Set Video Keyframe Interval
Re-encode a clip with a fixed keyframe (GOP) cadence — every 2 seconds, or an exact frame count — so players seek cleanly and streaming segments land on keyframe boundaries. Runs in your browser, nothing is uploaded.
About this tool
A keyframe (I-frame) is a fully self-contained picture; every other frame in a video is described relative to its neighbours. The distance between keyframes — the GOP, or group of pictures — decides how precisely a player can seek, and where a streaming packager is allowed to cut a segment. Most cameras, screen recorders and encoders leave that distance to the encoder, which places keyframes wherever it likes and inserts extra ones at scene changes.
This tool re-encodes a clip with a fixed cadence instead: one keyframe every N seconds, or an exact GOP size in frames. That is what HLS/DASH packaging, smooth scrubbing in an editor, and frame-accurate remote seeking all depend on.
Worked example
Upload a 10-second clip, leave Keyframe interval at 2 with unit seconds, and run it.
The tool builds and executes:
ffmpeg -i in.mp4 -force_key_frames expr:gte(t,n_forced*2) -sc_threshold 0 -flags +cgop \
-c:v libx264 -preset medium -crf 23 -pix_fmt yuv420p -c:a aac -b:a 128k \
-movflags +faststart out.mp4
The result is an MP4 with keyframes at 0 s, 2 s, 4 s, 6 s and 8 s — five evenly spaced entry
points. Switch the unit to frames and enter 60 and the flags become -g 60 -keyint_min 60
instead, which is exactly 2 seconds at 30 fps.
Choosing an interval
- 1–2 seconds — live and low-latency streaming; smallest startup delay, largest file.
- 2 seconds — the streaming default most platforms converge on.
- 4–10 seconds — on-demand video where bandwidth matters more than seek precision.
- Frames — when you need an exact GOP size to match a packager's segment length.
Limits
- Input up to 50 MB; output up to 60 MB.
- Interval: 0.1–60 seconds, or 1–3000 frames.
- Quality: CRF 1–51 (lower is better). True-lossless CRF 0 is not offered — it produces files far beyond the size cap.
- The output is always re-encoded H.264/AAC in a progressive MP4 with
+faststart. A keyframe cadence cannot be applied by stream copy, so some generation loss is unavoidable.
FAQ
What keyframe interval should I use for streaming?
Two seconds is the safe default — it is what most live platforms recommend and it divides evenly into the 2, 4 and 6 second segment lengths packagers use. Go down to 1 second only if you are chasing low latency, and up to 4–10 seconds for on-demand content where a smaller file matters more than seek precision.
Should I set the interval in seconds or frames?
Use seconds unless you have a reason not to. Seconds mode places keyframes by timestamp
(-force_key_frames), so it produces the right cadence no matter the frame rate — including
variable-frame-rate screen and phone recordings, where a frame count drifts. Use frames when a
tool downstream expects a specific GOP size; multiply your frame rate by the seconds you want
(30 fps × 2 s = 60 frames).
Why is there an option to allow extra keyframes at scene changes?
By default the tool passes -sc_threshold 0, which turns off scene-cut detection. Without that,
the encoder adds an unscheduled keyframe whenever the picture changes sharply — good for quality
on hard cuts, but it destroys the even spacing that segment alignment relies on. Tick the box if
you care about quality at cuts more than about a strictly fixed cadence.
What does "closed GOP" mean and should I leave it on?
In a closed GOP no frame refers to anything before its own keyframe, so a player can start decoding at any keyframe and a stream can switch bitrates there cleanly. Open GOPs compress marginally better but make those cut points less reliable. Leave it on unless you are optimising purely for file size.
Does this change the file without re-encoding?
No. Keyframe positions are baked into the encoded video stream, so changing the cadence requires a full re-encode — a stream copy can only preserve the keyframes that are already there. The quality slider (CRF) controls how much is lost in that re-encode; 18–20 is close to visually lossless.
How is this different from making a fragmented MP4?
This tool outputs a normal progressive MP4 whose keyframes are evenly spaced. A fragmented MP4 is a different container layout (a small init header followed by self-describing fragments) used by Media Source Extensions and DASH/CMAF players. If that is what you need, use the fragmented-MP4 tool instead; if you need a regular file that simply seeks and segments cleanly, this is the one.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool video-set-keyframe-interval 'url=https://example.com/input' 'interval=2' 'unit=seconds' 'scene_cut=true' 'closed_gop=true' 'quality=23' 'preset=medium'New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/video-set-keyframe-interval/?url=https://example.com/input&interval=2&unit=seconds&scene_cut=true&closed_gop=true&quality=23&preset=mediumMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.