(and I wonder where greynol is)

Hi guys, first of all sorry for my late reply. I was not aware of your postings (e-mail notification didn't work).
Thanks for your welcome message Rio.

And thanks for the technical aspects of your answers and for your kind help!

The question I still have is:
Is it possible to identify the music track via the #number ? (i.e. can I look-up the #number in some music database on the internet, etc.) ? A bit like the MusicBrainz ID or (- more unrelated though as it's only for whole releases -) the freeDB ID number. I guess not, as the bit value of the hash  is too low for that purpose. What do you know about this? ...

Calculate checksum

This function is found under the file menu.

Some CD players that actually can read digital audio do not necessarily read 100% correctly. The resultant files are then not exact copies of the originals. This can also happen if the CD is scratched, has fingerprints etc. It is hard to tell if a track is read perfectly only by listening to it. Checksums are therefor a good way to test if the CD player read 100% correctly. When a track is copied from a CD disc, Audiograbber automatically calculates a checksum. By reading the same track on two different CD players the checksums can be compared. If they are the same then the tracks are also the same and the reading is perfect.

But hey, readings do not usually start on exactly the same byte, so how can a checksum be calculated then? Yeah, a presumption for this is that the track begins and ends with silence. The checksum will then be calculated on only that part of the track that is over a value of 127.

(A sample from the CD can be between -32768 to +32767 (16 bits). -32768 means that the speaker's membrane is pulled back as much as possible, +32767 that it is pushed forward to maximum position and 0 that it is in its middle position. The more the membrane is moving back and forth the louder the speaker is playing. Samples in the interval -127 to +127 are interpreted as silence in Audiograbber. When a checksum is calculated, Audiograbber finds the first sample outside this interval. Then it finds where the file goes outside the interval for the last time and after that it starts to calculate the checksum. It does not matter if there is a bit of silence in the middle of the track, that part will also be included in the checksum.)

NOTE! If there is not enough silence (one frame = 2352 bytes) in either the beginning or the end of the track an X is added to the checksum. This indicates that other readings from the CD may give other checksums even if they are read in the same way. The checksum can not be used if it contains an X. 

By comparing checksums from tracks you have grabbed with your own CD with already known and confirmed correct checksums you can test if the CD reads the way it should. There are some correct checksums on http://www.audiograbber.com-us.net/checksums.html that you can compare with if you are lucky to have some of the CD's listed. Understand that you must have a copy of the exact same CD, it is not enough to have the same song.

You can report your own checksums on http://www.audiograbber.com-us.net/checksums.html. Those tracks should then have been read at least twice on a CD player that you are sure reads digital audio correctly. Report checksums from track 1,3 and 5. When you only want the checksum and not the entire track the function test comes in handy and you don't have to save the track on the hard disk.

Compare two files is another function that controls the CD's audio reading. If two checksums are not the same the compare two files function can see where the files are different. Checksums can also be calculated on tracks that have been read by other programs.