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February 25, 2014 / ftth

Is HLS today’s DASH (that “really” works in Flash) ?

The Dropbox team recently published some really interesting stuff about their video processing pipeline; the most interesting part for the sake of this post is that it uses HLS to unify streaming. Also, Justin.tv recently announced migrating to HLS, and last time i checked, Youtube was doing it’s live streaming in HLS for Flash as well.

Why migrate to fragmented http streaming (from rtmp) for (live) delivery ?

  • being HTTP based, firewalls don’t get too picky
  • being fragmented, it’s quite proxy/cache/CDN friendly (squid / varnish / cloudfront, …)
  • it’s highly seeking-friendly (no need to deploy special servers to do the job)

The downside is a larger protocol overhead when compared to rtmp, but it makes things simpler (as long as your Flash implementation is good !).

However, why migrate to HLS, and not HDS (Adobe’s own spin on fragmented HTTP streaming) ? After all, HDS is natively supported by the Flash plugin, while HLS is an Apple protocol…

The reason is : to keep complexity and costs down by using a single protocol for everything, using the native HLS for iOS clients (iPhones, iPads, Safari v6+), and Flash player for desktop. Of course, Adobe doesn’t provide HLS support, but some players do (like the excellent JWPlayer that we use).

To sum up, some people in the live streaming industry are migrating to HLS for delivery (not ingest), because HLS is a pragmatic DASH-like approach, that works today. No doubt that the future will be DASH, but today (and for some time probably), the only unified browser & mobile device live streaming protocol is HLS, with the help of Flash, again, and because of Apple, once more 🙂

And, by the way, at UbiCast we migrated most of our streaming services to HLS 6 months ago for the same reasons. Seeing such major players do the same just seems to confirm our approach.

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