Introduction

SynQR is an app designed to assist you in identifying and resolving audio/video synchronization issues in AV environments, including DAWs and video editing software. In digital AV playback systems, audio and video signals are typically processed by separate pieces of equipment, each of which may introduce latency due to processing times. Furthermore, many of the popular video codecs tend to have their own specific offsets. These delays can accumulate and cause audio and video to become out of sync.

SynQR uses your iPhone’s or iPad’s camera and mic to measure the delay between a pulse of light and sound, allowing you to identify any sync issues in your AV playback system. With this information, you can easily configure your setup to ensure that everything is spot on. Whether you’re using popular editing software like Pro Tools, Adobe Premiere, Blackmagic Resolve, AVID Media Composer, Final Cut X, Nuendo or Studio One you can use the offset information provided by SynQR to make the necessary adjustments and keep your audio and video signals perfectly synchronised.

Getting Started

Upon initial launch, SynQR will request permission to access your device’s camera and microphone. It’s essential to grant this access as it allows the app to capture audio and video data, enabling the performance of necessary calculations.

Calibration

All iOS devices, depending on their model series, introduce a delay themselves when recording audio and video data with high frame rates. To ensure reliable use of SynQR, it’s essential to determine and compensate for this offset. Upon the initial launch or following a major iOS update, the app will prompt you to calibrate your device. Please note that delay measurements can only be taken after completing the calibration process.

To calibrate your device, follow these steps:

Remove any protective cases or bumpers from your device.
Lay a white sheet of paper on a flat surface, like a table or desk.
Create a 10-20cm (4-8 inches) high “platform” next to the paper using a stack of books or a cardboard box.
Position your device on the platform, allowing its top part to extend over the edge, with the built-in camera aimed at the white paper.
Place one or more dark objects, such as a coin or pen, on the paper. Alternatively, use a sheet of paper with printed text. Aim to create a high contrast between light and dark areas in the “image” presented to the camera.

Now open the Settings view of the app by tapping on the ⚙️-icon or the three buttons arranged to the left of it.
In the Settings view, tap on the “calibrate offsets” field to open the Calibration view.
For devices featuring a built-in video light, it will be activated automatically to ensure optimal measurement results.

⚠️ Ensure that you conduct the calibration in an environment with flicker-free lighting. LED or halogen light sources may generate flicker that is not noticeable to the naked eye but can interfere with calibration, potentially rendering it impossible. Often, flicker can be detected in the SynQR viewfinder.

⚠️ If your device features a torch /video light, switch off all artificial light sources. If your device lacks a built-in video light, perform the calibration using natural daylight.

The message “Tap one side of the device” will appear. Give your device a small side bump so that it moves a few millimetres sideways.

⚠️ Be careful not to bump the device too hard to avoid it falling. You are responsible for the safety of your device.

The app will now measures the time difference between the movement in the image and the noise generated by tapping the device.
If the measurement is successful, the determined offset time will be displayed.

💡 Note: if the tap is too gentle, it won’t trigger a measurement. Conversely, if it’s too forceful, the measurement will be disregarded. With a bit of practice, you can quickly find the right intensity. Use your fingers only for tapping.

This procedure will be carried out multiple times until the app obtains a sufficient number of measurements. A minimum of eight measurements is required, but depending on ambient light and the “image” in use, more measurements may be necessary.
Once the calibration process is complete, the message “Calibration has finished” will appear. You can now close the view. The device offset is saved automatically.

💡SynQR will not require recalibration until the next major iOS update.

Settings View

After completing the calibration, SynQR is ready for the first measurement. If you have exited the Calibration View using the (x)- icon, the Settings View will open automatically. If you have exited the Calibration View with a slide gesture, you can access the Settings by tapping the ⚙️-icon.

Detection Modes

SynQR provides two distinct operating modes for measuring video/audio delays in your playback system.

“QR Code” mode: This mode measures a series of synchronization pulses using SynQR test files, which incorporate QR codes to control the app. (Download the test files from synqr.app/downloads.) This approach enables highly accurate measurements, independent of speed fluctuations or start delays in the playback system, by averaging values. However, a test file must be imported into the playback system before measurement, which may not always be feasible. The QR mode requires significantly fewer CPU resources and therefore also conserves the device’s battery.
„2-pop” mode: This mode measures the video/audio delay by utilising the 2-pop present in your video. SynQR identifies timecode or Foot & Frame counters within the video and employs this information to control the measurement. The counters can be either ‘burned in’ or generated in real time. This means you are independent of the SynQR test file.

⚠️ The counters need to be embedded directly into the video or, as in the case of AVID Pro Tools, displayed as a timecode overlay. Using separate displays or LED indicators for counters will lead to inaccurate results.

