Patent ID: 7397855
Filing Date: 2008-07-08
Classification: H04N

Abstract:
1. A rate controlling method for computing a reference quantization parameter, used in a transcoder having a variable length decoder, an inverse quantizer, a quantizer and a variable length encoder, the rate controlling method comprising: receiving an input quantization parameter and motion information for each of the macroblocks from the variable length decoder; analyzing the similarity of motion information between a current macroblock and its neighboring macroblocks to compute a scaling factor for the current macroblock when allocated within P- and B-pictures; computing a bit difference between a target outputting bit stream and a real outputting bit stream from the variable length encoder; estimating the fullness of a virtual buffer to encode the current macroblock in view of the scaling factor; and computing the reference parameter based on a target bit rate, the first quantization parameter and the bit difference; wherein said motion information is a motion vector, and said scaling factor is defined as the following: where “·” is operator for inner product, MV is the motion vector of the current macroblock, and MV