Discrete slope delta modulation with recovery means
First Claim
1. A method of processing an electrical signal by delta modulation comprisingconverting said electrical signal into compressed digital information by delta modulation,employing a plurality of slope tables each having a plurality of slope values in establishing said compressed digital information, andeffecting said compression by employing a code having a different value for each said slope value.
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Abstract
A method and apparatus for processing electrical signals by modifying delta modulation to discrete slope delta modulation includes converting its electrical signals into compressed digital information, and representing this digital information as a sequence of slops or deltas added to the past value of the representation. For each sample period, a slope is chosen from slope tables having multiple entries and each choice is represented by a Huffman code. Signal compression occurs in two steps: first the selection of a small number of possible slopes provides compression and also the most probable slopes are represented by the shortest Huffman codes providing additional compression. Depending on the history of the slope chosen, multiple tables can be accessed with different slop entries. Two check point values are provided which code absolute output levels instead of slopes in order to facilitate recovery of the signal in the event of transmission errors. Initial matching of a specific slope value sought in the same table wherein the next preceding value was found. In one embodiment, at least four slope tables each having at least four values is employed. The apparatus has components for performing the method.
80 Citations
31 Claims
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1. A method of processing an electrical signal by delta modulation comprising
converting said electrical signal into compressed digital information by delta modulation, employing a plurality of slope tables each having a plurality of slope values in establishing said compressed digital information, and effecting said compression by employing a code having a different value for each said slope value.
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20. Apparatus for processing an electrical signals by delta modulation comprising
conversion means for converting said electrical signal into compressed digital information by delta modulation, said conversion means having slope determining means for correselecting a slope table and a slope value within said table ponding to said electrical signal, and code means for converting said slope value corresponding to said electrical signal into said compressed digital information.
Specification