本文選題：HEVC　切入點(diǎn)：差錯(cuò)掩蓋(EC)　出處：《南京郵電大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：高效視頻編碼(HEVC)是最新一代視頻編碼標(biāo)準(zhǔn),能夠以一半的碼率獲得與H.264/AVC標(biāo)準(zhǔn)相同的編碼質(zhì)量。但是壓縮率的提升,使得視頻碼流對(duì)傳輸差錯(cuò)更加敏感,必須采取有效的差錯(cuò)控制措施。基于解碼端的差錯(cuò)掩蓋算法具有突出的優(yōu)點(diǎn),一直是差錯(cuò)控制算法的研究熱點(diǎn)。本文針對(duì)差錯(cuò)掩蓋算法進(jìn)行了研究,結(jié)合三種不同的差錯(cuò)狀況,發(fā)掘HEVC標(biāo)準(zhǔn)的編碼特點(diǎn),分別提出有效的差錯(cuò)掩蓋算法。主要工作及創(chuàng)新點(diǎn)如下:(1)對(duì)于HEVC碼流整幀丟失的情況,針對(duì)已有差錯(cuò)掩蓋算法的不足提出了基于PU的運(yùn)動(dòng)矢量外推差錯(cuò)掩蓋算法。首先建立HEVC標(biāo)準(zhǔn)下基于預(yù)測(cè)單元(PU)的MVE算法;然后對(duì)丟失幀進(jìn)行PU矢量外推,根據(jù)最小尺寸的外推PU塊,推測(cè)LCU的分割模式,由此確定當(dāng)前待掩蓋LCU的差錯(cuò)掩蓋基本單元(ECBU);接著對(duì)每個(gè)ECBU進(jìn)行基于PU的MVE掩蓋,從而完成該LCU的掩蓋。依次掩蓋每一個(gè)LCU,直至掩蓋完整個(gè)丟失幀。(2)對(duì)于HEVC碼流LCU丟失的情況,提出基于PU融合的加權(quán)BMA掩蓋算法。該算法首先根據(jù)相鄰幀之間的高度時(shí)域相關(guān)性,將丟失LCU的CU/PU分割模式假定為和其同位塊的相同;接著針對(duì)由率失真代價(jià)選擇出的運(yùn)動(dòng)矢量不一定代表視頻真正的運(yùn)動(dòng)的問(wèn)題,根據(jù)同位塊殘差能量判斷當(dāng)前的分割模式是否可靠,并將相鄰的不可靠PU進(jìn)行合理融合,完成對(duì)丟失LCU分割模式的優(yōu)化;然后是針對(duì)在HEVC標(biāo)準(zhǔn)下直接使用BMA算法的不足,建立權(quán)值圖進(jìn)行基于PU的BMA掩蓋,每掩蓋完一個(gè)PU都要更新一次權(quán)值圖,如此反復(fù)進(jìn)行直至掩蓋完整個(gè)丟失LCU。(3)鑒于在差錯(cuò)掩蓋算法中考慮視頻內(nèi)容特性的必要性,提出基于視頻內(nèi)容特性判斷的HEVC掩蓋算法。首先通過(guò)分析HEVC標(biāo)準(zhǔn)編碼樹(shù)單元分割為編碼單元(CU)時(shí)的特性,得出CU劃分深度與圖像的不同內(nèi)容分布有著密切的關(guān)系,可以由CU深度信息對(duì)CU所在圖像區(qū)域的內(nèi)容特征做出推斷——丟失LCU的深度由其空時(shí)域周?chē)_接收LCU的編碼深度信息來(lái)推測(cè)。如果判定丟失LCU所在圖像區(qū)域紋理簡(jiǎn)單、運(yùn)動(dòng)平緩,該丟失LCU應(yīng)用簡(jiǎn)便的掩蓋方法——運(yùn)動(dòng)矢量由相鄰正確接收編碼單元的運(yùn)動(dòng)矢量求均值得到,提高掩蓋效率。另外根據(jù)HEVC標(biāo)準(zhǔn)將CU編碼為幀內(nèi)模式時(shí)的特性,通過(guò)計(jì)算丟失LCU周?chē)_接收LCU編碼為幀內(nèi)模式的CU數(shù)量占總CU數(shù)量的比率,推測(cè)出該丟失LCU所在圖像區(qū)域是否屬于運(yùn)動(dòng)非常劇烈區(qū)域,如果屬于,應(yīng)該使用空域掩蓋算法,本文結(jié)合HEVC幀內(nèi)紋理角度預(yù)測(cè)技術(shù)提出了基于幀內(nèi)紋理角度模式的空域掩蓋算法;剩下圖像區(qū)域的內(nèi)容特性則屬于一般情況,采用基于PU融合的差錯(cuò)掩蓋算法就可以取得良好的掩蓋效果。論文最后對(duì)全文工作進(jìn)行了總結(jié),并對(duì)后續(xù)研究方向進(jìn)行了展望。
[Abstract]:High efficiency video coding (HEVC) is the latest generation video coding standard, which can achieve the same coding quality as H.264 / AVC standard at half bit rate. However, the improvement of compression ratio makes video stream more sensitive to transmission errors. It is necessary to take effective error control measures. The error concealment algorithm based on decoding has outstanding advantages and has always been the research hotspot of error control algorithm. In this paper, the error concealment algorithm is studied and combined with three different error situations. This paper explores the coding characteristics of HEVC standard and proposes effective error concealment algorithms respectively. The main work and innovation are as follows: 1) for the whole frame loss of HEVC bitstream, A motion vector extrapolation error concealment algorithm based on pu is proposed to overcome the shortcomings of existing error concealment algorithms. Firstly, the MVE algorithm based on prediction unit is established in HEVC standard, and then the lost frame is extrapolated by pu vector. According to the minimum size extrapolation pu block, the partition mode of LCU is inferred, and then the error concealment basic unit of current LCU is determined, and then each ECBU is masked by MVE based on pu. This masked the LCU. Each LCU is masked in turn until the entire lost frame. 