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Rate–distortion optimization (RDO) is a method of improving video quality in video compression. The name refers to the optimization of the amount of ''distortion'' (loss of video quality) against the amount of data required to encode the video, the ''rate''. While it is primarily used by video encoders, rate-distortion optimization can be used to improve quality in any encoding situation (image, video, audio, or otherwise) where decisions have to be made that affect both file size and quality simultaneously. ==Background== The classical method of making encoding decisions is for the video encoder to choose the result which yields the highest quality output image. However, this has the disadvantage that the choice it makes might require more bits while giving comparatively little quality benefit. One common example of this problem is in motion estimation, 〔D. T. Hoang, P. M. Long, and Jeffrey Vitter, (Rate-Distortion Optimizations for Motion Estimation in Low-Bitrate Video Coding ), ''IEEE Transactions on Circuits and Systems for Video Technology'', 8(4), August 1998, 488-500. A shorter version appears in ''Proceedings of the Digital Video Compression Conference'', IS&T/SPIE 1996 Symposium on Electronic Imaging: Science & Technology, 2668, San Jose, CA, January–February 1996, 18-27.〕 and in particular regarding the use of quarter pixel-precision motion estimation. Adding the extra precision to the motion of a block during motion estimation might increase quality, but in some cases that extra quality isn't worth the extra bits necessary to encode the motion vector to a higher precision. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rate–distortion optimization」の詳細全文を読む スポンサード リンク
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