+44 (1223) 979580 office@harkwood.co.uk Cambridge, UK
Documentation, firmware, test files, and answers to common questions. If you can’t find what you need, email sync-one2@harkwood.co.uk.
JUMP TO
DOCUMENATION
Sync-One2 V2 User Manual
PDF — full operating guide
Sync-One2 V2 API Manual
PDF — serial API reference
TEST FILES
Post-production and broadcast
Hundreds of files across resolutions, frame rates, and codecs – optimised for Pro Tools, Premiere, Final Cut Pro, and similar platforms.
Home cinema
The Spears & Munsil UHD HDR Benchmark Blu-ray includes dedicated Sync-One2 test patterns. HD Benchmark 2nd Edition users: measure the top or bottom flash bars and briefly pause playback to allow calibration.
Streaming service test files are available on request — email with the subject line “streaming service details”.
FREQUENTLY ASKED QUESTIONS
Frame Rates Matter
Your system works best when everything runs at the same frame rate from source to display. Frame rate conversion causes sync issues unless it’s an exact multiple – and Sync-One2 will show you these problems in real time.
You might see a repeating pattern in readings like +75, +73, +71, +69, +67, +75, +73… This tells you there’s frame rate conversion happening somewhere in your signal chain.
Here’s what works: if you’re playing 23.98 fps content, your display needs to run at 23.98 fps or 47.95 fps. Content at 24 fps needs 24 fps or 48 fps display rates. Even though 47.95 fps seems “close enough” to 48 fps, it’s not – you’ll still get sync drift.
Many home displays round frame rates to whole numbers on screen, so 23.98 fps content often shows as “24 fps”—but the actual rate matters for sync.
Bottom line: Set your source (Blu-ray player, Apple TV, etc.) to output the native frame rate of your content.
Where to Measure
Measure from your primary viewing position or the optimal viewing angle. While this might seem obvious, it makes more difference than you’d think. We’ve seen mixing desks 17 meters from the screen in large post-production facilities – distance affects timing.
Start Test Files from the Beginning
Our test files have a 10-second lead-in for good reason. This lets Sync-One2 calibrate to your environment and gives your playback system time to settle into a steady state. Starting and stopping test files midway can introduce timing errors unless your entire system runs from a master reference clock.
Turn Off Motion Smoothing
If your display (especially projectors) has motion smoothing or motion interpolation, turn it off while setting sync. This feature is the most common cause of jumpy, inconsistent readings with projectors. In fact, leave it off and enjoy the content the way the creator intended it to be.
What Causes Lip-Sync Problems?
Modern video processing on TVs and projectors takes time – the more complex the processing (4K, HDR, etc.), the longer it takes. Audio processing is much faster by comparison, so they get out of sync.
If you’re using a single TV with built-in speakers, everything should stay in sync because the TV delays the audio to match the video processing. But once you separate audio and video – sending audio to an AV receiver while video goes to a display – problems can happen. That’s why AV receivers have audio delay settings.
In post-production, audio and video exist as separate timeline elements, so they can slip relative to each other. Different codecs and tools can also introduce errors, which is why checking the final output is essential.
For more detailed technical information, check out avlatency.com.
How Bad Before People Notice?
People start noticing lip-sync errors when audio leads video by about 15-35 ms. Interestingly, if audio lags behind video, people don’t notice until around 80 ms – probably because we’re used to seeing things before hearing them (like watching someone speak across a room).
Manual adjustment is always subjective and prone to error. Everyone perceives timing differently, and different sources may have different error levels. The goal is to set up your base system as accurately as possible, so slight errors from individual sources go unnoticed.
What About HDMI Auto Lip-Sync?
HDMI 1.3+ does include auto lip-sync, where displays can send delay information back to sources. But it has limitations:
- It only covers the display’s processing delay, not your entire system
- It uses generic, averaged delay figures hard-coded by manufacturers
- It relies on sources knowing what to do with the delay information
- Some audio processors may pass this information onto the source, causing issues
It’s a start, but not a complete solution.
