Digital Video Questions? Answers from an Expert
While working with digital video editing, we often face questions that make us wonder. For example, have you ever wondered what role graphics cards have in digital video editing? Have you asked yourself when a fast disk might be a big help and when it doesn’t matter? What about RAM -- how much is enough, and is there a limit to how much Windows can use? And what about all this codec stuff? To get the answers to these and other complicated techno-digi-vid questions, Digital Media Net's Charlie White talked with Boxx Technologies Guru, Founder and Chief Technology Officer Todd Bryant, whose company has successfully dealt with these questions and much more. Prior to founding BOXX, Bryant held senior engineer positions at Micron, Texas Instruments, and Applied Materials.
DMN: What role do graphics cards have in digital video editing?
Bryant: Currently, not too much when it comes to most of the good digital video editing systems out there. There are, though, more and more companies that are looking into open GL calls, along with Direct X stuff to actually manipulate video in real time using the graphics processor. And they're very good at doing that -- that's what they're built for, is to pixel-push. If you look at companies that are doing this, like AST, I know they use some Open GL to accelerate some of their stuff. 5D uses the graphics accelerator to do a lot of effects. There are a lot of companies that are looking into this. Graphics cards are built for video processing, so I think that as you come forward, even us, we're looking at using it as a manipulation tool, as well. It's very good at doing color correction for you on the fly.
So there are a lot of things that are possible for hardware and software manufacturers to do with graphics cards. I just don't think they're exploited too much because the processors that are capable of doing this kind of stuff typically have not been available at a low enough price. Now they're starting to become more readily available. Most people don't want to go out and buy a Wildcat III, for example. But the price points have come down enough that it makes it almost worthwhile. With the Quadro4 stuff with NVidia bringing these very good video processing engines down to where they are very affordable, developers now, I think, are going to start looking at using that power that's in the graphics processor instead of using the CPU. You'll start seeing situations where you'll use it for preview, and then once you get everything set up, it saves it and then it has to software-render out the back end. But at least you're interactive with your material. There are some things in hardware are very difficult to do -- such as hard calls. When you look at software rendering it's sometimes still better than hardware rendering. There will be some things that developers may do with a graphics card for effects, making it more interactive than it would be for the final rendered effects, and as a last step you would software-render it in the background. But at least that would keep you interactive with your material.
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DMN: The graphics card also comes into play, for example, in Adobe Premiere, when you want the screen to redraw all the little picons on the timeline, and if you're using a faster graphics card, it'll redraw faster, and you won't have to sit and wait for that.
Bryant: That's correct. Where it comes into play right now is, how fast your interaction is. It may not be rendering, but it sure helps with the playback of material to the computer screen. On our Boxx system, the better the graphics card in the machine, the faster After Effects seems to work. After Effects always renders the image back to the screen for a preview -- you're not rendering back down to the disk array -- so the faster refresh the card has, the more interactive your material is. We've seen this, very much so, when we're looking at a simple Matrox 450 card versus a Quadro2 card. The difference is night-and-day. You're really herky-jerky with the G450 but the Quadro2 is very smooth, and it's more interactive. This is working with HD, 2K film rez. So it does come into play a little bit more with compositing, because compositors use the graphics card for a lot of refresh, and the faster the refresh, the faster your interactivity is. What people are doing now is, yeah, you can be interactive with it, but you're still going to have to place the comp into a render queue, to render all the frames because it's going to software render them.
DMN: You mentioned having a fast disk for After Effects. Isn't it true that your After Effects graphics are loaded into RAM and then rendered? Where do the disks come into play there?
Bryant: On After Effects, most users do RAM previews, but when it goes to rendering, it's rendering all down to the disk array. With After Effects composites, you can't render very fast, meaning frames per second. So the disk array doesn't play as much into that. When you come into something like when we're doing a one-second-dissolve in HD resolution with our BoxxHD system, right now it takes about 2.4 seconds for a one-second dissolve, we're using 100% of the CPUs while our next-generation stuff which is all Xeon-based we'll do a one second dissolve in 1.4 seconds. We can't go any faster because now we're limited to pulling data as quickly as we can off disk array. We're only using 17%-20% of the CPUs. So, we need faster disk arrays to get faster rendering.
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