Netflix will optimize encoding videos by title

Dec

16

2015

Netflix abandons his method to use fixed combinations of resolution and bit rate during playback of videos. The company is going on for a way to separately for each title to determine the optimal coding.

From 2010, Netflix is ​​already using H.264 / AVC to encode video and in that time is the ‘bitrate ladder in use. This method combines a bit rate to a resolution, in which, for example, a stream of 5800kbit / s is associated with a resolution of 1920×1080 pixels. The problem with this, recognizes Netflix, that bitrate for animated films is much higher than needed for a proper 1080p playback, while some movie scenes show still blocky image.

When disposing of the video quality of hundreds of video samples, using the peak signal-to-noise ratio or PSNR in dB, by the bitrate, were big differences. Some titles had 8000kbit / s is required in order to achieve acceptable PSNR of 38 dB, while other content with 2500kbit / s is sufficient to achieve 45dB. The one-size-fits-all method therefore can not provide the best video quality at given titles and bandwidth of viewers and it allows for redundant storage, concludes Netflix.

Netflix Peak Signal-To-Noise Ratio bitrate
In recent years Netflix matter proceeded to use a bitrate ladder for titles separately. The service looks a title which is the best combination of resolution bitrate, which is the highest bitrate to get the best perceived quality and how quality levels need to be encoded. This requires a production system that the collection Netflix scalable can convert.

Netflix per title ladder
Netflix per title ladder

Netflix performs test coding of individual titles in multiple resolutions and bit rate selections that are roughly 5 percent apart. When sampling the bit rate and quality will be measured and on that basis be determined curvatures for each resolution. The final per-title bitrate ladder is determined by selecting points that lie closest to the ideal curvature of the combination of quality and bitrate.

Netflix per title ladder
Netflix per title ladder

Netflix claims with the new method to be able to offer the same quality as today or even better, but while taking up less bandwidth. This would be particularly in countries with slow internet connections and mobile networks are important. ISPs have been complaining for some time that Netflix draws heavily on their networks. When measured last year showed Netflix to account for 5 to 10 percent of the data traffic at the former UPC, KPN while this year announced that the service 20 percent of its bandwidth on the wired network opsnoept. This pressure increases as Netflix will stream more 4K content to uhd TVs.

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