A method of video coding rate control by joint picture-layer and macroblock-layer is proposed in this paper. In picturelayer,
the number of bits in each frame is pre-allocated on the whole, and a reference quantization parameter is
determined. Then, according to rate-distortion principle, when each frame is encoded, the optimized quantization
parameter is selected for intra-frame different macroblocks with the minimal distortion. The result of simulation shows
that the proposed method of video coding rate control can reduce or avoid buffer from overflow or underflow efficiently,
stabilify the output bit-steam and improve the peak signal-noise-ratio (PSNR) of re-constructed video signal.
The strategy of sequence image coding rate control by picture layer and mcroblock is proposed in this paper. Rate control on picture layer actually allocates a number of target bits for current frame to be encoded. Based on this number, a reference quantization parameter is selected on picture layer. In the course of determining the quantization step of every macroblock in a frame, the characteristics of an image itself should be fully considered. The characteristic of the image by the distribution characteristics of the DCT coefficients is denoted and a best quantization parameter for every macroblock in a frame is selected. The complexity of the algorithm is analyzed and an improved method is proposed. The experiment shows that the rate control strategy proposed in this paper can effectively reduce and avoid the overflow and underflow of the encoder buffer, and the output bit rates tend to stabilization. The peak signal-to-noise ratio (PSNR) of the reconstructed image is raised.
A method of improved motion vector based on quantization errors in transcoding for wireless mobile Internet is proposed in this paper. The computational complexity of this scheme can be reduced. The control strategy of transcoder buffer is also discussed, and the number of coding bits on the picture layer in the whole is allocated, then different types of picture respectively are processed on the basis of frondose picture characteristics when each frame is coded. Finally optimal quantization parameter for every macroblock in a frame is select. The simulation results shows that this method can effectively speed up the transcoding without significant lose in quality. The output bit rate of the transcoder and the buffer fullness tend to be stabilized, and the peak signal-to-noise-ratio (PSNR) of the reconstructed picture is raised.
The basic concept of fractal and the mathematics of fractal compression are introduced in this paper, The basic principle and implementing method ofthe tradition fractal image compression are expound, A new method of sequence image fractal coding based on the visual character is proposed. In this coding algorithm, we use different fractal image coding method for different coding block after fully considering the statistic character, based on which we define the visual character of the coding block, then code the parameters of the iteration function by variably length coding. Consequently we obtain the higher compression ratio and the better decoding subjective quality.