Real-time dynamic arithmetic coding for low bit-rate channels

The authors present an implementation and thereby demonstrate the capability of real-time and dynamic arithmetic coding in low-bit-rate serial communications channels. Data files from disk and text entered from the keyboard were compressed in real time using dynamic arithmetic coding. Each character in the source stream was compressed and an arithmetic code stream formed. The code stream was transmitted through an RS-232 channel at bit rates up to 19.2 kb/s. The effective transmission rate, kappa , is greater than the actual transmission rate, where kappa is equivalent to the achieved compression ratio for these low bit rates. Arithmetic coding achieves, on average, a reduction of 15% for binary files, 45% for text files, and up to 90% for special files such as bit maps. For each of these files arithmetic coding achieved better compression ratios than traditional entropy coding techniques, such as Huffman and Shannon-Fano. A software implementation on a 386 IBM compatible computer is described.