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Rate control strategy in sequence image transcoding based on the quantizer optimization |
Li Xiaohui; Wu Xiaopei |
The Key Lab of Intelligent Computing and Signal Processing Ministry of Education Anhui Univ., Hefei 230039 China |
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Abstract In this paper, the status of transcoder buffer is analyzed. The conditions that have to be met by both the encoder and transcoder buffers for preventing the decoder buffer from underftowing or overflowing are derived also. A model of sequence image transcoding is established. A new rate control strategy based on the quantizer optimization is proposed, and the target number of bits firstly on picture layer based on the status of the buffer and the channel rate is allocated. Then the characteristics of the image by the distributed characteristics of the DCT coefficients are denoted and a best quantization parameter for every macroblock in a frame is selected. The experiment shows that this rate control strategy can effectively reduce or 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.
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Received: 10 October 2001
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