How it works
Marking the clip
Drag the handles on the filmstrip, type the start and end, or play to the spot and press Set in or Set out. The frame buttons step one frame at the video's measured rate. Play and Loop stay inside the clip.
Keyframe or exact
Most video stores a full picture only every so often (a keyframe) and the frames between as changes. Keyframe mode copies packets from the last keyframe at or before your in point to your out point: nothing is re-encoded, so it is fast and lossless, but the clip may start up to a few seconds early. The tool tells you where it really starts.
Exact mode decodes and re-encodes with WebCodecs, so the clip starts on the frame you chose; it is slower and slightly changes the picture.
Container
The output keeps the source's container unless you pick one of the others that can hold its codec. Audio is copied when the new container supports its codec and dropped otherwise in keyframe mode.
