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From: clouds@ccwf.cc.utexas.edu (Kathy Strong)
Newsgroups: comp.ivideodisc
Subject: Re: Questions
Message-ID: <40092@ut-emx.uucp>
Date: 23 Nov 90 17:05:54 GMT
References: <9676@jarthur.Claremont.EDU> <39907@ut-emx.uucp> <473@tcnz2.tcnz.co.nz>
Sender: news@ut-emx.uucp
Reply-To: clouds@ccwf.cc.utexas.edu (Kathy Strong)
Lines: 86

In article <473@tcnz2.tcnz.co.nz> greg@tcnz.co.nz (Greg Calkin) writes:
>
>Another novice question or two

I kept waiting for all those people who tell me I'm not alone to help
Greg out, but I guess they're all home for the Thanksgiving holidays. :-)
So here goes.


>1) How do you handle producing a videodisc to cope with VGA colour and to
>   cope with mono on a MAC, for instance. Are there standard image conversion
>   techniques to allow the production of a IV across a broad range of hardware.

The videodisc itself doesn't care about color standards, if I understand
what you're asking. The overlay card you choose will determine what kind
of graphics (i.e., how many colors and the HxW resolution) your monitor will
be able to display. On the PC-based system we're using, we have Visage 1910
overlay cards, which we use to display 640x480 x 256 color images (i.e.,
VGA resolution + 256 colors). In our case, it is given that the program will
only be shown on a workstation that is exactly like ours. I've worked with
a system where you could store images of different resolution in different
directories and the software would query the user for their resolution type
and then default to the appropriate directory... like this

At program creation, each graphic image is created twice: at EGA resolution
  and at VGA resolution.
EGA images are stored in directory \EGA
VGA images are stored in directory \VGA
Throughout program, when an image is required it is named \"dir"\saturn.pcx
  or whatever...

At runtime:
Program asks user: EGA? VGA? 
   User answers: VGA
Program records answer in variable "dir"
Then whenever an image is called it substitutes VGA for "dir" and finds
the image as \vga\saturn.pcx

If the user had replied EGA, it would look for the image in the EGA dir.

>2) If I show a constant frame on screen, how do I store running dialogue
>   without changing the picture. Similarly, can I store a screen then run
>   graphics or text over it without using more than 1 screen picture.

We do this by recording additional audio ("B track audio"), using the
features of our disc player (Pioneer LDV-8000) to "grab" the video frame,
then moving to the audio location, selecting audio B, and playing the bit.
Then, of course, you have to move to your NEXT video, then ungrab the frame
(if you do these in reverse order, you'll have some random picture--the
picture associated with the B-track audio). Not all players can do this.
Another solution would be to record your audio digitally (i.e., on the
computer's hard disk, not on the laserdisc). Then you just hold one frame
on the laserdisc and tell the computer to play the audio. Very wasteful of
HD space, and the quality isn't great, but it can be done.

>3) Is there a standard gaphics / text primitive language with sound i.e.
>   Show this frame, run this graphics program to highlight screen areas, with
>   this sound track running, all synchronised ?

You're asking about "authoring languages," I think. Most Mac applications 
seem to have centered on Hypercard/Supercard. I believe MacroMind Director 2.0
has some "authoring" built in.  I find Hypercard etc. a little generic to
be really useful as multimedia authoring tools. On the PC side there is
IconAuthor, Quest, Instant Replay, Guide.. (whoops, Guide is also a Mac
product). Amigas have AmigaVision, The Director... etc. Authoring languages
seem to be shaking out to one of two models: either a graphic-oriented 
model, where you build a flowchart and that is your program; or a language-
oriented one, like C or Pascal. 

>4) Where do the differences between PAL and NTSC come into things, or do
>   you roll your own format ?
>

I suspect that NTSC/PAL differences are going to be significant for your
choice of monitor, overlay card, videodisc, and videodisc player. I'm
not really up on this subject--anyone else?

--Kathy


-- 
...........................................................................
:   Kathy Strong               :  "Try our Hubble-Rita: just one shot,     :
:  (Clouds moving slowly)      :   and everything's blurry"                :
:   clouds@ccwf.cc.utexas.edu  :                           --El Arroyo     :
:..........................................................................: