Real-Time Previews
For a few years, we’ve seen special hardware that has been labeled "real time," but you’ll notice it is rarely claimed that you won’t need to render. And now we find that nearly every software editor also claims real time. Yet, when we fire up the editor and attempt to dump DV video back to our camcorders (DV In, DV Out), we find that the project still needs to be rendered. Most real-time hardware and software will provide real-time previews only.
But let’s not get too negative about this. While we feel a bit cheated that we don’t get real-time DV out from most solutions, real-time previews are extremely useful. At a minimum, real-time previews are not full-frame size or frame rate, but they do allow you to see what the final video might look like. And many of the real-time hardware cards output full-frame size and frame-rate video at full quality via an analog connection (S-video or composite RCA). This is no minor feature and is a huge boon to editors.
Basically, every software package released in the last year or so does real-time previews. The quality of those previews is entirely dependent on the complexity of the effects and the speed of the computer. Dual-CPU computers running at speeds up to 2.4GHz are very capable of producing real-time previews. Another important aspect of real-time previews is whether the application can output DV (through your camcorder and to a television), even a single frame, to a monitor in order to judge color, interlacing and masking.
Real-time preview software can have a little surprise for you at the end of the day. Imagine two experienced editors, one using Adobe Premiere 6.0 (not real time) and one using Sonic Foundry Vegas Video 3.0 (real-time software previews). As they edit the same project throughout the day, we notice the Vegas editor moving along much faster, previewing instantly, while the Premiere person waits for red render bars. Then, around 4 p.m., the boss wants to see a draft on DV videotape. While the Vegas user’s project is complete, it is now time to render the project to DV. The entire project: fades, titles, effects nothing is ready to go back to the camera. As you know, this can take a significant amount of time. The Premiere user, on the other hand, has not quite completed the editing, because editing itself has been slower. Still, render-as-you-edit delays mean that the project is DV-ready when editing is complete and an Export Timeline command is all that is required to output the project to DV.
Which is better? Vegas lovers will say that the uninterrupted workflow during editing is worth the cost of render time at the end; you need to take breaks occasionally, anyhow. Premiere aficionados will validly counter that the frequent 30-second renders throughout the day are a reasonable cost for being able to play back the timeline to DV, not to mention that you save space on your computer by not needing to create a finished AVI file.
We’re not going to take sides in this holy war except to say that you can wait now or wait later, but effects must be rendered at some point. And Premiere and Vegas are just two examples. In the wait-now camp, we find appliances like the Casablanca Kron and the Edirol DV7, both of which render effects when you insert them onto the timeline, but the timeline is always ready for DV. In the wait-later camp, you’ll find Apple Final Cut Pro, Avid and most Premiere real-time hardware solutions. And there are also hybrids, like Ulead MediaStudio Pro, which offer real-time previews, but can also render-as-you-go, if you prefer.
You can also achieve real-time previews with special hardware cards. These cards were primarily designed to make Premiere 6.0 (and earlier) do real-time previews and are irrelevant to anyone using any other applications (which all do real-time previews now, anyhow). Real-time preview cards for Premiere, such as the Matrox RT2500 and the Pinnacle Pro-ONE, are usually more capable than software-only solutions that rely on processor speed and can output full-frame-rate video to an S-video connection. There are some other advantages to using one of these cards, one being that the included hardware effects are quite beautiful. And when you consider that the cost of these cards typically includes not only Premiere, but also a whole host of other applications that would easily cost you more than the card if you had to buy them separately, the price is very reasonable.
Really Real Time
But, what we really want is real-time DV In, DV Out. We don’t want to have to render, ever again. With some limitations, that time is here. We would consider an editing environment (hardware and software) to be really real time if it could do the following without rendering: a solid black background, one layer of moving titles over video and crossfades. And it would need to be able to do this all at the same time (e.g. a rolling title sequence over a video clip fading in from black). This would accommodate 90 percent of everyday editing and would please us to no end. So what is out there that can do this?
The short answer is Canopus cards (such as the DVStorm) and Premiere. This solution is not perfect, and what about all of us who don’t use Premiere? Canopus cards are proprietary IEEE 1394 solutions that do not follow the OHCI standard, which is something to consider, although we haven’t seen or heard of problems associated with this strategy.
One final aspect of this worth emphasizing is that if you don’t need to go back to DV, many hardware solutions are really real time. A great example of this is NewTek’s Video Toaster 2, which does real-time, uncompressed, S-video or even component video out at all times. If you have professional uncompressed YUV video coming in, why would you even worry about whether the product does DV out?
Cheating Real Time
We’ve also seen another solution to the real-time dilemma that we really like: background rendering. Background rendering performs an end-run around the whole waiting game, automatically rendering edits as soon as you make them. Hopefully, by the time you are ready to preview the project, the sections that need rendering are already finished. Granted, the render didn’t happen in "real" real time, but if you don’t need to wait, we feel background rendering can completely satisfy the true spirit of real time.
Perhaps surprisingly, Apple’s beginner-level iMovie 2 leads the technology trend here with a great implementation of background rendering. Other great solutions include the DV7 editing appliance, the Toaster 2 and the new Pinnacle Edition editing software. We hope other developers are planning to include background rendering in their next releases.
Better than Real Time
Many of the solutions talked about in this article do real-time S-video, and if that is what you need, there are many excellent options available for you. But if you want real-time DV out, ask the manufacturer the following question, point blank:
"When I do a crossfade between two clips, will I need to wait before the video is ready to go back to a DV camcorder?"
Nothing can ever be better than real time. As computers get faster, rendering speeds will eventually be magnitudes faster than real time, but you can’t watch movies faster than real time, so it is all irrelevant once the magic threshold is reached.
[Sidebar: Is Real-Time DV Out Possible?]
Many of the real-time hardware systems discussed in this article do real-time S-video and even component out, but ony Canopus cards do real-time DV out. Canopus suggests that real-time DV out is not possible using the most common IEEE 1394 chipsets found on most IEEE 1394 cards. Canopus' solution was to design and build its own custom DV chipset (not OHCI compliant). Of course, this was not a cheap solution and Canopus cards demand a higher price, but are worth it if you need real-time DV out.