Introduction
Shorten is an early lossless audio compressor, written by Tony Robinson in the early
1990s at Cambridge University and later developed by SoftSound. In the late 1990s it
became the standard format for trading live concert recordings online, before FLAC
took its place. Many old archives of live music are still in .shn
files.
Structure
A Shorten file starts with the four bytes ajkg and a version byte. The
rest is a single bit stream with no byte-aligned structure: a header of variable-length
numbers giving the file type, channel count and block size, then a series of commands.
Each command says how to rebuild a block of samples for one channel, usually from a
linear prediction of the previous samples plus Rice-coded differences. The original
WAV or AIFF header is stored verbatim in the stream so that decoding rebuilds the whole
file. Shorten has no seek table, so a player has to decode from the start to reach a
point in the middle.
Links
Software
- FFmpeg – command-line tool that decodes Shorten, but cannot write it (Windows, macOS, Linux)
- VLC media player – free player for almost any audio or video file (Windows, macOS, Linux, mobile)