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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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greynol
post Jun 29 2011, 20:00
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Bottom-line on a "sure-fire way": no.


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gottogo99
post Jun 29 2011, 20:05
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It's not guaranteed, but if you look at a file in spectral view and there is a sharp cutoff at say 15kHz, there's a very good chance the file was lossy.
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greynol
post Jun 29 2011, 20:10
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...recorded from the radio, or simply low-pass filtered.

There is also the real possibility that the CD was sourced from such data. There have been examples of this happening with legitimate CDs posted on this forum and elsewhere.


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XeR0
post Jun 29 2011, 20:19
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QUOTE (gottogo99 @ Jun 29 2011, 15:05) *
It's not guaranteed, but if you look at a file in spectral view and there is a sharp cutoff at say 15kHz, there's a very good chance the file was lossy.

Yeah, I noticed the same thing and that was what I was using to make sure the FLAC's weren't lossy.

QUOTE (greynol @ Jun 29 2011, 15:10) *
...recorded from the radio, or simply low-pass filtered.

There is also the real possibility that the CD was sourced from such data. There have been examples of this happening with legitimate CDs posted on this forum and elsewhere.

Which is why I wanted to know if there was a way. In any case at least there are methods that work 90% of the time. Thanks for your replies.
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Rotareneg
post Jun 29 2011, 21:04
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Looking at a spectrogram of the audio is a good way to tell, but you need to look for more than just a low-pass filter.

Here are three spectrograms made with SoX that show what to look for:

First, the lossless original:



Next, Lame MP3 at -V5:



And lastly, Vorbis at -Q4:



The main thing I look for is the "holes" in the audio that the lossy compressors psycoacoustic model determined to be inaudible due to auditory masking.
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Canar
post Jun 29 2011, 21:29
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QUOTE (greynol @ Jun 29 2011, 12:10) *
There is also the real possibility that the CD was sourced from such data. There have been examples of this happening with legitimate CDs posted on this forum and elsewhere.
My personal favourite anecdote was buying a music CD by Orbital from Hong Kong. It was silver and pressed, but had no catalog number and was audibly MP3 sourced. I later found the MP3s that they had sourced from. The artifacts matched.

This post has been edited by Canar: Jun 29 2011, 21:30


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greynol
post Jun 29 2011, 21:35
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That's a good one.

I was referring to some of the titles on the Century Media label available on Amazon.


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XeR0
post Jun 29 2011, 21:39
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Rotareneg: Yeah, I use Sonic Visualizer and just go over to look for the holes you specified. Just ask greynol and he'll/she'll tell you how I was misguided by looking at spectrographs as the determining factor for audio quality instead of doing a proper ABX test wink.gif

QUOTE (Canar @ Jun 29 2011, 16:29) *
QUOTE (greynol @ Jun 29 2011, 12:10) *
There is also the real possibility that the CD was sourced from such data. There have been examples of this happening with legitimate CDs posted on this forum and elsewhere.
My personal favourite anecdote was buying a music CD by Orbital from Hong Kong. It was silver and pressed, but had no catalog number and was audibly MP3 sourced. I later found the MP3s that they had sourced from. The artifacts matched.

That sucks. The only only to really know (to my knowledge) if a CD is authentic is to buy it from the publisher themselves.
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greynol
post Jun 29 2011, 21:46
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QUOTE (XeR0 @ Jun 29 2011, 13:39) *
Just ask greynol and he'll/she'll tell you how I was misguided by looking at spectrographs as the determining factor for audio quality instead of doing a proper ABX test wink.gif

Nice non sequitur.

QUOTE (XeR0 @ Jun 29 2011, 13:39) *
The only only to really know (to my knowledge) if a CD is authentic is to buy it from the publisher themselves.

I guess Century Media doesn't qualify as a publisher?

This post has been edited by greynol: Jun 29 2011, 21:46


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DonP
post Jun 29 2011, 21:51
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QUOTE (XeR0 @ Jun 29 2011, 15:39) *
QUOTE (Canar @ Jun 29 2011, 16:29) *
My personal favourite anecdote was buying a music CD by Orbital from Hong Kong. It was silver and pressed, but had no catalog number and was audibly MP3 sourced. I later found the MP3s that they had sourced from. The artifacts matched.

That sucks. The only only to really know (to my knowledge) if a CD is authentic is to buy it from the publisher themselves.


Don't ya just hate it when a pirate publisher, doing enough volume for pressings, is too cheap to buy the real CD for their source material?
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XeR0
post Jun 29 2011, 22:12
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QUOTE (greynol @ Jun 29 2011, 16:46) *
QUOTE (XeR0 @ Jun 29 2011, 13:39) *
The only only to really know (to my knowledge) if a CD is authentic is to buy it from the publisher themselves.

I guess Century Media doesn't qualify as a publisher?

What I meant was this: Let's say for instance I wanted to buy an album called "Tales of the Inexpressible". A trustworthy publisher would be "Twisted Records" instead of "World Music of New Age". A good amount of research would show that the composers of the album founded Twisted Records and sell their music there. Therefore, the only real way to make sure that you're getting an authentic CD, would be to buy it from Twisted Records and not from any other obscure publisher.
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greynol
post Jun 29 2011, 22:31
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You're operating under the assumption that "Twisted Records" is competent in providing a CD that was sourced from lossless data.


