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Re: iPhone streaming Internet-Draft posted

From: Mark Nottingham <mnot@mnot.net>
Date: Thu, 30 Jul 2009 09:26:14 +0200
Cc: HTTP Working Group <ietf-http-wg@w3.org>, http-live-streaming-review@group.apple.com
Message-Id: <F04F353B-A87C-4A32-8629-45FD679CE12C@mnot.net>
To: David Singer <singer@apple.com>

On 30/07/2009, at 1:27 AM, David Singer wrote:
>>
>> The analogy that comes immediately to mind is PDFs; the approach  
>> you're taking is roughly equivalent to Adobe saying that PDF files  
>> should be split into a URI-per-page and then putting an index file  
>> on the site to link to each page.
>
> This approach doesn't work with CDNs, who don't support adding  
> custom headers to HTTP responses and cannot cache a single  
> infinitely-growing resource which is being supplied to them in real  
> time (i.e. a live video stream).

I assure you that they can and will find ways to address it if an  
approach like this is implemented widely; caching proxies generally  
already support range requests (and combining ranges) out of the box.  
Have you engaged with any to discuss this with them?


> On top of that, the client would depend on a single connection to a  
> single server for the life of the presentation, which prevents load- 
> balancing and makes failover considerably more difficult.

Nothing says that you have to make range requests on a single  
connection.


> The playlist approach has a few other advantages. Using a playlist  
> of segments gives the client enough information to switch between  
> streams of different quality dynamically. It also allows the content  
> provider to express a range of time in which a client may seek.

It would be extremely simple to add this information elsewhere; either  
in the format itself, or in headers.


>> 2) Apple has disclosed IPR <https://datatracker.ietf.org/ipr/1142/>  
>> for this draft.
>>
>> My layman's reading is that anyone who wants to host a stream using  
>> this technique requires a written license from you, including the  
>> possibility of paying a fee, once your patents are granted.
>>
>> Is there anything else we should know about this? As it is, (and  
>> only speaking as an implementer), this just gives me more  
>> motivation to use other techniques.
>
> I'm not qualified to speak to the legal implications of the IPR  
> disclosure. Note that we offered the QuickTime file format to ISO  
> (for MPEG-4) under the same terms.  Send me direct email and I'll  
> try to work with you to clarify this status.

Thanks, but I think it'd be better if Apple made a public statement  
about it, otherwise people will have the same concerns.

Cheers,


--
Mark Nottingham     http://www.mnot.net/
Received on Thursday, 30 July 2009 07:26:54 GMT

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