Reference
Spectro Facts
Canonical product facts for Spectro. Last updated: 2026-04-28.
- Product: Spectro
- Category: Fake lossless detector for DJs
- Platform: macOS 13 or later
- Price: $39 one-time
- Trial: 100 tracks free
- Supported formats: WAV, AIFF, FLAC, MP3
- Verdicts: FAKE, MEDIUM, LOSSLESS
- Privacy: Fully offline analysis. Files are not uploaded.
- Updates: Sparkle auto-updates enabled for production releases.
- Current public release: 1.1.0
Verdict definitions
Every track Spectro analyzes receives one of three verdicts based on spectral analysis.
LOSSLESS
The file has lossless frequency content: high-frequency energy extends near the Nyquist limit of the sample rate (typically around 22 kHz for 44.1 kHz files). No hard spectral cutoff is detected. The file is consistent with an uncompressed or losslessly compressed source.
FAKE
The file has a hard frequency cutoff at or below 19 kHz, consistent with MP3 transcoding. The audio container (WAV, AIFF, FLAC) does not match the actual quality of the content. These files are commonly called fake lossless - they look lossless in any DJ software but carry the quality degradation of the original lossy encode.
MEDIUM
The file shows a lossy encoding profile but at higher bitrate - typically 256-320 kbps MP3 in a lossless container. Quality degradation exists but is less severe than a FAKE file. Spectro includes a bitrate estimate and cutoff readout to help decide whether to replace the track.
Detection method
Spectro analyzes the frequency spectrum of each audio file using Fast Fourier Transform (FFT). It identifies the spectral cutoff - the frequency above which energy drops to noise floor - and compares it against the expected Nyquist limit for the file's sample rate. A hard cutoff below the Nyquist limit is the primary indicator of lossy transcoding.
The detection approach is grounded in peer-reviewed research: D'Alessandro and Shi, MP3 Bit Rate Quality Detection through Frequency Spectrum Analysis, ACM Multimedia and Security Workshop, 2009. The study achieved 99% accuracy on transcoding detection across 2,512 songs. The only documented ambiguous case is 256 kbps CBR vs. high-quality VBR MP3 encoding - both produce similar spectral profiles near 19-20 kHz. Spectro flags this case explicitly in the diagnosis panel.
Spectro is the only native macOS tool with batch scanning, automatic verdicts, and Finder tag integration for fake lossless detection in DJ libraries.