A DSP algorithm which processes the signals from five microphone elements, which elements are physically arranged and electrically combined such that the resulting composite stereo signals, left total and right total, or the resulting AC-3 encoded AES signal, produce a surround image and are compatible with current industry standard surround decoders. No external encoding equipment is required. This technology is easy to use, low cost and suitable for mass production at relatively low cost.

A "surround image" is defined for the purposes of the present technology as the orientation of five microphone elements so as to section the acoustic environment to be recorded into five regions that capture the main features of a stage environment (the environment of, for example, a live play produced on the stage of a commercial theater). These regions are labeled stage left (or left), stage right (or right), center stage (or center), and ambient (or rear). As has been shown in the theater industry and the commercial movie industry, this sectioning of the acoustic environment creates the most realistic sound from the point of view of the listener. Very likely, this is due to the familiarity of listeners with live entertainment, conventionally viewed and heard in real-life stage environments. The microphone system of this technology differs from all other microphone systems by employing, and faithfully receiving for realistic reproduction, a surround image. Figure 1 shows the orientation of the five microphone elements of this technology and how they appear in the acoustic environment in order to create this surround image. Current electronic technology dictates that audio signals be transmitted and stored in a stereo format. For this reason, the microphone element signals are encoded into stereo, either analog, for compatibility with DOLBY PRO LOGIC™ surround decoders, or digital (AES) for compatibility Dolby Digital 5.1™ surround decoders.

This technology provides a portable embedded surround recording solution for utilizing a microphone array and an encoding process for producing a signal equivalent to that required by Dolby Digital 5.1™ surround decoders.This technology provides a portable embedded surround recording solution which is free from the limitations of the current technology and which provides a surround image and localization of recorded sound for portable video recording systems. The algorithm is very small; forty lines of code in total. It only utilizes 12 memory sockets on the typical DSP. Due to it's very small size, it does not create additional overhead within the DSP as many other algorithms do. It is written in ANZI-C and as a result it is very portable to many DSP platforms. Currently it has been ported to the Alesis and Texas Instruments DSP product lines.

A typical camcorder has between two and three recording channels on board today to enable recording in stereo with a center channel. On many camcorders the center channel is derived from the left and right channel. To enable recording in surround sound, additional microphone channels are added in the rear along with the SSM algorithm which we describe below.:In the case where there are fFive microphone channels on board, apsules A (left), B (center), C (right), and D (left rear) and E (right rear) are designated serially about a common axis, so as to separate the sound field into four regions of a plane. The plane is divided into four quadrant areas by orthogonal axis lines X/-X and Y/-Y having an intersection generally at the center of the plane, with a line Q1 bisecting a first and third quadrants of the plane, and line Q2 bisecting a second and fourth quadrants of the plane. Sound waves from a Q2 direction in the plane excite capsule A (left) to produce signal Ea, sound waves from a Y direction in the plane excite capsule B (center) to produce signal Eb, sound waves from a Q1 direction in the plane excite capsule C (right) to produce signal Ec, sound waves from a Q3 direction in the plane excite capsule D (left rear) to produce signal Ed and sound waves from a Q4 direction in the plane excite capsule E (left rear) to produce signal Ee. Translating circuitry provide signals containing information distinguishing between soundwaves from the Q1, Y, Q2, Q3 and Q4 directions. Signal processing circuitry has input connections to the translating circuitry, and output connections delivering two separate output signals analogous respectively to the Q1, Y, and Q3 directions, and the Q2, Y, and Q4 directions.

Figure 1