I have just borrowed a Syncheck 3 from Mike Woods at Dirty Dog Audio Ltd, the UK distributor of SYNCHECK and will be using it for a series of forthcoming test on video codecs/hardware in Pro Tools 11.1.3, so I thought a quick introduction would be helpful to those who haven’t met this device yet (you really should know about it if you are serious about post!).
Syncheck was developed by Richard Fairbanks, an Emmy-nominated re-recording mixer, editor, sound supervisor and owner of Manhattan’s Pharoah Audio, and is now on its third hardware iteration.
Syncheck was conceived to work out with absolute certainty the sync delay of your visual playback system and also, and somewhat more importantly, how robust the sync is and whether there is any drift – but more on that later. So, when your client asks is that in sync, you can answer with certainty, knowing that your playback system is calibrated and corrected, and you are not seeing hardware errors.
SYNCHECK 3 - How Does it Work?
Syncheck has on board sound and light detectors that register the leading edge of the sound and light burst from a test file, and measures how much time occurs between them. Simples!
The LED display shows whether audio or video is ahead (i.e which occurs first), and what the delay is, measured in fames and also in milliseconds, from hundredths of a frame up to half a second! (where at which even your mum would notice the sync!). This is all achieved at an accuracy of +/- 0.03 milliseconds (that’s about 0.15% of a frame at 25fps!), and in real time too.
Syncheck 3 has a buffer of 40 measurements and will store these for you. It can calculate average error, and the “span” (maximum deviation).
Syncheck will work from 12-60fps and test files are available in many common frame rates (i.e. 24, 25 29.97) and a multitude of codecs (DVpal, DNxHD, ProRes and so on), either by optical disc or from the Syncheck ftp site. Syncheck also helpfully make an optional DVD with 5.1 AC3 and DTS test files, such as pink noise (for speaker calibration) as well the sync test sequences, so that you can calibrate your DVD/home theatre playback system.
If you need to measure in a noisy environment or where the noise of the audio blips would be a problem to others (trade shows or offices etc), the unit thoughtfully comes with a mini XLR input and lead.
SYNCHECK 3 - In Use
- Load the test file into Pro Tools
- route the audio output to your monitoring system
- set the frame rate of the video files on Syncheck 3
- point Syncheck 3 at your screen
- clear the buffer on Syncheck 3
- press play on Pro Tools
It really is that easy. For good performance please note that loop playback is not recommended, as this is not the most accurate form of video playback; instead spot multiple instances of the test file concurrently in the timeline.
It is recommended to start playback from a black frame (such as one frame before the second flash/pip) as Syncheck looks for the change from black to white.
SYNCHECK 3 - How To Measure Drift/Span
There are many places for errors in sync to occur (most of which are beyond the scope of this article), but in essence performance is down to video codec/wrapper, video computer hardware and video display hardware (see my forthcoming Pro Tools 11 video test series for more information). There are two sorts of errors:
- Fixed errors - which are mostly hardware related, such as how long your plasma screen takes to react (display latency), or if your video and audio are running at different rates (i.e. where you will see drift).
- Variable errors - which are more software/hardware inter-related. Conventional start and end blips (i.e in film) are unable to measure these.
Syncheck provide test files with a flash and sync blip every second to measure the fixed errors.
Most importantly though, they also provide continuously variable test files, which can measure random sync, and therefore capture the span of any subtly continuously variable sync (such as poor codec performance).
SYNCHECK 3 - How Does It Perform?
In conclusion, Syncheck is simple to use, effective and quite frankly without peer! If you do post (or indeed care about sync), you need one of these. Very highly recommended indeed – in fact, a total must!