ffmpeg实战教程第4集 视频格式转换 MP4 MKV

知识延伸：

I,P，B帧和PTS，DTS的关系

基本概念：

Intra frames, also known as intra pictures, are frames that represent images without motion relative to the current scene. These I frames typically serve as a reference point for decoding subsequent frames within the same GOP (Group of Pictures), which is a unit of video compression used in MPEG standards. They are created by compressing the original image data to a manageable size while retaining its essential visual information for random access playback. The I frame can be viewed as a compressed version of an image after encoding processes have b