Opus 转 FLAC
把 Opus 文件转成 FLAC，存放到支持范围更广的无损格式里。
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Opus
The most efficient audio codec available, built for the modern web. Excellent quality even at very low bitrates.
FLAC
Lossless compressed audio — CD quality at roughly half the size of WAV. The archival format of choice for music collections.