What is adaptive bit rate?

Adaptive bitrate (ABR) streaming refers to a technology that lets playback clients switch between various bitrate versions of a stream on the fly to accommodate changing network conditions, CPU constraints, and display capabilities. This streaming method can provide optimal image and sound quality for the viewer. The client controls switching based on client-side factors, and Wowza Streaming Engine™ software performs the server-side switching, which is transparent to the user. 


ABR streaming requires multiple versions of a file or live stream. Each version is encoded with a different bitrate, and each file or live stream encoded for ABR streaming must be keyframe aligned with the corresponding files or streams. The Wowza Transcoder is used to transrate one high-quality stream into several bitrate versions that are always keyframe aligned and suitable for ABR streaming. For video on demand streaming, the encoding process must be able to produce keyframe-aligned sets.


Media Server software supports ABR for HTTP clients that use HLS (cupertino), HDS (sanjose), or Silverlight (smooth) streaming, and Flash RTMP clients that use Flash Dynamic Streaming.  Media Server software does not support ABR for RTP/RTSP or multicast play.

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