How can I tell music has been an MP3? Quantitative Measurement of Fidelity
Dave wrote:
I have been disappointed with the audio quality of some CDs I have
bought recently. Is there a free program I can use to get an accepted
measurement of fidelity? (like a signal to noise ratio)
No, you can only listen.
I have my suspicious that some may have been stored an MP3s and then
"unripped" in the factory. So how can I tell for certain if my CD has
been an MP3, or other lossy format? I'd hope mp3 storage would leave
different markers than the original tape, for example.
This will never be the case for a major label release. However, as an
increasing number of records are issued by amateurs who don't necessarily
have a clue what they are doing, you may find this on some small releases.
More likely you are heaving the massive overcompression and limiting
which is currently fashionable. Everybody wants their recordings to be
louder, not necessarily to sound good.
To get a good measure I'd expect some Fourier transforms and signal
analysis to be done, so this should be relevant to sci.physics.
If you play back a recording made with a perceptual encoder like MP3
uses, and you look at the spectrum with an FFT (using a program like
SpectraFOO or some other free FFT application), it will be very obvious
that something goofy has been going on. You'll see these big square
blocks of spectrum popping in and out.
If, on the other hand, you play back a heavily limited recording on an
FFT application, you won't see much other than that the plot is a lot
denser than it otherwise would be.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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