Implementing Surround

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Implementing Surround

Nov 1, 2006 12:00 PM, By Don Danko, CBRE CBNT

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Don Danko, VP of engineering and operations for WGUC, prepares a surround recording for playback.

As one of the industry-leading classical radio stations in the country, it has been 90.9 WGUC's mission from day one to offer the highest quality musical experience to our highly discriminating listeners. So when WGUC initially made the transition to HD Radio in 2003 we were looking forward to the added benefits it would bring, such as the ability to broadcast 5.1 surround sound.

WGUC recording engineers began producing recordings of the world-renowned Cincinnati Symphony Orchestra and other notable ensembles in surround a number of years ago. These recordings provided the first programming for the station's surround-sound broadcasts. The next step would be to expand WGUC's surround-sound broadcasts to include commercially available recordings as well.

To do this, we evaluated many surround recording formats. There are unique characteristics to all of them, but for our use, we needed something that worked in our existing stereo infrastructure that would provide a rich surround experience.

The Neural Surround Downmix has the capability of transporting 5.1 surround through our stereo infrastructure. The Neural process works because it is based on the principle that natural stereo and 5.1 content are two-dimensional (width and depth spatial attributes). The Neural Surround Downmix corrects overlaps of the signal sources in intensity, time, coherence, polarity and phase before the surround channels are combined and �watermarked� in the stereo downmix. In reverse, is the Neural Surround Upmix. The Neural Surround Upmix renders any two-channel audio source (stereo, matrix encoded stereo, Lt, Rt or Neural surround content) as surround sound. The Neural Upmix can simultaneously position individual elements within the surround field creating image stability by placing audio exactly where it would be heard.

For example, mono or pan-pot stereo will image in front of the listener, whereas stereo containing depth information will surround the listener. The Neural Surround Upmix allows the recording engineer to monitor stereo production and transport the 5.1 surround content encoded by the Neural Downmix.

Starting a project

When Neural Audio came to us with the proposition of actually researching the availability of 5.1 classical recordings and then encoding that content into a stereo stream for broadcast in analog and digital formats, we were certainly interested; especially because we had been testing the Neural Surround Mix/Edit System as well as other systems. We began researching not only the content and how it could be imported into our current infrastructure, but also the performance of the Neural Audio Neural Surround system as well. We came across several complications that had to be resolved.

The first issue was ensuring that the Neural Surround Downmix was of the highest quality. With the help of the Cincinnati Public Radio Audio Recording and Mastering Engineer Alex Kosiorek we had complete control of our created content. But we wanted to ensure content that originated elsewhere was at least of an equally high standard. After a collaborative effort focused on quality control, we were pleased that the Neural Surround Downmix was able to produce a stereo downmix that accurately represented the original content whether monitored in mono, stereo or Neural 5.1 Surround Sound. It is important to note that task was not easy in itself, and being able to accomplish it was quite remarkable.

The next step was obtaining the surround sound content and deploying it in our existing infrastructure, including importing the large audio files into our Enco Digital Audio Delivery (DAD) system. This is where Neural Audio swung into action. They contacted two classical labels, Telarc and Deutsche Grammophon, for permission to encode their available 5.1 content for stereo. After permission was secured, Neural took the 4.0 and 5.1 original content and captured that on DVD-A or SACD, and using software-based batch conversion watermarked the uncompressed WAV files for stereo. We also worked together to convert the ID tag information produced by the batch conversion software so that it imported accurately into our Enco System. Now all Neural Surround downmix files are stored as linear audio broadcast WAV files for playback on WGUC-FM. We were quite pleased that we were able to resolve many of the conversion and ID tag issues, a testament to Neural's customer service and commitment.

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The Neural Downmix (top) and Upmix were used to encode and monitor the surround material for stereo transmission.

�The whole idea is to keep everything lossless to avoid codec artifacts while at the same time watermarking the files for stereo,� said Neural Product Line Manager Dave Casey. �The 5.1 WAV files are quite large, 30MB per minute. But with the Neural Downmix, the files were reduced to a manageable size, which allowed us to easily place the watermarked content on to WGUC's Enco automation system so the files just slid into the musical lineup.�

In looking back on the project, both Casey and I agreed that the longest part of the effort was the search for the 5.1 classical content because we had a fairly large universe from which to search, including international recordings.

We are extremely excited about 5.1 because it allows us to offer an all enveloping sound experience for our digital listeners, placing them front and center in the best seats in the concert house. But it also provides a richer stereo environment and pleasing surround sound experience for analog listeners as well. In partnership with Neural, we will continue our search for the best 5.1 classical content as we expand the surround library for our play list.

Danko is vice president of engineering and operations, Cincinnati Public Radio.