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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?

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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:

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+1 Clever and fun to look at! – thirtythreeforty Oct 15 '13 at 6:07
Of course, one could add high frequency noise to the audio decoded from the lossy compressed file before encoding into a lossless file, but that is probably too much of a trouble, so this method is pretty cool for 99% of the cases :-) – Alexander Shcheblikin May 17 '14 at 21:16

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

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1+ re: frequency rolloff. As a quick test, loading any suspect file into any media player with a spectrogram visualization plugin (foobar comes to mind) will likely show a complete absence of any higher frequency components to the file in question, as well as a flat-topped cut-off appearance to primarily high frequency things like cymbal hits. – Dylan B. Apr 30 '10 at 21:41
Just because I would like more information about digital recordings, It doesn't mean I'm pirating music. There are some cds in bootleg circles that are all legal and legit. comes to mind.… – GmonC May 1 '10 at 4:16
@GmonC: The snarky answer wasn't meant to be serious. I apologize if I offended you. – afrazier Jan 4 '11 at 17:54
no problem, you didn't offend me! I didn't mean to be too serious in my comment as well, it was just a clarification. You gave a good answer, that's why you received 3 upvotes (myself included :) – GmonC Jan 18 '11 at 1:19
Both these programs are absolutely not reliable – Thom Wiggers May 4 '12 at 14:32

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

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