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True FLAC vs. Fake FLAC
XeR0
post Jun 29 2011, 19:58
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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?

This post has been edited by XeR0: Jun 29 2011, 19:59
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Joseph93
post Oct 12 2011, 05:13
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3 things:

1. hi I am new

2. 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

3. If anyone has Max, I threw together a patch the other day which allows you to compare the quality of two audio files in realtime (by looking at their spectrograms; they play simultaneously). I successfully used it to tell the difference between files of varying bitrate, even between 256kbps and 320kbps mp3s. you can also use vst spectrograms with it if you prefer. If anyone is interested I can upload it

This post has been edited by Joseph93: Oct 12 2011, 05:14
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saratoga
post Oct 12 2011, 05:44
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QUOTE (Joseph93 @ Oct 12 2011, 00:13) *
3 things:

1. hi I am new

2. 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


QUOTE
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 [2]. 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.

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Posts in this topic
- XeR0   True FLAC vs. Fake FLAC   Jun 29 2011, 19:58
- - greynol   Bottom-line on a "sure-fire way": no.   Jun 29 2011, 20:00
- - gottogo99   It's not guaranteed, but if you look at a file...   Jun 29 2011, 20:05
- - greynol   ...recorded from the radio, or simply low-pass fil...   Jun 29 2011, 20:10
|- - Canar   QUOTE (greynol @ Jun 29 2011, 12:10) Ther...   Jun 29 2011, 21:29
- - XeR0   QUOTE (gottogo99 @ Jun 29 2011, 15:05) It...   Jun 29 2011, 20:19
- - Rotareneg   Looking at a spectrogram of the audio is a good wa...   Jun 29 2011, 21:04
|- - ChrisC7   QUOTE (Rotareneg @ Jun 29 2011, 22:04) Lo...   Aug 7 2011, 09:55
- - greynol   That's a good one. I was referring to some of...   Jun 29 2011, 21:35
|- - frozenspeed   QUOTE (greynol @ Jun 29 2011, 13:35) That...   Oct 9 2011, 04:40
|- - r0k   Hi. I've read this topic with some interest es...   Oct 9 2011, 19:01
- - XeR0   Rotareneg: Yeah, I use Sonic Visualizer and just g...   Jun 29 2011, 21:39
|- - greynol   QUOTE (XeR0 @ Jun 29 2011, 13:39) Just as...   Jun 29 2011, 21:46
||- - d_headshot   QUOTE (greynol @ Jun 29 2011, 15:46) I gu...   Jun 30 2011, 05:05
|- - DonP   QUOTE (XeR0 @ Jun 29 2011, 15:39) QUOTE (...   Jun 29 2011, 21:51
- - XeR0   QUOTE (greynol @ Jun 29 2011, 16:46) QUOT...   Jun 29 2011, 22:12
|- - dreamliner77   QUOTE (XeR0 @ Jun 29 2011, 17:12) QUOTE (...   Oct 8 2011, 20:15
- - greynol   You're operating under the assumption that ...   Jun 29 2011, 22:31
- - XeR0   QUOTE (greynol @ Jun 29 2011, 17:31) You...   Jun 29 2011, 22:40
- - greynol   I regret to say I don't find that all composer...   Jun 29 2011, 22:48
|- - Canar   QUOTE (greynol @ Jun 29 2011, 14:48) I re...   Jun 29 2011, 23:09
- - XeR0   QUOTE (greynol @ Jun 29 2011, 17:48) I re...   Jun 29 2011, 22:55
- - XeR0   QUOTE (Canar @ Jun 29 2011, 18:09) Knowin...   Jun 30 2011, 00:01
- - greynol   QUOTE (XeR0 @ Jun 29 2011, 14:12) A good ...   Jun 30 2011, 00:28
- - Goratrix   Also, when you think about it, the OP's questi...   Jun 30 2011, 09:38
|- - greynol   QUOTE (Goratrix @ Jun 30 2011, 01:38) On ...   Jun 30 2011, 16:50
|- - Goratrix   QUOTE (greynol @ Jun 30 2011, 17:50) QUOT...   Jun 30 2011, 17:28
- - xnor   As well as creating flac files by ripping CDs you ...   Jun 30 2011, 15:17
- - greynol   You get a match against a verified yet errant subm...   Jun 30 2011, 17:34
|- - Goratrix   QUOTE (greynol @ Jun 30 2011, 18:34) You ...   Jun 30 2011, 17:55
