Method and apparatus for frame memory compression

摘要

A method for frame memory compression divides each of a plurality of image frames in a frame memory into a plurality of blocks and quantizes a plurality of pixel values inside each block according to a predefined parameter, thereby generating a quantized block and a plurality of removed bits from the binary representation of the plurality of pixel values. A predictor is used to produce a residual block for the quantized block. A variable length encoder takes the residual block as an input and produces a coded bitstream. A packing unit is used to take the coded bitstream and the number of removed bits generated by the quantizer as inputs, so as to produce an entire codeword sequence of the block that meets a target bit rate by using a structure called group of blocks (GOB) to flexibly share available spaces of the blocks in the same GOB.

主权项

1. A method for frame memory compression, adapted to a video processor at least including a quantizer, a predictor, a variable length encoder, and a packing unit, said method comprising:
dividing each of a plurality of image frames in a frame memory into a plurality of blocks for taking a block as a compression unit; applying said quantizer to quantize a plurality of pixel values inside said block according to a predefined parameter, thereby generating a quantized block and a plurality of removed bits from a binary representation of said plurality of pixel values; applying said predictor to produce a residual block for said quantized block; applying said variable length encoder to take said residual block as an input and produce a coded bitstream; and applying said packing unit to take said coded bitstream and said plurality of removed bits generated by said quantizer as inputs, so as to produce an entire codeword sequence of said block that meets a target bit rate by using a structure called group of blocks (GOB) to flexibly share available spaces of the blocks in the same GOB; wherein said packing unit checks whether or not a length of said coded bitstream is less than said target bit rate, and a cutting and a filling are performed when the length equals to or exceeds said target bit rate, and a compensation is performed when the length is less than said target bit rate, said cutting being operated by removing a (k+1)-th codeword used in said variable length encoder exceeding said target bit rate from said coded bitstream and choosing a best matched codeword to replace the (k+1)-th codeword, where k is a codeword index, such that the total length of k successive codewords used in said variable length encoder is smaller than said target bit rate, but the total length of the k+1 successive codewords used in said variable length encoder is larger than said target bit rate.