Author Topic: How can I tell if a flac file comes from an mp3?  (Read 8244 times)

0 Members and 1 Guest are viewing this topic.

Offline Purple Orchid

  • Newfan
  • **
  • Posts: 156
  • Karma: 2
How can I tell if a flac file comes from an mp3?
« on: September 05, 2008, 23:07:17 »

I've seen that some of you "run a frequency analysis"on files and find the files come from mp3s, could you be more specific about how to do this?
The files I suspect come from mp3 are here:
http://johnnylove-fuzztone.blogspot.com/2008/07/joy-division-paradiso-club-amsterdam.html
and started suspecting because of the gaps on a few tracks...
Thanks!
...when suddenly, behind a tree, I appear
strange mixture of the one-before-the-last wanderer
and first stowaway on the trip to Venus.
Half melon on the head and the stripes of the shirt painted on the skin,
but only you see me...


Offline japanesebaby

  • Curefan Master
  • *****
  • Posts: 4758
  • Karma: 206
Re: How can I tell if a flac file comes from an mp3?
« Reply #1 on: September 06, 2008, 00:13:58 »
you can find some instructions for instance here:
http://wiki.dimeadozen.org/index.php/DimeFAQ:How_to_analyze_an_audio_file_for_lossiness#Frequency_curve_analysis

"the frequency curve" analysis is the one to pay attention to.
the detailed look of the frequency analysis depends slightly on the audio editor/software which you're using.
by the way, although the dime page lists Audacity, it really cannot be recommend because it does not provide wide enough frequency scale (you can see it doesn't go bellow -80 dB and that isn't quite enough). :!:
also, one must note that minidisc recordings are actually lossy (although often treated as being lossless by traders). so a frequency analysis of a minidisc recording can sometimes look very much like mp3 source for an untrained eye.

i used to have some other sites bookmarked but i'm in a bit of a hurry now and can't seem to find them right now, sorry.
and sorry, i also have no time to download and check those JD files myself right now.)

Ay, in the very temple of Delight
Veil'd Melancholy has her sovran shrine

Offline bluewater

  • Newfan
  • **
  • Posts: 144
  • Karma: 6
Re: How can I tell if a flac file comes from an mp3?
« Reply #2 on: September 06, 2008, 17:33:44 »
Try tau analyzer. It gives false positives but if it says a file is not mp3, then it is most likely not.

http://true-audio.com/Analyzer.project
Life's too short to listen to lossy music

Offline Purple Orchid

  • Newfan
  • **
  • Posts: 156
  • Karma: 2
Re: How can I tell if a flac file comes from an mp3?
« Reply #3 on: September 09, 2008, 19:17:04 »
Many thanks japanese baby and bluewater!!!

I'm installed the TAU analyzer and now I'm checking lots of my CDRs!!!
...when suddenly, behind a tree, I appear
strange mixture of the one-before-the-last wanderer
and first stowaway on the trip to Venus.
Half melon on the head and the stripes of the shirt painted on the skin,
but only you see me...

Offline Purple Orchid

  • Newfan
  • **
  • Posts: 156
  • Karma: 2
Re: How can I tell if a flac file comes from an mp3?
« Reply #4 on: September 18, 2008, 17:47:27 »
Many thanks again for your replies!!

I have put a few of my cdrs thru de TAU analyzer, and found a few surprises, like, I have this CDR copy of the Itch japanese EP by Radiohead, which I thought was made from mp3s, but all the tracks resulted CD sourced except for one (I don't think the guy who sold it to me would have copied all tracks from cds except for one, because anyway, many are not available on other cds..)
(and by the way, those JD files even when the sound is not excellent, there are gaps between a few tracks and the frequency is very much on the low part, turned out to be CD sourced...)
...when suddenly, behind a tree, I appear
strange mixture of the one-before-the-last wanderer
and first stowaway on the trip to Venus.
Half melon on the head and the stripes of the shirt painted on the skin,
but only you see me...


Offline lostflower4

  • Curefan Master
  • *****
  • Posts: 2613
  • Karma: 108
    • The Imaginary Lemurs Cure Site
Re: How can I tell if a flac file comes from an mp3?
« Reply #5 on: September 21, 2008, 03:20:26 »
I dislike programs like TAU Analyzer and such (even Trader's Little Helper has a similar feature now), because they are often taken as the absolute and final word on these matters, yet they are often wrong!

Take, for example, sources with 32 kHz DAT in the lineage. Obviously these are going to look lossy since a 32 kHz sample rate has a maximum upper frequency of 16K (just where the cutoff is for most mp3 sources). There are are a lot of these sources since DAT tapers would often record at the lower bandwidth to increase recording time.

And yes, minidisc can look similar to mp3, although there are some distinctions. This link is pretty interesting:

http://www.thetradersden.org/forums/showthread.php?t=8003


This format was not as simple as some may think!

Even newer mp3 codecs can produce results that look better than the typical "16K dropoff" rule of thumb that is so commonly used, so you really gotta be careful.

Heck, I could take an mp3, dub it to cassette, and re-record it back to my computer, and it would "look" lossless — because the noise from the cassette would fill in the higher frequencies.

Stuff encoded in Dolby Digital really has no dropoff at all, as the encoding algorithm for that format works in a different way than most other lossy codecs.

All that tests can really give you is evidence, but it's really best to find out the details behind the source, if possible. There's really no black and white way of doing this, although some programs like to give this illusion.

But in the end, you can really get a lot more information by looking at a frequency analysis yourself compared to what an automated program will tell you. I prefer to use Adobe Audition myself.

 

Related Topics

  Subject / Started by Replies Last post
4 Replies
4283 Views
Last post October 14, 2005, 08:28:16
by j
1 Replies
2064 Views
Last post March 21, 2006, 15:02:52
by Tof
11 Replies
6975 Views
Last post October 25, 2006, 21:46:42
by lostflower4
25 Replies
20375 Views
Last post June 16, 2008, 14:57:06
by japanesebaby
11 Replies
8855 Views
Last post August 04, 2015, 12:27:51
by brotewlle
1 Replies
1467 Views
Last post December 28, 2014, 14:50:46
by dsanchez
0 Replies
486 Views
Last post July 28, 2016, 14:48:50
by PookieWookie