It’s taken a while to get it right, but I’ve now got a “set and forget” sync between OT and Live. The way I work is to do all the composition on the OT, and just keep feeding it material from Live. OT is master, Live is slaved, the OT midi sync offset in Live is about -12.8ms in my case. (128k buffer). That’s while monitoring on the OT, with Live coming in through a Thru machine. Yes- it takes a couple bars for Live to sync up, when starting up. However, once it’s locked I don’t have any drift, just some barely perceptible jitter (and I mean barely). Don’t even think about tempo changes with this setup though. Terrible. Audio back to the OT is captured perfectly, but audio from the OT to Live needs the start point adjusted a bit. I use a different amount of midi sync offset to record perfectly synced clips INTO Live.
I’ve done a ton of experiments to get to the numbers I use, but now it works the same way all the time, every time, without an external clock sync device. One thing I’ve noticed though, is that Live’s response to a sync input is non-linear. Meaning, the -12.8ms offset that sounds rock-solid at 120bpm introduces a slight offset between OT and Live at 85bpm. We’re talking really minor here (like an additional -2ms, which some folks might not even care about. I’m OCD for solid sync though.
The non-linearity thing is actually a huge revelation for me, and answers so many baffling Live sync questions I’ve had in the past. I’ll probably put together a list of all the midi sync offsets needed for all my most used tempos, dial 'em in when needed, and be done.
I’m not clear whether there are any external clock options out there that do not require a computer in the equation, but I’d be interested to know!
The interface is an iConnectivity iCA4+, by the way.