- - XeR0   QUOTE (Goratrix @ Jun 30 2011, 04:38) Als...   Jun 30 2011, 17:56
- - greynol   Assuming you're using a tool configured to sho...   Jun 30 2011, 18:01
- - Porcus   QUOTE (greynol @ Jun 29 2011, 16:46) QUOT...   Aug 7 2011, 13:59
- - astroidmist   There used to be a freeware DOS command line/conso...   Oct 8 2011, 06:41
|- - Northpack   QUOTE (astroidmist @ Oct 8 2011, 05:41) T...   Oct 8 2011, 12:00
|- - astroidmist   QUOTE (Northpack @ Oct 8 2011, 05:00) QUO...   Oct 21 2011, 23:00
- - soviet123   ...From what I've read, you can use Goldwave (...   Oct 9 2011, 20:35
|- - r0k   QUOTE (soviet123 @ Oct 9 2011, 21:35) ......   Oct 10 2011, 09:46
- - Northpack   QUOTE (r0k @ Oct 9 2011, 18:01) Can anyon...   Oct 10 2011, 10:14
|- - r0k   QUOTE You should really try the AuCDtect tools I t...   Oct 10 2011, 10:49
|- - Northpack   QUOTE (r0k @ Oct 10 2011, 09:49) Unfortun...   Oct 10 2011, 11:04
|- - r0k   QUOTE (Northpack @ Oct 10 2011, 12:04) Th...   Oct 10 2011, 11:13
|- - Northpack   QUOTE (r0k @ Oct 10 2011, 11:13) I've...   Oct 10 2011, 14:57
- - r0k   Not sure why i can no longer edit my previous post...   Oct 10 2011, 13:28
- - dhromed   Have you notified them?   Oct 10 2011, 13:42
- - r0k   I havn't contacted them yet because i first wa...   Oct 10 2011, 15:59
- - _mē_   QUOTE You should really try the AuCDtect tools I t...   Oct 11 2011, 12:59
- - r0k   By "False positives" do you mean files w...   Oct 11 2011, 17:24
|- - Northpack   QUOTE (r0k @ Oct 11 2011, 16:24) By ...   Oct 11 2011, 17:34
- - _mē_   By false positive I mean that the file is fine, bu...   Oct 11 2011, 20:56
|- - djchristian   QUOTE (_mē_ @ Oct 11 2011, 21:56) By fals...   Jan 6 2012, 03:50
- - Joseph93   3 things: 1. hi I am new 2. I recently stumbled ...   Oct 12 2011, 05:13
|- - saratoga   QUOTE (Joseph93 @ Oct 12 2011, 00:13) 3 t...   Oct 12 2011, 05:44
|- - Joseph93   QUOTE (saratoga @ Oct 12 2011, 05:44) It ...   Oct 12 2011, 06:19
|- - saratoga   QUOTE (Joseph93 @ Oct 12 2011, 01:19) So ...   Oct 12 2011, 06:49
- - greynol   I've seen examples of both false positives and...   Oct 12 2011, 05:22
|- - r0k   QUOTE (greynol @ Oct 12 2011, 06:22) I...   Oct 12 2011, 12:37
|- - mjb2006   QUOTE (r0k @ Oct 12 2011, 05:37) I have r...   Oct 12 2011, 22:03
- - Joseph93   QUOTE It doesn't do what people in this thread...   Oct 12 2011, 07:01
|- - saratoga   QUOTE (Joseph93 @ Oct 12 2011, 02:01) QUO...   Oct 12 2011, 07:09
- - Joseph93   QUOTE If you know that the file was encoded with a...   Oct 12 2011, 07:28
|- - saratoga   QUOTE (Joseph93 @ Oct 12 2011, 02:28) Yes...   Oct 12 2011, 07:41
- - testyou   QUOTE Some/many are also just not very technologic...   Oct 13 2011, 09:52
- - r0k   And then, there are people who are not even musici...   Oct 13 2011, 15:31
- - knutinh   I have noticed that mp3s commonly add a large erro...   Oct 16 2011, 00:20
- - 2Bdecided   On exceptionally pure tone-like signals you can se...   Oct 17 2011, 10:42
- - db1989   Second result on Google (not sure which version): ...   Jan 6 2012, 16:26
- - Ubulord   QUOTE (XeR0 @ Jun 29 2011, 18:58) I know ...   Sep 1 2013, 11:27
- - claudiod   I have two J.S. Bach cds (Das Wohltemperierte Klav...   Sep 1 2013, 12:15
|- - Nessuno   QUOTE (claudiod @ Sep 1 2013, 13:15) I ha...   Sep 2 2013, 09:14
- - Alexa   Can anybody tell if these are both fake: ? w...   Oct 11 2013, 19:01
|- - saratoga   QUOTE (Alexa @ Oct 11 2013, 14:01) Can an...   Oct 11 2013, 22:20
|- - Rescator   And as pointed out earlier by folks, lowpass does ...   Oct 12 2013, 02:44
- - Glenda   One other reason I like engineers who use the PM2 ...   Oct 12 2013, 10:49
|- - saratoga   QUOTE (Glenda @ Oct 12 2013, 05:49) you c...   Oct 12 2013, 17:52
- - alekksander   use spek.cc and verify by spectrum. just consider ...   Oct 26 2013, 17:19


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