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How To tell between a 'real' FLAC and a 'fake' FLAC?

Discussion in 'Sound Science' started by chinesekiwi, Aug 31, 2009.
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  1. chinesekiwi
    I know this question's been asked before and there was a program that someone mentioned that looked at the files via spectrograms and gave you readings such as indicating the peak kHz readings etc.... but couldn't find the thread.

    If anyone can give me a link to that program = great! [​IMG]
     
  2. leeperry
  3. AtomikPi
    Sure.
    Spectro - Freeware Audio File Analyzer

    By the way, you'll probably want to know that with LAME mp3's you'll get around 16 khz for 128 and around 19-20 for v0 and 320 (cd is around 22 khz) although of course for more information, Google is your friend.

    edit: also the above program is the best I've found - it reads flac natively, is super fast and lightweight, and is easy to use.
     
  4. chinesekiwi
    ^
    That's the one.
    Anyway, I know about the encoding limitations [​IMG]
    Also lossy, at least with mp3's, also cut outs information within the audible spectrum.
     
  5. DeusEx
    now that's why one of my FLAC folders sounds so bad...
     
  6. Jany
    Ill show you how i detect fake FLAC [​IMG]

    Software: Spectro
    Homepage: http://spectro.enpts.com/

    FLAC vs MP3[320kbps]:
    [​IMG]

    MP3[128kbps <lol>]:
    [​IMG]

    After analyze fake flac you will see same specro like on source mp3.
    TIP: Not always you will have 22,1KHz but that don't means its fake.
    When i spectred full quality human sound solo, spectro is low xP
    On website are good news, author will add multiple scan option [​IMG]
     
    pedronet likes this.
  7. khaos974
    I woudn't be sure the difference is as clear as you make it, some recordings, for example CDs that were made from old recordings (the 60s ot the 70s), sometime simply don't contain high frequencies at all, or at a very low level. Similarly, I have some CDs which were recorded at a whooping -35dB average to allow for really high dynamics, and these contain very little HF info too. Do I need to talk about badly mixed pop music for which the samples used were already MP3s at the production stage?
     
    So looking for the missing frequencies is a bad method.
     
  8. Pratt
    Yea, I think there is more to it then just Freq. analyzing, especially because that's easy to get confused even for those who think they know what they are doing. It's a bit arbitrary and or misleading sometimes at least. I wish there was some simple definitive program one could use to scan lossless files to see if they truly are, without having to figure out freq. spectrums for each recording. I haven't found any yet; I've even used some on some cd's I knew were lossless because I ripped them myself and I got weird freq. spectrums and less than 100% probability for being lossless, sometimes even 70 to 80% probability for being lossy.
     
    I don't trust any program. The only way to truly know you have lossless is to buy and rip the cd yourself of course.

     
     
     
     
     
     
     
     
    SleathX1 likes this.
  9. svyr

    +1 transfers from old tapes/digital tapes for classical sometimes you get a FR from about 100hz to 8khz :D... Sometimes whatever digital format they were stored in could well be a variation of Mpeg (l2, l3 :D ) so Cut-offs and inspecting the higher end spectrum for artifacts is a bit hit and miss.

    Tau is for CDs, Aucdtect/Audiochecker (and a better AUCDTect GUI http://y-soft.org/English/products/auCDtect-Task-Manager/ ) are for encoded lossless files (basically it's a GUI on top of AUCDTect and WV,FLAC,APE, etc decoders. Decodes to wav, passes the wav to aucdtect and spits out the log.

    Aucdtect is not very well regarded. It uses the analysis techniques described in http://en.true-audio.com/Tau_Analyzer_-_Aucdtect_Algorithm_Details
    which appear to be sound, but people argue it doesn't spot non mp3 compression too well, especially at higher bitrates (ogg, aac, etc)

    It also won't tell you whether someone decided to volume level the entire CD before encoding it :D ...


    Anyway, if anyone has ACM access and can pull http://portal.acm.org/citation.cfm?id=1597828 for us, I'd be interested to have a read (or anything on the similar theme that follow on from it or relates to it) . edit: ooh found it http://www.fileden.com/files/2009/2/14/2321055/My%20Documents/MP3%20Bit%20Rate%20Quality%20Detection%20through%20Frequency.pdf or something like http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4490000 / http://www.csie.nctu.edu.tw/~cmliu/Courses/Compression/Artifacts.pdf , since the other one is not cited... :D (unfortunately there aren't automated tools for the later papers :D ). UNfortunately, most papers seem to deal with low bitrate artifacts for things like VoIP, or watermarking or forensics...
     
  10. xnor

    Exactly. Unless you ripped the tracks on your own you simply cannot tell what happened to the files.

    That's why there exist tools like AccurateRip for example.
     
  11. svyr

    ah, good point. If you have a tool that takes an AR log/cue file or just the plain flacs and verifies the CRCs that's probably a good indication. e.g. cuetools can do it, it think : http://forum.dbpoweramp.com/showthread.php?t=23610 or they mention a foobar plugin and that app: http://www.hydrogenaudio.org/forums/index.php?showtopic=87503



    ^ well, there we go...
     
  12. Dobrescu George
    i am using audacity.... it is hard to understand, it takes time and effort to read it's graphics, and it makes a little- to no sense... but it shows which is flac which is not flac.... because it shows if the information contained in the song is expanded or not, and it shows if the song has unaudible-but present parts...l.
     
    squallkiercosa likes this.
  13. Fatalethal
    weird... i tried selecting all the songs i ripped using dbpoweramp but it says failed when attempting to load the song into the spectro
     
  14. Dobrescu George
    ok, fatalletal.... it is about how they were encoded, i have this problem too... encod a flac with flac encoder, for the name of what is right in this world....
     
  15. aqua11alta
     
    Quote:


    Hi. can you tell me more about that? How do you tell which is 'fake'/'real' flac? I just downloaded Audacity and chose the function 'Analyze' --> 'Plot Spectrum', but I don't know how to translate the the spectrum :frowning2:
     
    thanks
     
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