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Avid Pan & Zoom

One of the long-desired feature requests for Avid users has been the ability to do "motion control" moves - ala Ken Burns' documentaries - on high resolution stills. There are several excellent products that allow you to do this in the AVX effects architecture, namely Boris FX or RED and Stage Tools' MovingPicture and Profound Effects' Move. Now, Avid has finally delivered its own AVX software - called Avid Pan & Zoom - to deliver this oft-used effect and the really good news is, it's free for just registering your copy of Avid Xpress DV.

After registering, you can download the installer from the web and the unlocking code is then emailed to you. The installation is fairly simple and the first time you attempt to import a file through the plug-in's interface, you are prompted to type in the code.

Most AVX effects are written for both Mac and PC and this one is no exception. I only attempted the Mac installation, which went very smoothly, including a fairly quick download that I accomplished through - horror of horrors - my AOL dial-up account! I also tried the download on my company's T1 line, which managed to accomplish the task in about 30 seconds. I won't go through the install procedure, since it is fairly easy, self-explanatory and well documented.

Using the plug-in is also a piece of cake, although for some editors who have not played with AVX plug-ins very much, there are several fairly counter-intuitive steps to the process.

The first part of the process that is less than intuitive is that because the high-res file that you want to "Pan & Zoom" must be imported into the plug-in itself, the actual piece of video that you drop the effect on in the timeline has nothing to do with what you will see when the effect plays! You can cut ANYTHING into the timeline for the duration that you want to "Pan & Zoom." Anything, that is, except filler. I tried that. It doesn't work. The easiest thing to do, I suppose would be to import your high-res file as a regular clip, probably using the Square pixel, Maintain (meaning "maintain aspect ratio" of the file) and Resize setting in the import dialog. Also, make sure you import it with a long enough duration. The duration of the import does not effect memory or storage usage, so you might as well make it 30 seconds or so instead of the 10-second default. But as I said, you don't need to import the file into a bin at all. You could cut 20 seconds of your Aunt Milly from your brother's wedding into your timeline. It just doesn't matter.

Once you have a clip in your timeline, there are a couple of different ways you can access the Pan & Zoom effect. You can press Shift-F10 to open the Effects Editing Toolset, choose the Avid Pan & Zoom effect and place the effect, or you can hit command-8 (Mac) or control-8 (PC) to call up the effects palette. At the top of the list of effects on the left side should be Avid AVX RT. Select that and Avid Pan & Zoom appears on the right side of the Effects Palette. Drag the Pan and Zoom icon to the clip in the timeline.

Once the effect is on the clip, click on the Effects icon to go into Effects Mode In the Effects Editor window, you'll encounter the second fairly non-intuitive step. To load the hi-res image, you click on the Custom UI button at the top left of the Effects Editor window. This calls up a browser that allows you to locate the file and import it.

After that, things will make sense with or without the users manual. But let's take a look at the Effects Editor window from top to bottom. The first thing is the Display mode. The two options here are Source and Target. Neither has anything to do with the final rendered image. In Source Mode, you will see the entire image scaled to fit inside the desktop display. This allows you a kind of "birds-eye view" of your moves, which are indicated by a TV aspect rectangle superimposed over the image. This is the easiest mode to use when planning your moves. In Target Mode, you see what the final output will look like. This is a good mode to use for previewing your moves. If you do use this mode in combination with the real-time filtering options, don't worry about the pixelated quality of the image. The quality of the render will be determined by the filter mode chosen just before the render is executed.

Size is the parameter that determines how far into the image you zoom in or out. This is pretty self-explanatory. If you are adjusting this parameter while viewing in Source Mode, the larger the magnification, the smaller the rectangle will be. This is because the rectangle is indicating the area that will be displayed on the monitor on output.

The Position parameter is also fairly obvious. The X parameter adjusts sideways or horizontally, the Y parameter adjusts up and down or vertically. (If you ever wanted a mnemonic to help remember this, I always thought that the X could look either like the ends of arrows pointing up and down or side to side, but the top of the Y looks like the end of an arrow pointing down.) You can certainly use these sliders, but the primary intuitive interface for making positional adjustments is dragging the rectangle in Source Mode or dragging the "crosshair" in Target Mode. For fine detail movements while the X and Y parameters are active, you can use the arrow keys on the keyboard or even numeric entries.

In order to see movement, you must have a different size and/or Position set for at least two keyframes. The default when you create a Pan &Zoom effect is that there are only two keyframes and both of them are selected. To see movement you need to pick one or the other of the keyframes and adjust its parameters so they are different from the other keyframe. Multiple keyframes can be placed on the effect timeline.

