shorten reduces the size of waveform files (such as audio) using
Huffman coding of prediction residuals and optional additional
quantisation. In lossless mode the amount of compression obtained
depends on the nature of the waveform. Those composing of low
frequencies and low amplitudes give the best compression, which may
be 2:1 or better. Lossy compression operates by specifying a minimum
acceptable segmental signal to noise ratio or a maximum bit rate. Lossy
compression operates by zeroing the lower order bits of the waveform,
so retaining waveform shape.
