Timecode vs. Genlock: Why timecode may not be enough to keep your set in sync

By Henri Rapp

The common assumption is that by feeding timecode to camera you will keep camera and sound in sync. Unfortunately this is not so, Timecode and Sync are not the same thing. Timecode is in fact only metadata to identify how the first frame is labeled for time when the camera begins rolling. Once a camera starts recording, it ignores external timecode and uses its own internal clock to record. The problem you get here is the camera clock is not calibrated to the external sound recorder’s clock, and slowly they will drift apart as you continue to record. This is especially problematic for productions that require a long roll time (30 minutes plus), such as Reality TV or Event Coverage. This can cause endless headaches in post when you match the audio and video with timecode, and by the end of the clip the video is noticeably out of sync with the audio. The solution here is Genlock.

What is Genlock?

Genlock originated in the early days of broadcast and video switching systems. Genlock was used to keep cameras, and other video sources’ frames in sync to avoid nasty artifacts introduced when switching from one source to another. These days most switchers can compensate for this rather than feeding black burst to every source from a central clock. In the HD world Genlock is still hanging around, but these days it uses a protocol called Tri-Level Sync to clock both the frame rate and line rate. This is especially important for 3D two camera rigs. Because Genlock clocks the capturing of frames on a camera, it can be used to keep the picture from drifting from the audio over time.

Keeping Set in Sync with Timecode, Genlock, & Word Clock

In order to keep every device in sync, you need to have everything clocked by one central master clock. The cameras need to be fed timecode and genlock, and the audio recorder needs timecode and word clock. I decided for my rig to use Timecode Systems :Wave Master Clock. This acts as a generator for Word Clock & Genlock and is slaved to my Sound Devices 664 for Timecode. With an additional 9 pin Lemo to USB data cable, I am able to control metadata, arm and disarm tracks, start and stop recording, and more on my Sound Devices recorder. The Timecode Systems UltraSync Ones get rejammed twice per second via 865 MHz to 923 MHz Worldwide ISM bands. Each camera gets an UltraSync One that outputs timecode and genlock keeping the camera perfectly in sync with everything else on set.

Common Cameras That Can Be Genlocked

Here is a few examples of commonly used cameras that can be Genlocked (Some, like the FS7 for example, require additional accessories to take Genlock and Timecode):

Arri: Arri Amira, Arri Alexa, Arri Alexa Mini

RED Digital Cinema: Red Weapon, Red Epic, Red Scarlet, & Red Raven

Sony: Sony FS7, Sony F5, Sony F55, & Sony F65

Canon: Canon C700, Canon C500, Canon C300 Mark II, & Canon C300 Mark I

Panasonic: Panasonic HPX-2000, Panasonic HPX-250, Panasonic P2HD, Panasonic Varicam 35

About The Author:

Henri Rapp is a Location Sound Recordist & Recording Studio Engineer in Cleveland, Ohio. When not out in the field I also do audio post-production for video and produce music out of Bad Racket Recording Studio in Cleveland.

Woowave DreamSync is a software application that automatically synchronizes video with audio recorded on a separate device. Double-system recording still persists as the most reliable method for capturing high quality audio, and is essential when using DSLR cameras, which offer great images, but are awkward for recording audio. While other audio syncing methods exist, Woowave DreamSync is rather unique in that it’s a stand-alone application that merges audio and video into single clips that are easily managed and can be imported into any nonlinear editing system.

DreamSync’s user interface
FEATURES
As stated, the main feature differentiating Woowave DreamSync from other audio/video synchronizing methods is that it’s a standalone application that is NLE-agnostic. Beyond that, it’s streamlined by a graphic design that distills the process into a simple drag-and-drop procedure.

Woowave DreamSync runs on Mac OS 10.10 and higher. A Windows version is currently in development. With Woowave DreamSync, the overall workflow is pretty much the same as with other synching methods. You must record scratch audio into the camera when shooting and this is usually accomplished with the on-camera microphone. At the same time, you record audio on a separate digital recorder with an optimally placed, high quality mic. This frees up the sound person to use a boom pole and audio mixer to maintain proper audio levels. The main drawback of this methodology is in syncing up the audio in post production. Existing methods work within editing software and require you to import audio and video separately and then sync them within the NLE. This can be a confusing process, as it requires careful management of numerous audio and video clips. Woowave DreamSync allows you to sync your clips before bringing them into an NLE, which simplifies the process.

But it’s really the elegant graphic interface that distinguishes this solution over other methods. It is so intuitively designed that all you need to do is look at it and you know how to use it.

The Woowave DreamSync interface window is clear and uncluttered. It has two boxes on the left. One is where you drag the audio clip that you want to use. The other window is where you track the video clips that you want to sync to that audio clip. Once you have dragged your audio and video clips into their respective bins, you simply press the sync button and wait for Dream-Sync to do its work.

