Inspect and Safely Concatenate Local Clips

What it does

Inspect codec, profile, geometry, pixel format, frame-rate metadata, time base, audio parameters, stream order and codec extradata hashes. Generate a JSON plan and escaped ffconcat manifest. Default execution allows stream copy only for conservatively compatible H.264 and optional AAC.

How to use

Start with --dry-run. Remove it to save only the plan and manifest. Add --output joined.mp4 --execute to concatenate. Incompatible clips are blocked unless --normalize is explicit. Normalization scales with padding, sets square pixels and fixed fps, and produces H.264 plus 48 kHz stereo AAC, synthesizing silence for audio-less clips.

Requirements

Python 3.10 or newer and separately installed FFmpeg/ffprobe. No Python packages or binaries are bundled. FFmpeg must provide libx264 and AAC for reencoded exports.

Caveats

No shell, upload or URL downloading. Output files must be new. Normalization is lossy and needs temporary disk space. Only one video, at most one audio and no extra streams are accepted. Metadata matching is not proof of perfect packet timing; inspect joins. Arbitrary codecs are not accepted for copy mode. It does not download arbitrary YouTube URLs.