When copying a dvd-movie, afther ripping I use the dvd-shrink movie only mode, and remove all the unwanted subtitles and audio. Thereafther, I encode/rebuild it with DVD-RB+HC encoder. Great quality, but I don't want to go <70% compression.

There are three types of audio streams:
- 2.0 stereo
- 5.1 Dolby Digital
- DTS

Off Course, I prefer DTS. Some movies have all these streams, others only have the DD stream (so no stereo!?)

Sometimes I can only choose DTS, because otherwise it will be encoded to much (DVD-RB, HC-encoder, it's really as good as CCE) My question is; can this movie still be viewed at a tv with only stereo? (so the speakers of the TV)

Also, why do some movies also have a stereo track + DD, while others only have a 5.1 DD stream...? 5.1 also plays as stereo when needed I suppose...

Hope you can help me to understand the above, it's all quite confusing....

DTS will NOT play on a system that has only stereo.

any films that you've backed up and included only the DTS audio will have no audio if you try to play them on a device that cannot decode the DTS.

the 5.1 and 2.0 audio selections will play on anything as far as i know.

if you want your backups to be playable regardless of what you're playing it on then you'll have to either include both audio tracks (DTS and either 5.1 or 2.0) or include just the 5.1 or 2.0 and save space/compression at the expense of the better audio.

When having a film with 5.1DD and a stereo stream, isit it then the right decision to only keep the 5.1 stream while this can also be played as a stereo stream, or am I missing something?

yes, this is correct. 5.1 and 2.0 will both paly on anything (with 5.0 having the better quality) so it's a good idea to hang onto the 5.1 audio unless you're looking at some serious compression and are trying to save space on the disc.

often times 2.0 audio isn't for the movie anyway...it's the director commentary so i would double check this for any discs for which you've ONLY kept the 2.0 audio.

a great way to do any double checking is to either burn to a dvd+/-RW and test it out before burning to a DVD+/-R or to save as an ISO before burning at all then mounting that ISO on a virtual drive to test the settings you've chosen on your computer.

keeping 5.0 audio for all discs is a safe bet.