Not sure about quality

[Alkoholik Ivan]

Hi
 
Few of my Audio CDs, which I was certain were just mp3s ripped into the Audio CD format, appear to have bitrate above 1900 kbps (VLC says so in the file statistics). Is it possible these really are copied original CDs, or can those still be just "bloated" mp3s?
I hope you can understand my question
 
Thanks

 

[Alkoholik Ivan]

The codec detected by VLC is PCM S16 LE (araw).

 

[proton007]

Well, if you've used the option to create audio cd's then even mp3 will be converted into wav in order to work as audio cd.
My guess is its bloated mp3. But you can compare files with the original cd if you have one to ensure.

 

[Alkoholik Ivan]

I tried doing a FFT of my 320 kbps mp3 and the "unknown-original-format" Audio CD track. The time should be the same, even though it wasn't as easy, since the Audio CD tracks are few seconds longer than my mp3s.
Can something be decoded out of this? Is the audio CD track true high quality recording or is it just mp3 bloated into cda?
http://i47.tinypic.com/2ch3ora.png

 

[proton007]

If the signal was the same, both the mp3 and mp3 bloated into wav will be the same when you do the fourier analysis.
What you need is the original cd if you have one.

 

[Alkoholik Ivan]

Shoot. Without the original audio CDs there is no way of telling? That's too bad, but thank you anyway.

 

[proton007]

Another thing you can try is see low level noise in the frequency analysis. CDs will have a uniformly distributed noise, as displayed here (Fig 1): 
http://www.stereophile.com/features/308mp3cd
 
If you don't see this, chances are its compressed.

 

[Alkoholik Ivan]

How can I check for distortion in a certain frequency, when I only have songs? There are no harmonic sine waves...

 

[proton007]

Not at certain frequency, just do a fourier analysis of any part of the song, preferably the quiet parts. This underlying noise is present in most cds. MP3 will remove this noise.
Here's what I did, two sections of a song, flac vs mp3, first one is non-silent region:
 

 
On the right is MP3, see how it cuts at 20k Hz, while flac continues further.
 
Second, the silent section at the end:

 
The MP3 is left, the flac one is on right, you can see the differences for yourself. The MP3 produces spikes at certain frequencies and attenuates them, while the right side is the original.

 

[Alkoholik Ivan]

 
It looks as if it really is somehow less lossy, doesn't it?

 

[Alkoholik Ivan]

This should be the same moment at the start of the song. Can it be clearly said, that the Audio CD was ripped from an original CD, or can it still be just a bloated 128kbps mp3?

 

[Alkoholik Ivan]

Guise pls.

 

[proton007]

I thought you got your answer already?

 

[Alkoholik Ivan]

Not an explicit one...