I have a question about Data Rates.

Question

Hello All.
This is a bit of a noob question I'm sure. I don't think I really understand Data Rates and how it applies to Motion... therefore I'm not even sure what kind of questions to ask. I've been reading up online and thought I would ask some questions here. Thanks to all in advance.
I've never really worried about Data Rates until now. I am creating an Apple Motion piece with about 15 different video clips in it. And 1/2 of them have alpha channels.
What exactly is Data Rate? Is it the rate in which video clip data is read (in bits/second) from the Disc and placed into my screen? In Motion- is the Data Rate for video only? What if the clip has audio? If a HDD is simply a plastic disc with a dye read by "1" laser... how come my computer can pull "2" files off the disc at the same time? Is that what data transfer is all about? Is that were RAM comes into play?
I have crunched my clips as much as I can. They are short clips (10-15seconds each). I've compressed them with the Animation codec to preserve the Alpha channel and sized them proportionally smaller (320x240). This dropped their data rate significantly. I've also taken out any audio that was associated with them.
Is data rate what is slowing my system down?
The data rates are all under 2MBs. Some are as low as 230Kbs. They were MUCH higher. However, my animation still plays VERY slowly.
I'm running a 3GigRam Powerbook Pro 2.33GHz.
I store all my media on a 1TB GRaid Firewire 800 drive. However for portability I'm using a USB 2 smartdisk external drive. I think the speed is 5200rpm.
I'm guessing this all plays into the speed at which motion can function.
If I total my data rate transfer I get somewhere in the vicinity of 11MBs/second. Is that what motion needs for it to play smoothly a 11MBs/second data connection? USB 2.0 is like what 480Mbs/second. So there is no way it's going to play quickly. What if I played it from my hard drive? What is the data rate of my internal HDD?
I guess my overall question is.
#1. Is my thinking correct on all of these topics? Do my bits, bytes and megs make sense. Is my thought process correct?
#2. Barring getting a new machine or buying new hardware. What can I do to speed up this workflow? Working with 15 different video clips is bogging Motion down and becoming frustrating to work with. Even if only 3-4 of the clips are up at a time it bogs things down. Especially if I throw on a glow effect or something.
Any help is greatly appreciated.
-Fraky

Answer 1

Data rate DOES make a difference, but I'd say your real problem has more to do with the fact that you're working on a Powerbook. Motion's real time capabilities derive from the capability of the video card. Not the processor. Some cards do better than others, but laptops are not even recommended for running Motion.
To improve your workflow on a laptop will be limited, but there are a few things that you can try.
Make sure that thumbnails and previews are turned off.
Make sure that you are operating in Draft Mode.
Lower the display resolution to half, or quarter.
Don't expect to be getting real time playback. Treat it more like After Effects.
Compressing your clips into smaller Animations does help because it lowers the data rate, but you're still dealing with the animation codec which is a high data rate codec. Unfortunately, it sounds necessary in your case because you're dealing with alpha channels.
The data rate comes into play with your setup trying to play through your USB drive. USB drives are never recommended for editing or Motion work. Their throughput is not consistent enough for video work. a small FW drive would be better, though your real problem as I said is the Powerbook.
If you must work on the powerbook, then don't expect real-time playback. Instead, build your animation, step through it, and do RAM previews to view sections in real time.
I hope this helps.
Andy