Are dolby digital and AC-3 the same?

Thanks for the information. but one of you say yes, and the other says no... I guess the most pressing question is will my harman kardon reciever (which can decode AC-3) decode a DVD move encoded with a Dolby Digital signal

Julpay- unless I am wrong the only practical difference is in the interconnects. AC-3 usually is output as an RF signal, I think, while DD is usually output as either toslink or digital co-ax. Could be wrong on this, tho.

I know the receiver has an optical input....would this send the signal over?

A bit more light to help confuse.Did you know the AC-3 from the LD transport can not be carried by a Illuminatins D-60? It requires a video cable.I also had the same Pioneer AC-3processor. I sold mine to get Lazer DTS capability,before DVD came out.Kthresh said nothing that contradicted anything I said. You may have percieved it that way ,I didn't.On my present processor setup,I have the DD/DTS, input on one coax with signal recognition. Then I have the AC3 from the LD as a seprate coax input. Now the point I missed, is the question I don't know the ans to. As in, will your piece do DD,from a dvd player? Well, If it doesn't MSB,or others can do a chip upgrade cheap,I would guess.

Yes, Dolby Digital and AC-3 are the same "technology". All the comments about how it is hooked up have nothing to do with the Dolby circuitry.