ActionCheese Sync 0.5.0

Free, open-source multicam sync for Premiere and DaVinci Resolve. Aligns
footage by its sound, so cameras whose clocks were never set still land
together.

ActionCheese — Multicam Remote is on the App Store

The app this one was built as a companion to is out. Up to four iPhones
rolling together on one word, with shared timecode, no Wi-Fi, no laptop and no
crew — and a shoot folder from it opens here already in sync, because the
phones were on one clock when they recorded.

Free to start: https://apps.apple.com/app/id6820252527

And everything from 0.4.1 to 0.4.4, in one place

Those were patches, and this app does not put a window in front of you for a
patch — so if you have been updating along the way, you have had the fixes
without being told what they were. They are all in the what's-new window now,
and under Help › What's New whenever you want them again. The short
version:

• Better sync on music. A correlation peak no better than the next one
  along is no longer treated as a match. Dance-floor music repeats, so it
  throws up alignments that score alike, and taking one on faith is what sent
  clips minutes out of place. On the wedding that prompted this, clips landing
  on the exact frame went from 18 of 41 to 30.
• Accuracy set from measurement, not from two shoots. The test a match has
  to pass is now calibrated against thousands of labelled trials on real
  footage. Matches between recordings that share no moment at all used to get
  through about a third of the time; now closer to one in thirty. The
  instrument is in the repository as tools/calibrate.py, so the numbers can
  be checked rather than taken on trust.
• "In separate synced groups" now explains itself. Two recordings from one
  device never overlap, so sound cannot relate them. When that splits a shoot
  into groups, the clips inside each group are frame-accurate and only the
  joins between them are open — and the report says so, including whether a
  group's position came from a device clock or was simply appended.
• Two crashes fixed. 0.4.0 raised at the end of every sync; 0.4.1 saved
  comparison reports to nowhere, silently. An unexpected error in the window
  now shows itself instead of vanishing.

Worth knowing when you shoot

Sync needs real overlap. With 6 seconds of common sound the matcher finds the
right alignment about one time in six; with a minute, nine times in ten; with
two minutes, almost always. If you stop and restart a recorder mid-event, let
it run for half a minute while a camera is rolling — without any overlap there
is nothing to correlate, and no software can recover it.

Requirements: Apple silicon Mac, macOS 11 or later. Intel Macs are not
supported. ffmpeg is bundled, so nothing else to install.

400 tests pass.