How can old movies be in surround sound?

Episode 1098 (22:53)

Charles from New York, NY

Charles is annoyed with Netflix' attempts to encode movies in mono that are being decoded into stereo. He's also noticing that old movies on Blu-ray are doing the same thing. Is there a new 2 channel stereo to 5.1 surround conversion technology going on? David says that there are certain older movies that have remixed in Blu-ray and it's likely those are the movies that have been used, and Netflix is likely using that remixed master. Scott says that Dolby Pro-Logic can also take a standard stereo signal and spread it out over Dolby 5.1 surround.