Niels Mayer wrote: > On Sat, Apr 11, 2009 at 10:20 PM, Asiri Rathnayake < > asiri.rathnay...@gmail.com> wrote: > >> I was thinking of a usecase where users can play an attachment for an >> example. >> >> I'm pretty new to streaming content, but to enable streaming of attachments >> (audio, video) we would have to store them on files instead in database >> entries right? and then may be we can use JMF ( >> http://java.sun.com/products/java-media/jmf/index.jsp) for streaming. > > > If you're playing back an Xwiki attachment as streaming media, there's > plenty of problems because the entire stack is not designed for streaming... > > On the server-end, things are limited not by Xwiki itself, but by the use of > Java and Servlets, which ends up being incredibly heavy-weight for streaming > large data files. The issue with large-files and streaming media (e.g. > video) is that the "download" happens over a very long period of time; > streaming playback by definition means you're not downloading entire files > before play-back; instead, you use a small buffer and hope that network can > keep the buffer filled while the data plays back at a slow "real-time" > data-rate. > > Even if xwiki's db access could be made "incremental" or "paged", with > multiple users streaming simultaneously, a java/servlet based system > requires huge amounts of overhead per connection. It's easy to run out of > memory, or max-threads. The worst part about this architecture, as opposed > to more traditional practices in C/C++ using > select()<http://en.wikipedia.org/wiki/Select_%28Unix%29>and > nonblocking > I/O<http://en.wikipedia.org/wiki/Non-blocking_I/O#Select.28.2Fpoll.29_loops>, > is that most of those threads are basically doing *nothing* most of the > time, and when they are, they are sending out packet of data and then going > back to sleep... Of course, the servlet spec allows streaming, and there are > implementations of servlet-streaming that are quite straightforward to > implement, but may have performance/overhead issues anyways in real-use, > e.g.: > http://www.longtailvideo.com/support/forum/Modules/14410/Servlet-Streaming
Modern containers have support for NIO and long-lasting requests (cometd). It's just a matter of configuration. > IMHO, the leading implementations are still in C/C++ -- just find one that's > active, mature, and widely used, treat it as a black box, and use whatever > combination of arcane configuration commands needed to get it integrated:* > *The > most interesting option for Xwiki integration is > mod_h264_streaming<http://h264.code-shop.com/trac/>since it would run > in Apache and many already "front" their Xwiki with > apache and mod_jk. (This option might provide and easier > authentication&access-control integration w/ Xwiki). Some other standalone > implementations include: Darwin Streaming Server by > Apple<http://developer.apple.com/darwin/projects/streaming/>, > ViTooKi <http://vitooki.sourceforge.net/>, > Catra<http://www.catrasoftware.it/Streaming/CatraStreamingPlatform.htm>. > Those might do the job better for managing a site full of streaming > servers, but may be harder to integrate. > > I haven't looked at JMF solution for streaming.... nor do I see anything > about it that would make the task easier or the issues I mentioned go away. > Please let us know what you find out regarding JMF's performance and > integration capabilities! JMF would just help on the streaming side, but there are many other tools that can do that. The hard part is the database, and the way we handle attachments. -- Sergiu Dumitriu http://purl.org/net/sergiu/ _______________________________________________ devs mailing list devs@xwiki.org http://lists.xwiki.org/mailman/listinfo/devs
