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Bulk spectral analysis?
joeg
post Jul 27 2013, 13:21
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I know you can scan individual files to determine if a lossless file was created from a lossless source (ie. not just converted from a mp3). However, I can't find anything to do this for my whole library. Is there any program/plugin that will analyze each file and give a report of any files that don't extend to the 22khz range?

Thanks!
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Kohlrabi
post Jul 27 2013, 15:02
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A lowpass is neither a necessary nor a sufficient condition of lossy audio encoding. I'd strongly advise you against to rely on looking at spectrograms to identify transcodes. The safest way to ensure that you have the highest fidelity lossless version is to either rip the audio from CD yourself, or buy from stores offering lossless audio*.

*I'm perfectly aware of the fact that buying either a CD or a lossless digital download does not ensure that no lossy encoding took place in audio processing, but generally these options are as good as it gets.

This post has been edited by Kohlrabi: Jul 27 2013, 15:08


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joeg
post Jul 27 2013, 15:07
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I understand it's not 100% conclusive... but at least it can help me identify any low-hanging fruit in my collection.

Any recommendations for software that will help me do this in bulk?
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[JAZ]
post Jul 27 2013, 15:14
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The top frequency range of a song does not determine its autenticity. That assumes that all songs have components up to (in this case) 22Khz.

There are several reasons why this could not be the case, even with legitimate files:
Originally, CDs were supposed to have a range up to 20Khz, the extra 2Khz were used for a soft filter rolloff.
Said that, probably most of the songs made in the 21st century don't use that (even though, since they tend to use a higher sampling rate, the resampler needs to filter it somehow, so you might have it up to 21.5 or so, not necessarily 22Khz).

Next, it obviously depends on content. Synthetized music most probably have sounds up (and above) 22Khz. Sampled music (either recorded live or mixed) might or might not extend that much, depending on the genre and mastering process.

The only thing that would most probably determine a lossy file is a sharp cutoff at frequencies quite below 22Khz, like 16Khz ( 32Khz sampling rate and filter of 128Kbps mp3) or 11Khz.
(It could also mean a sample coming from a lower sampling rate, which shouldn't be usual nowadays, but would be not so strange in music from the nineties).

At last, sometimes it is intentional to have a sound that *sounds like lo-fi*. Say. like if it was a telephone sound, or imitating chip music.. whatever..


If you want to have a better guess (although still that, a guess), you should use TAU Analyzer : http://en.true-audio.com/Tau_Analyzer_-_CD...ticity_Detector, but that's to be used with CD's, or maybe its original console program that worked with wavs : http://www.hydrogenaudio.org/forums/index....showtopic=27910 (See download link on the first post).

Those alone cannot scan your library, but you could use the second and some scripting to do so.

This post has been edited by [JAZ]: Jul 27 2013, 15:15
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joeg
post Jul 27 2013, 15:26
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Thank you for the info.

I realize it is a guess. I'm not going to axe anything that fails the scan just based on that, but at least I can take the results and look a little closer at them to see if they are or aren't authentic.

I'll take a look at those, but it would be far too much of an endeavor to convert to wavs. My library is ALAC/FLAC.
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Rollin
post Jul 27 2013, 16:30
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To not convert to wav, you can use foobar2000+fooCDtect: http://translate.google.ru/translate?sl=ru...-60&act=url (original page is in russian)
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joeg
post Jul 27 2013, 20:32
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by endeavor, i mean it's a hassle to convert my collection because it's quite large.
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adamjk
post Jul 27 2013, 22:53
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Try this one Link
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joeg
post Jul 28 2013, 17:30
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QUOTE (adamjk @ Jul 27 2013, 17:53) *
Try this one Link


Thats perfect! Thank you!!!
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