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”.

Awesome.


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