H.263中全零系數(shù)塊預(yù)測(cè)的新方法
A novel early prediction method of all-zero coefficients in h.263
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摘要: 用H.263標(biāo)準(zhǔn)對(duì)甚低碼率圖像編碼時(shí)，經(jīng)過(guò)幀間預(yù)測(cè)后得到的運(yùn)動(dòng)補(bǔ)償數(shù)據(jù)通常很小，對(duì)這些數(shù)據(jù)再進(jìn)行DCT和量化后往往成為全零塊，Alice Yu算法和周算法是預(yù)先判別全零系數(shù)塊的較為有效的方法，但在對(duì)較為復(fù)雜的序列圖像進(jìn)行預(yù)測(cè)時(shí)分別出現(xiàn)了較大程度的誤判和漏判。針對(duì)這些缺點(diǎn)，該文提出了一種新的全零系數(shù)塊的判別方法，它具有能隨量化級(jí)的變化自適應(yīng)地調(diào)整全零塊的判斷閾值、無(wú)需任何附加運(yùn)算和對(duì)圖像序列內(nèi)容復(fù)雜程度不敏感的優(yōu)點(diǎn)，將該方法應(yīng)用于H.263編碼器中，對(duì)Miss America和News圖像序列進(jìn)行仿真實(shí)驗(yàn)。實(shí)驗(yàn)表明，大約有40％-80％的塊可以在做DCT和量化前被判別為全零系數(shù)塊，大大減少了編碼的時(shí)間，同時(shí)圖像質(zhì)量的下降控制在0.0005 dB以內(nèi)。
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關(guān)鍵詞:
- 量化; 運(yùn)動(dòng)補(bǔ)償; 全零系數(shù)塊
Abstract: For most sequences at very low bit rates, the value of motion compensation data usually is very small, and will all be reduced into zero after DCT and quantization. Alice Yu method(1997) and Zhou method(1998) both are effective to predicting these All-Zero Coefficients (AZC) blocks, but these two methods will, to a large extent, mis-justice and leak out the AZC blocks respectively, especially for complex sequences. In order to overcome these disadvantages, a new method of early predicting AZC blocks is proposed in this paper. In this method, no additional computation is needed and the threshold can be changed with the quantization level. Applying this method to H.2G3 encoder, about 40%-80% blocks of Miss America and News picture sequences can be determined to be AZC blocks before DCT and quantization. It can greatly reduce the encoding computation time and is very useful to the software implementation of H.263 in real-time. In addition, PSNR of decoding sequences is controlled within O.OOOSdB. -
ITU-T, Draft ITU-T Recommendation H.263: Video coding for low bit rate communication,ITU-T, Mar. 1996.[2]ITU-T, Draft ITU-T Recommendation H.263+: Video coding for low bit rate comnunication,ITU-T, Sep. 1997.[3]Alice Yu, R. Lee, M. Flynn, Early detection of all-zero coefficients in H.263, Proceedings of the picture coding symposium, Berlin, Gernany, 1997, 159-164.[4]周璇,譚徑微,余松煜,H 263中預(yù)先判別全零系數(shù)的新方法,上海交通大學(xué)學(xué)報(bào),1998,32(9),107-109. -
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