Guides

Video stutters after export: find and fix duplicate frames

Everything played smoothly in the timeline, but in the finished export – or only at QC – the motion catches for a moment: the video looks choppy or jerky, or seems to freeze for a split second. Usually this is a duplicate frame, also called a freeze frame, repeated frame or frozen frame: one frame repeats while the camera or subject keeps moving. At 25 frames per second it lasts only 40 milliseconds – easy to miss in the timeline, but visible as a small stutter on playback.

How to recognise a duplicate frame

Step through the suspicious spot frame by frame – in Premiere Pro and QuickTime Player with the arrow keys. If a frame shows exactly the same picture as the one before while something in the shot is moving, it is a duplicate frame.

How to find duplicate frames without stepping through every frame: How to detect duplicate frames in a video.

Not every still picture is a mistake: photos, still graphics, fades to black and calm shots hold on purpose. It is a stutter when one or two frames stop in the middle of a movement.

The most common causes

• Frame rate conversion: 23.976 or 24 fps footage in a 25 fps sequence – roughly one stutter per second. Cause and fix
• Slowed-down clip: speed below 100 %, even 95 % or 99 % – regularly every few frames. Cause and fix
• Doubled frames: 25p footage in 50p – every frame twice. Error or delivery format?
• At a cut or transition: the footage runs out for the transition, or a Frame Hold sits at the end of the clip. Cause and fix
• Variable frame rate: phone or screen recordings – single, irregular hitches. Cause and fix

Rule of thumb: stutters at regular intervals almost always point to a frame rate or speed conversion; single ones rather to the footage or the edit.

Find the spot in your project

1. Note the timecode of the spot in the finished file.
2. If the sequence was not exported from its start (in and out points), add the start point of the export.
3. Go to the spot in the sequence, select the clip and use right-click → Reveal in Project to see its frame rate (“Media Frame Rate” column).
4. Open it in the Source Monitor with Match Frame (F) and step through frame by frame to see whether the repeat is already in the source footage.

Fix it – depending on the cause

In Premiere Pro this usually means: conform the clip’s frame rate (Interpret Footage), undo an unwanted speed change, shorten a transition, or set the clip’s Time Interpolation to “Optical Flow” so in-between frames are calculated instead of repeated. The exact steps are in the guides linked above. Then export again and check the new file.

Repair a finished file without the project

If the project is no longer at hand, the finished file can be repaired as well – in After Effects:

1. Import the file and drag it onto the “New Composition” icon – the composition takes over size, frame rate and length.
2. Select the layer → Layer → Time → Enable Time Remapping and replace the duplicate frames with in-between frames (keyframes or an expression).
3. Layer → Frame Blending → Pixel Motion, and turn on the composition’s “Frame Blending” switch – only then are the in-between frames created.
4. Check every spot frame by frame and export again at the same frame rate.

The length stays the same and the audio stays in sync. FreezeFramesFinder creates the matching Time Remap expression for every spot it finds.