Variable frame rate (VFR)
Also known as: VFR, variable fps
Video whose frame rate changes during the recording instead of staying fixed. Phones and screen recorders produce it, and editors sometimes struggle with it.
Updated
What it means
Most cameras record at a constant frame rate, such as 30 or 60 frames per second, every second of the clip. Variable frame rate video lets the timing of frames change: the device may drop to fewer frames in dark scenes, under heavy load, or when the picture barely changes.
Phones are the most common source. To keep exposure bright in low light, or to save power, they quietly lower the frame rate and raise it again when conditions improve. Screen recordings and some streaming captures also produce VFR.
For playback this is invisible. For editing, it can cause trouble.
How it works in practice
Many editing apps expect constant frame rate. When they meet VFR footage, audio can drift out of sync, frames can stutter, and cuts can land slightly off. Modern editors handle VFR better than older ones, but problems still appear on long clips.
The common fix is to convert VFR clips to a constant frame rate before editing, matching the timeline frame rate. Free transcoding tools can do this, and some editors offer a conform option on import. Some phones also have a setting to lock the frame rate, which avoids the issue entirely.
Action cameras record constant frame rate, so VFR usually comes from the phone clips mixed into an action edit.
What to watch out for
Do not assume a phone clip is 30 fps just because the camera app said so. Check the file properties, which often show both an average and a maximum rate. A clip with a low minimum rate in dark scenes will show visible stutter in a smooth edit.
Converting VFR to constant frame rate can duplicate or drop frames, which may look slightly jerky. It is still better than audio drift, which ruins talking shots.
For slow motion, VFR is especially awkward, because the timing of frames is no longer predictable when you stretch them.
How RawClip handles it
RawClip accepts phone clips together with action-camera footage. If a phone clip shows stutter, convert it to a constant frame rate before upload, and the AI includes it smoothly in your highlight.