## 什么是ffmpeg

ffmpeg is a very fast video and audio converter that can also grab from a live audio/video source. It can also
convert between arbitrary sample rates and resize video on the fly with a high quality polyphase filter.

## 原理

ffmpeg命令都是长的吓人，但是基本原理还是简单的

## 实战

-c 表示拷贝流

### 第二种加入字幕方法

ffmpeg compilation

Stream copy is a mode selected by supplying the copy parameter to the ‘-codec’ option. It makes ffmpeg omit the decoding and encoding step for the specified stream, so it does only demuxing and muxing. It is useful for changing the container format or modifying container-level metadata. The diagram above will, in this case, simplify to this:

ffmpeg根本不需要做什么加码啊，解码啊。。直接分流和混流就行了,当然快了～