如果您只想提取音频流没有重新编码只是做：

If you just want to extract the audio stream without re-encoding just do:

ffmpeg -i input-video.avi -vn -acodec copy output-audio.aac

• -vn 没有视频


• -acodec copy 说使用与之相同的音频流。


• -vn is no video.
• -acodec copy says use the same audio stream that's already in there.

读取输出以查看它是什么编解码器，设置正确的文件扩展名。

Read the output to see what codec it is, to set the right filename extension.