COMPRESSION OF .WAV FILES
This forms the crux of the discussion on compression. The main objective is to be able to compress an audio file of .wav extension , which obviously means that the user needs to select an appropriate sound file with .wav extension.
You can select a sound file (typically referred to as signal) by clicking on the 'File' menu , and using the 'Load signal' option.
You will be asked to select a file.
After you select the file, the signal is displayed for demonstration purposes only.
Note that, at this stage, you should not press the "Compress" button. Doing so will lead to erroneous operations as wavelet and decomposition level have not been specified as yet.
So make sure that these fields are entered with appropriate data before you press "compress" button. For wavelet, choose an orthogonal wavelet.
When you press the "compress" button , after some delay depending upon the speed of your machine and length of your signal, you will get some results of the compression operation.
Also, now you can "Save" some results or plot the original and compression signal for comparison. You can also plot the original wavelet coefficients and the compressed wavelet coefficients and see for yourself the difference between them. The threshold level is provided in this figure. Notice that approximation coefficients are not altered by the compression. Only the details are affected.
You may load a new signal for analysis, and repeat the procedure as often as you deem necessary.