Sharovatov’s Weblog

Apple submitted HTTP Live Streaming spec to IETF

Posted in http by sharovatov on 2 May 2009

As I’ve blogged recently, nearly a year ago Microsoft proposed an approach for adaptive video streaming over HTTP – Smooth Streaming. As Microsoft didn’t apply for a patent for this technology, I was hoping to see the same beautiful approach implemented in modules for other web-servers, or even as web-applications – as it’s really easy to implement.

The mistake Microsoft did was that they didn’t submit this technology standard to IETF to make it RFC – and that’s what Apple’s doing at the moment.

Yes, I’m not mistaken – Apple copied the whole idea, called it HTTP Live Streaming and submitted to IETF.

Yes, there’re differences, but they are absolutely insignificant:

  • Apple spec suggests extending M3U format for a playlist – Microsoft uses SMIL-compliant ISMC client-manifest file (i.e. playlist)
  • Apple spec defines that the server creates the playlist – in Microsoft approach the encoder creates the playlist
  • Apple spec defines encryption for media files – Microsoft doesn’t

And the whole specification that’s been proposed is weird – I think they just wanted to submit it as soon as possible before Microsoft Smooth Streaming approach gets popularity and becomes de-facto standard.

Here’s what jumped at me when I was reading the spec:

  1. section 6.2.3. Reloading the Playlist file – why specify the expiration time of the playlist separately when HTTP 1.1 already has flexible methods for
    setting expiration time of the resource?
  2. encryption – what’s the purpose of encrypting media files when there’s HTTPS? And if there’s a purpose – HTTP already provides a place where encryption could be "plugged in" – Transfer-Encoding, why didn’t Apple just
    register another transfer-coding in IANA?
  3. EXT-X-ALLOW-CACHE – why add this if HTTP already gives flexible tools to control caching?

So as I see it – Apple was just a little bit in a hurry to propose this “standard” – looks like they took Microsoft idea, added some proprietary bits and bobs without thinking them through, didn’t use what HTTP natively provides but bravely called the draft “HTTP Live Streaming”.


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