Tips for Technicians
Ein Techniker-Tipp

Streaming from Simple Sites

Data can “stream” from simple HTML sites. You need’t contact your web master to get data flowing. Let me tell you, how.
Daten können von simplen HTML-Servern »strömen«. Hier steht wie.

Streaming means that data is already shown before all the file has been transferred to your local PC. That’s nice for sound and video files, as well as for pdf documents. For continuous webcasts as from radio stations it’s a must.
   Technically you’ll find two types of streaming. The finer one is controlled by special stream servers. They interact with your PC (the client) to agree on flow speed, and to adapt it according to bandwidth. I won’t go into that. The second type of streaming, a sort of poor man’s ersatz, is HTML streaming off standard sites. We’ll only speak about this.
   Now my server here is nothing special. And my browser is a standard Netscape Communicator 4.7, like Microsoft’s Explorer freely available.

Your first have to be sure that your browser supports streaming. For sound (and video) you might have to install the Real Audio player; be sure not to have your browser active (turned on) when installing it! With pdf files you might have a problem however. If your browser displays the alternative “show or store” when you click onto a pdf (or any other streamable data) – then you’ve lost out before you even started. In this case you have Adobe’s Acrobat reader (AcroRd32.exe) running as external application, which is only called upon when the browser has satisfied the full download of the pdf file. You must have the pdf reader running as plugin within your browser! Then you see the acrobat reader within the frame of the browser, not running as separate program. A hint: When printing pdf files, use the printer button of the Acrobat controls (nearer to the text), not the one of the browser!
   A direct way to make Adobe’s Acrobat a plug in (Adobe calls it “byte serving”, see
http://www.adobe.com/support/techguides/acrobat/byteserve/byteserv01.html#plug-in): You locate file Nppdf32.dll on your PC and copy it into the folder Netscape\Navigator\Programs\Plugins. What they don’t tell you, is that you better remove the application call within Netscape (settings, Navigator, applications, Acrobat. For the extension pdf it must say: “controlled by plugin”, not “controlled by Acrobat”). Test it with http://www.Joern.com/streamt.pdf.

Now to the preparation of the data on your server.
   To “stream” pictures, incidentally, you have to code them as “progressive jpg”. See the difference between normal top-to-bottom jpg (heavens first, people later ...) at Dallmayr’s (with music) or at
http://medien.informatik.uni-ulm.de/lehre/webeng_2000/beispiele/media/progressive-jpg.html. The progressive jpg is the right picture there. You need special encoders, see for example http://skylinetools.com/imagelib/ for this. (I have no experience with progressive jpg, inputs welcome.)
   To stream audio (or video) for the Real Player all you have to do is not to reference directly to the (large) file with the actual audio or video. Again: Do not link to .rm files! You must make a tiny additional text file on your server, called something.ram. You then link to this file only. (The mechanism is described in
http://www.html.about.com/compute/html/library/weekly/aa071000b.htm).
   Let me show you: If you hit this link to my little audio file
http://www.Joern.com/casabl.rm you won’t hear it straight away. It will load all the 514 kByte first. You wait. However if you hit my link http://www.joern.com/casabl.ram this will wake up your player and get it starting. After a few seconds of buffering you hear the sound, while the rest of the data streams in in the background. And here’s the secret: file casabl.ram is a straight text file containing only the text http://www.Joern.De/casabl.rm (31 bytes). It must however show the full absolute http://... address, which even can be on a different server. (Careful not to point with the ram file to your own hard disk – the music then plays only on your PC!)
   To stream midi files is tricky. They typically are so small that streaming does not apply. Have a look at my “Casablanca” page
http://www.Joern.com/tipsn29.htm for this and more.
   To stream video or any other thing playable with the Real Player, just refer to this type of content in the ram file. Try it
here, a file – clip1.ram – that just contains (in this case) http://home5.swipnet.se/~w-55183/casablanca/timegoes.wav. If you hit the wav link directly, you’ll get the whole package before the thing starts – at least I think so ... With the competing Windows Media Player .mov files I’m not so familiar – enjoy the Muppets in Manahmanah. You may also “embed” music and even videos into your page, see my (German) Casablanca page – you are welcome to have a look at it’s source code as well. When you embed, the viewer will have to wait to see your page until all the stuff is loaded, however.
   To stream printable documents, pdf files, they must be optimized for that at creation. Adobe calls it “byte serving”. For more see
http://www.adobe.com/support/techguides/acrobat/byteserve/byteservmain.html. As I have no Acrobat writer, I can’t tell you more about it, but it seems quite straightforward and usual to do. Then put this pfd file on your server and it will work without further ado. (Sometimes it won’t, as for example with http://www.Joern.com/ebrosch.pdf, but I might still find out why. Help is welcome!)

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