What is Keyframe Interval?
Keyframe interval is the distance, measured in frames or time, between random-access points from which decoding can start cleanly. These points often use intra-coded pictures, but not every I-frame is necessarily an independent random-access point.
How Keyframe Interval works
The interval is an encoder and packaging constraint that shapes the group-of-pictures structure. Between random-access pictures, predictive frames reuse information across time, improving efficiency but increasing the amount a decoder must obtain before it can start cleanly. Encoders may place additional scene-cut keyframes, so a configured maximum does not necessarily create perfectly uniform spacing. Packaging then coordinates access points across renditions and segment boundaries for switching, seeking, thumbnails, and error recovery.
Key facts
- An intra-coded picture is not automatically a closed random-access point in every codec; leading pictures or references across the boundary can still affect clean entry.
- Adaptive renditions need matching random-access times, not merely the same nominal interval, or a bitrate switch can require decoding unavailable references.
- Expressing the setting only in frames changes its time duration when frame rate changes; time-based validation catches ladder outputs with inconsistent GOP lengths.
When Keyframe Interval matters
Longer intervals usually improve compression, while shorter intervals support faster seeking, switching, startup, and recovery. Segment boundaries may require aligned keyframes for reliable adaptive playback.