电子化评审系统视频编解码技术研究

摘要

In e-assessment system, it is very important to compress the high-definition video efficiently. With in-depth studies on high efficient video coding, a VBR parallel coding technology based on last scene prediction is proposed.Thenovel bit-rate control method allocates the bits accurately for each frame,which not only saves band width effectively, but also improves subjective picture quality.In addition, in order to implement real-time high-definition video coding, a parallel coding algorithm that can be implemented simultaneously in multiple levels, including frame level, slice level, macro-block level and pixel level is also presenled.The test results show that, compared to the x264 encoder, proposed video encoder gets 30% saving on bit-rate, about 1.5 times increases on computational efficiency, and delay reduction of about 100 ms~200 ms.%具备高清、低延时和高压缩率品质的视频编解码技术是确保电子化评审顺利实施的核心关键技术.对高效视频编解码技术进行了深入研究,提出了一种基于动态场景快速预测的可变码率并行编码技术,该技术基于H.264视频编码框架,通过对当前编码画面复杂度和场景变化率的准确分析,并参考若干帧已编码图像的各类编码特性统计信息,为当前画面分配合理的码率,从而不仅有效地节省了带宽,还保证了画面质量的稳定性.另外,为实现高清视频实时编码,还采用了一种可在帧级、块组级、宏块级和像素级等多个层次同时实施的并行编码算法.对大量具有不同运动特征的国际标准视频测试序列进行的测试表明,所提出的视频编解码技术相对于此前综合效果最优的x264编码器,在同等的解码图像质量条件下,带宽平均节省约30％,运算效率提高约1.5倍,延时减少100～200ms.