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Browser requirements

If I were to make a report on paper, I could send the actual paper print-out to the person I wanted to read it. I would not have to worry much about what it would look like for him/her, since it was the very paper I myself had had in my hand, that he/she would have gotten.

If I were to make a report on a video tape, it would still be fairly simple, but I would have to make sure, that that person were able to view the video tape format I had used, e.g. Super-VHS PAL. And of course, it would be absolutely necessary that the person had a VCR in the first place.

Now that I am making a report as a multimedia document on the Web, what then? As a first prerequisite, the person should have a Web browser (such as Netscape), running on a machine with access to the Net. In more details, the browser requirements for this multimedia report are:

Ability to show the different occurring content types:
As discussed earlier, there are several different ``classes'' of content types, e.g. still images, movies, and 3D scenes, and within these classes there are several different ``formats''. These latter each have a distinct so-called MIME type. When a Web server sends some data (e.g. the contents of a GIF file), it also sends the MIME type, so that the Web browser (e.g. Netscape) knows what kind of data it is getting. The Web browser then has a table (the mailcap), that specifies what to do with a number of different MIME types; it could either handle it itself, or it could send it to an external viewer.

Here is an example of all the different MIME types that I use in this Web exhibition. Try to click on it and see what happens. If your browser just lets you save the file without displaying it, help might be found further down. Note, that I will explain later what these files show.

Text, plain
Text, HTML (that is what you are reading right now ;-)
Still image, GIF
Movie, MPEG (here: MPEG-1 video bitstream)
Movie, QuickTime (here: Animation coded)
Movie, Animated GIF
3D Scene, Inventor
3D Scene, VRML
Page description language, PostScript

Ability to show the HTML markup used:
I have used HTML version 2.2, that have tags for making tables. If you see a nicely formatted 3 by 3 table right below this, your browser understands these tags:

type style
smart red short
rather silly puce tall

(courtesy Lamport 1986 ;-)

Ability to make interactive forms:
In this project I have also used interactive forms. For these, the browser needs to render the associated HTML tags correctly, accept input from the user, and send it in the right way to the Web server. An example of a form follows here. It will return an HTML document telling you what value you submitted.
input a number!


Ability to decompress compressed files:
I have often compressed Inventor and VRML files using gzip, since their size is reduced a factor of tex2html_wrap_inline852 5 that way. Here is a gzip'ed Inventor file.

If all of the above worked for you, you do not have to read through the rest of this section!

So, what kind of setup fulfills all of the above requirements? To start with the three last ones (tables, forms, and gzip): just get Netscape version 2 or later. I have been running version 2.02 myself.

To be able to view all the above mentioned MIME types, you have to:

If you are running on a Silicon Graphics computer like I am, you could use the following mailcap:
video/mpeg; mpeg_play %s >/dev/null 2>&1; \
        description="MPEG Movie"; \

video/quicktime; movieplayer -nofork %s >/dev/null 2>&1; \
        compose=moviemaker %s; \
        description="QuickTime Movie"; \

application/x-inventor; ivview %s >/dev/null 2>&1

x-world/x-vrml;  /usr/local/bin/webspace -remote %s -URL %u ; \
        description="VRML document"

application/postscript; ghostview %s; \
        description="PostScript Language";
The syntax is actually quite simple, it is ``MIME_type; viewer %s'', where %s will be substituted by the name of the temporary file containing the data. Netscape spawns external viewers using the Bourne Shell (/bin/sh), and ``>/dev/null 2>&1'' is the syntax for throwing away standard output and standard error, so that one does not have to click ``OK'' on all the messages like ``could not allocate whatever color'', or ``played movie at foo frames per second''.

Note, that the MIME types text/plain, text/html, and image/gif are not mentioned, and therefore they will be handled by Netscape itself. This is important, since an external GIF viewer might not be able to view animated GIFs - this is the case for xv and imgview. Note, that both the system-wide and your personal mailcap file has not to map image/gif to anything for this to work.

About the viewers I am using, and possible alternatives:

A final comment is about speed, e.g. the speed with which you can play a movie. Here at the Observatory, we have a number of Silicon Graphics Indys with typically 32 Mbytes of RAM and a 100 MHz R4000 CPU. They run as X-terminals, and the typical user will via them log in to a computer with more RAM and a faster CPU (say, an R8000). However, for playing movies, I have found a speed factor of 4-25 in favor of the Indy! Therefore, I advise you to run Netscape and thus the movie viewers locally, if you have the same type of computer setup as we do, or even better, to make the comparison yourself.

next up previous contents
Next: On using LaTeX2HTML Up: Introduction Previous: 3D Scenes

Web Exhibition: Null Geodesics Around a Kerr Black Hole

Bo Milvang-Jensen (
Mon Jun 17 11:54:08 MDT 1996