Synced !

A project log for Atomic Synchronator

Beyond '67 SMPTE timecode, an affordable GPS based AUX syncing track format for dual-system sound or multicam setups: YaLTC

Raymond LutzRaymond Lutz 09/11/2021 at 14:170 Comments

As a test for assessing system performance, the same pilot tone (a continuous sinus wave of 220 Hz) has been recorded simultaneously by two devices: a ZOOM H4n Pro and a FUJIFILM X-E1) alongside their atomicsynchronator dongle (recordings where started one after the other so they were off sync by approx. 3 seconds)

Each devices recorded two channels: the common 220Hz CSW and the YaLTC signal from their respective synchronator (an Adafruit Feather based for the H4n and a Trinket M0 one for the FUJI). The camera was used as a stereo sound recorder: the movie itself being discarded.

The two tone tracks have been synchronized using the timestamp deduced from their YaLTC track and mixed into a single stereo file (the earlier recording is simply trimmed of the exact samples number so they start at the same time). Below are the decoding program output; we see the H4n (ZM-YaLTC.wav) was started 39.247354 - 36.062314 seconds earlier. Take note: 7 out of  8 of those yummy digits are significant!

The precision of the sync process is then given by how much the left and right 220 Hz recordings are out of phase:

They're out of sync by a mere 4 samples: a 83 μs offset! (for reference, typical video frames are spaced 33000 μs apart). Cool.