What are HLS (HTTP Live Streaming), HDS (HTTP Dynamic Streaming), Smooth (Silverlight) Streaming?

HLS, HDS, and Smooth Streaming (also referred to in Wowza Streaming Engine™ software as “cupertino”, “sanjose,” and “smooth” streams) are used, respectively, by iOS, Flash, and Silverlight clients to play segmented video and audio files that have been downloaded to a player over HTTP. These stream types vary in detail but work similarly. Wowza Streaming Engine™ software segments live streams and multimedia files into small files (chunks) for delivery to requesting HTTP playback clients. HTTP clients use a manifest file generated by Wowza Streaming Engine software to order requests for the chunks of a stream. Streaming Engine software breaks chunks on keyframes, although not usually on every keyframe; however, each chunk will contain at least one keyframe.

HTTP Live Streaming avoids the network problems sometimes associated with RTMP streaming, which can be blocked in some networks and may require port configuration on the delivery side. On the positive side, HTTP streams are easier to cache and they work with proxy servers. (You cannot proxy RTMP).

Also, ABR streaming is better supported in HTTP clients than in Flash RTMP clients. ABR is built into the HTTP streaming protocols. HTTP clients are able to constantly measure client-side bandwidth calculated by chunk size and download time, whereas RTMP must employ a separate process to measure bandwidth and requires a custom player to implement ABR streaming.

The chunks Wowza creates for HTTP streaming are not written to disk; they are kept in memory.

Wowza does not support ingest of HLS, HDS, or Smooth Streams.

HLS  is a streaming media protocol developed for use in iOS devices by Apple, Inc. Despite the name, “HTTP Live Streaming,” both live and on-demand streaming is supported with HLS. Many set-top boxes, recent Android devices, VLC, and other players support HLS play.

HDS was developed by Adobe for use with Flash player applications. OSMF (Open Source Media Framework) is used in Flash players that play HDS streams.

Smooth Streaming was developed by Microsoft for use with Silverlight player applications.

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