How Netflix Offline Downloads Optimize Mobile Storage

Last week, Netflix introduced the ability to download content for offline viewing, while also making some changes to its codecs to make sure the downloads don’t eat up a lot of storage while maintaining good video quality. Turns out Netflix is encoding its downloadable videos with a different type of H.264/AVC than the one it uses to stream videos, Variety is reporting.

Netflix

What’s actually interesting is that Netflix’s encoding team knows different scenes in different movies require vastly different amounts of data. For instance, an action scene with a lot of visual noise contains a lot more visual information than a scenic shot of a blue sky, and animated movies in general are much easier to encode than live-action films. For that matter, it tweaks its encoding settings for each and every title, which also helps it to deliver better streams to users with slower internet connections.

For its new download option, the company is taking the idea one step further: Instead of changing these settings per title, Netflix is cutting each and every video into one-to-three-minute-long chunks. Computers then analyze the visual complexity of each and every of these clips, and encode with settings that are optimized for its visual complexity. The resulting potential bandwidth savings are significant.

Videos encoded with H.264/AVC High still use up to 19% less bandwidth on average. In other words: iPhone users could theoretically be able to save five episodes of “Black Mirror” with the same amount of space on their phone that would have been occupied by four episodes with Netflix’s existing technology.

Netflix is now planning to bring both chunk-based encoding as well as new encoders to mobile streaming in the coming months as well.

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