MSP; "A Primer on Compression" - Peabody Computer Music

Tutorial 1: Peak LimitingThe patcher C1. Peak Limiting illustrates the use of the omx.peaklim~ object. You can see it inaction by applying any signal with varying levels. Most pop music is heavily compressed, andwon't do much here. Try raw drum recordings if you have any, or classical music orrecordings of spoken word.The meters show the level of the input, the action of the amplifier, and the output level. If youincrease the input gain, you will see the level increase to a point, but then the gain slamsdown so that the output won't be allowed to reach the distortion point. You can then lowerthe output gain to get the original signal level with the peaks removed, as shown in figure 1.Figure 1. Peak limiting before (top) and after (Input +10 Threshold -1, output –10.)If you raise the threshold, distortion can occur and will be very audible. If you lower thethreshold, the gain indicator will be mostly in the low position, and the overall effect will be alot quieter. Raising the output gain will restore the original signal level, but you will find quietspots in the input contain things you didn't notice before. The overall impression of loudnessshould be much stronger than before. This is heavy limiting.7