System for variable length code data stream position arrangement

Abstract

An entropy code look up table processes incoming data and provides an n-bit output signal having an entropy code word and a bit.sub.-- length output signal. Entropy code words are successively packed without spacing bits into two sixteen-bit latches. An arithmetic unit keeps track of accumulated sizes of packed, unconveyed entropy code words. The n-bit output signal is converted into a thirty-two bit signal with spacing bits on either side of a current entropy code word. Using the accumulated size information, flow through multiplexer units insert spacing bits in bit positions corresponding to bit positions currently occupied by packed entropy code words. Any remaining bits in the thirty-two bit output signal are preferably set to logical zeros. With the current entropy code word properly aligned in the thirty-two bit output signal, a path selection logic unit utilizes the accumulated size information and a unary decoder to form a sixteen bit output signal. Previously packed entropy code word(s) occupy the most significant bit(s). The remaining bit(s) are set to logical values of the current entropy code word most significant bits. These sixteen bits are written into a selected latch, and the thirty-two bit output signal least significant sixteen bits are written into the other latch. The arithmetic unit determines the number unconveyed, packed entropy code word bits. If the number is greater than fifteen, at least one of the latches is full. This number is used by the path selection logic unit to properly select the most significant latch.