copy — both boundaries are already keyframe-aligned (or close enough); a single
stream copy handles the whole range. No re-encode, no join.
encode — the whole selection sits inside a single GOP (no keyframe between start
and end). It's re-encoded whole, but since it's at most one GOP (a few seconds on
typical livestream encodes) this is cheap regardless of how long the overall clip is.
encode-then-copy — the general case. Only the small head span from the requested
start up to the next keyframe is re-encoded; everything from that keyframe to the
requested end is a pure stream copy. Audio is stream-copied once for the full trim
range and muxed at the end.
One trim plan produced by planSmartCut.
copy— both boundaries are already keyframe-aligned (or close enough); a single stream copy handles the whole range. No re-encode, no join.encode— the whole selection sits inside a single GOP (no keyframe between start and end). It's re-encoded whole, but since it's at most one GOP (a few seconds on typical livestream encodes) this is cheap regardless of how long the overall clip is.encode-then-copy— the general case. Only the small head span from the requested start up to the next keyframe is re-encoded; everything from that keyframe to the requested end is a pure stream copy. Audio is stream-copied once for the full trim range and muxed at the end.