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.