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I'm not talking about any concrete language here. I want to analyse the MP3 file, so I want to get some information about sound from specific second (i don't know, tone/height/frequency of sound). How those data is stored in single file?

Piotrek
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3 Answers3

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Unless you have weeks (months?) available to play with it, I would recommend using an existing MP3 decoding library to pull the decoded audio out of the file. In C/C++, there's libMAD or libmpg123, as well as the Windows components. In C#, you can use NAudio or NLayer.

Once you have the decoded data, you'll need to run a FFT, DFT, or DCT over it to convert to frequency & amplitude. The FFT is probably your best bet, though the DFT may give a less "noisy" analysis. YMMV.

Note that all three of the transforms provide amplitude values you can convert to decibel values.

ioctlLR
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there are some useful MP3 Librarys where you get information about your MP3 file.

If you use C# it could be NAudio. http://naudio.codeplex.com/

derdida
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I recommend the program xxd and google for the first steps.

First of all i would look into its binary code. 

xxd -b file.mp3

Viewing it as ASCII also exposes some information. 

xxd file.mp3

That was my first steps.