TECH

The DJ Sez system is split into two major components. The graphical component is simply a smart video player. All of the experience's graphics have been prerendered into a large movie file in the interest of playback speed and audio synchronization. The video player is aware of activity on the Jam-O-Drum itself so it can correctly cue and play the various video sequences. This works on the same principle as seeking between multiple chapters or scenes on a DVD.

A separate piece of software, named "Scratch", was written to produce the high-fidelity scratching sounds and drum beats. Scratch works by reading the current position of each turntable via a joystick-like interface. The motions of the turntables are used to generate record "scratching" sounds. The scratching sounds are affected by the velocity and direction of the turntable motions in an effort to produce realistic sounds. Initially, we found the joystick responses to be sluggish, creating noticeable latency between the scratching motions and their associated scratching sounds. This latency was reduced by tweaking the turntable hardware at the expense of a performance degradation on the computer. The audio response was quite good, but few CPU cycles were left to drive the experience's graphical elements. Therefore, the decision was made to move "Scratch" (and the turntables' joystick interfaces) to a machine of its own.

This represents our current configuration of two machines connected via an IPC system over Ethernet. Because the two applications ("Scratch" and the video player), which now live on separate machines, don't need to communicate frequently, this compromise raised few problems.

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LOGIC FLOW OF DJ SEZ