Guides

How to detect duplicate frames in a video

Before broadcast QC, before delivering to a client, or as quality control in your team: if you want to be sure an export contains no stutter from duplicate or frozen frames, you basically have three options.

1. By hand, frame by frame

Step through the video with the arrow keys in a player or in Premiere Pro. It costs nothing, but at 25 frames per second it is tedious: a three-minute piece has 4,500 frames. Single duplicate frames are easy to miss – especially in calm shots and right at cuts.

2. FFmpeg filters on the command line

FFmpeg comes with two filters you can try for this:

• freezedetect reports sections in which the picture barely changes for a minimum duration – two seconds by default. It is meant for frozen video and long stills, not for a single duplicate frame in the middle of a movement. Set the duration very short and it also fires on calm shots, photos and graphics.
• mpdecimate drops frames that barely differ from the previous one and reports this with verbose output. Here too, calm shots and intentional stills show up just like real stutters – you have to go through the list by hand.

ffmpeg -i export.mp4 -vf freezedetect -map 0:v:0 -f null -
ffmpeg -i export.mp4 -vf mpdecimate -loglevel debug -f null - 2>&1 | grep drop

Both are free and good for technically minded users. Neither gives you timecodes in your editor’s format, the cause, or the steps to fix it.

3. A video QC tool: FreezeFramesFinder

FreezeFramesFinder is built for exactly this: drop in your exports, and it lists every duplicate frame with timecode, preview image, the probable cause – for example a 23.976 to 25 fps conversion or a slowed-down clip – and the steps to fix it in Premiere Pro and After Effects. Intentional stills such as photos, graphics and fades to black are listed separately and do not count as errors. Reports are available as HTML, CSV or JSON, and whole folders can be checked from the command line.

Which option fits?

• A single short clip, enough time: by hand.
• Finding long frozen sections, technically minded: FFmpeg with freezedetect.
• Regular deliveries, broadcast QC, several people in a team: a QC tool that finds single duplicate frames and tells you the cause right away.

Why exports stutter in the first place: Video stutters after export.