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Re: RAM and quartz composer


On Nov 20, 2005, at 1:06 AM, Aaron Hilton wrote:

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)?

This project will involve the modeling of financial data. The forms will be created in maya and composited with other audio and video content.

There will be 2 monitors per topic. One monitor is a touchscreen interactive running at 1280 x 1024. The second monitor is a projector running at 1024 x 768.

The touchscreen monitor will contain X number of animations depending on menu selections made by the user. I imagine these to be canned animations that play frequently and repeatedly. The projector may also consist of canned animations but there may be some requirement of real time rendering of financial models. These models will be created in Maya? and have data associated with them using QC. This screen will also have video and audio files associated with the models

This is a quasi public financial exhibit that will be started in the morning run the same content all day long for 5 years.

My ambition is to load 2 graphics cards (7800s) into a Quad processor G5 and then tie content from many sources together using QC. This is just and exhibit it only has to look real.


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.

We may have redundant hardware for this, but I will note that a short start-up time is probably a good feature. Long start up time is bad if not necessary.

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. 

This is why I thought more memory would be good.

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).

I'm definitely curious. Maybe I'm stuck in 1990's but it seems like this will still running the machine towards it's limits and I want to provide resources for every optimization trick that may be needed.



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.


This was my impression, and there is some sort of display linking that can be done with identical cards. I don't know if I need that but it seems I may be better off going with identical cards, rather then introduce needless variation.



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>)
 >Re: RAM and quartz composer (From: Aaron Hilton <email@hidden>)



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