3 things:1. hi I am new2. I recently stumbled across a paper which details an algorithm that, with a very high success rate, guess the bit rate of an audio file just using data from the file's high-frequency spectrum. If developed further it could remove the need to visually inspect a spectrogram etc. and would be much faster.http://www.fileden.com/files/2009/2/14/232...20Frequency.pdf
In order to obtain the feature data, the source MP3 files were each decompressed into a 1411 kbps WAV file using the Fraunhofer IIS MP3 Surround Commandline Decoder V1.4 . This was done because audio files in this format can easily be read into MATLAB, and as we have demonstrated, transcoding to a higher bit rate does not affect the frequency characteristics of the audio which we are observing.
It is, in my opinion, not a good sign when the author of a paper does not understand that WAV is a lossless format and so resorts to arguing that "transcoding" to PCM probably doesn't change the audio. Regardless, all that paper demonstrates is that if you know that LAME 3.97 was used with default lowpass for each bitrate, you can figure out the source bitrate by looking at the lowpass setting.
So does the paper actually not do what it claims it does?
I don't see any reliance on prior knowledge concerning the "history" of the file in question.
It doesn't do what people in this thread are interested in though.
Suggest reading section 2, "procedure". They train their model using the same encoder and settings they will then attempt to detect. Without this the system is useless.
QuoteIt doesn't do what people in this thread are interested in though.once you have an algorithm which can estimate original bit rates of a transcoded lossless format, getting a yes/no answer to the question "are my flacs 'real'?" seems trivial.
QuoteSuggest reading section 2, "procedure". They train their model using the same encoder and settings they will then attempt to detect. Without this the system is useless.Correct.I still don't see any reliance on prior knowledge concerning the "history" of the file in question. Of course any algorithm of this nature needs information about what it is looking for!
If you know that the file was encoded with a given lame version, then you already know the answer to the question "are my flacs that I've created from my LAME mp3s 'real'" is "No".
As I said above, the prior knowledge is the encoder and settings (aside from bitrate) used to create the file in question.
Yes but surely the OP was referring to a situation where the file history is unknown.
(Suggest reading OP.)
Even in this case the algorithm should be able to take arbitrary WAVs
QuoteAs I said above, the prior knowledge is the encoder and settings (aside from bitrate) used to create the file in question.No. The prior knowledge is the information about the frequency characteristics of lame-encoded mp3s.
What I am saying is that once you have trained the algorithm, you can then take arbitrary WAVs (or flacs, or whatever) and use the algorithm on them.
I've seen examples of both false positives and false negatives.
I have receive the answer from Qobuz. They have checked the file and think at has been through some MPA compression. They will ask the producer for a true original and offered me a free album to compensate. They were pretty quick to react too. Good point for them
Some/many are also just not very technologically savvy.
Quote from: astroidmist on 08 October, 2011, 01:41:20 AMThere used to be a freeware DOS command line/console program that could examine a WAV and tell if it came from an MP3.It's called AuCDtect and does a spectrum analysis looking for patters introduced by lossy compression. It works very well, you'll hardly ever get a false negative. There a windows frontend called Tau Analyzer and even a foobar plugin, all avaiable here: http://en.true-audio.com
There used to be a freeware DOS command line/console program that could examine a WAV and tell if it came from an MP3.
By false positive I mean that the file is fine, but detected as lossy.Tau Analyser uses the same engine as auCDtect, so you can decode to wav and use auCDtect directly or automate it with fooCDtect or another frontend.
I know the topic title sounds absolutely absurd but hear me out. I've tested my FLAC collection by encoding them into V0 MP3. I then decoded the MP3 back to WAV and then compressed it in FLAC. My question is: unless you've ripped the files yourself, how would you know the FLAC file you have is ACTUALLY lossless instead of an MP3 converted into FLAC? I've used the TEST option in FLAC frontend and it doesn't give a result. I have used Audiotester and it does say the file failed because it's TRUNCATED.Bottom-line: Is there a sure-fire way of knowing that a FLAC file is truly lossless and not a derivative of a lossy file?
I have two J.S. Bach cds (Das Wohltemperierte Klavier I and II, Leonhardt, Harmonia Mundi/BMG Classics) which I believe to be legitimate, and sound perfectly.Yet Audiochecker finds them to be 99% MPEG. It may have something to do with being a single instrument (harpsichord), so they may have used a lowpass filter to reduce noise in the higher frequencies where a cembalo is not supposed to be.So we can't trust checking software completely.
Can anybody tell if these are both fake:
you can't have an MP3 HDCD file.