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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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Northpack
post Oct 10 2011, 10:14
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QUOTE (r0k @ Oct 9 2011, 18:01) *
Can anyone give me a clue why i got so many differences. It doesn't look like the lossy paterns showed in a previous post so i guess both a re lossless, but it looks like they come from 2 different versions of the same song. blink.gif I don't think this album was re-mastered.

For me they look like sourced from two different lossy encodes, the latter being normalized to a higher level.

QUOTE (soviet123 @ Oct 9 2011, 19:35) *
...From what I've read, you can use Goldwave (a piece of software) to check the frequency graphs (much like post #35 above). Since lossy never (or almost never) reaches above 20k, it should be easily discernible.

That's wrong. Lowpass filtering below 20kHz is often a feature of lossy encoding but not necessarily. On the other hand, lowpass filtering is often deliberately utilized during mastering, to get rid of high frequency noise and distortion, so there are many tracks showing a low pass filter which were not subject to lossy compression.

You should really try the AuCDtect tools I told you about. They are much more advanced than any spectrogram guesswork by eye.

Also note that if a file shows signs of lossy compression it isn't necessarily the distributor to blaim. Nowadays many musicians pretty carelessly use lossy formats to record and trade samples and whole tracks (in fact they do for quite a while, think of MiniDisc recorders). Some artists, like NIN, have used MP3-like artifacts as artistics means.

This post has been edited by Northpack: Oct 10 2011, 10:30
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r0k
post Oct 10 2011, 10:49
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QUOTE
You should really try the AuCDtect tools I told you about. They are much more advanced than any spectrogram guesswork by eye.

Unfortunately, this application only seems to works on physical CDs. I was trying to analyse FLAC files i bought as digital downloads.

EDIT : what makes you tell they were lossy? I tried looking for "holes" in the spectrum as on post #6 rather than just a pass filter and didn't see those. Is there something else to look for?

This post has been edited by r0k: Oct 10 2011, 10:51
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Northpack
post Oct 10 2011, 11:04
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QUOTE (r0k @ Oct 10 2011, 09:49) *
Unfortunately, this application only seems to works on physical CDs. I was trying to analyse FLAC files i bought as digital downloads.

That's right, that Tau Analyzer frontend really should be updated to support analyzing lossless files. However, there's the command line tool and there's the foobar component to analyse files. Or, if you want to use the frontend, you could make a virtual image from your FLACs.
QUOTE
EDIT : what makes you tell they were lossy? I tried looking for "holes" in the spectrum as on post #6 rather than just a pass filter and didn't see those. Is there something else to look for?

Of course it doesn't look like the spectrum from post #6 because that shows a time scale of ~4 seconds whereas your spectrum shows a time scale of ~260 seconds. You wouldn't look at a sattelite image of the country you live in and wonder why you can't see your house on it, wouldn't you? wink.gif
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r0k
post Oct 10 2011, 11:13
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QUOTE (Northpack @ Oct 10 2011, 12:04) *
That's right, that Tau Analyzer frontend really should be updated to support analyzing lossless files. However, there's the command line tool and there's the foobar component to analyse files. Or, if you want to use the frontend, you could make a virtual image from your FLACs.

Ah. I'll try to get the command line tool as soon as their web page stops giving me errors.
QUOTE
Of course it doesn't look like the spectrum from post #6 because that shows a time scale of ~4 seconds whereas your spectrum shows a time scale of ~260 seconds. You wouldn't look at a sattelite image of the country you live in and wonder why you can't see your house on it, wouldn't you? wink.gif

Well, of course i would first take a magnifying glass laugh.gif
Silly me, i didn't notice the timescale on the first screenshots and wrongly guessed this was an entire track unsure.gif

EDIT : Northpack : Thanks a million times for pointing my sillyness.
I've re-analysed my files, selecting a 5 seconds portion, and here is the result :

File i got in torrent


Legal file from Qobuz


This one clearly has been lossy - compressed.
I'll check by re-downloading the files as wav but i feel like they are stealing us, especially since they charge an extra fee for "lossless".
Looks like i'll keep buying cheap mp3 and then downloading flacs from torrents when i can't get a physical copy of an album mad.gif

This post has been edited by r0k: Oct 10 2011, 11:39
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Northpack
post Oct 10 2011, 14:57
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QUOTE (r0k @ Oct 10 2011, 11:13) *
I've re-analysed my files, selecting a 5 seconds portion, and here is the result :

The one from Qobuz is from a lossy source for sure. But the first one is definetely not from the same file as one of the spectrograms in your first post. Are you sure those spectrograms are not just left and right channels from the Quobuz file?
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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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