Keyframe
A complete video frame stored without reference to other frames. Video codecs only save full data every few seconds (keyframes); between them, only the changes are stored (delta frames). Seeking in a video jumps to the nearest keyframe.
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A keyframe (also called an I-frame or intra-frame) is a complete, independently encoded video frame that contains all the pixel data for that moment in the video. Between keyframes, video codecs only store the difference (delta) from the previous frame — this is the basis of most video compression.
How Video Compression Uses Keyframes
Instead of storing 24–60 complete frames per second, a compressed video stores:
- I-frames (keyframes) — complete frames, stored every N frames
- P-frames (predicted frames) — stores only what changed from the previous frame
- B-frames (bidirectional frames) — stores changes from both previous and next frames
A typical H.264 stream has one keyframe every 2–5 seconds (48–150 frames at 30 fps).
Why Keyframes Matter
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Seeking — when you jump to a position in a video, the player seeks to the nearest preceding keyframe. If keyframes are infrequent, seeking is less accurate.
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Editing — video editing software requires a keyframe to make a precise cut. Cuts made between keyframes require re-encoding the surrounding segment.
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Streaming — more frequent keyframes allow faster seeking and quicker recovery after network interruptions, but increase file size.
Keyframe Interval in Settings
- For streaming/live video: keyframe every 1–2 seconds (30–60 frames)
- For local storage: keyframe every 5–10 seconds (150–300 frames) for smaller files
- For editing: keyframe every frame (lossless-like; large files)