[1.28] The disc says Dolby Digital. Why do I get 2-channel surround audio?

Some discs (many from Columbia TriStar) have 2-channel Dolby Surround audio (or plain stereo) on track one and 5.1-channel audio on track two. Some studios create separate sound mixes optimized for Dolby Surround or stereo, and they feel the default track should match the majority of sound systems in use. Unless you specifically select the 5.1-channel track (with the audio button on the remote or with the on-screen menu) the player will play the default 2-channel track. (Some players have a feature to automatically select the first 5.1 track.)

Dolby Digital doesn't necessarily mean 5.1 channels. See 1.23 and 3.6.