So as it turns out, Vicon’s Giganet can’t count… no really.
We’ve got timecode printing to the reference video, but a bit of a problem.
It’s counting frames wrong. spot the probelem:
…6, 7, 8, 19, 10, 11, 12, 13, 14, 15, 16, 17, 18, 29, 20, 21…
Yup, 19 does come after 8. It looks to me like someone is incrementing their tens a loop too early.
I wasn’t sure at this point what was causing the counting problem – The generator in the Giganet, the timecode reader, or Metus.
Spoiler: It was the Giganet.
Now I remembered the Vicon rep telling me, “Yea, don’t trust the timecode generator”… but how bad could it be really? Well, armed with an audio recording of the LTC signal (it’s binary audio) and a decoding sheet, I took to manually decoding the timecode to discover for myself.
I'm prety sure the waveform shouldn't be shaped like that either...
As it turns out, pretty bad. The Giganet’s LTC timecode output changes volatge every set (it should be continuous) and also increments the tens unit one loop to early as I saw before. So that’s why it’s got the bad reputation for timecode. I contacted the Vicon support guys (awesome btw) and they’d not seen it deconstructed like this before, so that’s something. But yea, essentially, someone who programmed the timecode hardware in the giganet did an oopsie, and it got impliemented into the hardware of every Giganet they sold.
Plan B: External timecode generators.
Seeing as we couldn’t use the internal generation, I went for an external TC generator. Now these things aren’t cheap, and justifiying a £1000 clock to your boss is quite the challenge! Thanfully, we were able to utilise the LTC timecode output of a Sony FS7 camera with the XCDA extension unit to prove the fix with an external generator.
We went for the Denecke SB-T generator as it came very well recommended, ran on batteries and mains, and was basically “set and forget” for settings on a back trim switch. I must say, the build quality of the milled aluminium casing is otherworldly.
Denecke SB-T Timecode Generator
Delivered, plugged in, and not a peep of the problem since! It now runs through an line level audio distribution amplifier so we have timecode on the Giganet, Reference recordings and jam syncs for the Cara headset and any extra cameras and audio kit we might be using.
Now things aren’t perfect still – we’re running at 125fps with a PAL timecode base as our reference cameras can’t shoot full 30, only 29.976, but that’s a problem for another budget and day.