A transcoding scheme for the High Efficiency Video Coding (HEVC) is proposed that allows any partial frame modification to be followed by a partial re-compression of only the modified areas, while guaranteeing identical reconstruction of non-modified areas. To this end, first, syntax elements of all Coding Units (CU) in the frame are parsed and decoded according to their scan order. Then CUs that are collocated with a replaced area are re-encoded with new content to generate a partial set of new syntax elements. In order to avoid spatial propagation of the decoding mismatch due to the new content, CUs on the border of the replaced area are losslessly coded such that reconstruction of immediately neighboring CUs in the scan order are protected from the modification. The proposed method has been implemented on top of the HEVC test Model (HM) in All-Intra (AI) coding configuration and experiments show that, depending on the test parameters, it can offer both a bitrate saving (up to 4% in terms of BD-BR) and a transcoding acceleration (up to 83%) compared to a full transcoding scheme.

翻译：提出了一种面向高效视频编码（HEVC）的转码方案，该方案允许对任意部分帧修改后仅对修改区域进行部分重压缩，同时保证未修改区域的重建结果完全一致。为此，首先根据扫描顺序解析并解码帧内所有编码单元（CU）的语法元素；然后对与替换区域共位的CU进行新内容的重编码，生成部分新的语法元素集。为避免新内容导致的解码失配空间传播，对替换区域边界处的CU进行无损编码，从而在扫描顺序上保护相邻CU的重建结果不受修改影响。该方法已在HEVC测试模型（HM）的全帧内（AI）编码配置上实现，实验表明，根据测试参数的不同，相较于全转码方案，该方法既能节省码率（BD-BR最多可降低4%），又能加速转码过程（最高可加速83%）。