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Topic: How to find out if a WAV has been generated from a MP3 (Read 18237 times) previous topic - next topic
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How to find out if a WAV has been generated from a MP3

Reply #25 –
Quote from: timcupery on
Quote from: greynol on
You do realize that your results are specific to a particular codec, its version, and settings used, correct?

yeah. and also to the source material.

No, in my experiments, it was not.

The results were verified by encoding uncompressed “.wav” files containing “real music” material with spectra “vivid” up to 22 kHz, and white noise “.wav” files created at 44,1 up to 192 kHz sampling frequencies, containing linear spectrum up to 96 kHz. For the “white noise”, at levels “-6 dB”, “-20 dB” and “-50 dB”.

And with the settings cited before (mp3 CBR 320 kbit/s and mp3 CBR 256 kbit/s), the results were equal for every bitrate cited regardless of source material.

How to find out if a WAV has been generated from a MP3

Reply #26 –
I think he's going to the more general point about lossy-lossy transcoding.  Encoding @320 isn't going to add high frequencies back that were removed by a previous lossy encode at a lower bitrate.

Re: How to find out if a WAV has been generated from a MP3

Reply #27 –
Hello, I am new here and just want to share my experience on how to identify real Wav/Flac are generated from a mp3 file in simple way.
Most of the time when I received Wav/Flac files I am using application called auCDtect Task Manager (https://codecpack.co/download/auCDtect-Task-Manager.html) - for which will analyse whether those file is real or not.

On the contrary, you can make an experience to convert a mp3 file into wav (sampling rate 44100,16 Bit Depth) using Cool Edit Pro or Adobe Audition and altered them with an effect called SandBrush ( 4Front DX and VST plugins - https://www.kvraudio.com/  or  http://old.yohng.com/mb.html ), and save it into new wav file name.
The next step is analyse this saved file in auCDtect Task Manager, to my surprise it's identified to as real 100% wav file.

I hope guys here who expert in spectrum analysis can give short explanation to the above mentioned manipulation.

Cheers,
tutemachine

Re: How to find out if a WAV has been generated from a MP3

Reply #28 –
auCDtects is like us.
It can detect low bit rate MP3 and is totally at loss at high bit rates.
It probably simply looks at the high frequencies because low bit rate MP3 rolls of the treble.
Use a tool like Sandbrush you add high frequencies hence auCDtect will fail.

To the best of my knowledge, there is no app able to discern between lossless and high bit rate lossy in a reliable way.
You might search this forum on "auCDtect"
You might have a look here as well:https://losslessaudiochecker.com/
Doesn't work either.


TheWellTemperedComputer.com

Re: How to find out if a WAV has been generated from a MP3

Reply #29 –
Even simply converting to PCM with dithering is sufficient to fool both of those detectors.
 

Re: How to find out if a WAV has been generated from a MP3

Reply #30 –
A more reliable method is to generate zoomed in spectrograms from the beginning and end of each track where the amplitude is changing from high to low, and look for blockiness or the cutoff frequency stepping up and down. Make a subtraction of the two channels and look at that too. This can be automated with a SoX command-line. It is important that the spectrograms show a short duration of time, not the entire file. Even if some high frequencies, distortion or shaped noise has been added, you can still usually see the original and the noise superimposed one onto the other.