QR Code Mode

Upon first opening the app, SynQR’s VIDEO MODE is set to “QR Code” by default. The Settings view will appear as follows:

Settings View – Video Mode set to QR code

In “QR Code” mode, there are no additional settings options besides the choice of frame rate. Under FRAME RATE SETTINGS, you can select the playback frame rate used by your playback system. Additionally, SynQR is capable of automatically detecting the frame rate based on the start titles of the SynQR test file. For videos with frame rates of 23.976 or 29.97, please use the settings for 24fps and 30fps respectively.

2-Pop Mode

If you decide to set the DETECTION MODE to “2-Pop,” s everal additional options will appear beneath the toggle.

Settings View – Video Type set to 2Pop Detection Mode

SynQR utilizes the counter within your video to initiate and halt measurements. This can be either a timecode or a feet & frame counter. You can select the appropriate option under “What Counter Type Is In Your Video.”

Various standards exist for the timecode position of the 2-pops. While 00:00:06:00 is commonly used in North America, xx:59:58:00 is prevalent in Europe and other regions. Examine the 2-pop position in your video and configure SynQR accordingly. In all cases, the hour value is irrelevant.

If your 2-pop is located at a different timecode, you can enter it under “custom TC.”

Feet & Frames

In case you are using a Feet & Frame counter, set “What Counter Type Is In Your Video” to “Feet&Frame” as appropriate. This mode is exclusively available for 24fps. The 2-pop is expected at 9+00 feet.

Please note: Feet&Frames counter detection is currently in beta.

💡All settings are saved automatically and will be reloaded the next time you launch the app.💡

Device Offset

This column displays the most recently determined device offset and provides access to the Calibration View, allowing for new calibration initiation.

Store

In the store, you can unlock additional capabilities for SynQR through In-App Purchases. Currently, the Pro Feature Bundle is the only one available, but we plan to introduce more functions for specific applications in the future.

Show Guides Again

In the Main View and Calibration View, guides will automatically appear when you use the app for the first time. You can select within the guides to stop them from appearing. However, if you ever wish to have them reappear automatically, you can reset this behavior here.”

Check Sync

After calibrating SynQR and configuring your preferences, you are now ready to measure the audio/video delay of your playback system.

Check Sync Screen

The Check Sync Screen consists of five sections. The top section displays the most important messages. For example, when you first start the app, you will be prompted to calibrate your device; before the measurement begins, there is a brief instruction on what to do, and after a successful measurement, the result is displayed here.

The viewfinder is located below the top section. Aim it at your display monitor, TV, or projector for measurement. Similar to the built-in iOS camera app, you can zoom with a pinch gesture and focus with a tap. Pictograms appear as reminders when the app starts and can be dismissed with a tap.

In the row beneath the viewfinder, SynQR displays the value of the counter if present in the frame. In QR mode, you will be informed if a QR code could be detected in the video.

The fourth section presents and evaluates all measurement results. On the left, the current value and an average of the measurement is shown. Measurements with significant deviations from the average are included in the calculation with a lower weight (median). The minimum and maximum values, as well as the number of considered measurements, are also displayed. Duration indicates how long the calculation of the last measurement value took.

To the right of this section, a list of all previously captured values will be displayed. Measurements that did not yield results will appear as blank lines.

The bottom area of the Check Sync Screen presents your preference values, including the device’s offset, the chosen frame rate, and the selected counter type—either Timecode (TC) or Feet & Frames. By tapping on these fields or the ⚙️-icon, you can access the Settings View.

By tapping on the 🗑-symbol, you can clear all previously recorded values. This is helpful if you have adjusted the delay in your playback system and wish to measure the modified audio/video offset.

Measurement in QR Mode

Import the SynQR test file with the appropriate frame rate into your playback system. If your image format is 1:2.35, use a test file with “wide” in the filename. For all other image formats, use a test file without this addition.
Set your playback position to the beginning of the test file, so that the start title is displayed. In the start title, you will see a rectangle with four QR codes in the corners. Aim the camera at your playback monitor, ensuring the entire marked rectangle of the start title is visible in the viewfinder.
Tap on one of the QR codes to focus the camera on that area.
Below the viewfinder, the message “QR Code detected” should appear.
If you have set a different playback frame rate, a message will show that SynQR has been adjusted to the frame rate of the test file.
Start the video playback and continue to point the camera at the screen.
You will now see the delay for each detected test signal.
Allow the test file to run for several measurements.
Based on the displayed average, you can now perform a delay compensation in your playback system.
For a new measurement, reset the old values with a tap on the 🗑-symbol and repeat the measuring process.

Measurement in 2-Pop Mode

Ensure the playback frame rate set in the Settings View matches the frame rate of your project, and correct it if necessary. For videos with frame rates of 23.976 or 29.97, please use the settings for 24fps and 30fps respectively.
Set your playback position three to five seconds before the 2-pop.
Aim the camera at your playback screen and try to get the entire height of your image into the viewfinder and include the counter.
Tap the counter in your video within the viewfinder to focus the camera.
Below the viewfinder, the current value of the counter should now be displayed.
Start the video playback and continue to point the camera at the screen.
When a 2-pop is detected, the audio/video delay will be displayed.
Playback systems may exhibit slightly different delays with each start. Therefore, play the 2-pop several times (~5 times).
Based on the displayed average, you can now perform a delay compensation in your playback system.
For a new measurement, reset the old values with a tap on the 🗑-symbol and repeat the measuring process.

