AC3 audio without decoder

[bob122480]

I'm trying to burn a dvd for a friend that does not have a DD5.1 decoder on his dvd player or receiver and I was wondering is AC3 6 channel downconverted to 2 channel when there is no decoder? I played the dvd in DD 5.1 with the dvd player and no receiver and I was in fact getting sound. How is this possible? The reason for this question is that the AC3 audio is more than a gig smaller than the 2 channel Stereo LPCM so i would be able to get far less video compression if i used the AC3 instead. Thanks

[lechtin]

Even without a DD decoder, the AC3 stream is downconverted to be output through the analog 2-channel output of the DVD-player. I run a cheap DVD player without decoder through a Dolby Prologic (no DD decoder) using the analog outputs and have never had a problem. A lot of my discs only have a AC3 DD5.1 soundtrack and it still works. I guess it may depend on the player, but both my players work that way (Apex and Norcent)

[Gazorgan]

Most of my backups are 5.1 audio, but my cheap bedroom player has 2 channel output. The player will down convert to 2 channel, as well as spit out the same thing to optical/coaxial automatically. I've seen very few players with 6 channels out.

[bob122480]

hey thanks for you help. I have a follow up question. Why does a dvd player down convert AC3 but not DTS if they're both 5.1 channels?

[bugster]

hey thanks for you help. I have a follow up question. Why does a dvd player down convert AC3 but not DTS if they're both 5.1 channels?

DVD specs state that all movies must have at least one audio channel which must be one of Ac3, LPCM or, in europe, mp2, though I believe the mp2 requirement has recently been dropped. As this means that a movie may have ac3 5.1 as its only soundtrack, all players must also be able to downmix ac3 5.1 to analog stereo as the lowest common denominator. DTS is an extra format and not formally part of the DVD requirements.