So all those years of hobby photography finally came to you and you decided to quit your job and go “Pro Filmmaker”. Who needs film school, especially now that you’ve got the time to sharpen everything you’ve learned and what’s more, now the passion burns like never before.
You’ve probably scoured the Internet at some point to find the best film camera options, and eventually back tracked to a top-notch DSLR with the ISO strength to photograph Mars. It also probably has a magic exposure wheel and about half a million short filmmakers rolling tons of footage each day. You’ve fought your way up the lenses ladder and finally settled for a decent mix ranging from primes, to wide-angles that are now your go to lenses for life.
That’s a story known all too well BUT, for some reasons things don’t SOUND quite right (pun intended). You now discover that your mastery of film making is hinging on one pointless cancer called ‘Dialogue’ (a.k.a Production Sound a.k.a Sync Sound). You launch a quest for mics, recorders, etc., when you discover that it’s not something you ever thought existed and your pockets are about running dry. The local sound guy wants quite a cut, and after a few odd months spent in dismissal and denial, you finally decide to hire him. He wants to know what cameras you’re using and is probably disappointed already that you don’t know what *sticks* are… (because you see, clapper sticks are the AD’s responsibility). After a massive tussle, you convince him to record only to discover his sound won’t be on your camera. Now there’s a whole other world of sound editors needed to help you get the visuals and sound in sync.
You search persistently but everyone seems to have a different problem altogether and a different solution to each problem, and a few mentions of the mythical “Timecode“. Bah! Blackmagic… you think to yourself, and move on to discover there’s no real solution but to have PluralEyes or something equally painful in your pockets until much later, you find that timecode is everywhere, surrounded by words like drop-frame, genlock, smart slates, timecode buddy units, iPad slates, etc., etc. What’s worse, almost everything else outside your edit table like Colour grading, Sound design and Editing, Picture changes, heck probably even switching your computer on begins to read…. TIMECODE PLEASE!
SO! here you are…
Timecode: What it is, and isn’t
Simply put, timecode is a way to assign a number to each frame. In 1 second of 24fps footage, the frames would be numbered 1 through 24. As the clock ticks up, separate counters are available to keep track of seconds,minutes and hours. This is a standard identified by SMPTE (simptee), which defines other finer details like voltage level, frame rates, connector pin configurations, etc, so that everyone can be on one standard.
Ideally, timecode is captured as the snapshot in time when the camera/sound begins to roll, and then gets stored in the metadata of the clip. The editing softwares, or other similar end applications can then begin to read the first snapshot and increment in frames, defining an ID for every frame that was shot subsequently. Some recorders also incorporate a snapshot of the end timecode, which helps add another level of ID for each clip.
Frame locked: How is video recorded
Now, if there were a video clip with a said ID, and an audio clip with a Timecode start stamp close to that ID, the data is similar and most usually in sync. With that said, timecode isn’t inherently a synchronisation method. To understand this, one has to understand how video is recorded.
Warning: Jargon ahead!
For a moment, one has to imagine that all modern recording gear is absent, and our video camera literally takes 24 photographs in a second. If there were a second camera that was also set to record at the same time, there is a chance that when the shutter of camera A was open, at a certain instance in time, camera B’s shutter was closed. This means that where one camera has a picture, the other has none. These cameras, though fed with timecode, are not in sync. To achieve this type of sync, one needs to employ a separate signal called genlock, which is a signal external to the cameras (usually), that tells both cameras the precise moment at which to fire their shutters. It is good to know that such a system exists, because it deals with having accurate sync between all recording devices, which isn’t a property that Timecode really offers. Using genlock by itself may not be sufficient, because it requires elaborate calibrations. However, if one has an accurate Timecode generator, and all camera devices are fed with the same Timecode signal, they are usually able to achieve a similar sync.
-end of jargon-
One major factor concerning genlock is that it is often able to interpret an SMPTE timecode input. Because of advancements in post-production software to interpret SMPTE timecode, it is usually safe to assume that using timecode will bring the user a fair degree of reliable sync, though it wasn’t designed for it. More importantly, footage with timecode information is just easier to handle at postproduction. The whole goal is to simplify postproduction workflows between multiple departments like DI colour grading, Sound Editing, and multiple Video editor workflows.
Despite its complex nature, shooting with Timecode is also possible on DSLRs and iPhones or similar devices that don’t support a Timecode input. To learn more, check out this article focussing on just those aspects of bringing timecode to mobile workflows.
Keeping track of Framerate
Moving on, SMPTE timecode only supports framerates up to 30fps NDF, which means that it cannot be applied framerates like 60 or 120, but that is not a major concern; more often than not, such footage is shot to be slowed down later. However, if the cameras change to higher framerates and are trying to store timecodes as metadata, it will be inaccurate and fairly unusable in most circumstances.
Timecode Clocks: Telling time with Crystals
The next challenge is one at a deeper electromechanical level. Most modern clocks or timing electronics function by counting pulses generated by what is called a quartz crystal. The crystal oscillates at high frequencies when excited electrically, and is considered to produce faithful pulses at very precise intervals of time when combined with specific timing circuitry. Quartz crystals have become integral members of CPU, GPU clocking because of their ability of oscillate at frequencies in the GHz range. These are qualities of a good crystal and no amount of electronics can improve clock accuracy the way a good crystal can, which brings us to the point where we realise that a device with a good crystal can often cost an arm and a leg. More importantly, a good timecode generator requires a good crystal so that it doesn’t accidentally slip in its pulse. Any slip in its pulse would mean that a frame is numbered or Identified with a few fractions of milliseconds of inaccuracy. This inaccuracy adds up over long periods, and leads to a phenomenon known as ‘drift’, which can be very frustrating to fight. In a nutshell, things can go out of sync by many minutes, or worse, keep weaving in and out of sync.
This is where good timecode generation simply means faithful timecode generation. A well equipped sound recordist is usually able to solve this problem because good audio recording equipment usually brings good crystals built-in and thus, is usually able to generate faithful timecode (normally under 0.1 – 1seconds of drift over 12+ hours of rolling).