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Showing posts from April, 2017

HOWTO Use temporal scalability to adapt video bitrates

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We have talked many times about video scalability (VP9 SVC, Simulcast) and how it enables modern RTC infrastructures to provide high quality multiparty experiences while maintaining low infrastructure costs (re-encoding the video is more expensive and also degrades the media quality).  This approach was popularised by Vidyo and can be seen in modern platforms like OpenTok and services like Hangouts/Meet these days.

Typically we talk about temporal and spatial scalability although you can also have quality scalability.   With spatial scalability you generate multiple versions of the video with different resolutions.  In case of temporal scalability the sequence of frames is encoded in a way so that some frames can be dropped in the server and the resulting frames sequence can be still decoded in the receiver side.

This is an example of a typical VP8 encoding with 2 temporal layers where the base layer (blue frames) don't depend on the higher layer (yellow frames):



This type of enco…