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Topic: How to tell if a file is transcoded from lossy to lossy? (Read 10241 times) previous topic - next topic
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How to tell if a file is transcoded from lossy to lossy?

Hello!
Here's the deal: I have two same mp3 albums. One is encoded at 192 the other at 320 kbps. The trouble that I have is establishing the real source between the two. I suspect that they come from the same source because their tags and lengths are identical. Is the 320 one transcoded from the 192 one or the other way around (if so, then great!)?
I tried to establish it with Audition. Here's what I get from frequency analysis:
[a href="http://img55.imageshack.us/my.php?image=192kbpspm1.jpg" target="_blank"] ) is the 320kbps encoded album. Or am I wrong? Are there any other ways of establishing it?

Thanks for your replies!

How to tell if a file is transcoded from lossy to lossy?

Reply #1
You can't do that for sure if you don't have the lossless original as a reference (i.e. compare "lossless->lossy" with the test sample). If both lossy encoders use similar psycho-acustic models identification is nearly impossible.

I think in your case you were just lucky, because both settings use quite different data reduction models.

How to tell if a file is transcoded from lossy to lossy?

Reply #2
I'm not sure if I understand you quite well. (Or maybe the other way around.)  My point is:
If the 192kbps sample lacks frequencies above some value (say 18kHz), than there is no way you could transcode this sample into 320kbps with those frequencies all of a sudden present. So therefore the 192kbps sample must have been obtained from the 320kbps sample.

How to tell if a file is transcoded from lossy to lossy?

Reply #3
If the 192kbps sample lacks frequencies above some value (say 18kHz), than there is no way you could transcode this sample into 320kbps with those frequencies all of a sudden present.


Not true ... almost every wav editor allows you to add calculated 'virtual' high frequency content via a DSP plugin. Creative's X-Fi soundcard can do that in hardware ...

Missing or present frequency content can't be used to determine a sound file's encoding/transcoding history ...
The name was Plex The Ripper, not Jack The Ripper

How to tell if a file is transcoded from lossy to lossy?

Reply #4
How do you know that either one was derived from the other? Couldn't they both have been derived from a common source?

How to tell if a file is transcoded from lossy to lossy?

Reply #5
How do you know that either one was derived from the other? Couldn't they both have been derived from a common source?


As I said. I'm just guessing. The tags are identical, lengths too. Actually it doesn't matter really. I just wanted to know if you could tell if one lossy file was transcoded from the other. So to sum it up: there's really no way of telling them apart aside from listening to them.
BTW: How do you add high frequencies in Audition, so that the 192kbps analysis graph looks the same as the 320 one?

 
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