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XeR0
post Jun 29 2011, 22:40
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QUOTE (greynol @ Jun 29 2011, 17:31) *
You're operating under the assumption that "Twisted Records" is competent in providing a CD that was sourced from lossless data.

Given the fact that "Twisted Records" is run by the very composers of the album in question, I can safely assume the CD's I buy from them are sourced from lossless data. As a matter of fact, the closest you can get to the source is by downloading/buying from the creators themselves. At the end of the day however, you can only do so much before it's out of your hand.
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greynol
post Jun 29 2011, 22:48
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I regret to say I don't find that all composers are very tech-savvy. As such, I wouldn't be so certain that you assumption is all that safe.

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XeR0
post Jun 29 2011, 22:55
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QUOTE (greynol @ Jun 29 2011, 17:48) *
I regret to say I don't find that all composers are very tech-savvy. As such, I wouldn't be so certain that you assumption is all that safe.

I don't disagree at all. Like I said, you can only do so much before you reach a point where things are out of your hand. If the composer him/her-self doesn't know much about tech, there's no one else in the world that can do a better job given that the source file is with the composer and the only access to the "source" elsewhere is through the CD albums they release which is of questionable quality. Therefore, the best you can do is to buy it from the publisher/composer themselves.

To contribute to the original topic, I would like to add that Audiotester from vuplayer.com has indicated that the "fake" FLAC file failed the test. So, besides checking the spectrographs of each FLAC file, Audiotester is a much more convenient alternative.
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Canar
post Jun 29 2011, 23:09
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QUOTE (greynol @ Jun 29 2011, 14:48) *
I regret to say I don't find that all composers are very tech-savvy. As such, I wouldn't be so certain that you assumption is all that safe.
Knowing a bit more about Twisted Records would be reassuring. Simon Posford, the founder of Twisted Records and the primary member of Shpongle, is known for deeply technical audio wizardry.

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XeR0
post Jun 30 2011, 00:01
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QUOTE (Canar @ Jun 29 2011, 18:09) *
Knowing a bit more about Twisted Records would be reassuring. Simon Posford, the founder of Twisted Records and the primary member of Shpongle, is known for deeply technical audio wizardry.

My point exactly. However, I'm sure some people haven't had the pleasure of knowing Simon Posford as well as his expertise in audio production. In which case, I didn't feel was necessary to elaborate. The bottom-line: The best you can do to make sure you've got the best is to get it from the source or the closest thing to the source.
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greynol
post Jun 30 2011, 00:28
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QUOTE (XeR0 @ Jun 29 2011, 14:12) *
A good amount of research would show that the composers of the album founded Twisted Records and sell their music there.

...and would apparently instill a high degree of confidence that a CD obtained from them directly would be lossless; I clearly hadn't conducted a good amount of research.

After a bit of googling, I'm sure knowing him would be pleasurable, but I'm a bit skeptical I would derive much pleasure in his expertise in audio production.

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d_headshot
post Jun 30 2011, 05:05
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QUOTE (greynol @ Jun 29 2011, 15:46) *
I guess Century Media doesn't qualify as a publisher?


Not a very good publisher imo since they've consistently brickwalled all of their releases that I've bought mad.gif

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Goratrix
post Jun 30 2011, 09:38
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Also, when you think about it, the OP's question really doesn't make sense. The result of a FLAC compression is a lossless image of the source. In case you input a mp3-compressed audio, does that make the resulting FLAC "non-lossless" or "fake"? No, it doesn't. It makes it a perfect lossless version of the source material, regardless of what the source material is :-)))))

On another note, if we are talking about identifing "fake FLAC" in files obtained by...ehm, questionable means, then AccurateRip comes in quite handy cool.gif

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xnor
post Jun 30 2011, 15:17
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As well as creating flac files by ripping CDs you actually bought. tongue.gif

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greynol
post Jun 30 2011, 16:50
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QUOTE (Goratrix @ Jun 30 2011, 01:38) *
On another note, if we are talking about identifing "fake FLAC" in files obtained by...ehm, questionable means, then AccurateRip comes in quite handy cool.gif

Yeah, 'cause there's no way anyone would ever submit downloads back to the AR database. rolleyes.gif


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Goratrix
post Jun 30 2011, 17:28
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QUOTE (greynol @ Jun 30 2011, 17:50) *
QUOTE (Goratrix @ Jun 30 2011, 01:38) *
On another note, if we are talking about identifing "fake FLAC" in files obtained by...ehm, questionable means, then AccurateRip comes in quite handy cool.gif

Yeah, 'cause there's no way anyone would ever submit downloads back to the AR database. rolleyes.gif


Did I say it's 100% accurate? No, I didn't. Is it helpful and useful most of the time? Yes it in fact is, as the volume of fake and poisoned entries is very small compared to the geniune entries.
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greynol
post Jun 30 2011, 17:34
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You get a match against a verified yet errant submission from a download and it doesn't matter how many submissions from legitimate sources are made.

This post has been edited by greynol: Jun 30 2011, 17:35


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