基于最佳量化的序列圖像編碼轉(zhuǎn)換碼率控制策略
Rate control strategy in sequence image transcoding based on the quantizer optimization
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摘要: 該文分析了編碼轉(zhuǎn)換緩沖區(qū)的狀態(tài),導(dǎo)出了編碼轉(zhuǎn)換緩沖區(qū)為防止解碼器緩沖區(qū)下溢和上溢應(yīng)滿(mǎn)足的條件,建立了序列圖像編碼轉(zhuǎn)換模型。并根據(jù)編碼轉(zhuǎn)換緩沖器的狀態(tài)和信道速率,為待編碼幀在圖像層上預(yù)分配目的序列圖像編碼比特?cái)?shù),使用DCT系數(shù)分布特性來(lái)表征圖像特性。繼而為幀內(nèi)每一具體宏塊選定最佳量化因子,提出了基于最佳量化的碼率控制策略,模擬實(shí)驗(yàn)表明,該碼率控制策略能有效地減少、避免緩沖區(qū)出現(xiàn)上、下溢的情況,使輸出碼率趨于穩(wěn)定,提高了重建序列圖像的信噪比。
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關(guān)鍵詞:
- 序列圖像; 編碼轉(zhuǎn)換; 最佳量化; 碼率控制
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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