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From Broadcast Stereo to 5.1 for HD with Soundfield's UPM-1

Soundfield UPM-1

SoundField, the UK-based manufacturer and supplier of multi-capsule mic systems for stereo and surround audio capture in the broadcast and audio recording markets, has begun shipping the first quantities of its latest product, the UPM-1 stereo-to-5.1 converter, to satisfy international pre-orders.

Aimed at the broadcast market, the UPM-1 is a 19-inch rack processor designed to create 5.1 material from old programme material which only has a stereo soundtrack. Such 'legacy' programming is a problem for companies broadcasting in high definition with 5.1 surround audio, because listeners find it distracting when modern HD shows are broadcast in 5.1 surround and then the audio narrows to a very 'flat-sounding' two channels for older material. This kind of distracting switch can occur even within one show; all the modern content in an HD sports show will be in 5.1, but older clips of past sporting events usually have only a stereo soundtrack. To modern HD broadcasters, this kind of repeated expansion and contraction of the audio soundscape is unacceptable. The UPM-1 provides a fast, easy-to-use solution.

The UPM-1 distinguishes itself from other available stereo-to-surround processes in several ways. It works not by adding reverb or using phase shifts to generate new material for the rear channels in a 5.1 soundscape; in fact, the UPM-1 adds nothing ‘new’ to the audio at all. All of the material in the 5.1 mix that appears at the processor’s outputs is derived from spatial information present in the original stereo signal. What's more, the UPM-1's processing is adaptive, changing with the input signal, rather than remaining constant irrespective of input.

The UPM-1 generates 5.1 from two channels by analysing the original stereo audio using a patented algorithm which separates the audio into its so-called Direct and Ambient components. The former encompasses the ‘dryer’, less reverberant components in the original sound (for example those elements that would have been close to the microphone when the audio was recorded), while the latter refers to the more reverberant components (ie. those sound sources that would have been further away at the time of recording). These elements can then be processed separately and routed in different proportions to the 5.1 mix if required, using the UPM-1's simple front-panel rotary controls. In addition to discrete controls for the input level and individual 5.1 output channels, the level of the Direct sound component in the original signal may be adjusted independently from that of the Ambient sound in the rear channels, and the Ambient component in the front three channels. The UPM-1 also offers control over the perceived width of the front three channels, and over whether the material appearing at the front centre of the 5.1 soundscape will be routed only to the Centre channel or equally to the Left and Right channels (‘phantom centre’).

To take a practical example, if an archive clip of a sports broadcast in stereo is put through the UPM-1, it will be possible to alter the level of the acoustically dry commentary found in the phantom centre of the stereo mix without affecting the reverberant crowd ambience. Similarly, sending some of the reverberant crowd noise to the rear channels of the 5.1 mix is possible without also routing the sound of the ball being kicked on the pitch or the voice of the commentator to the surround speakers.

"There have been solutions for broadcasters who want to use archive stereo material on 5.1 HD transmissions before," comments Ken Giles, Managing Director of SoundField, "but the UPM-1 really has something to offer broadcasters in terms of its unique approach, operational speed and simplicity — you plug it in, put stereo into it, and immediately you have broadcast-ready digital 5.1 audio that still sounds like the original signal, not swamped with extra reverb and processing. We're certain this ease of use has been a key factor in the high level of interest and the healthy pre-orders the UPM-1 has generated."

The first UPM-1s began shipping from SoundField's head office in early May, following pre-orders to Canada, the USA, Germany, Scandanavia, Italy, and within the UK, the international satellite broadcaster Sky. For more information on the UPM-1, call SoundField on +44 1924 201089, or go to www.soundfield.com.

Click here to view the Soundfield UPM-1 in the Studiocare web Store