View Full Version : How to test for MP3-source?


Vanity Must Die
08-31-2004, 07:19 AM
Hello, I recently recieved a promo of a Beta Band gig, and I have a sneaking suspicion that some, if not all of it is MP3-sourced. I know there's a program that can analyse the audio spectrum or something to test for this, but I forget what it is.

Any help would be much appreciated.

transluscent
08-31-2004, 03:53 PM
analfreq!

StillBecomingApart
08-31-2004, 04:21 PM
If i had time, i'd write a program to tell if a wave file is mp3 sourced. Or FM sourced.

severin
08-31-2004, 04:38 PM
i don't think you can ever say for sure...

one possible sign is a sharp drop at 16khz in an frequency analysis. but this can also come from a bad fm or md@lp2/lp4 or even from a dat which recorded at 32 khz afaik (i'm sure someone will correct me if i'm wrong).

another sign would be a couple of silent samples at the end of the file which are always created when a file is encoded to mp3. this cause very little gaps at the track transitions. so when you burn a cd from it and you get tiny gaps between tracks thats either mp3, bad mastering or a tao in the lineage

all this stuff you can possible find out using a pogram like cool edit or soundforge

Vanity Must Die
08-31-2004, 07:23 PM
Does this look MP3-sourced to you?

Dead
08-31-2004, 08:41 PM
Not familiar with that program but it does look like a big drop right at 16khz so yes.

Rider
08-31-2004, 08:58 PM
I need a spectral view from EAC to tell you anything you really can't tell anything just by looking at frequency graphs.

Rider
08-31-2004, 09:00 PM
Originally posted by severin
i don't think you can ever say for sure...

one possible sign is a sharp drop at 16khz in an frequency analysis. but this can also come from a bad fm or md@lp2/lp4 or even from a dat which recorded at 32 khz afaik (i'm sure someone will correct me if i'm wrong).

another sign would be a couple of silent samples at the end of the file which are always created when a file is encoded to mp3. this cause very little gaps at the track transitions. so when you burn a cd from it and you get tiny gaps between tracks thats either mp3, bad mastering or a tao in the lineage

all this stuff you can possible find out using a pogram like cool edit or soundforge


You can tell a lot from spectral views. You can actually look and see where the codec has cut out certain frequencies bellow 16k. You can see where it masked stuff.

Rider
08-31-2004, 09:01 PM
Originally posted by StillBecomingApart
If i had time, i'd write a program to tell if a wave file is mp3 sourced. Or FM sourced.

Several people have tried writing programs that can tell, non of them work. When you rund known sources through them you get all kinds of crazy results.

Vanity Must Die
09-01-2004, 01:01 PM
How difficult is it to get a CD screened?

This 'promo' comes in a cardboard sleeve with all the right logos on both the sleeve and the CD. If it's a fake, it's well-done.

StillBecomingApart
09-01-2004, 05:29 PM
Originally posted by Rider


Several people have tried writing programs that can tell, non of them work. When you rund known sources through them you get all kinds of crazy results.

LOL!

anti
09-05-2004, 06:06 AM
i have a quick question

i know if its mp3 the frequence drops sharply at around 15khz
but what about if its fm?
could an fm recording be mistaken for mp3?

Rider
09-05-2004, 02:54 PM
Originally posted by anti
i have a quick question

i know if its mp3 the frequence drops sharply at around 15khz
but what about if its fm?
could an fm recording be mistaken for mp3?

no FM recordings have a spike in them if I remember correctly it's at 19k. And map3s do not always drop of at 16k. I've seen mp3s that drop off at 19k you really need to look at a spectral view and zoom in and look at the sound.

ProgressChrome
09-07-2004, 04:48 PM
Originally posted by Rider


FM recordings have a spike in them if I remember correctly it's at 19k.


as far as I know, FM cuts off at 15khz, which would make the 19khz spike pretty strange

robween
09-07-2004, 04:53 PM
i have no idea what any of this means. i barely know what an mp3 is:confused:

Rider
09-07-2004, 08:59 PM
Originally posted by ProgressChrome



as far as I know, FM cuts off at 15khz, which would make the 19khz spike pretty strange

nope theres a iinaudible buzz that will be in every FM it shows up as a bump a frequency chart and perfectly drawn straight line acrossed the screen on a spectral view.

I'm trying to dig up a picture of it. It's not part of the music which may be why your confused, it's a technical flaw of FM broadcasts.

Once the groove is back up I'll post links to stuff on there, but right now I can't find a good picture of what I'm talking about.

Rider
09-07-2004, 09:24 PM
http://home.cfl.rr.com/zwan/tn.gif

see the red stripe above the music.

edit: forgot to thank U2lynne for digging around in the offline version of the groove to find this for me.

ProgressChrome
09-09-2004, 06:50 PM
ahhh, i getcha... i did not realize the 19k noise was there.... interesting
a very easy noise to remove luckily

Rider
09-09-2004, 07:27 PM
Originally posted by ProgressChrome
ahhh, i getcha... i did not realize the 19k noise was there.... interesting
a very easy noise to remove luckily

No problem I love teaching people about this kind of stuff, it's one of the reasons I was made a mod on the groove. I'm still learning alot it's amzing how much you can tell once you learn what to look for. Like some people can look at a zoomed in close up and tell right away if it's MD or MP3, I'm still learning that part.