作为对视频转换编码及码率控制研究的基础，本文首先介绍了几种主要的视频编码标准。
As the basis of the following research on transcoding and rate control, several related video coding standards are introduced in this thesis first.
可伸缩性视频转换编码算法是大型分层视频组播系统层次化代理自适应机制的核心技术。
Scalable video transcoding is the key technology of a adaptive mechanism for hierarchical agents in a large-scale layered video multicast.
实验表明，算法在MPEG - 4水印视频经过滤波、旋转、尺度变化、代码转换编码等处理后，水印在可见性和鲁棒性等方面取得了良好的效果。
From the experiment results, it indicates that, after the watermarked MPEG-4 video suffer filtering, rotation, scaling and transcoding, the watermark possesses good imperceptibility and robustness.
视频空间分辨率下变换转换编码过程的运算量较大，受实时性、输出码率的限制，转换后的图像质量会有一定程度的下降。
Video transcoding for reduced spatial resolution needs a lot of computation. Restricted by real-time demand, the quality of transcoded stream will decrease in variant degree.
视频空间分辨率下变换转换编码过程的运算量较大，受实时性、输出码率的限制，转换后的图像质量会有一定程度的下降。
Video transcoding for reduced spatial resolution needs a lot of computation. Restricted by real-time demand, the quality of transcoded stream will decrease in variant degree.
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