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Topic: [TOS #9] Lossless fake (Read 4062 times) previous topic - next topic
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[TOS #9] Lossless fake

Hi.

I recently got a WAV file that was sent to me as "lossless" but which I discovered to be a fake (using Spek). I happen to have the exact same song ripped from vinyl in MP3 since around year 2000 (vinyl clicks & pops match 100%).

So it's obvious someone took that MP3 and somehow edited it to bump up the frequency spectrogram cut-off from original MP3 16KHz to 22 KHz. There still is a visible line at 16 KHz in the WAV that is a clue that it's fake, but everything above that is added in somehow.

The question I have now is: How did he do that ?

I uploaded both the MP3 and the WAV file in case anyone wants to take a look and compare.

Re: Lossless fake

Reply #1
Some sort of exciter DSP. IIRC there was one in Nero audio editor years ago. It would scan audio for high frequencies and add harmonics. That is the basic.

Re: Lossless fake

Reply #2
Here's another example of basically perfect fakery.

Remember, MP3 was first. The WAV was made by modifying the MP3.

There are plenty of WAV/FLAC tracks being sold on-line in web shops as lossless and when you look at the spectrum, they are clearly lossy material. If one can simply "fix" that like in the examples above and pass it on as lossless, that's pretty scary.

Re: Lossless fake

Reply #3
I added one more ZIP archive containing lossy MP3, fake lossless FLAC and real lossless FLAC for those regularly dealing with lossless files, so this comparison package can help them learn to spot the differencess between legit and fake lossless files.

Basically, looking at the missing part of the spectrogram (as compared to the MP3), the faked part of it is pretty dull / featureless, compared to the same part in the real lossless file. The fake one contains "monotonous" noise, straight vertical lines. That's how I would interpret it.

 
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