Troubleshooting

Calibration – Measurement doesn’t start

The lateral push may not be strong enough. Try tapping the device a little harder.
Did you remove the phone from its case? A case can prevent the device from being moved sufficiently by the push.

Calibration – Measurement yields no result

The lateral push might be too strong. Try it a bit gentler.
Ambient light may flicker too much. If your device has a built-in video light, turn off all other light sources. If there’s no video light available, identify the lamp causing the flickering in your surroundings and turn it off. Use daylight if possible.
Avoid Shadows! Ensure that your hand or arm isn’t casting a shadow in the area captured by SynQR. Moving shadows in the viewfinder can significantly affect the measurement results.
Contrast in the image could be too weak. Attempt using other, larger, or darker objects on the paper.
There may be too much ambient noise. Ensure you conduct the measurements in a quiet environment. Transient noises, in particular, can interfere with the algorithm.
Ensure the environment isn’t too dark. Adequate lighting is vital for accurate calibration.

Calibration – Measurements yield very different results

Ambient light may flicker too much. Refer to the “Calibration – Measurement yields no result” section.
Avoid Shadows! Ensure that your hand or arm isn’t casting a shadow in the area captured by SynQR. Moving shadows in the viewfinder can significantly affect the measurement results.
Are you using a protective case for your device? Protective cases and bumpers can distort the result. Remove them for calibration.
Are you using an object to bump the device? Hard objects like coins can distort the result. Use your fingertip or fingernail for bumping.
Are you using an object with a strong inherent sound as a “pedestal” for the phone? Objects like cups, glasses, or wooden boxes can produce a strong sound when the device resting on them is bumped and distort the measurement result.
There may be too much ambient noise. Ensure you conduct the measurements in a quiet environment.

QR Code Mode – no QR code detected

Camera image is blurry. Tap on one of the QR codes in the viewfinder to focus the image.
Camera image too small? Zoom in a bit, ensuring that all QR codes of the test film remain visible.

QR Code Mode – measurement does not start

Camera image is blurry. Tap on one of the QR codes in the viewfinder to focus the image.
Is the frame rate set correctly? Adjust the setting if necessary.
Are there light reflections on your video screen? Ensure that all QR codes are free from light reflections and easily recognizable by the app.
Is your playback system set to interlaced while using a test file with progressive image display, or vice versa?

QR Code Mode – individual measurements of a series measurement do not start

Not all QR codes can be “seen” by the camera. Make sure to keep your device steady and and all QR codes are visible in the viewfinder.
You have already taken a series of measurements, and the device has heated up as a result. iOS limits the app’s computing power. If necessary, take a break to let the device cool down.

QR Code Mode – measurement yields no result

Refer to the suggestions in “QR Code Mode – measurement does not start”
Too much ambient noise. Make sure to conduct the measurements in a quiet environment.
Audio/video delay too large. SynQR can detect a delay of +/- 400ms.

2-Pop Mode – no counter recognized

Camera image is blurry. Tap on the counter in the viewfinder to focus on this area.
Camera image too small? Zoom in slightly, ensuring the entire height of the video image is visible in the viewfinder.
Incorrect frame rate set?
Incorrect timecode for the position of the 2-pop set?

2-Pop Mode – measurement does not start

See suggestions in “2-Pop Mode – no counter recognized”
Light reflections on your video screen? Make sure the counter is free from light reflections and easily recognizable by the app.
Incorrect frame rate set?
Incorrect timecode for the position of the 2-Pop set?

2-Pop Mode – measurement yields no result

See suggestions in “2-Pop Mode – measurement does not start”
Too much ambient noise. Make sure to conduct the measurements in a quiet environment.
Audio/video delay too large. SynQR can detect a delay of +/- 350ms.

2-pop Mode – individual measurements of a series measurement do not start

Keep your device steady and the counter always in the viewfinder.
You have already taken a series of measurements, causing the device to heat up. As a result, iOS limits the app’s computing power. If necessary, take a break to let the device cool down.

Significantly fluctuating measurement results

Fluctuations of a few milliseconds are not unusual in digital video playback systems. Specifically, when using computer screens for video playback or unsynchronized video sources, this value can be around +/-20ms.

Deviation of measurements compared to analog measuring devices

SynQR works with a video recording frame rate of 240fps. Therefore, the temporal resolution is lower than with analog measuring devices. The typical deviation of individual measurements is around +/-4ms. However, the average of the measurements usually approaches the results of analog devices and is often identical to them.
If there is a greater deviation, make sure that the analog measuring device is adjusted to the ambient brightness. Especially in very dark rooms with bright image playback, the appropriate settings should be checked. Note that image brightness and contrast as well as sound level have a much bigger influence on analogue devices then they have on SynQR.