CAJ | 학술논문

针对屏幕中同时出现视频和文字图片时现有码率控制方法的局限性，提出一种新的码率控制方法。以视频缓存检验器和恒定码率因子控制模式为基础，通过视频窗口检测算法将屏幕内容划分为视频区域和非视频区域，并对不同的区域采取不同的码率控制算法。结合视频区域识别算法，新的码率控制方法分别对帧层和宏块层采用如下方法实现优化：对于帧层，若当前帧为 P帧且在I帧周围一定范围内，则该帧通过采用P_SKIP模式降低非视频区域的帧率以补偿I帧的整体质量，提高屏幕视频序列的整体视觉效果；对于宏块层，则根据当前宏块所处区域(视频区域或非视频区域)对宏块量化参数及其波动范围作一定调整。实验结果表明，与x264原有的VBV+CRF模式相比，新的码率控制方法获得的主观评价评分要高40%。
침대병막중동시출현시빈화문자도편시현유마솔공제방법적국한성，제출일충신적마솔공제방법。이시빈완존검험기화항정마솔인자공제모식위기출，통과시빈창구검측산법장병막내용화분위시빈구역화비시빈구역，병대불동적구역채취불동적마솔공제산법。결합시빈구역식별산법，신적마솔공제방법분별대정층화굉괴층채용여하방법실현우화：대우정층，약당전정위 P정차재I정주위일정범위내，칙해정통과채용P_SKIP모식강저비시빈구역적정솔이보상I정적정체질량，제고병막시빈서렬적정체시각효과；대우굉괴층，칙근거당전굉괴소처구역(시빈구역혹비시빈구역)대굉괴양화삼수급기파동범위작일정조정。실험결과표명，여x264원유적VBV+CRF모식상비，신적마솔공제방법획득적주관평개평분요고40%。
With the quick development of modern distance education, screen coding for encoding screen content appears, a new rate control method is proposed for the characteristic of screen content that includes videos, text and pictures. It is based on the Video Buffer Verifier(VBV) and Constant Rate Factor(CRF) mode and divides the screen content into video area and non-video area using a video recognition algorithm which can recognize the position of the video window on the screen. Combining with the video recognition algorithm, the new rate control method respectively improves rate control method of the frame layer and the macro block layer through following method. For frame layer, if the current frame is a P-frame, and the P-frame is within a certain range around the I-frame, this frame lowers the frame rate of non-video area by adopting P_SKIP into the non-video area to enhance quality of the nearest I-frame so that improves the overall visual effect of the screen sequence. For macro block layer, the new rate control method adjusts the value of Quantization Parameter(QP) and limits its fluctuation range by the location of the current macro block, whether it is in video area or not. Experimental results prove that the new rate control method can score 40%more than the original VBV+CRF mode in the subjective assessment.