Conference bgsdev::multimedia_services

496.0. "How to download jpeg/mpeg files and show them to user." by APACHE::CHAMBERS () Wed Mar 19 1997 17:56

What we're looking into is what tools might be available that run on Digital
Unix that can act as browser (usually netscape) helpers and/or plugins (whatever
the difference is), accepting a jpeg or mpeg-1,2 movie from the connection and
showing it in a little window on the screen.  We keep seeing clues that it is
doable, but the clues never quite add up to something that works.

The latest try has been with alphavcr.  There seem to be several things wrong
with the way it works:  First, the entire file is downloaded into /tmp/, giving
the poor user a loooooong wait, since these files tend to be rather large.  Then
what usually happens is the /tmp partition fills up entirely, and netscape dies.
If the file is small enough to fit, alphavcr does come up and start showing it.
But it only shows one frame every N seconds, where N ranges from 2 to 15 or so;
it makes big jumps between frames.  This doesn't give the users a good feel for
what was in the clip.  And at the end of the clip, a bunch of error windows pop
up; when you hit their OK buttons, they and the alphavcr window disappear with
a bright flash, leaving behind a 12-MB core file, thus further clogging the
disk partition.

Is there anything around that works better?  Or a way to configure alphavcr 
to do the job better?

One thing that does occur to me:  For most of our purposes, it would be much
better to produce a small window with a shrunken picture, and 15 frames/sec
would be plenty good for the job.  The idea is to point at a list of clips
and see a "thumbnail" or "preview" or whatever version.  It doesn't need to
be full-sized; it just needs to be good enough to give the viewer a feel for
what's there.  So one thing that might help would be a "condenser" program
that the CGI script on the other end can run to reduce a full-size mpeg file
to a much smaller file.  

Is there any such software for D-Unix?  Is is perhaps already sitting on my
4.0B installations disks, but I don't recognize it?

You need to go research the difference between helpers and
plug-ins.  It's signficant.

/tmp is not a good place to load your Web surfing detritus.
/usr/tmp typically has much more space.

AVI files have the index at the end, so your are going to have
to load them no matter what.

MPEG-1 and MPEG-2 files could be played as they are downloaded
if you set up Netscape to do so, but I'm not sure whether or
not AlphaVCR has this capability.  You could also try Xanim,
the public domain player to see if it behaves any better.

Crashes are always bugs and should have PTTs filed.

Tom