- Rip the 4 DVDs with makemkv.
- Merge the 4 files using this guide [HowTo]: joining multi-part movies files with MKVtoolnix GUI
- apply any compression you see fit, using Handbrake or similar tools
- I recommend you to stay with the MKV format. You can edit the chapter list (which you hopefully preserved when compressing the file) and add names of the songs
- a little extra info here (yes, I know the post is older, but it is still applicable): https://forums.plex.tv/t/so-how-do-you-all-handle-concert-videos/133621/3
