GOP (group of pictures)

What it means

In compressed video, frames come in groups. Each group of pictures begins with a keyframe, a full image that can be decoded on its own, followed by predicted frames that only describe differences. The number of frames from one keyframe to the next is the GOP length.

A short GOP, or even a GOP of one as in All-Intra recording, makes every frame easy to reach and very robust. A long GOP saves more space, because fewer full frames are stored. Most cameras pick a GOP around half a second to a couple of seconds.

The GOP also decides where a stream can start playing or be cut cleanly without re-encoding.

How it works in practice

When you export video, encoders often let you set a keyframe interval. Streaming platforms recommend specific intervals, often around two seconds, so their players can switch quality smoothly. For uploads, a sensible interval keeps the file compatible and seekable.

Lossless trimming tools, which cut files without re-encoding, can only cut at keyframes. That is why a quick trim in such a tool sometimes starts a little earlier or later than you asked. The same limit applies to remuxing, which changes the container without touching the frames.

In editing apps, GOP structure affects how responsive the timeline feels with Long GOP files.

What to watch out for

An extremely long GOP saves a little space but makes seeking slow and errors hard to recover from: a damaged keyframe can corrupt every frame that depends on it until the next keyframe. Very short GOPs waste Bitrate on full frames and lower quality at the same file size.

Do not change GOP settings blindly on export. Defaults in good encoders are tuned for quality and compatibility, and odd values can cause stutter on some players. Only adjust them when a platform or workflow asks for a specific interval, and test the result on a couple of devices before relying on it.