Stone_The_Rock
New member
Good question raised on Home Theater Forum: how do you actually know whether a 2.0 track on a disc is straight stereo or Dolby Surround encoded, with surround information matrixed into those two channels waiting to be pulled back out. Disc covers list channel counts, not encoding, and the online databases only sometimes note it.
The honest answer is that there's no reliable label. The AC-3 bitstream does carry a flag that says the content is Dolby Surround encoded, but plenty of receivers either ignore it or never surface it to you, and studios have been careless about setting it for decades. So you end up doing it by ear, which is less awful than it sounds. Play a dialogue scene with matrix decoding switched on and listen to the centre. Properly encoded material locks dialogue firmly in the middle and puts ambience and effects behind you with a clear sense of intent. Straight stereo run through the same decoder tends to smear, dialogue drifts, and music gets pulled apart in a way that sounds wrong within about thirty seconds.
The rough guide by era helps too. Anything mixed for theatrical release from the late seventies through the nineties was almost certainly Dolby Stereo, meaning a matrixed 2.0 on the disc is the four-channel theatrical mix and should be decoded. A 2.0 on a modern release, or on a TV show, is usually just stereo, and forcing matrix decoding on it does more harm than good.
Does anyone's receiver actually display the Dolby Surround flag when it's present? Mine never has, across three brands.
The honest answer is that there's no reliable label. The AC-3 bitstream does carry a flag that says the content is Dolby Surround encoded, but plenty of receivers either ignore it or never surface it to you, and studios have been careless about setting it for decades. So you end up doing it by ear, which is less awful than it sounds. Play a dialogue scene with matrix decoding switched on and listen to the centre. Properly encoded material locks dialogue firmly in the middle and puts ambience and effects behind you with a clear sense of intent. Straight stereo run through the same decoder tends to smear, dialogue drifts, and music gets pulled apart in a way that sounds wrong within about thirty seconds.
The rough guide by era helps too. Anything mixed for theatrical release from the late seventies through the nineties was almost certainly Dolby Stereo, meaning a matrixed 2.0 on the disc is the four-channel theatrical mix and should be decoded. A 2.0 on a modern release, or on a TV show, is usually just stereo, and forcing matrix decoding on it does more harm than good.
Does anyone's receiver actually display the Dolby Surround flag when it's present? Mine never has, across three brands.
