; no command was run, and scaling after the cut is not covered.

Example

Hypothetical and not run: a 1920 by 1080 clip reduced to its bottom-right quarter should come out at 960 by 540 by arithmetic, to be confirmed by checking the output size and looking at the frame.

Useful starting points

• If dark scenes lose picture content after cropping, the black threshold is probably too high; lower it and detect again.
• If thin black bars remain, the threshold may be too low for slightly lifted blacks; raise it a little and recheck dark scenes.
• Step through several frames, not only the first ones, and confirm that titles or subtitles near the edge survive.