Since there seems to be a steady stream of people claiming that a lossless process isn't lossless I've decided to write a mini guide showing how the user can themselves check to see if a process was indeed lossless. Hopefully this will help some gain a better understanding of what lossless is.
For the purposes of this mini tutorial I'll be compressing a file using Wavpack. You can use this methodology for any lossless process, you just need to know how to decompress that file back to wav.
The guide below will be specific to Windows OS's but the principles are true for any other OS. The text within the code boxes are copied from my DOS prompt. To access your command prompt go to Start > Run > Cmd.
Create a new folder in root called lossless and put in this folder your wav file.
C:\lossless>dir
Volume in drive C has no label.
Volume Serial Number is AC06-24BF
Directory of C:\lossless
04/08/2005 09:20 <DIR> .
04/08/2005 09:20 <DIR> ..
04/08/2005 09:19 50,862,044 01._Neighborhood_#1_(Tunnels).wav
1 File(s) 50,862,044 bytes
2 Dir(s) 1,017,434,112 bytes free
C:\lossless>
Compress your wav file with your lossless compressor.
C:\lossless>wavpack -h 01._Neighborhood_#1_(Tunnels).wav
WAVPACK Hybrid Lossless Wavefile Compressor Win32 Version 4.2 2005-04-02
Copyright (c) 1998 - 2005 Conifer Software. All Rights Reserved.
created 01._Neighborhood_#1_(Tunnels).wv in 12.38 secs (lossless, 33.34%)
C:\lossless>
Now we have our compressed file you'll need to rename this file so that when we come to decompress the file it will not over write the original file.
C:\lossless>dir
Volume in drive C has no label.
Volume Serial Number is AC06-24BF
Directory of C:\lossless
04/08/2005 09:26 <DIR> .
04/08/2005 09:26 <DIR> ..
04/08/2005 09:19 50,862,044 01._Neighborhood_#1_(Tunnels).wav
04/08/2005 09:22 33,905,312 01._Neighborhood_#1_(Tunnels)[new].wv
2 File(s) 84,767,356 bytes
2 Dir(s) 983,523,328 bytes free
C:\lossless>
Next we will decode the .wv file.
C:\lossless>wvunpack "C:\lossless\01. Neighborhood #1 (Tunnels)[new].wv"
WVUNPACK Hybrid Lossless Wavefile Decompressor Win32 Version 4.2 2005-04-02
Copyright (c) 1998 - 2005 Conifer Software. All Rights Reserved.
file C:\lossless\01. Neighborhood #1 (Tunnels)[new].wv not found!
C:\lossless>wvunpack "01._Neighborhood_#1_(Tunnels)[new].wv"
WVUNPACK Hybrid Lossless Wavefile Decompressor Win32 Version 4.2 2005-04-02
Copyright (c) 1998 - 2005 Conifer Software. All Rights Reserved.
restored 01._Neighborhood_#1_(Tunnels)[new].wav in 8.46 secs (lossless, 33.34%)
C:\lossless>
You should now have the new decompressed file in your folder.
Now comes the essential part in being able to check if a process is lossless. We do this by running a binary file compare using Windows' FC function. What this does is compare two files and if there are any differences they will be printed to the screen.
C:\lossless>FC /B C:\lossless\01._Neighborhood_#1_(Tunnels).wav C:\lossless\01._Neighborhood_#1_(Tunnels)[new].wav
Comparing files C:\LOSSLESS\01._Neighborhood_#1_(Tunnels).wav and C:\LOSSLESS\01
._NEIGHBORHOOD_#1_(TUNNELS)[NEW].WAV
FC: no differences encountered
C:\lossless>
As you can see, the above process was perfectly free from any kind of loss and we can be confident this is the case since FC reports no differences encountered.
[span style='font-size:8pt;line-height:100%']edit: command changed to FC /B, thanks zZzZzZz[/span]