Its called DDL, or Dolby Digital Live.
Originally Posted by Suntan
If you still want to get 5.1 surround and your receiver only supports DD, there are motherboards and/or sound cards that support the decoding of surround tracks and then re-encode them into Dolby Digital 5.1 in real time. This would then be sent out the Optical port to the receiver and the receiver will then process it just like it would normally process Dolby Digital soundtracks.
Originally Posted by mhench
if you have a direct show based player, you can use ac3filter to decode dts and re-encode to AC3.
it is free. google it. (http://ac3filter.net) setting it up with your player is up to you however
I am only familiar with zoom player.