Check if a FLAC download is genuine lossless
Drop a FLAC file to check whether its frequency content actually extends to the full spectrum, or whether it appears to be a re-encoded lossy file.
Lossy Source Heuristic Analyzer
Analyzes the frequency spectrum of your audio file to look for high-frequency cutoff patterns associated with lossy encoding. Results indicate a risk level — not a definitive verdict. A genuine recording can also show high-frequency rolloff. All analysis is local.
Key features
- Local processing
- No upload required
- High-frequency rolloff reference
- Detected cutoff frequency
- Spectrum visualization
How detection works
The tool decodes the audio locally and runs a fast Fourier transform to find the highest frequency with significant energy. If the energy drops sharply well below the Nyquist limit — at 16 kHz, 18 kHz, or 20 kHz — the file likely originated from a lossy source.
Understanding the verdict
"Genuine" means energy extends to within 3% of Nyquist. "Likely genuine" means 20 kHz or higher. "Suspicious" means energy cuts off between 16–20 kHz, a range typical of 192–256 kbps MP3. "Lossy" means cutoff below 16.5 kHz, typical of 128 kbps or lower.
Limitations
Frequency analysis is a heuristic. Some legitimate recordings have natural high-frequency rolloff. Some lossy sources may not trigger this check. Always use this as one data point, not a definitive verdict.
Common use cases
Audit a music library for pseudo-lossless files
Spot "upscaled" FLAC files — MP3 or AAC sources re-wrapped in a lossless container — before they waste storage space.
Verify a rip before archiving
After ripping a CD or copying from a streaming download, verify the resulting FLAC actually contains full-spectrum content.
Frequently asked questions
Can this tool definitively prove a file is fake lossless?
No. This is a heuristic indicator based on frequency content — not proof. Frequency analysis is a strong clue but not definitive. Some recordings naturally lack high-frequency content. Some encoders apply transparent high-frequency limiting. Treat the result as a reference hint, not a final verdict.
What cutoff is typical for MP3?
MP3 128 kbps typically cuts around 16 kHz. 192 kbps around 18–19 kHz. 256 kbps around 19.5–20 kHz. 320 kbps often extends to 20+ kHz.
Is my audio uploaded?
No. Everything runs locally in your browser.
About this page
Lossy Source Heuristic Analyzer is part of OFPlayer's local-first music workflow. The page is designed to explain the feature, tool, or guide in plain language before you open the interactive app experience.
OFPlayer focuses on personal music collections, browser-based utility tools, WebDAV and Subsonic/Navidrome workflows, privacy-first playback, and lightweight library management. Files stay under your control, and the website avoids account-based lock-in.
Useful next pages from here include Audio Spectrum Viewer、Audio Metadata Viewer、Audio Format Converter、GitHub. These internal links help you continue from overview, to setup, to actual playback or tool usage without losing context.