Dvd vs computer dolby digital sound

ok here’s what i have. i have copied all the video files from a dvd using either dvd43 or anydvd. everything worked fine there. i am using powerdvd for playback. i have a soundblaster audigy with optical outputs. i am using these outputs to send the dolby digtal signal to my receiver. it seems though that the sound is slighty different than when i play the dvd on my panasonic player also using optical outputs. shouldn’t ac3 code be the same whether from a dvd player or computer.