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Re: RAM and quartz composer

Hi Ben,

Attempting to avoid hitting the hard drive at all costs may actually hamper what you're trying to do. So, with that, what are you trying to do (technically, not specifically)?

An example where hitting the HDD is likely a good thing is streaming of video. Imagine the visual processing pipeline as a giant waterfall. It looks really good if you can organize things so the data streams off the drive, gets decoded on an on-demand basis, and rolls that onto the screen. To make things move smoothly (if you're a budding programmer) you can "preroll" your video sources with the quicktime APIs and feed that data on demand. Why would this be good? You relieve yourself of long start-up times, and open the door to more content-heavy options. I am not sure if QC has an option to explicitly pre-roll its video sources but it is likely already doing that for you by default (Pierre?).

Pre-loading everything into ram could take a long time, on the order of 5-10min for 3GB of content, and likely much longer if you have hundreds of clips. I'm assuming you are designing this system for some sort of live presentation. In the event of a crash (already a bad thing), having a long start-up time becomes disastrous.

There are other reasons to use streaming over loading everything into RAM, but those reasons get deeply technical and have everything to do with the magic of making the operating system work smoothly. In case you're curious the OS can use some tricks like - memory mapping of streaming data eliminating redundant storage in paged memory, swapping out unused RAM for more caching head-space, and copy-on- write allocation (very important for the video decompression sequence).

Anyway, enough blathering on my part. If you're smart with what video clips are streamed, stored in ram compressed, or stored in ram uncompressed, then you shouldn't have any problems with swap impacting your frame-rate no matter your quantity of RAM (2-4-8GB).

Finally, keep an eye on your RAM usage with Activity Monitor. In my opinion even 2GB is excessive, with well compressed video you could have an hour worth of clips in memory, with more ready nearly instantly with streaming. If you expect to do a lot of work with Motion 2, then by all means load that puppy to the gills with RAM, it'll use it!! But IMHO, QC won't really benefit. The difference? When editing in Motion, scrubbing demands everything to be in RAM, but QC plays mostly linearly so streaming works fine.

Sounds like you're going to be playing with some mighty impressive hardware. Btw, I don't think the Quadro will give you much more power over the 7800. The Quadro is specifically tuned for CAD applications with lots of line-rendering speed and precision but slightly slower overall rendering performance. (I could be wrong on that though!) Anyway, some tricky considerations when money is no object!

Good luck!
- Aaron.

On 19-Nov-05, at 10:49 AM, Ben Greenfield wrote:


On Nov 18, 2005, at 9:29 PM, John C. Randolph wrote:


On Nov 18, 2005, at 5:16 PM, Ben Greenfield wrote:

All things being equal is there a compelling reason to specify 8 GB over 4 GB of ram?

Should I start with 4 and see where I stand?

I'd start with one, actually.

Ok, I just don't want to have to hit the hard-drive while running. I may still start with 4 GB

Is the best graphic card a simple question?

My guess is that it is one of 2 Nvidia cards that has 512MB installed for ram. I was going to start with the 7800 and then if needed move to the Quadro 4500. This choice seems obvious because there are no other choices.

Running QC compositions isn't particularly memory-intensive. 


It seems like a want to avoid the HD at all costs.

Thanks,

Ben



-jcr

John C. Randolph <email@hidden> (408) 914-0013
Roaming Cocoa Engineer,
Available for your projects at great Expense and Inconvenience.




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References: 
 >RAM and quartz composer (From: Ben Greenfield <email@hidden>)
 >Re: RAM and quartz composer (From: "John C. Randolph" <email@hidden>)
 >Re: RAM and quartz composer (From: Ben Greenfield <email@hidden>)



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