[PD] Fading between 4 videos - performance issues

[Christian Klippel]

hi all,

Am Dienstag 13 Dezember 2005 18:22 schrieb chris clepper:
[...snip...]
>
> Premiere is probably not texturing the video using OpenGL, but rather
> using simple accelerated overlays.
>
> > How do you intend to improve things?
> > What alternativs do I have?
> > Does it run smoothly in Mac? Is this a PC-only issue?
>
> I easily get 4 720p24 clips on a dual G5 and at least 3 1080i60 ones.
> At least 6 DV clips are possible as well.
>

the real bottleneck here isnt the cpu, nor the gfx card, but the bus, either 
agp, pci, whatever. for a dual g5 it just sucks to handle only 4 clips, as 
well as for any other modern machine.

open gl isnt meant for doing video stuff, thats it. you cant expect your 
machine to pump excessive amounts of data through the bus to the card just 
because that particular card's open-gl is fast. it wouldnt be a big problem 
to project the same video onto many objects with little effort, since it 
would be uploaded only once. but having three videos means 3 times the data 
is flowing through the bus.

you could also use plain framebuffer cards, either rgb or yuv, and the net 
result would be the same. many high end video editing solutions a few year 
agos had their own scsi bus on the video card, to bypass all that and thus 
allowing for many streams "at once on the fly"

im pretty sure that it would be more performant to do the raw mixing on the 
host cpu and the use the result to feed gem...... even more when doing that 
with optimized mmx/sse/altivec code. the gfx card may be theortical able to 
that as well, probably more complex arrangements as well, but it comes to an 
halt when it comes to transfer the seperate streams to the card ....

maybe a way would be to implement the decompression onto the gfx card itself, 
so that the compressed streams can go directly to the card, either mpeg, 
mjpeg, or whatever.

greets,

chris