LosslessCut Stream Editor AI Skill Guide (Claude)

Overview & Engine Architecture

LosslessCut (mifi/lossless-cut) is an Electron UI over FFmpeg stream copy (-c copy). Lossless cuts must start on decoder keyframes (IDR/I). Keyframe cut snaps start to a nearby keyframe (often earlier). Experimental Smart Cut re-encodes only from the desired start to the next keyframe, then copies the rest — unsupported for many files/codecs/multi-video-track cases.

Projects use .llc JSON5, schema version 2: mediaFileName, cutSegments[{ start, end?, name, tags?, selected? }].