Multi-code-book variable length decoder

Abstract

A multi-code-book variable length decoder for decoding an input bit stream containing a plurality of variable length code words includes a plurality of individual variable length decoders and a controller. Each of the individual variable length decoders receives the input bit stream and decodes the input bit stream according to a different respective code book. The controller receives the input bit stream and, for each successive code word contained in the input bit stream, selects a correct one of the plurality of individual variable length decoders for decoding that code word. Each of the individual variable length decoders, when selected, operates in an active decoding mode to decode each successive bit of the input bit stream until detecting an end of a current code word contained in the input bit stream, and when not selected, operates in a passive decoding mode to pre-decode each successive bit of the input bit stream as if it were an initial bit of a next code word contained in the input bit stream, and belonging to its own code book. Each of the individual variable length decoders, when selected, produces an end-of-word signal upon detecting the end of the current code word. The controller receives the end-of-word signals produced by the individual variable length decoders, and, in response thereto, makes a decision as to which one of the individual variable length decoders is the correct one for decoding the next code word. Each of the individual variable length decoders, when selected, produces a decoded word at its output. The decoded words produced by the individual variable length decoders are multiplexed by a multiplexer which produces a decoded word stream at its output. The controller determines the type of each successive code word contained in the input bit stream according to a prescribed communication protocol, e.g., an MPEG protocol, and makes the decision as to which one of the individual variable length decoders is the correct one, on the basis of this determination. The operation of the individual variable length decoders is thus fully pipelined, so that no input buffers are needed to compensate for decision latency of the controller.

Dependencies are inferred from the claim text.