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Blackmagic Design Boosts Video Quality

Howard Brock
Serial digital interface signals provide the highest quality high- or standard-definition television images and can carry multiple channels of embedded digital audio, as well as timecode, via a single coax cable. Virtually all nonlinear editing systems are equipped for SDI connectivity, but very few such systems in the rental market are based upon this superior signal format due to the cost of digital routers and the complexity of digital audio mixers.


Traditionally, nonlinear editing systems have been based upon a "bottom up" approach in terms of signal quality. Using the least common denominator of analog composite video and balanced or unbalanced analog audio guaranteed that the worst device in the system (generally a VHS machine) could get a compatible signal, albeit to the detriment of other devices which could handle higher quality signals. When the need came to add even higher quality digital signals, such paths were added "on top" of the composite base, resulting in more wires, more complexity and more operational nightmares.

Taking a "top down" approach with the highest quality signal being used for the majority of the signal pathsóand converted to lower quality formats only where absolutely requiredóhas many benefits. However, until recently this has been an expensive and unwieldy proposition, as SDI-to-analog signal conversion devices had been either too expensive or less than ideally packaged for use within the confines of a small editing system.

With the introduction of Blackmagic Design's Mini Converters, both of these problems have been addressed and it's now possible to gain the benefits of a "top down" system without incurring a costly penalty. We took advantage of this in constructing new editing packages based on Avid's Mojo DX, which is virtually the same product as the company's flagship Nitris DX, but has two analog audio channels and lacks analog I/O. As I didn't really need the missing analog connectivity, I was able to apply the cost savings realized towards SDI routing and conversion devices. The resulting configuration is both simpler to use and superior in terms of signal quality. And the new system uses far less wiring than a traditional configuration, which provided a reduction in weight, construction time and complexity.

Our new Mojo DX system features a HD-SDI 4x4 router and two Blackmagic Design SDI-to-audio Mini Converters which can de-embed up to eight channels of audio from the HD-SDI video signal being fed to the monitor. As we're still reliant on DVD recorders, Blackmagic's SDI-to-analog and analog-to-SDI Mini Converters are installed to allow the DVD recorder to appear as another SDI device on the router. The SDI-to-analog Mini Converter even does HD to SD downconversions, so our clients never have to worry about feeding an HD signal to the DVD recorder.

We have two systems now out in the field producing network promos and program elements for a nationally televised awards show. Client reaction has been positive and we're anticipating further deployments. While our primary focus is on building units for the rental market, we're also anticipating the fabrication of systems for end users too.

Howard Brock is the president of Runway Inc. and an Emmy-winning editor for his work on Fame. He can be contacted

For additional information, contact Blackmagic Design at 408 954 0500 or