Is that file really 320? The spectrogram doesn't lie.
Lossy encoders cut the top off the spectrum, and re-encoding can't put it back — a '320kbps' file made from a 128 still carries the 128's scar. Drop a file and read its real history.
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How to read the spectrogram
Time runs left to right; frequency runs bottom to top; brightness is energy. Real full-quality audio fades out gradually toward the top. A lossy encode leaves a hard horizontal ceiling instead — a shelf where the encoder said "nobody will miss this" and deleted everything above it. The shelf's height is the file's true birth certificate: around 16 kHz says 128 kbps, around 19 kHz says 192–256, and energy pushing past 20 kHz says genuine 320 or lossless.
The verdict card does that reading for you and calls out the one thing sellers of re-encoded files hope you never check: the label on the box can be rewritten; the shelf cannot. Sample diggers, DJs buying packs, and anyone archiving a collection should make this a habit — thirty seconds here saves a lifetime of dull hi-hats.
Frequently asked questions
How can you tell an MP3's real quality?
Lossy encoders discard high frequencies to save space: 128 kbps typically cuts everything above ~16 kHz, 192 around ~18–19 kHz, and 320 keeps content past 20 kHz. That cutoff shelf is permanent — the tool measures where your file's energy actually stops and compares it to what the file claims to be.
What is a 'fake 320' or upscaled MP3?
A low-bitrate file re-encoded at a higher bitrate. The new file is bigger and labeled 320 kbps, but the audio still ends at the old cutoff — bigger box, same loss. They're everywhere on file-sharing sites and old sample folders.
Can a real 320 kbps file still fail the check?
Rarely, honestly: some legitimate sources are low-pass filtered (old masters, vinyl rips, certain synth-only tracks with little natural high end). The verdict card reports the measured cutoff and lets you eyeball the spectrogram — the shelf's shape usually settles it.
Does this work on WAV and FLAC files?
Yes — and it's the most fun there. A WAV or FLAC with a hard 16 kHz shelf was made from a lossy source; 'lossless' packaging doesn't launder a lossy past.