Abstract: In a digital encoder, truncation is controlled by the fullness of the output rate-smoothing buffer. A signal compression system is shown for processing a stream of fixed length digital sample signals, such as audio signals, which system includes a linear digital compression filter for compression filtering the sample signal stream and generating a stream of compression-filtered signals. The compression-filtered stream is encoded by an encoder which implements a variable word length truncated code. The encoder output is supplied to a buffer for transmission to a communication channel. The encoder is controllably operable in a normal mode and in an out of range (OOR) mode. In the OOR operating mode an OOR code word together with the compression filtered signal is sent to the buffer. Buffer underflow is controlled by operation in the OOR mode when the buffer is empty or near empty.

Abstract: Encoding and decoding method and apparatus are disclosed including a decoder for decoding a stream of encoded digital data words which have been encoded by an encoder using variable length code words in which the code words comprise a single group of 0 bits followed by a single group of 1 bits. The 0 bits and 1 bits are separately counted (46), and the combined counts are used to address a read only memory (54) containing the decoded digital data words. The decoded digital data word is read out from the addressed memory location. Also disclosed is an AND gate array 70 of rows and columns of AND gates (90-1 etc.), in which the number of 0s in the code word determines which row is energized, and the number of 1s in the code word determines which column is energized. The energized AND gate is indicative of the decoded digital data word.

Abstract: A music data compression system is disclosed which includes an analog to digital converter for converting the analog music signal to digital sample signal form, a digital compression filter for compression filtering the digital sample signals, and an encoder for truncated Huffman encoding the compression filter output. An entropy setting unit is included in the system for step control of the signal supplied to the digital compression filter in accordance with one or more threshold levels of the envelope of the music signal, and for reducing the entropy of the signal with increases in the energy level of the music signal. Different codes may be implemented in accordance with the threshold(s), and an identifying code word is inserted in the Huffman encoded stream. A decoder, digital reconstruction filter, and digital to analog converter are used to reconstruct the analog music signal.

Abstract: Method and apparatus for decoding Huffman encoded words are disclosed which include the use of logic gates connected in the form of a binary decoding tree which includes branches, interior and leaf nodes. Bits of the encoded word are sequentially supplied to gates of the binary tree. Simultaneously, gate enable signals are supplied to gates of the binary tree. Both the data bits and enable signals are supplied to gates at increasingly higher levels of the binary tree. When an output is obtained from a gate associated with one of the leaf nodes of the tree, the process of sequentially supplying data bits and enable signals to gates of the binary tree is repeated for the next encoded word. The original data words are regenerated by use of outputs from said gates associated with leaf nodes of the binary tree.