Tapered Quantization
Basically from what I understood, it would be something like this....
In the quantization graph, we usually see a wave and the corresponding amplitudes marked at the axes and all those amplitude values are equally spaced from each other.
But according to tapered quantization, the constantly repeating values of the amplitudes will follow a finely spaced pattern in the plotter but with the values that appear rarely, those amplitude points/ values would face an non-equal pattern in between them(they would be marked or placed far away from each other).