What Displays Work?
Sync-One2 works with any display – LED/OLED TVs, plasma, front or rear projection – at any resolution or frame rate. For front projectors in bright rooms, you might need to position Sync-One2 in the projector beam for better detection.
What’s Self-Calibration?
Sync-One2 calibrates automatically when powered on or returning to measurement mode. It measures ambient light to filter out lighting flicker and adjusts microphone gain for background noise. This takes a few seconds and makes operation much more reliable.
The light and audio sensors also have adjustable trigger levels that you can modify in the menus if your environment requires it. They default to maximum sensitivity.
How Accurate Is It?
Very accurate. Internal timing resolution is 0.01 milliseconds. The smallest detectable difference between a flash and beep is 0.05 milliseconds. All statistics use this high-resolution data. The display rounds to the nearest millisecond or 1/1000th of a frame for readability.
Troubleshooting Detection Issues
Most detection problems come from:
- Not having Sync-One2 in the measurement position during calibration
- Having test files playing past the lead-in time during calibration
Detection only works when beeps and flashes are louder/brighter than the levels detected during calibration. If Sync-One2 calibrates while a test is playing, it can helpfully calibrate out the signals you want to detect.
In spaces with long reverberation times, increase the mask time to let sounds decay before Sync-One2 re-arms for the next measurement.
Just like speakers have positive and negative terminals for a reason, all speakers in your system need the same polarity. When they don’t match, some speakers work out of phase with others, creating weird sound – especially noticeable as you move around the room.
Professional systems can have dozens of speakers (think lecture halls with ceiling speakers on 70V/100V lines). If just one speaker gets wired backwards – and yes, this happens more than you’d think – certain areas will sound very wrong. The fun part? Identifying the offending speaker.
Good news: since firmware v2.3.0, Sync-One2 v2 includes free speaker polarity testing. Please update your firmware, and you’ll be all set.
How to use it:
- Download the test file for speaker polarity from the test file page.
- Go to Speaker Polarity test from the main menu and wait for calibration
- Play the test file (disable any system EQ if possible)
- Hold Sync-One2 a few centimeters from each speaker for a few seconds
- It’ll show “Positive” or “Negative” – all speakers should show the same result
- If any show the opposite, check their wiring
This makes system commissioning much simpler and more reliable.
What’s New in v2?
The most obvious changes are two additional connectors:
- 3.5mm audio input: Connect directly to headphone or line outputs instead of using the internal microphone (automatic switchover, menu override available)
- USB Mini-B: Appears as a serial port on Windows, Mac, or Linux for data logging and API control
Other improvements:
- Firmware upgradeable by end users
- Custom startup splash text (via API or permanent programming at the time of order)
- Adjustable mask time for reverberant spaces
- Enhanced sensor sensitivity
- Brighter blue display (was white)
- API interface for automated testing and detailed reporting
Support and Feature Codes
Support Code: Contains unit-specific information (serial number, firmware, features) for easier technical support.
Feature Code: Enables specific enhanced features on individual Sync-One2 v2 units.
What About Original Version Support?
Full support continues for original versions with valid warranties. We maintain spare parts for repairs and physical damage.
Unit Won’t Turn On
Hold the On button for a few seconds. Sync-One2 v2 performs internal verification checks during startup – the display activates once these are complete.
“Waiting for PC” Message
This appears if internal firmware verification fails, usually from an interrupted firmware upgrade. Download fresh firmware from our support pages and try the upgrade again.
If this happens at first power-on and then resolves after 30 seconds, contact us – the odds of this are literally 1 in 4,294,967,296. If this keeps happening on your Sync-One2, please get in touch. It is easily fixable, but we need the unit back to work magic. Oh, and consider buying a lottery ticket.
