There is one catch to using vsync that not many know about. This illustrates it pretty well:
[gemwin 60] with pix_movie playing back a 29.97 fps DV clip:
print: 6.001
print: 27.532
print: 5.823
print:
27.144
print: 6.313
print: 27.383
print: 5.992
print: 28.492
print: 4.613
print: 29.411
print: 3.936
print: 28.189
Note that every other frame pattern. Why is that? The low number is probably a fairly accurate number for the CPU to fetch the frame from disk, decode and then fling it up onto the GPU for texturing, but what about the other number? Add the two numbers together and they are almost exactly the time for two frames to render (about 33 ms at 60fps). The reason is that the driver will wait on the 'no load' frame for the next sync before returning which is why it runs too long.
On 10/12/07, cyrille henry <cyrille.henry@la-kitchen.fr> wrote:
gemhead 50
|
t b b
| |
realtime
|
print
you should have only 50.
what i've got is :
print: 46.48
print: 52.183
print: 52.213
print: 46.474
print: 52.186
print: 46.505
print: 52.192
print: 52.179
print: 46.512
print: 52.174
print: 52.209
print: 46.484
print: 52.179
print: 46.512
print: 52.159
(with audio off, nothing else than the gemwin and this 4 object in the patch)
this jitter make it impossible to compute 1 and only 1 frame for each frame on the screen, even with sync on vblank.