In thetechnical details of Panosonic DVD-RV31S it says:

DTS (Digital Theater Systems) output: Yes
DTS (Digital Theater Systems) surround decoding: No

What does that mean ???

It means that this player will output the encoded DTS bitstream, but not a decoded DTS analog signal. So you'd need a receiver with DTS decoding, processor with DTS decoding, or external DTS decoder to get DTS from this player.

The above is correct

Sony makes a player that outputs a decoded DTS signal. The model is 570D. (If you need one)

I found out about this the hard way; I ran an optical cable from my DVD to my DTS amp but could not get DTS to work (even though DD5.1 worked fine). Apparently the player won't spit out the required information to the amp; thus no DTS for me without a new player (sigh)...

Panasonic also makes a couple of models that will output a decoded dts soundtrack via 5.1 output (RCA jacks). I think the RV-30/80 offer this feature, as well as their older A320 model.

Not sure how your player's menu options work but most will have an audio selection for DTS. You have to put it to on or DTS. On My Sony 530 it says PCM or DTS and you select DTS and then select DTS to on. Read your manual to find out for sure. First thing is to look for a dts logo on your player. If there isn't one, you're out of luck.

Thanks for the tip William, but my player just doesn't cut it (it's an older model)...