Multi-camera video production is commonplace, especially for studio broadcast but also for coverage of conferences, concerts and numerous other live events. When events are edited live with a vision switcher, synchronisation is automatic, but when events are recorded to tape, hard disk or other storage media, synchronisation for editing becomes a critical issue.

My early experience was with film production and there, even with a single camera, synchronisation between film and audio tape was crucially important. The camera assistant would always have a properly prepared clapper board ready at the head or tail of each and every shot. At the call 'Mark it!' the clapper would be snapped firmly down providing a clear audio and visual synchronisation point for the film editor.

With single-camera video shoots synchronisation is automatic so there's no need for a clapper board, although it can still be useful for identifying scenes and take information.

We've done numerous multi-camera video shoots covering everything from punk bands to trauma surgery and we have relied on a good old-fashioned clapper board as a simple but effective way of establishing sync points. The loud 'clap' is clearly visible in the audio waveforms and so sync is achieved by simply sliding the various clips along the timeline until the visible spikes line up. Of course, if one or other  camera is turned off during the shoot, a new sync point will required, usually by adding a 'tail slate' at the end of the take.

This approach, which harks back to the earliest days of post silent era movies, is slightly clumsy but it works. But given the immense power of digital processing in the video world, wouldn't it be great if someone had invented a kind of 'digital slate' that could make audio synchronisation automatic? Well they have. The engineers at Singular Software have come up with an ingenious approach to sync'ing which is fast accurate and simple to use.

Every waveform has its own unique characteristics which in effect become its 'digital fingerprint'.  Simultaneously recorded audio tracks will have nearly identical fingerprints and this is where PluralEyes' magic comes in. When presented with a couple of video clips recorded from two video cameras, PluralEyes takes a few moments to analyse the wave forms, then decides whether or not they have come from a common source. If they are sync'able, PluralEyes aligns them perfectly after just one click.

Some clips may contain sections that are not in sync, and PluralEyes can detect these sections and split the clips so that non-sync sections are clearly separated from sync ones.

Fine tuning the analysis

I found that the default settings worked remarkably well on most clips. Some difficulties may arise when recorded audio levels are too low or if the signal to noise ratio is poor. In this case you simply click on the button to change options and select whichever ones are most likely to help solve the problem. Briefly, the options are as follows:

Preserve order (events are chronological)

This tells the software that the clips on your timeline were recorded in chronological order, thereby reducing the effort and time PluralEyes takes to sync the clips.

Level audio

Similar to a 'normalise' option in audio editors, this option is useful for evening out the levels that might vary too much, due to different types of microphones or subject to mic distance. The processing takes a little extra time but it's probably worth leaving this option on in most situations

Use media markers

By adding named markers at known sync points in each clip you can help PluralEyes work faster to achieve sync. Multiple markers are possible, provided they are given unique names, such as 'Start' and 'End' in each of the clips.

Try really hard

With its self-explanatory name, this option forces PluralEyes to really 'go for it' in its efforts to find sync. Allow up to ten times for time for the extra processing and only use this option for clips with known problems.

Allow subframe audio offsets

Especially effective in NLEs such as Vegas that can work to the sub-frame level, this option is sufficiently precise to prevent phase distortion issues. The downside is that Vegas may conclude that the audio is actually out of sync and will colour the audio clip pink to reflect this. If pink upsets you, don't use this option.

PluralEyes is not a standalone program but a plugin - or in Vegas-speak an 'extension' that resides under Tools>Extensions>PluralEyes. Use the customise toolbar option to have its button live on the toolbar.

PluralEyes supports both 32- and 64-bit versions of Vegas Pro and the license allows use on two different computers. It won't work with Vegas Studio.

PluralEyes is also available for Final Cut Pro.

Summary

This is an ingenious piece of software that is very well implemented, although somewhat expensive. However, once it's on your system you'll probably never feel the need to use a clapper board again (although those sync points would allow PluralEyes to work extremely effectively). PluralEyes will find a use in any situation in which multiple audio sources are used, in both video and audio production situations. It's a real time saver that will become as automatic to use as your ripple edit button or your Shuttle Pro - one of those tools that, once used, will never be left out of the workflow.

Vendor: Singular Software (online purchase)  www.singularsoftware.com

Price: USD$149

 

AusCam Ratings

Performance: 9

Documentation: 7

Features: 9 

Installation:   8

Value: 8

Help:  9

We Liked:   Ingenious concept, ease of use; speed of operation, useful options

We Didn't Like:  Somewhat expensive for a plugin

 

 

 

 

By David Smith

Dr David Smith is a physiologist-turned-film maker. David was Associate Producer of the IMAX feature Australia Land Beyond Time and was Senior Researcher on the ABC TV series Nature of Australia. He wrote and hosted David Smith's Earthwatch on ABCTV and was 'resident zoologist' on the Don Lane and Bert Newton Shows.

In 1987 David set up his company, imaginACTION pty ltd (www.imaginaction.net.au) and has sinced written, directed and/or filmed numerous documentaries and educational multimedia projects. He has also written six books, including two Penguin eco-thrillers. Over the past five years David has moved towards medical and health-related projects, including trauma surgery, schizophrenia and emergency medicine.

David is a Fellow of the Royal Society for the Arts and a professional member of the AFI and has always been keen to share his knowledge, especially with young budding film makers. David can be contacted at david@imaginaction.net.au.

 

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