2) for the HEVC bitstream LCU loss, A weighted BMA masking algorithm based on pu fusion is proposed. Firstly, according to the high temporal correlation between adjacent frames, the CU/PU segmentation mode of lost LCU is assumed to be the same as that of the same block. Then, aiming at the problem that the motion vector selected by rate-distortion cost does not necessarily represent the real motion of video, judging whether the current segmentation mode is reliable or not according to the residual energy of the same block, and merging the adjacent unreliable pu reasonably. The optimization of the missing LCU segmentation mode is completed, and then the weight map is established to cover the BMA based on pu, aiming at the deficiency of using the BMA algorithm directly under the HEVC standard. Every time a pu is covered up, the weight value graph is updated once. In view of the need to consider video content characteristics in error concealment algorithms, This paper proposes a HEVC concealment algorithm based on video content characteristic judgment. Firstly, by analyzing the characteristics of the HEVC standard coding tree unit when it is divided into the encoding unit (CUU), it is concluded that the depth of the CU partition is closely related to the different content distribution of the image. CU depth information can be used to infer the content features of the image region in which the CU is located-the depth of the missing LCU can be inferred by correctly receiving the encoding depth information of the LCU around its space-time domain. If it is simple to determine the texture of the image region in which the LCU is lost, The lost LCU uses a simple concealment method, the motion vector is obtained from the mean value of the motion vector of the adjacent correct receiving coding unit, which improves the concealment efficiency. In addition, according to the HEVC standard, the CU is encoded into the intra-frame mode. By calculating the ratio of the number of CU encoded by the received LCU to the total number of CUs around the lost LCU, it is inferred whether the image region of the lost LCU belongs to the highly moving region. If so, the spatial domain masking algorithm should be used. In this paper, a spatial domain masking algorithm based on intra-frame texture angle pattern is proposed based on HEVC intra texture angle prediction technology, and the content characteristics of the remaining image regions are general. The error concealment algorithm based on pu fusion can achieve good concealment effect. Finally, the paper summarizes the work of this paper, and looks forward to the future research direction.
【學(xué)位授予單位】：南京郵電大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN919.81

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