Jan,

Thank you for the *very* helpful information on M-JPEG! I saw something on the
jpeg.org site that suggested that there was an ongoing attempt to create a standard
for M-JPEG but, with several strong competing formats floating around, it might
be many years before everyone complies with the new standard...

I looked at the AVI file format extensions relating to M-JPEG. Like Quicktime, it's
packed with all kind of options and variations--useful for the professional, but they
certainly complicate things...

Given the current lack of a universal M-JPEG format, the lack of a universal file
format, the lack of soundtrack support (except as part of a QT or AVI file), and the
fact that I'm not even sure that the individual frames of M-JPEG are compatible
with our still-image JPEG plugin, I'm satisfied that creating a new file format for
Squeak JPEG movies is appropriate. If and when we write converters between
Squeak's JPEG movie files and AVI, QT, and/or the Berkeley multimedia group file
formats for M-JPEG, writing the Squeak side will be trivial.

My primary goal for Squeak's JPEG movies was to create a simple, authorable movie
format in Squeak that kids, teachers, and hobbiests could have fun with. By keeping
it extremely simple, I hope to encourage experimentation with iMovie-like editors
written in Squeak, the ability to create 3-D movies by rendering frames into a JPEG
movie, and even simple tasks like scaling movies to a new size or cropping them
(as Mark Guzdial discussed doing with GraphicConverter)--all with complete
portability across Squeak platforms (assuming the IJPEG Group JPEG library is as
portable as it's supposed to be). As long as we have a least one way to import movies
into Squeak--and that's doable via individual frames, as well as from MPEG movies--
then we've achieved that goal. Of course, being able to import from additional formats
would add convenience, but I suspect that there are formats that it would be more
useful to import than M-JPEG, such as DV. (Although I've never worked with digital
video in ANY form myself--this is new territory for me.) The ability to export
from Squeak movies into some widely used format would also be useful. Again,
using QT Pro, I think that can be done by exporting the Squeak movie as individual
frames, but there might be a more convient format.

Jan, can you suggest a simple but widely supported import/export format? It has
to be something we can encode from Squeak, of course. Maybe M-JPEG AVI or QT?
Although there *are* open-source C libraries for doing MPEG encoding, it's my understanding
that various patents apply to the MPEG encoding process, especially to MP3 sound
encoding, so we would need to get permission from the patent holders to distribute
such code with Squeak.

	-- John

P.S. Jan wrote:
>- all these details can be ignored if of you just want to play little 
>videos on your computer screen, if you want to produce video that shows up 
>on the Discovery Channel, you have to get it right

Yep, I appreciate that doing digital video seriously is major undertaking--all the more
after reading your message! Fortunately, the goal of Squeak JPEG movies is just
to play with video on the computer screen. Thus, we can avoid all those messy
things like frame interlace, non-square pixels, partial scan lines, etc.