[icecast] seek, pause etc using icecast ?

Michael Smith msmith at xiph.org
Wed Sep 3 18:41:34 PDT 2003



On Thursday 04 September 2003 08:20, W. Kevin Pedigo wrote:
> On Wed, 2003-09-03 at 21:58, Erlend Simonsen wrote:
> > Hirendra Hindocha <hiren_hindocha at comcast.net> writes:
> > >> No. icecast2 is a streaming server, so it... streams.
> > >
> > > Good point. I wonder how the other servers (Real Server ,Quicktime etc)
> > > do it. Any inputs on any other streaming servers that lets a client
> > > seek/fast forward /rewind ?
> >
> > They probably do it client side by buffring the stream.
>
> No, they do it using RTSP methods, which inherantly contain the correct
> "time" for the frame.  By requesting a specific "time", you get a the
> frames that correspong, thus you can seek without relying on client side
> buffering.  Note that not all QuickTime or RealMedia files are served by
> proper streaming servers.  You need two things for server side
> seeking.... a seekable source, and a seek-aware protocol.  If all you
> want to do is get the file to the client, HTTP works just fine.  And
> while the file, when it arrives, will be seekable, HTTP doesn't
> understand seeking, so downloading quicktime files off an HREF from a
> web page doesn't get you all the cool goodies that RealServer or the
> Darwin Streaming Server get you.  Which is why they invented the "embed"
> tag.
>

Well, this is mostly right... but seeking with HTTP is entirely possible 
However, you have to build it up from byte-range 'seek' requests, not using a 
time-offset. This makes doing it efficiently quite difficult.

That's what the Range header is for.

See also http://www.annodex.net/TR/uri_fragments.html for an internet-draft 
attempting to specify a media-and-transport-neutral way of specifying this 
sort of thing. I think they have an apache module implementing it as a 
proof-of-concept.

Mike

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