The story behind fake-320 MP3s — how they get made, why they spread, and how to systematically catch them at library scale.
Fake-320 MP3s have been around since the early days of file sharing. The pattern is always the same: someone gets a lower-bitrate MP3 (128 or 192 kbps), re-encodes it to 320, and the new file claims 320 kbps in its tag even though the audio has no new information. The original encoder discarded high frequencies during the first encode, and no amount of subsequent re-encoding restores them. Twenty years later these files are still everywhere — forum packs, free download sites, USB sticks shared between DJs, archives rescued from old drives. If you've built a music library over a decade, you almost certainly have hundreds of them mixed in with your real 320s.
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Rekordbox · Serato DJ · VirtualDJ (incl. Favorite Folders) on Windows 10+ and macOS (Apple Silicon + Intel).
The real cost of fake-320s isn't disk space — it's the slow degradation of your library's overall quality, which compounds every time you DJ on a system better than what you tested on. A track that sounds fine on AirPods can sound noticeably off on a club PA. Library-wide FFT scoring is the only way to know what's actually in your collection. Music Library Doctor scores every file with FFT analysis, lets you sort by score, and surfaces the worst offenders so you can fix the audio problems you didn't know you had. It's not about chasing perfection — it's about not playing fake-320s through a $50,000 sound system.
Not reliably. A real 320 and a fake-320 of the same track length will be similar sizes. The fake's audio is what's different, not the file size — which is why FFT analysis is the right tool, not file inspection.
Almost never. The big legitimate stores have quality controls on the source files. The fake-320 problem is mostly outside those channels — forum packs, P2P, free pack sites, USBs traded between DJs.
That's a judgment call. If you have backups or the track is replaceable, deleting is fine. If the fake-320 is the only copy you have of a hard-to-find track, keep it and replace when you can. Smart Upgrade* is built for that path.
About the same — sometimes slightly worse because the second encoding adds its own subtle artifacts. The fake's main sin is the misleading tag and the wasted disk space, not new audible damage.
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