wjs-syncing-multicam

Compute a single time offset for each multi-source recording of the same event using audio cross-correlation, and emit a .sync.json sidecar next to each original. Originals are never modified, copied, or re-encoded. Downstream tools use -itsoffset to apply the offset at consume time.

Setup & commands

The implementation lives in the open-source polysync pip package (https://pypi.org/project/polysync/ · https://github.com/jianshuo/polysync) — this skill no longer ships its own scripts. Ensure it's installed, then drive it via its CLI:

python3 -m pip install -U polysync      # needs ffmpeg/ffprobe on PATH

polysync sync   REFERENCE SOURCE        # align SOURCE to REFERENCE, write sidecars
polysync sync   REFERENCE SOURCE --partial   # source covers only part of the session
polysync verify REFERENCE SOURCE SOURCE.sync.json   # independent residual check

Run one polysync sync per non-reference angle (reference first, same reference each time). The sections below document the algorithm, the sidecar schema, and the gotchas baked into the package — read them to interpret output and choose flags.

Design principle — sidecar over re-encode