 a point at which it is annoying. This is a much greater problem at low bandwidths (POTS or ISDN BRI) than at speeds of 384 Kbps, or especially 224 Kbps, because the codec has less room to maneuver. Other quality reduction techniques are sometimes used in video compression. One we have not yet mentioned has to do with color. If a color coding system were to represent a video image using only one bit per pixel, the picture would be monochrome. Bits could take only two values. A zero would represent an absence of light while a one would portray light of a single frequency, white or red, for instance. A coding system of this type has a single bit plane. Additional colors are added to the system with multiple bit planes. The total number of planes used to represent an image is a bit-map. The more bits in the map, the better the resolution. With a two-bit-plane, four color values can be represented: 00, 01, 11 and 10. Bit planes containing eight bits can represent 256 discrete values. When R, G, and B are each assigned eight bits, millions of color combinations can be created (256). Each time an additional bit is added to a bit plane, the picture's resolution doubles. Unfortunately, SO does the bandwidth required to transmit the uncompressed image. Video Communications: The Whole Picture AUDIO COMPRESSION As we asserted earlier, human speech has attributes that lend themselves to efficient compression. Compression can eliminate pauses between words. Amplitudes rise and fall predictably. We also instructed that PCM coding results in eight-bit samples. While this is true, we have omitted a step. Samples are quantized at 212 (4,096 values) and then compressed to eight bits (256 values) using logarithmic encoding. This process is called companding, it is a contraction of the words compress and expand. Companding is performed in accordance with either u-Law (pronounced "mu-Law") or A-law; u-Law is used in North America and Japan, and A-Law is used elsewhere. When compressing voice, logarithmic modeling works better than li