Hi pure people,
I am new to pure but an experienced software developer.
I use PD for an interactive audio installation and especially GEM for the actual video processing and movement detection. Allthough it works fine on my development plattform, an old ibook G4, a few differences of the behaviour betweeb Mac and Windows of some GEM objects make me worry.

My development machine (on the go... is an old ibook with tiger (and an ati 9200) and a new pc with xp sp2 and a geforce 7600. The target plattform will likely be a pc also with xp sp2.
The software I use is the pd-extended 0.38-4 release.

My development works as this: I use a movie that is prerecorded and shows movement of a single object (like an elevator moving up and down with stops in between).
My patch is partially build like the GEM documentation example Gem - 04.video - 0.3.movement_detection.pd. Additionally to this I have subpatches that do movement analysis patches for speed and accelleration of a single moving object.

On the mac (with an ATI 9200) the initial view of the prerecorded movie is quite dark and the basic movement detection is very sensible and works quite well (and also the analysis).
On windows (with a geforce 7600) it is different. The movie looks quite normal, with the normal brightness (the mac was very dark), and the movement detection is very insensitive and does not really work.

Things that I recognized and resulting questions:
1. Is there a difference in initial values the GEM objects have if there is no explicit initialisation?

2. The colormodel seems to be different. A color of 1 1 1 is black on the ibook (with the ATI card) and white at the PC (with the geforce)

3. What reason can it have, that the displayed video on the mac (with the given example) is initially way darker than expected.

4. On the mac, the prerecorded movie cycles infinitely with the auto option of pix_film whereas pure on windows stops after one cycle. Is there a reason for this behaviour?

5. Is there actually a difference between the way GEM objects are initialized between Windows and Mac and also between different opengl vendors (like the color model between ati and nvidia).

Hope someone can share some experiences with GEM and how to work around the difficulties of GEM on different plattforms.

Regards,
Michael.