I have an audio CD image and I'd like to create a CD Extra from it containing some files as "bonus material". I don't want to lose pause length between tracks, CD text etc. So rebuilding the audio part from single tracks should be avoided. Is there any software allowing to import a CD image for the audio part?
Unfortunately there is no way I know of to add data to an existing, finalized audio CD image. This is because the table of contents has already been finalized, and does not include any data that wasn't already present at burn-time.
I've made a lot of mixed-content CDs though, so this should be pretty easy.
I would simply rip the CD audio tracks back to WAV files, and make a note of the CD-TEXT for each track as well as the gaps between each track.
Then, create a new mixed-content project in Nero or any program that supports this. Add your data to the data part, and add your audio WAV files to the audio part. Then add back the CD-TEXT and gap times for each track, usually by right-clicking the track name.
Now burn it and you'll have a CD that plays as audio in a regular audio CD player, but also shows data when inserted into a computer. You can also insert an autorun.inf file to make a default action happen (such as launch media player) when the CD is inserted into most computers.