SRS Circle Surround VST Pro Plug-in

Although many audio professionals may not be aware, in the last ten years SRS Labs has become a behind-the-scenes audio technology powerhouse, creating over a dozen audio, voice, and surround sound technologies that have been licensed to large consumer electronic manufacturers like Microsoft, Sony, RCA, Philips, Pioneer, Marantz, Mitsubishi, Hitachi, Sharp, and Samsung. Indeed, over 350 million products, from televisions, DVD players, mobile phones, computer software, audio/video receivers, and portable audio systems, already feature one or more of SRS’s audio techniques. One of these technologies, Circle Surround, is now being used by broadcasters such as ABC, CBS, NBC, ESPN, ESPN 2, ESPN HD, FOX, FX, TNT, PBS, and over two dozen programs, including the 55th Annual Prime Time Emmy Awards, X Games, NFL, and NBA telecasts. Broadcasters are fond of Circle Surround (or CS for short) because it enables any program telecast in stereo to deliver up to 6.1 surround sound to its viewers without any change to their distribution or broadcast infrastructure. Now, with the new Circle Surround VST Pro plug-in, it’s now possible for anyone with a VST-enabled DAW to deliver CS-encoded audio content without the need of outboard hardware.

Some Background

Circle Surround is actually a matrix encoder that allows a surround mix (anything up to 6.1) to be encoded into a stereo track, stream or file. If no decoder is present upon playback, the listener hears a normal stereo program. But if a CS decoder is present (and most new consumer electronics hardware have them), then the stereo is unfolded into discrete LCR, LCRS, 5.1, or 6.1, depending on the format of the original program before encoding.

Although designed for 2-channel mediums such as broadcast television, radio, or Internet streams, Circle Surround-encoded material can also be stored for playback over mediums like VHS, PC and console games, DVDs, and CDs. CS-encoded material is backward compatible with all existing playback formats from mono to 5.1-channel audio decoding (such as Dolby Pro Logic, Pro Logic II, PL, PLII, NEO:6, and Logic 7), although the best performance is achieved with a CS decoder.

Plug-In Details

The CS plug-in tested works with any VST-compliant DAW software (such as Nuendo or Cubase) on either a Mac or PC. If you’re a Pro Tools user, CS is also available as a TDM plug-in as well. As with most software, the actual performance will vary depending upon the horsepower of the computer. SRS suggests a PC with a minimum of a 1 GHz processor with at least 384 MB of RAM and running Windows XP or Professional Edition, or a 500 MHz Mac G4 running OS X 10.2 or higher. The software is PACE copy protected and can be authorized to run on only one computer. CS works at sample rates of 44.1, 48, and 96 kHz.

The encoder is placed on an insert of the 5.1 master channel and, when the Edit window for it is called up, displays a simple panel with only one user changeable parameter. It shows seven input presence indicators that glow green with signal and red upon clipping. A stereo output level ladder indicator shows the Lt/Rt content, with level presence at –54 dB and clipping at 0 dB. The only user parameter is a Bass Management in/out button in the middle of the screen, which diverts frequencies 80 Hz and below to the subwoofer when enabled.

The Circle Surround decoder, which is also included in the package, is supplied so the engineer can check the effect of the encode and has far more flexibility than the encoder. It has two Input Presence indicators for the input, and a ladder indicator for each of the seven outputs. The Output Level section also has a Trim control for each channel and a Test button that enables a –12 dB pink noise signal to automatically rotate between the output channels. A test Pause button stops the movement of the test signal on the speaker currently playing the test tone.

The Decode mode select allows you to choose the playback monitor mode to check the compatibility with different output arrangements. Mono, stereo, LCRS, and Circle Surround are available via buttons. A Center Mode section allows the front Center and Rear Center (for 6.1) channels to be enabled. When the Circle Surround mode is engaged, another section called Post Process allows SRS’s other widely distributed technologies, TruBass and Dialog Clarity, to be enabled. Both are post-processing effects that provide listeners with added control over content playback in order to adjust for their listening environment.

TruBass is a patented SRS technology that enhances bass performance utilizing SRS’s proprietary psychoacoustic techniques. These techniques restore the perception of fundamental low frequencies by dynamically augmenting harmonics. Controls include an LFE button that directs the processing to the LFE channel only and adjusts the filter from 60 to 40 Hz. The Front button directs TruBass to the Left and Right speakers only. A level control determines the level of
processing used.

Dialog Clarity is designed to compensate for dialog masking that often occurs during playback under certain conditions. By the time audio is compressed, decompressed, transmitted, and played back on a home theater or computer system, dialog may not be as understandable as it was during production, so Dialog Clarity is an attempt to improve intelligibility. An Enable button puts the process in the circuit while a level control adjusts the amount.

In Use

CS is extremely easy to use since there’s really not a lot that you can do during encoding. The fun part was listening to the results with the decoder, which can be inserted directly after the encoder to get an immediate before-and-after comparison. Like any matrix system, the steering can be a bit disconcerting as the end result is not a perfect representation of the program that went into the encoder. While the low-end remains solid, source material with a lot of high-frequency content, especially if moving, seemed to lose its localization a bit, which is to be expected. That said, CS does a remarkable job of squeezing a 5.1 mix down to stereo then back again. No wonder it’s becoming a favorite of broadcasters.

If you’re currently providing audio for broadcast, or just looking for a way to play back 5.1 mixes without resorting to authoring a DVD, SRS Circle Surround VST Pro is the way to go. Not only is it compatible with any matrix encoder available, but it’s ease of use makes it a winner. SRS Circle Surround VST Pro has a MSRP of $499.

Surround Professional Magazine