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Fake flac identification

Discussion in 'Sound Science' started by swansboy, Nov 23, 2016.
  1. Swansboy
    Hi guys, I use a software call Spek to identify fake flac files. It shows frequency range of the files and a cut off around 15 Khz usually means (unless the songs was recorded like that) a fake flac. However, something bugs me about this analysis. Suppose Spek shows the frequency response of a file is around 22 Khz (which is usually the case with authentic files) but it still sounds bad. Could it simply be a case of bad recording or could it still be fake somehow? 
    Here is an example below. Is it possible the following file could be a fake flac though it looks there is no frequency cut off? 
  2. castleofargh Contributor
    it's close to useless. a frequency cut off around 16khz will only happen on really low bitrate mp3. you can do a all lot of things to a song without losing high freqs. and then the flac could simply be some bad vinyl rip where the ultrasounds are mainly noise.
    when you download random stuff online, you take that chance.
  3. Swansboy
    Sorry if this is a noobish question, just to confirm if I understand you correctly: if a flac has high frequencies and still sounds bad, it could just be a bad rip and definitely won't be fake?  
  4. castleofargh Contributor
    define fake. if by that you mean something lossy converted back to flac, or something ruined on purpose, then you won't always have a clear way to tell aside from having the original track.
  5. Swansboy
    Yes, I meant flac that has been converted from a lossy format yet somehow the highs are not cut off (if that is possible). It seems the only way to confirm is to listen to the original track as you suggested.  
  6. sonitus mirus
    Most likely the only way to tell for certain would be if either you made the FLAC or the file could be verified using an AcurateRip/CUETools image.  
  7. Swansboy
    Could you please explain how AcurateRip / CUETools image works? Sorry, I am completely unaware of these tools. 
  8. Roger5
    AccurateRip just provides a database of images/checksums that allows tools that implement it to validate your rip against others to confirm its accuracy.
  9. Swansboy
    Thanks for the explanation. 
  10. Roger5
    No problem.  dBpoweramp is the software tool most closely associated to AccurateRip.
  11. sonitus mirus
    More on CUETools, though I have not used it myself.
    The 2 use cases that might be beneficial to your needs would probably be (1) applying offset correction if needed and (2) verifying album image against the AccruateRip database.
    I'm not certain if this tool could be used in this manner for a single song or if it only verifies the full album.  
    Another option might be to use the Foobar file integrity verifier tool.
    Foobar is free, but it only works on Windows operating system with the file integrity checker, as far as I know.
  12. vcoheda Contributor
    i use this program. seems reasonably accurate.
    a quick google search also came up with this one although i haven't used it.
  13. zareliman
    Today I used the Lossless Audio Checker from:

    It failed to detect my test files. Only detected about 1/10 MP3 to FLAC conversions.
    Also gave false positive for about 1/10 EAC ripped FLAC.
    Doesn't do what the AES paper claimed to do. I checked and there's an older version that was different but I couldn't find it.

    Digging deeper I found that most lossless checkers are based upon auCDtect, so I downloaded the Task Manager:


    This tool worked with my test files 100% (for both MP3 to FLAC positive test and true EAC rip negative test).
    Then I tried a "lossless" FLAC from a reputable digital download website. The algorithm says MPEG with high confidence. I even tried another record from same artist/label I had ripped from a physical CD to check if there was an issue with the master/label but the tracks checked OK on auCDtect.
    I sent an email to the customer support of this "reputable" digital download website, waiting for an answer. I think I'm entitled to a refund but they delivered FLAC and it's "lossless" to the lossy source (so they can claim is still lossless ?). What do you think about this ?
  14. Roseval
    Can't blame them for not detecting MP3 as they state on their website they implemented this for AAC only
    I had couple of CDs flagged as "upsampled"
    What they do is detect the highest frequency. If this is substantial lower than then sample rate, they flag it as upsampled.
    A weird and very confusing use of "upsampled".
    I do think it a nice concept but badly implemented..
  15. zareliman

    For some reason older versions detected MPEG, don't know what happened. They changed the GUI, the name, everything.

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