Research On Transcoding For Multiview Video

Transcoding is defined as the conversion of one coded signal to another.Video transcoding is the operation of converting a video from one format intoanother format. A format is defined by such characteristics as the bit rate, frame rate,spatial resolution, coding syntax, and content. However, traditional transcodingmethod only applies to single view video. In recent years, multiview video isbecoming more and more popular because of better visual experience. Generalspeaking, multiview video is captured by different cameras on different positions atthe same time instance. Therefore, multiview video often has a larger amount of data.To transmit over various networks and store or play on different devices,transcoding for multiview video bit reduction is in badly need.We propose a fast transcoder for multiview video bit reduction. Considering themodes used in original video stream is very similar with that in transcoded video,the mode information extracted from original stream is utlized in our transcoder.Besides, the video content in adjacent views is almost the same so that the modes ofcorresponding MBs in adjacent views are also similar. Therefore, we utilized themode information of adjacent views. Then only a group of candidate modes areconsiderd for current MB when transcoding and much time is saved for modedecision.Since inter view reference is used in multiview video coding, the codinginformation for inter view reference shall be utilized when transcoding. Inspired bymotion vector (MV) refinement algorithm in H.264/AVC transcoding, we proposeddisparity (DV) refinement algorithm in proposed transcoder. The motion anddisparitu search center is calculated by the input MV/DV and the predicted one andthe search range is far smaller. Therefore, the most time consuming motion anddisparity search calculation in video coding is simplied.Besides, the number of reference frames in multiview video coding is morethan that in H.264/AVC. Through our simulation experiments, we find that there issome correlation in selected reference pictures before and after tranccoding. Theselected reference frames information in original stream is utilized in proposedtranscoder to accelerate the mode decision and search calculation. Considering themode used for transcoding may be different from that in input stream, we proposed adominant reference picture selection algorithm and sometimes the iterative searchfor bi-prediction can be omitted. The tranccoding efficiency is improved further.The simulation experiment results show that the proposed multiview videotranscoder saves over90%time compared to fully decode and re-encode transcoder while maintaining a high RD performance.