Battle of the Software NLEs, Part 3: Slow Motion and Image Stabilization
Our Battle of the Software NLEs series continues with a look at two key effects for pro video editors: slow motion and image stabilization. While slow motion is popularly used to enhance detail during action shots and add drama, image stabilization is more of a corrective, reducing shakiness on footage that couldn't be shot with a tripod. Once again, we face off our five familiar contenders: Adobe Premiere Pro, Apple Final Cut Pro, Avid Xpress Pro, Pinnacle Liquid Edition, and Sony Vegas.
Welcome back to our four-part series on software NLE performance and workflow. In the first two installments we explored chromakey and overlay, followed by HDV editing. In this episode, we'll turn our attention to two essential features that often have been lacking in mainstream prosumer nonlinear editors: slow motion (a.k.a. motion control) and image stabilization.
In earlier articles exploring the more sophisticated and pro-centric features of NLEs, such as Stephen F. Nathans' "Pro Tools, Pro Tasks" (March, pp. 22-29), we've found NLE vendors pointing us to third-party plug-ins and other alternative sources for most effective motion control and stabilization performance. In some cases, these plug-ins have been cheap and accessible and fit well into existing workflow; in other cases, they've tipped the cost and usability scales away from the NLE in question.
Nearly all the tools we're examining in this series—Adobe Premiere Pro, Apple Final Cut Pro, Avid Xpress Studio, Pinnacle Liquid Edition, and Sony Vegas—have come out in new versions since last we explored these issues. Most recently, Avid has announced an incremental upgrade to Xpress Pro to add HDV support, something that was lacking when we did our HDV editing tests. We'll update the HDV results on www.eventdv.net after we get the HDV-capable version of Xpress Pro in for testing.
Slow motion is a popular effect used to provide greater detail during action shots and also for dramatic effect. Editors use two techniques to produce slow-motion videos. The easy way is frame replication, where the editor simply reproduces the same frame for a longer period; say, one extra frame for each original frame when cutting speed to 50% of original, or three extra frames for each original frame when cutting speed to 25%. Though the frame detail remains sharp, the video looks choppy because of the longer period each frame displays.
Otherwise, editors use interpolated techniques to create "tweener" frames between the original frames. When cutting speed to 25% of the original, for example, the editor would create three frames between each original, analyzing the original frames and attempting to create intermediate frames that simulate what the frames would look like if actually captured at 120 frames per second and slowed to 30. These techniques can smooth the motion, but since the editors essentially are making up information, they also have a tendency to create artifacts in the video.
Tweening techniques work least effectively when the video contains fine detail because it's difficult to create tweener frames that don't contain obvious imperfections. Using a golf video for our tests, we created a slow-motion video with every interpolative technique available in each program and analyzed the quality and smoothness of the results.
We also noted whether an editor could create dynamic speed changes, like slowing from 100% to 25% over one second, rather than static speed changes that are more visually abrupt. When available, we used this feature to slow dynamically the speed of another golf video and commented on the feature's ease of use.
Adobe Premiere Pro
Premiere Pro has a simple static speed control that lets you change speed by percentage or by setting a new duration. Check the Frame Blend checkbox in the Field Options screen accessed by right-clicking on the clip, and Premiere will interpolate between frames, which often results in two or three club shafts showing in the same frame, with minimal background shimmer, a problem that plagued other editors.
Otherwise, it's simple frame replication, with a distinct choppy look. Premiere Pro does not offer variable-speed changes.
Apple Final Cut Pro
Final Cut Pro also offers frame replication and frame blending, though we noticed significant shimmer in the background with frame blending applied. Without frame blending, Final Cut displayed both fields in each frame, which usually resulted in two club shafts in every frame (see Figure 1).
Perhaps de-interlacing and progressive output would eliminate this artifact, but other editors avoided this problem without the extra work. Accordingly, neither alternative worked particularly well with our test clip.