Apps work, but have three fundamental limitations. Camera-based measurement is limited to whole frames — before you start, you’re capped by the camera’s frame rate. The OS adds timing overhead while juggling other tasks, and modern phones process audio and video to “improve” it. Finally, correction factors are needed per device and OS version, and change with software updates.
For occasional rough checks, an app is fine. For professional, repeatable results, you need dedicated hardware.
Some playback systems show 2112 samples of audio latency due to AAC encoding – that’s 44 ms delay at 48 kHz (roughly 1 frame at 24/25 fps, 2 frames at 50/60 fps). Not all decoders compensate for this. These are known as the priming samples at the start of AAC files.
For best accuracy, use PCM test files. If you primarily use AAC audio, test with AAC files to match your real-world usage.
More technical details: Apple’s AAC documentation
Thanks to DXOMARK for the technical analysis identifying this issue.
If you have a query about Sync-One2 not found in the FAQ, please e-mail sync-one2@harkwood.co.uk with your Sync-One2 serial number if available.
Sync-One2 v2 users can generate a support code from the System Info menu option. When the serial number and firmware revision are shown, press and hold the down arrow key, and a support code will be displayed after a few seconds. The code is displayed while the down arrow key is held down. This code identifies the unit, firmware revision, and any installed/activated options.
Suggestions for any special, additional features or tweaks are welcome, as is any feedback on Sync-One2 in general, good or bad. We love feedback.
FIRMWARE
The current version of Sync-One2 firmware is v2.3.1.
Standard installation from serial number A22F7000
Update stops unexpectedly: If Windows reports “USB port type is unassigned”, check that your antivirus software hasn’t blocked the port.
Failed update recovery: If the update failed and your Sync-One2 entered API control mode, refer to the instruction document for steps to enter firmware update mode.
v2.3.1 (November 16, 2023)
- Fix: Re-enabled performance optimisations that were accidentally removed in v2.3.0
v2.3.0 (March 28, 2023)
- New Feature: Added Speaker Polarity testing
- Note: Requires a specific test file from the Test Files section of the Sync-One2 website
v2.2.4 (July 14, 2022)
- Fix: Corrected certain API commands
- Required for: Python API control example usage
v2.2.3 (January 27, 2022)
- Improvement: Enhanced API START command to return error when external audio is configured but no external audio connection exists
v2.2.2 (October 15, 2021)
- Fix: Resolved auto shutoff issue when USB port is connected (corrects v2.2.1 problem)
- New Feature: Added Auto Off trigger message display when timeout expires
v2.2.1 (October 7, 2021)
- Fix: Compatibility update for OLED display module changes (affects serial numbers A22B3000 and higher only)
v2.2.0 (August 10, 2021)
- New Features: API calls for audio and video trigger level settings (requested by Dolby)
- Enhancement: Additional API commands for statistics management
v2.1.1 (April 5, 2020)
- New Feature: Extended mode for measuring sync errors up to ±3000 ms (±3 seconds) – requested by Hisense for product development
- Improvement: Increased maximum frame rate calculations from 99 to 120
v2.0.3 (February 18, 2019)
- Fix: Enabled custom splash messages with special characters (previously limited to alphanumeric only)
v2.0.2 (September 12, 2018)
- Fix: Improved video calibration and detection for low-light environments like post-production facilities with large projection displays
- Acknowledgment: Thanks to Goldcrest (Soho, London) and HHB for providing access to their Dolby ATMOS facility for testing
v2.0.1
- Internal field testing release
v2.0.0
Initial Sync-One2 v2 release
Understanding Version Numbers
Firmware versions use a three-part numbering system: major.minor.patch
- Major Version: Significant new features and/or hardware changes
- Minor Version: New features from development roadmap or customer requests
- Patch Version: Bug fixes and corrections
Custom Features
Need something specific for your environment?
Custom modifications can be developed and integrated into the main firmware. Updates that benefit everyone are free.
If you require something specific to you, features can be permanently activated using feature codes through the API interface on a per-serial-number basis.