Hardware And Software Reviews
By Read G. Burgan
Digital audio restoration divides into two categories: real-time and non-linear. In the first category are products like CEDAR whose hardware is legendary in its ability to restore audio in real time. Sonic Foundryís Sound Forge is a good example of the second category where sound must first be transferred to computer after which various restoration tools can be applied.
Each of these approaches has its advantages and disadvantages. With real-time processing, you can hear the digitally restored sound immediately, but you may not completely remove all offending noise from badly degraded sources.
Non-linear restoration requires that you first transfer the sound from its original source to a computer file. Once saved to hard drive, any number of tools and filters can be applied to clean up the sound including the manual removal of noise that eludes automatic processing tools. What you lose in time you gain in a potentially cleaner sound.
The creators of Diamond Cut have pioneered a software solution that provides the best of both worlds: real-time and non-linear restoration. Their latest entries -- DC-Six and DC-Live -- continue to provide high quality restoration tools while pioneering new approaches that suggest where all digital restoration software may be in the future.
For those of us in radio, the real-time capability provides a means of airing live any source that can benefit from restoration technology. The most obvious applications are playing long play records and reel-to-reel tapes.
By adding the appropriate filters to DCís Multi-Filter and then clicking on the Live mode, any audio coming into your computerís duplex sound card will come out of the output with the various digital tools applied.
More Ways To Remove Noise
Previous versions already had several impulse filters along with a robust continuous noise filter. The current version adds more ways to remove noise. The EZ Clean filter is designed to provide a ďhands offĒ approach to removing pops, clicks and broadband noise.
It contains three adjustable sliders for removing scratch (large impulse noise), crackles (small impulse noise) and hiss (broadband noise) along with a hum filter that can be toggled between off, 60 Hz or 50 Hz. What sets this tool apart from others is that aside from adjusting the degree of attenuation, the continuous noise filter (hiss) needs no other adjustment.
Traditionally broadband noise reduction has required the user to first create a noise sample that is than used by the filter as a pattern in removing the noise. DCís EZ Clean filter actually identifies the pattern of noise and adjusts itself accordingly as it is applied.
Since it takes the filter some time to identify the noise and begin to eliminate it, one needs to add some typical noise content at the front of the sound to give the filter time to reach its maximum effectiveness. There is little doubt in my mind but that this is the direction that noise reduction will be moving towards in the future.
Similarly, DC has added a mode to its existing Continuous Noise Filter that also automatically evaluates the sound and applies its own noise reduction based on the noise content. Unlike the EZ Clean Filter, the Auto Spectrum CNF mode has additional controls that allow the user to fine tune the degree of noise reduction.
These include Attack, Release, Attenuation and FFT size. For the casual user, the EZ Clean filter or the Auto Spectrum CNF mode will almost certainly provide satisfactory results. But for the professional user, the Normal CNF mode of the Continuos Noise Filter is still probably the best means of insuring the maximum removal of noise with minimal artifacts.
The Live version has an additional mode: Forensic AFDF. This mode applies an even more aggressive noise reduction that is able to extract sound from a higher noise environment but with a lesser fidelity and the possibility of some artifacts.
Other New Features
Increasingly the emphasis is on higher sampling and bit rates. If your sound card will support it, DC-Six/Live will support a sampling rate as high as 192 kHz and at 32 bit resolution.
Under its CD Prep menu, DC has added a ďFind And Mark Silent PassagesĒ utility. This makes it fast and easy to mark individual tracks for burning CDís.
Buried in the Batch File Editor is a new utility called ďAuto Leveling.Ē While similar to the usual Normalize function found in most digital audio editors, Auto Leveling examines the loudness of all of the sound files in the batch and then normalizes them to sound equal in volume.
Most normalizing tools simply increase the gain of the sound file based on the highest peaks. This utility evaluates all of the files in the group to be batch processed and attempts to average out their rms levels. For radio stations, this could help to provide a more consistent listening level when using disparate sound sources.
If you already use another digital audio editor, you should now be able to use your favorite DirectX Plug-Inís in DC Six/Live. Because the designers of DirectX Plug-Inís donít always follow the same conventions, itís possible that some DirectX Plug-Inís may not function under DCís DirectX interface. I found that most of mine worked. A small minority did not.
DC-Six/Live lets you log the output of the Live function directly to hard drive so that the file can be saved and further processed if desired. DC Live also lets you log the original, unprocessed sound to a separate file. For those who need to archive the original unprocessed sound, this is a very valuable feature. Essentially you can restore the sound in real time and still have permanent files of both the original and processed files.
DC Six/Live have been carefully tweaked to reduce the demand of your computerís CPU. This means that when you do real-time restoration you will be able to chain more plug-inís before experiencing glitching without having to upgrade your computer. It also means that in many cases the time for non-linear processing will be even faster than before.
As with past versions, DC Six/Live contains hundreds of presets that make it easy to use tools and filters with little or no previous experience. And the 400 plus page Userís Manual is an invaluable source of information on almost any conceivable question related to audio and digital audio including record equalization curves and even such mundane information as resistor color codes.
Generally, one expects to pay a fair amount of money for digital audio plug-insí that are dedicated to noise removal. Diamond Cut Productions has broken the mold by providing not just noise reduction tools, but an entire digital editing suite with dozens of high quality audio tools including equalization, compression and reverb -- all at a price that is less than many charge for just a set of noise removal plug-ins.
Both DC-Six and DC Live share a core of impressively effective restoration tools. DC-Live adds high powered tools aimed at forensic applications and comes at a higher price tag: $1399 for DC-Live vs. $199 for DC-Six.
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Tracer Technologies 3600 Board Rd. York, PA 17402 Phone-717 764 9240 Fax- 717 764 9254 Toll Free Order Line- 866 260 6376 http://www.tracertek.com/
Read Burgan is a free lance writer and a former public radio station manager specializing in digital audio restoration who can be reached at (906) 296-0652 or through e-mail at email@example.com
DC Six/DC Live
Digital Audio Restoration Software
New automatic noise reduction tools
Many tools require less CPU power than previous versions
Supports up to 192 Khz/32 bit processing
Hundreds of great presets
Super Userís Manual
Some DirectX Plug-Inís may not be supported