AAC 转 Opus
把 AAC 音频重新编码成 Opus，在音质相当的情况下文件体积更小。
来自
To
AAC
Raw AAC audio — MP3's successor, used in streaming and broadcasting. Efficient, but fewer apps open bare AAC files.
Opus
The most efficient audio codec available, built for the modern web. Excellent quality even at very low bitrates.