The Velocity parameter is a slight departure from typical Avid-speak. In all of the other Avid effects, this is referred to as Acceleration. Velocity is a little more involved than the typical Avid Acceleration command, but basically does the same thing. Most 3D "ADO" style moves don't look very good with no acceleration or "velocity." It makes the move look too mechanical. This is especially true of the kind of moves that Avid Pan & Zoom is designed for. All natural movements have a gradual acceleration at their beginning and a gradual deceleration at their end. Animators call this "ease in" and "ease out." The Velocity parameter has two components. One to regulate the way the move begins - Velocity In - and the other to regulate the way the move ends - Velocity Out. The Velocity In choices include Linear, Ease In and Constant. The Velocity Out choices include Linear, Ease Out, Constant and Hold. If you only program a two-keyframe effect, your choice is pretty basic. You use Ease In and Ease Out.

For multi-keyframe moves, your choices are more complex. You probably don't want to use Ease In and Ease Out for each keyframe, because your move will end up "bouncing" between keyframes like a car continually slowing down then accelerating at a series of stop signs. Chances are you only want the move to accelerate at the start of the first keyframe and decelerate only into the last keyframe. To do this, the Velocity In on the first keyframe should be set to Ease In and the Velocity Out to Linear. Each subsequent keyframe should be set to Linear for both Velocity In and Velocity Out until the final keyframe, which should be set to a Velocity In of Linear and a Velocity Out of Ease Out. This is because Linear for Velocity In describes the acceleration of the move from the selected keyframe to the halfway point between it and the following keyframe (e.g. the first half of the move to the next keyframe), while Linear for Velocity Out describes the acceleration from halfway to the next keyframe to the next keyframe (e.g. the second half of the move to the next keyframe). As a word of warning, this process is described backwards in the documentation.

The other choices for acceleration are Constant - which means the keyframe will not be regarded in the velocity calculation - and Hold - which means that there will be no movement at all until the next keyframe and the value of the next keyframe will be ignored. Experiment with these choices while using the Real-time filter before committing any of these movements to render.

The Path parameter determines how the position is interpolated between keyframes. The options here are Linear and Spline. With Linear interpretation, the path from one keyframe to the next is a straight line, like the ball in a game of Pong or pool. With Spline, the path is more like a slalom skier, creating a graceful, curved path from one position to the next.

Filtering determines the actual render quality of your move. This is going to take a little experimentation for you to find a mode that delivers the quality you want. I won't attempt to make a subjective determination of the quality of each filtration method, but I did do some subjective render speed experiments using the same multi-keyframed move on the same image. Here are the Filtration types and the render times on a 10 second move:

	Realtime		no render time
	Triangle		2:20
	Quadratic		2:20
	Cubic		2:36
	B-spline		2:42 (the best overall choice for quality and performance)
	Gaussian		2:21
	Hi Quality		3:50
	Ultra High		8:30

This is probably a good time to mention a little tip that most experienced Avid editors probably know already. When you start a render, you can see either the percentage of the render that has been completed by hitting "P" on your keyboard, or the estimated time to complete the render, along with the amount of time already spent rendering the effect by hitting "T" on your keyboard. More advanced Avid products also have a great, though little known feature, in the Render Settings, which allows you to watch the render progress. This doesn't take any noticeable hit in render speed and allows you to see "renders gone bad" before you waste a huge amount of time rendering. As soon as you notice that you've forgotten to turn on some parameter or the effect doesn't look right, you can stop the render without waiting to see the entire thing. I always have this setting turned on when I'm editing on boxes with the option.

The Background choice allows you to fill in any areas of the screen if the Pan & Zoom hi-res image doesn't fill all of the screen. Your choices are to choose a colored background or to use video from the timeline.

Don't let Advanced Parameters scare you. You can be fairly sure that Source has Square Pixels is the correct answer for nearly any hi resolution image. Non-square pixels are really only for frames captured from video. Similarly in the Levels setting, ITU-R-601 is for "video level" signals, which you probably aren't importing. The RGB settings are for images that have 0,0,0 as a base RGB black level and 255, 255, 255 for white. These are then mapped to the video black and white levels. You'll see different information in the documentation than what I've listed here, but Avid has confirmed the above information is correct.

Finally, there are the Cache settings to consider. Video resolution should only be used if there are multiple images back to back and very little RAM; you're better off using Image resolution or, better yet, Multi resolution before you render. Multi resolution is the best option as it makes render performance significantly faster. Free Current RAM is an option that can be exercised to free up RAM after a clip is rendered. Cache All sets the same parameters for all instances of the plug-in in the sequence.

Other than a few little gotchas, this is an easy to use effects interface that allows you access to the look of a high-end motion control stand. An ideal solution for everything from wedding and educational videos to documentaries. For additional similar tools from 3rd party vendors, check out: http://www.avid.com/partners/avx/displaypartners.html

Steve Hullfish produces and edits trailers, TV spots, and DVDs for Big Idea Productions, who just released their first major motion pictures to theaters in the US: Jonah - a VeggieTales Movie. His first book, with co-author Jaime Fowler, Color Correction for Digital Video: Using Desktop Tools to Perfect Your Image, will be released in November of 2002 by CMP Books. It provides detailed, step-by-step advice on color correction, including examples using the new color correction tools in Avid Xpress DV v3.5.