Lower video resolution can deliver better quality, says Netflix

Streamer now assessing individual files and changing resolution to fit networks and devices

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Netflix has revealed a new plan for ensuring its videos arrive in your device looking their best, which can sometimes mean streaming them in lower resolution.

The streamer calls its new scheme “Per-Title Encode Optimization”. As the name implies, the company is now analysing the content it offers and delivering it in different resolutions depending on the nature of the program.

In the past, Netflix developed a “ladder” in which it chose “bitrates … sufficient to encode the stream at that resolution without significant encoding artifacts”. The ladder therefore matches bitrates to resolutions.

These days, the company's decided that approach was a bit arbitrary because it can result in artefacts appearing during busy moments of a complex film, while also using rather more resources than were required to stream something simpler, wasting storage and network resources along the way.

The company's therefore asking subscribers to compare “an animation title where the content is 'simple', that is, the video frames are composed mostly of flat regions with no camera or film grain noise and minimal motion between frames” with “an action movie that has significantly more temporal motion and spatial texture than the animation title. It has scenes with fast-moving objects, quick scene changes, explosions and water splashes.”

When delivering the latter, Netlflix says, it could go for 1920x1080 resolution at 4300 kbps, but is better off going for 1280x720 because the former would produce encoding artefacts which are “typically more annoying and visible than blurring introduced by downscaling (before the encode) then upsampling at the member’s device.”

Subscribers, the post says, should end up getting a better result even if they find themselves watching in lower resolution. At other times when the nature of content makes it possible – think those nice, simple, cartoons- the company pledges to pack in more pixels (there's lots more detail about the choices behind optimisation in Netflix's post).

Netflix is a known Docker user, and this kind of dynamic encoding sounds like just the kind of thing that containers would be good at. El Reg therefore suspects that the company's new streaming regime is a result of recent advances in software and the availability of cloud-scale resources to power them. Which is impressive and all very nice: now let's imagine when this stuff gets pressed into service for things that matter rather more than crisper video on fondleslabs. ®




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