Umm, I'm going to disagree a little bit with Foxtrot and Slappy (no offense, guys!). While many DVD players have built-in decoding for DD and/or DTS, many do not. It has become a fairly common feature on DVD players which also provide DVD-A and SACD playback (i.e. "universal" players). However, I checked the list of DVD players that Crutchfield currently sells (a pretty good variety of popular makes/models) and less than half provide built-in decoders.
The Dolby Digital/DTS logo on the player does not guarantee the decoder is built in. It may only pass the signal digitally for external decoding/processing. The best way to tell if the player has built-in decoding is to check 'round back for the "5.1" analog outputs. There will be six standard RCA jacks labelled "sub", "center", "front left" yadda yadda.. Or bring up the players's setup menu or check the owner's manual.
Keep in mind any player will be able to play at least one of the (several) soundtrack options encoded on the DVD. However, you will have to decode the DD/DTS soundtrack at some point if you want to enjoy discrete multichannel sound. Make sure you have the right connections on your preamp/receiver to take advantage of a built-in decoder - it is useless for discrete multichannel playback if your receiver/preamp lacks a set of proper 5.1 analog inputs. Otherwise, just use the stereo analog outs to your tv or stereo to get basic stereo sound (or even Pro Logic) as suggested above. -JZ