iphone as Master Clock?

I was shooting recently with Knoxville soundie Scott Minor. He told me about an iphone app that he and a friend developed that seems like it could be pretty useful. It’s called JumpStartLTC. It’s a a timecode generator that uses the processor cycles of the phone’s computer as a timing reference. It outputs the result to the iphone’s headphone jack.

Since the app is only $20, I figured it was worth a try. It’s not the same as a lockbox, since it can’t receive timecode… it can only output. But it’s reported to be very accurate… Scott says that he saw virtually no drift after leaving it running for two days.

It’s a simple app that has four buttons. One sets the hour (in 1-hour increments), another button resets to zero, the third button starts and stops, and the fourth button starts the clock at the time of day. There’s also a volume control, and of course, a timecode display.

The JumpStartLTC screen is pretty simple.

The JumpStartLTC screen is pretty simple.

Let’s consider a DSLR shoot, I do quite a few of these. While Canon says the latest 5d has timecode, there’s no way to jam the camera that I’m aware of. So the 5d may “have” timecode, but it’s really just a glorified counter. My 664, on the other hand, has a timecode generator with full timecode capabilities. It can jam to received timecode, or output a timecode signal (via BNC connectors) to act as a master clock.

So here’s a possible workflow for the 5d. With the iphone set to time of day, jam the 664 to the iphone using a 3.5mm-BNC cable. You can buy these for around $12… I made one for about three bucks. Now the iphone becomes a timecode display that you can flash at the 5d at the beginning of each take. Now in post, it’s just a matter of matching up the numbers. Most people just use PluralEyes for this, and that usually works fine, but this is just an extra layer of protection… if something happens to the scratch audio track on the 5d, PluralEyes won’t work, so this is another layer of safety. It isn’t a substitute for a lockbox (can’t imagine why anyone would expect a $20 app to replace a $600 device) but you might find it handy.

UPDATE: As an experiment, I used JumpStart on a 5D shoot yesterday (with country music artist Jerrod Niemann about his upcoming album release) to test how it would work. It pretty much works as advertised… though there were a few caveats. I learned that putting the phone to sleep freezes the timecode counter, so I had to restart the time of day and re-jam the recorder to the phone. This got old fairly quickly, so I left the counter running between takes to see how long it would last. I got a low battery warning after about 2 1/2 hours. I might try one of those iphone battery backs to see if I get more runtime. It also freezes if you remove the headphone jack, so it needs to stay connected as well. A useful addition to the program might be a “dim” button that would reduce the screen brightness and lower the volume on the audio TC output signal to save battery life.

I couldn’t tell, but it looked like there were a few frames of offset between the timecode on the iphone and the timecode in my recorder, but it would take a camera test to see for sure. It also appeared that pressing Time Of Day on JumpStart gives you a different offset each time, so once you start Jumpstart, it’s best to leave it running until lunchtime.

Taping my phone to my slate gave me a visual timecode readout for the camera... not essential, but it probably won't hurt to have it.

Taping my phone to my slate gave me a visual timecode readout for the camera… not essential, but it probably won’t hurt to have it.

About the only other downside was that I couldn’t use my phone for on-set photos, which I try to shoot whenever I’m on set, or check my messages (though it does briefly display incoming text messages). I always stay off my phone when I’m working, but there’s always downtime where you can fire off a quick note. But as a general rule, I never take calls when I’m on the set.

SECOND UPDATE: In the end, I abandoned this workflow. I just didn’t have the confidence that the iPhone could maintain sync. The only way I could come close is to re-sync the phone before every shot, and that took far too long. I finally ponied up the cash and bought a real timecode slate from Denecke. It wasn’t cheap, but it works great and I generally don’t have sync issues anymore, the slate matches the TC in my recorder within a frame or two per day. Cameras are a different story… most drift pretty badly in comparison… but the connector on the Denecke is bidirectional, meaning I can re-jam the cameras using the slate cable as an output, or I can connect the slate to the master clock (my 664) and by just switching it off and then back on again, the slate sees the cable as an input and re-jams itself. I love the thing!

One response to “iphone as Master Clock?

  1. Movieslate for ios is also very good though I found I prefer using it on the Ipad. I have found a lot of these Prosumer camera setups that have timecode seem to have issues with being accurate. I recently worked on a short film where the camera synced with my Roland R-88 as slave. Everything looked right for the 5 day shoot but in post the video was stamped with timecode that was an hour ahead and a minute behind what the camera was set for and what it was sending out. On the last days video it actually jumped an hour behind. It just goes to show redundancy is key if you want to save time and your sanity. Also pluraleyes while being a great tool should never be completely relied upon. Its certainly saved me a lot of headache but there has been many times where it refused to sync or “kinda” sync. Its great advice to have one more way to keep timecode accurate.

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