vi riporto un interessantissimo post su come analizzare e verificare i vostri file HD acquistati con Audacity, noto editor audio GNU.
Download version 1.3.12 Beta. I tried 1.2.6, but it was not reliable for FLAC files. Audacity is free, but you can donate at the Get Involved tab, then choose Donate. I did. This is a good program and will help us improve the hiRez music that we listen to but letting the producers know that we are checking their work. (repeating myself.)
I run it on XP. They say it will work with Windows 7, XP and Vista and Mac, including OS X 10.6
When you have it installed, open Audacity. Go to: View -> Show Clipping. Click on Show Clipping. It will bring up a check mark. Now when clipping is detected, red lines will be inserted in the waveform display.
Go to: Edit -> Preferences (at the bottom of the menu). Select “Spectrograms.” I have been using min freq = 1000, max freq = 40000, window size = 2048.
The window size is associated with the FFT program. A larger window is slower. These choices seem okay.
Now go to: File -> Open. Navigate to a WAV, AIFF or FLAC file. They support other formats, too. Select and click Open.
The first display is the Waveform, which shows sound amplitude. It also shows the red clipping mark, if clipping is detected.
To see the frequency spectrum, click on the inverted triangle on the left side of the spectrum, which I tried to circle on the screenshot below.
When you click on the triangle, a menu drops down. Click on Spectrum. Then, count slowly to fifteen. Audacity is slow here. And there is no indication that it is working on anything. Just wait.
You are now looking at the frequency distribution for the track. You can see if it really is a hiRez recording. And also can see any problems that were created in the production process.
If you want to save a PNG screenshot, like above, go to: Help -> Screenshot Tools. In the dialog box, first, choose the folder in which to save the images. Then I have clicked on “Capture Window Only.” This gives you the Audacity whole screen. In the next section of choices, you can choose “Track Panel” and it will save only the spectrum portion of the window. Audacity does not tell you that the operation is done. You have to look in your folder.
When you Close the file or Exit from Audacity, the program will ask if you want to save your changes. Definitely choose NO. Audacity is an editing program. Unless you are deliberately editing the hiRez file, you don’t want to save anything.
I think this is everything. It can only help if we can check on the quality of the recording process.
This description is based on an entire week of experience with Audacity (tongue firmly in cheek). But I am very impressed with its ease of use. Please add descriptions of the interesting features that I have missed. I would still like to know how to tell if the recording uses over 16 bits of amplitude data. This is different from the clipping issue.