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Is there a way of checking that the so-called FLAC or WAVPACK audio file was originally encoded from a lossless source (WAV, CDA, APE, etc.) instead of a lossy source (MP3, AAC, ATRAC, etc.)?

Say I have a lossy MP3 audio file (5.17Mb, 87% compressed from its original, source unknown). I then encode it to another lossless format, say FLAC or WAVPACK.

The size increases (23.14Mb, 39% compressed from its original, source MP3)! ID tags, etc, remain the same and there's no way of checking the integrity of its origin.

How do I go about doing that?

Raystafarian
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cornel
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3 Answers3

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The best way to determine if something has been sourced from a lossy source, is creating a spectrogram:

Lossless Spectrogram

One can clearly see that it goes up to the 22.1kHz a proper CD has.

When transcoded to a lossy MP3 128kbps, you can clearly see the destructive work of the encoder:

Lossy V2 Spectrogram

More details and examples here: http://blowfish.be/eac/Spectral/spectral.html

Thom Wiggers
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There's no way to definitely tell one way or the other whether a given lossless file was directly ripped from a CD or reencoded from another lossy format. There's a couple programs available that try to determine the likelihood that a given file has a lossy source though:

What these programs do is analyze the file looking for characteristics that may indicate that they were once lossy encoded. Stuff like sharp rolloff of audio > 16 KHz, audio not aligned to CD frames, signals indicative of encoding flaws like pre-echo, etc.

There's also the snarky answer: Quit pirating music and go buy the CD or track. :-p

bvargo
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afrazier
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Complete mathematical analysis will show "holes" in the frequencies of the audio, commensurate with the psychoacoustic parameters used in the initial lossy compression.

Ignacio Vazquez-Abrams
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