Image Number 8 for United States Patent #5438643.
Apparatus for recording an information signal as bit-compressed digital data. The apparatus comprises a bit compressor and a recording system. The bit compressor receives the information signal as digital data. The digital data include bits, and the bits include redundant bits. The bit compressor compresses the digital data by removing only the redundant bits from the digital data to generate the bit-compressed digital data at a variable bit rate. The redundant bits are bits that result in a quantizing noise level lower than an allowed noise level at which the quantizing noise is imperceptible to a human auditory sense. The allowable noise level is determined by a masking threshold and a minimum audibility limit. The recording system receives the bit-compressed digital data from the bit compressor and records the bit-compressed data on a recording medium.