Method for controlling the encoder output bit rate in a block-based video encoder, and corresponding video encoder apparatus

摘要

Constant-bitrate rate control is very useful for real-time video transmission. However, it is difficult to realize a good CBR rate control in an MPEG4-AVC video codec. According to the invention, an adapted rho-domain rate control processing for real-time rate control is applied, whereby rho is the percentage of zero amplitude transform coefficients following quantisation. A couple of tables are used for mapping between the quantization parameters and rho. A detailed analysis at transform-level is carried out in order to get the slope of the relationship between the bitrate and rho. The slope of the linear model is constrained by a look-ahead procedure with respect to the neighbour frames or blocks.