转码Transcode

转码是把素材从一种编码转到另一种——MOV / MKV → MP4 是最常见的场景。

• 什么时候转：本机打不开、或平台只收某种格式——一条命令转掉。
• 转的是编码：容器可以顺手换，但画质变化来自编码那一层（见 容器（封装）、编码器）。
• 转码有损吗：转到有损编码就有损——无损编码之间搬运才零损失。
• 最适合交给命令行：重复、批量、要求一致的转码，FFmpeg 一次做完（见 转码 的兄弟活 CRF（质量参数））。

Transcoding moves material from one codec to another — MOV / MKV → MP4 is the everyday case.

• When to transcode: the file will not open locally, or the platform only takes one format — one command converts it.
• What changes is the codec: the container can swap along the way, but quality shifts come from the codec layer (see Container, Codec).
• Is it lossy?: going to a lossy codec is lossy — carrying between lossless codecs is the only zero-loss move.
• Born for the command line: repeated, batch, consistency-demanding conversions — FFmpeg does them in one go (with its quality dial at CRF).