Woowave DreamSync analyzes the two clips and merges them into one. The inferior audio that was recorded with the video is replaced by the high quality audio from the audio clip. It works for dialogue or music. For music videos, the studio track can be supplied and merged with camera footage. All that is necessary is that the video camera records a scratch track of the final audio during the shoot.

Once the audio and video have been merged, it is displayed on a graphic timeline. Here, you can trim unwanted footage from the head and tail of the clip before exporting.

Woowave DreamSync offers several exporting options. Apple ProRes 422 with linear PCM audio is the default, which is ideal for bringing the new clip into any NLE for editing, including Final Cut Pro, Adobe Premiere, Avid Media Composer, and Sony Vegas. However, you can also choose to export QuickTime H.264 in resolutions of 1920x1080, 1280x720 and 640x480. Woowave DreamSync also offers a number of MPEG-4 options including 1080p, 720p, 480p, and codecs optimized for cell phones, Wi-Fi and Apple TV. Once you choose your export format, the product is a single clip with your video synced to the high quality audio clip.

The big advantage that comes with Woowave DreamSync is speed and ease of use. As the new clips are discreet movie files, they can be easily stored, transferred or shared.

IN USE
I set up a pair of Canon T2i DSLR cameras in a typical two-camera arrangement. One was set for a wide shot and the other for a close-up. The cameras were set up to record audio using on-camera microphones, which is essential for syncing. The desired “final” audio was recorded using a properly placed microphone and a Tascam digital audio recorder. This was a typical interview situation where the goal was to have pristine audio recorded on a separate device while the cameras recorded scratch audio that will be synced later to the external recording device audio.

I intentionally turned the cameras on and off during the interview to test the sync capability of Woowave DreamSync. It’s common for cameras to be turned on and off while shooting a scene, interview or event, and this is one of the reasons syncing software is necessary. Clapping a slate at the start of the shoot will not determine a sync point if cameras are run intermittently.

After completing the interview I had three memory cards; one from the audio recorder and one from each of the cameras.

I then opened up Woowave DreamSync and dragged the audio wave file from the Tascam into the audio window. Next I dragged four shots from the same camera into the video window. (Woowave DreamSync syncs up to four shots at a time. You just have to be careful that they are all from the same camera, as they will ultimately be merged into one continuous clip.)

I then pressed the sync button and Woowave DreamSync performed the synchronizing task perfectly. It made one timeline with the four clips linked to the areas of matching audio. There were black spaces between the clips when the camera was not running. I exported the timeline as ProRes 422 and was ready to start editing.

I then decided to test Woowave DreamSync for its ability to work in a music video production environment. In this situation I played pre-recorded music through a speaker which provided the audio backdrop for two mobile cameras. I again used two Canon T2i DSLR cameras recording video and scratch audio from the music source. The plan was to later match up the picture from the cameras to the pre-recorded music track.

As in the previous test, I intentionally turned both cameras on and off repeatedly as the music selection played. At the end of this process I had two memory cards from the cameras containing numerous shots from the music session.

In Woowave DreamSync, I used the studio-recorded music as the audio track. The live cameras recorded this during the shoot for reference. When I synchronized the video with the studio track in Woowave DreamSync, most of the clips lined up perfectly. There were two that were out of place, and I concluded that this was due to the fact that the camera did not record the audio faithfully.

Overall, I was very impressed with the ease and efficiency of Woowave DreamSync. However, it may occasionally misalign some clips, so the user has to be careful to record audio as clearly as possible with the cameras so that they will match more easily with the external audio source.

There have been several noticeable improvements to the latest version of Woowave DreamSync. XML exports capability has been added, which expands file portability for professional users. And the new version offers batch synchronizing capability, including the ability to drag and drop multiple camera angles, audio clips, and projects into the interface.

In addition, Woowave DreamSync has an unusually attentive customer support system. If you encounter problems in synchronizing your clips that you can’t solve, you can send them in and they’ll fix things for you. Also, I need to mention that the one-time cost for buying the software includes all future updates.

SUMMARY
Woowave DreamSync is an excellent product that’s constantly getting better. As more options are added and algorithms continually refined, it may turn out to be one of the hottest products to hit the video editing software market in years. The beauty of Woowave DreamSync lies in both its simplicity and efficient performance. Rather than inundate the user with a vast array of confusing options, Woowave DreamSync simplifies audio synchronizing so that the editor is free to focus on more creative aspects of editing. It’s a wonderfully designed, yet sophisticated, software solution that’s actually fun to use.

Geoff Poister, Ph.D., is a member of the film and television faculty at Boston University and a regular contributor toTV Technology.

FAST FACTS

APPLICATION
Syncing video and audio from multiple sources

KEY FEATURES
Ease of use, speed, low one-time purchase price, free upgrades

PRICE
$199 MSRP

CONTACT
DreamSync

www.dreamsyncapp.com