fast compression for waveform files. 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.