How can you tell if a lossless file was converted to lossless from lossy?
Jul 23, 2009 at 6:10 PM Thread Starter Post #1 of 11


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Jun 21, 2009
So how do people know a flac/wav was not converted to that format from a lossy format? I see people being able to make that distinction. What do they use to be able to tell this? Is there a program or tool that makes this determination easy? What should you look for? Thanks for any help.
Jul 23, 2009 at 6:21 PM Post #2 of 11
I use a program called Tau Analyzer. Basically, if the frequency drastically rolls off before 22kHz, it has come from a lossy source. However, it's not true with certain lossy encoders like Nero's AAC encoder which has no roll off. With MP3's there always will be roll off at higher frequencies.
Jul 24, 2009 at 12:52 AM Post #5 of 11
So what's going on in this example? I see a faint line across the top that would lead me to believe there was roll off at 16K but it's not really cut off as there is valid information above that point.
Jul 24, 2009 at 3:59 AM Post #9 of 11

Originally Posted by Berlioz /img/forum/go_quote.gif
So basically you're just looking for that horizontal line?

I thought that was what mattered but it seems not. I have no experience looking at these frequency plots. But after thinking about it, it seems that solid line is just strength at that frequency, especially given there is additional information above it.

Note Spectro gave 21.4 when the line was well below that level.

However I notice Spectro will give a roll-off at a lower level when there is clearly information above it. I don't understand that, unless the algorithm that picks the roll-off point is just being fooled.
Jul 25, 2009 at 1:09 AM Post #10 of 11
Well I believe that sometimes horizontal lines result from interference that's not removed in mastering. It's especially common in live music. The horizontal line is NOT a cutoff. For reference, here's an example of a 128 kb/s mp3 cutoff (transcoded from flac right now):


I think your file is a legitimate rip because if it were an mp3, there would be a CLEAN BREAK; that fuzziness or whatever is probably just a result of a not great recording.
Aug 18, 2009 at 5:44 PM Post #11 of 11
There's a very simple application called Audiochecker (auCDtect.exe). It analyzes the spectrum and gives you a probability value if the file was ripped from a CD or transcoded e.g. from MP3.

But this is just an estimation, so there are exceptions. (bad recording ..)

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