Digital recording and playback method and apparatus

Abstract

A recording-playback system is disclosed wherein analog signals are converted to digital form which then are compressed and encoded using a variable length code. The encoded signals are temporarily stored in a buffer memory from which they are read out to a variable speed recorder for recording thereof. The rate at which the encoded signals are read out to the recorder and the recording speed are controlled in direct proportion to the percent fullness of the buffer memory for recording with substantially constant bit density on the recording medium. The ratio of the buffer memory read out rate and recording speed may be selected for recording with a substantially maximum bit density. A playback unit for the system includes a variable speed playback for playing back the recorded digital signals. The signals are temporarily stored in a buffer memory, from which memory they are read out to a decoder which operates at a substantially constant word rate. The speed of operation of the variable speed playback means is controlled in inverse proportion to the fullness of the buffer memory to maintain a supply of signals for use by the decoder. The decoded signals are supplied to a digital decompression filter for digital reconstruction thereof. A digital to analog converter converts the digital signals to analog form.