MARCH 25, 2021

Pro Tools | Sync X: Why Precision Sync Is Critical for Your Workflow

Sync X in studio

Pro Tools | Sync X is the successor to Avid's Pro Tools | SYNC HD synchronization interface. As an audio specialist at Avid, I often help studios and suppliers configure new Pro Tools systems, and a common question I hear is, "What do I need a Sync peripheral for?"

Like SYNC HD, Sync X lets you synchronize Pro Tools | HD systems with just about any kind of audio or video hardware. That could be external video reference generators, video playback devices, specialty master clocks, digital mixers, MIDI workstations, and, of course, other Pro Tools systems and DAWs. It also enables Pro Tools to precisely align audio playback with video output... more on that in a moment.

Sync Revision

To recap some first principles, there are two things that can be synchronized between your devices—position and speed. Timeline position, or positional reference, is communicated with timecode, making sure Pro Tools and external devices start at the same place. Playback speed is locked across your system using a clock reference, which prevents playback drift and digital audio clicks. Sync X gives your Pro Tools system the ability to follow or generate timecode (as LTC or MTC) and many flavors of clock such as Word Clock, Video Reference, 10 MHz, and Bi-phase.

Frame Edge Alignment

So, our two key sync data points are position ("Where are we?") and clock ("How fast are we going?"). But when synchronizing sound with video, there's one more thing to know: when exactly does each new frame of picture get displayed? Without knowing this, Pro Tools and your video output device will be locked to the same timecode position and clock speed, but video refresh could be offset by up to a frame. This will be different each time you start playback.

unsynced video playback
Without a common video reference, video frames cannot be displayed exactly in line with your Pro Tools timecode position.

To bring everything into line, devices can use a common frame edge reference, which tells the video player when to display each frame, letting Pro Tools align audio with near sample accuracy.

synced video playback
With a frame edge reference, Pro Tools can align audio playback to video output refresh with near sample accuracy.

Imagine a marching band on parade. Each row of musicians is at the same place (positional reference) and marches at the same speed (clock reference). But without the band leader calling which foot to lead with, the marchers may all walk out of step.

marching band
Video reference is the key to keeping your audio and video perfectly in step.

Video reference (sometimes called tri-level, house sync, or black burst) is responsible for calling "left-right-left" in the studio. It's simply a video signal of the same format as your project, which all devices use as a common grid.

Does Frame Edge Sync Make A Difference?

This key question often comes up when specifying a Pro Tools system for audio post—especially for a room that doesn't need to sync with external hardware.

I've spoken with many professional dialogue and effects editors who can see the difference when audio is frame edge aligned. In fact, I've often heard an editor report that something doesn't feel right, or seems inconsistent, and then discovered that the video reference to Pro Tools or their video card was missing.

With many of us spending time on video conferences and watching shows via multiple sources and devices, we've become accustomed to loose video sync. But in a professional audio post production environment, you need to trust that sync is precise and consistent throughout the creative, QC, and delivery phases.

Independent Production

Traditionally, audio post production and pro music recording systems have been static installations inside facilities. Increasingly, Pro Tools systems may be configured as mobile rigs or installed in remote locations. Sync X has been designed for independence, with an onboard video reference generator and multiple reference and word clock outputs. This means Sync X can operate as a central sync hub and removes the need for external reference, patch panels, or distribution amps.

Even in a facility, the idea of central "house sync" is less relevant, as there are many different video formats in use today. With Sync X, you can switch to the internal reference when working on a project with a different format to the main external reference. Sync X also has a handy feature for auto-detecting the video reference input for when you do need to lock to other systems.

Built for Pro Tools

Sync X connects directly to Pro Tools via the DigiSerial port found on Pro Tools | HDX and HD Native hardware. This provides a reliable, low latency connection that's independent of the OS and host USB busses. Support for Loop Sync is maintained, which is used on the HD series Pro Tools interfaces.

Sync X can be set up and remote-controlled directly from Pro Tools. The Session Setup window provides a central location for configuring Clock Reference, Video Reference, and Positional Reference.

Music Production

I've talked a lot about working to picture, but sync is also a requirement in many music production scenarios. If you're working with a traditional multitrack recorder, or a console with its own automation system, Sync X interprets incoming LTC. In fact, it can even track playback speed from the timecode stream if there's no separate clock.

The most important requirement for clocking in music applications is uncompromised audio quality. Sync X has next-generation JetPLL clocking technology, providing a faster and more accurate lock, with low jitter for the best quality capture. The Sync X clock is temperature-compensated for consistency, whether it's in an air-conditioned machine room or a hot control room. Support has been added for 10 MHz "atomic" clock sources, which are popular in high-end studios and scoring stages, and AES3id BNC connections.

Generation X

Sync X lets Pro Tools connect to both legacy and emerging sync and video formats. It can be the independent backbone of your studio, and it plays nicely with others.

Sync X unit seen from the top and front

  • Simon Sherbourne headshot

    I’m a Pro Audio Solutions Specialist at Avid, with a background in sound design and mixing. I’m also a regular contributor to Sound on Sound magazine.

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