Apparatus and method for pipelining variable length decode and inverse quantization operations in a hybrid motion-compensated and transform coded video decoder

Abstract

A method for pipelining variable length decode and inverse quantization operations in a hybrid motion-compensated and transform coded video decoder includes the step of mapping a new code word to a look-up table to retrieve a code word length, a zero-run length, and a quantized level. A new linear, zig-zagged position of a current coefficient is identified from the zero-run length and a previous zero-run length. The code word length is added to a current bitstream position to yield a new bitstream position. A quantization matrix coefficient from the new linear, zig-zagged position of the current coefficient is selected. The quantized level is multiplied by a predetermined value to produce a quantization product. In the case of inter block processing, a quantized level sign value is added to the quantization product. In the case of intra block processing, the quantization product does not include the quantization level sign. The quantization product is multiplied by a quantization matrix coefficient to form a derived quantization value. The derived quantization value is divided by a predetermined word length to produce a final quantization value. The new linear, zig-zagged position of the current coefficient is converted to a two-dimensional display position. The final quantization value is written at the display position.