[whatwg] Media protocols and state
ian at hixie.ch
Fri Oct 12 22:17:55 PDT 2007
On Mon, 2 Apr 2007, Kevin Calhoun wrote:
> I've been evaluating the behavior of the HTMLMediaElement in the current
> working draft in light of the various network protocols and player
> behaviors that I'm familiar with, and I think the current specification
> of loading behavior and the definitions of the buffering, buffered, and
> bufferingRate attributes are too restrictive.
> Players can be divided roughly into two classes according to their
> handling of data transfer:
> 1. Data availability precedes playability, seekability, etc.
> Typical case: the client requests a media resource via a transfer
> protocol such as http and caches the data it receives. It defers
> playback until enough of the resource is cached for playback to proceed
> without interruption. Seeking is limited to the range of the media
> that's available locally.
> 2. Data is loaded on demand in response to a request to perform an
> operation, e.g. play or seek
> Typical case: in response to a request to play a media resource, the
> client negotiates with a server to initiate a streaming session, such as
> an rtp session. Playback proceeds as soon as a minimal amount of data is
> buffered. Seeking may occur within the full range of the media; when it
> occurs the client asks the server to stream from the new media time.
> Of course many variants and elaborations of these two strategies are
> possible. In particular I don't mean to suggest that file transfer
> protocols are suitable only for the former category or that streaming
> protocols are suitable only for the latter.
> In the discussions that led to Apple's proposal for media states we made
> an effort to accommodate a variety of media access protocols. For
> example, in order to permit appropriate restrictions on seeking
> operations we expose the notion of the range of media that's available,
> not the range of media that's buffered, and leave the definition of
> "availability" up to the UA to accord with the transfer protocol and
> caching scheme in use. We also tried to stay away from the term
> "download", as it implies a file transfer.
> Clearly the two broad classes I mention above are very general; would it
> be helpful to discuss player behaviors in more depth? How well does the
> current proposal succeed in allowing custom controllers to be
> implemented that work with a variety of protocols?
As far as I can tell, both of the cases above are in fact handled by the
current specification. Could you elaborate on how you think the current
spec is too restrictive?
Ian Hickson U+1047E )\._.,--....,'``. fL
http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,.
Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
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