Netflix’s Adaptive Streaming Algorithm Will Make Videos Sound Better

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The opening scene of season two of Netflix’s Stranger Things, a popular horror series that appeals to pretty much everyone who grew up in the 1980s, would sound great to the average ear. A little loud, maybe, since it’s a cacophony of car chase sounds. But shortly after season two was released in October of 2017, Netflix’s internal sound technicians noticed it didn’t actually sound great. There was an issue with the mix, says Scott Kramer, Netflix’s manager of sound technology. “A lot of it was mushy,” he says.

Words like “mushy” and “smeared” are ones that Kramer and his team use often when describing audio that just isn’t quite as crisp as it should be. It’s these kinds of observations, ones barely discernible to the average ear, that led Netflix to spend the past several months working on a solution that would make audio across all of its programming—both original shows and licensed content—sound better.

Doing this required more than just bumping up the bit rate on its audio streams. Instead, the company borrowed some tricks from its adaptive video streaming process, which uses machine learning to recognize network conditions (read: the strength of your internet connection) and