Hi it's me again with my quest for speed. In older posts in Isadora user group about performance speed in different versions of OSX there was a talk a known bug from apple about display performance in some apps including Isadora. In numbers it's true that from 10.2.7 to 10.3 there was a a lag in speed. Problem seems to be solved in 10.3.2. But to my eyes there was something that wasn't just fine.
So i did a home-made non-scientific test on this machine configuration: Powerbook G4 1.25 GHZ 15.2" Aluminium model. 1 GB RAM. Isadora 1.0. Testing three OS versions.
I did a simple patch that shows what i'm talking about. It's playing a movie (320x240 photo jpg 30 fps from internal disk) at speed 1 with an alpha mask scrolling very fast revealling the movie under. Here are two examples comparing the recording of the same patch. Output settings where at 640x480 on svideo output. Recorded on DV tape with camera analog in.
| cycles | vpo | fps |
| 90 to 120 | 72 to 76 | 28 to 29 |
LFO is pretty fast on this alpha mask and the image quality is quite ok, no major drop frames and good fps
| cycles | vpo | fps |
| 18 to 24 | 60 to 80 | 18 to 24 |
I didn't put a clip because it's almost the same as in 10.3.2 below.
Backup everything, update your OS, reopen the same Isadora document, et voilà ! You get the same serious drops as in 10.3 but a performance increase in numbers compared to 10.3.
| cycles | vpo | fps |
| 90 to 110 | 72 to 76 | 26 to 29 |
So those stripes are not supposed to be cut in half on the vertical axis.
This display lag reminds me of old ATI cards that i used to have on older G3 and G4 . It happens or is more visible when there's a lot of horizontal movement.
so what's going on ? I guess it is a specific problem of ati cards on my model of powerbook and ATI drivers ?