Final Cut also offers variable speed changes, but the control is very obtuse, especially compared to the simple elegance of Sony Vegas. For example, all other tools apply the dynamic speed changes only within the selected clip. In Final Cut, if you change the speed of a single clip, it potentially affects all clips past or future on the timeline. Click preview, and you could end up watching a clip located before or after on that clip on the timeline, scratching your head and wondering why. There's definitely potential for usability improvement here.
Avid Xpress Pro HD
Avid offers four interpolation techniques for static speed changes: Duplicated fields, Both fields, Interpolated fields, and VTR style, while providing no real direction as to application. Our tests revealed Duplicated fields and Both fields to be simple frame replication, with one frame displayed for four frames. The video looked choppy, with minimal background shimmer. Both fields were slightly sharper.
Interpolated fields produced high-quality tweener frames with the appropriate one club shaft per frame, but also displayed unacceptable background shimmer and a jittery effect where the frames bounced one or two pixels up and down during display. VTR style merely exaggerated both negative effects. Perhaps these techniques would prove effective on video with minimal detail, but on our test clip, they were a wash.
Avid doesn't offer true variable-speed controls, but does provide several variable-speed presets that might be useful in some projects, like 0%-100% (a.k.a. speed bump), which starts out at full speed, then slows to 50% at mid-clip, then jumps back up to 100%.
Pinnacle Liquid Edition
Pinnacle Liquid Edition offers six interpolation techniques, but four are frame-based, and intended for use in film production. The two field-based effects are Mix fields and Cut fields. Mix fields produced the smoothest video in the roundup, with no shimmer or shake, though multiple club shafts were visible during playback. Cut fields was slightly less smooth, but each frame displayed only one shaft. Overall, Cut fields was probably the best quality we saw in the roundup.
In terms of ease of use, Edition's variable speed control sits squarely between Vegas' sublimely simple tool and Final Cut's over-complicated controls. Plan on at least 30 minutes for first-time use and arming yourself with a good third-party manual (we used the excellent Visual QuickStart Guide from Peachpit Press, edited by EventDV's own Jeff Sauer).
When applying a slow-motion effect in Vegas, you can force frame smoothing—or interpolation—or disable it, which activates frame duplication. Though we liked the individual frame quality of the frame smoothing technique, it was accompanied by some background shimmer, which the de-interlace filter did not eliminate.
Notwithstanding these quality issues, what we absolutely adore about Vegas is the simplicity of its variable speed control. You simply apply a "velocity envelope," which is a rubber band control like that often used for variable volume control. To vary the speed of a clip, you right-click to add a control point, which you then drag up to increase speed, or down to decrease it (Figure 2). Our only complaint is that Vegas doesn't automatically adjust clip length to account for the speed changes, but this is a common problem shared by most programs.
The first rule of shooting video is to always use a tripod. While this works in some settings, sometimes it's simply not possible, which leads to shaky video. Recognizing this fact, four of five programs in the review offer an image stabilization feature, with Edition out in the cold. (Pinnacle typically recommends that users rely on its Commotion effects software for image stabilization, but that's an additional $499 investment.)
Interestingly, image stabilization in software works much like image stabilization in hardware. Specifically, the software senses motion in the image, either automatically or with cues from the user, compensates by shifting the frame in the appropriate direction, and then zooms into the frame to hide the edges created by the shifting frame.
Not all programs perform these functions automatically. For example, some force you to identify a static object in the scene, while others force you to zoom into the clip manually to eliminate the edges, which can also be time-consuming.
Accordingly, when testing these features, we evaluated both ease of use and output quality. We tested stabilization with three scenes: handheld footage of a parade, a shot of a tour guide on a bouncing bus, and a concert shot with a handheld camera.
Premiere Pro hits the daily double, with the best ease of use and output quality courtesy of the surprisingly functional SteadyMove plug-in from 2d3. There are two simple controls to apply (or not; we used the defaults), and the plug-in tracks the motion automatically, zooms in automatically, and produces stable, artifact-free video, as shown in Figure 3.
Final Cut can work automatically, but also lets you manually track objects with keyframes, an option we used in an attempt to maximize quality. Our efforts were not rewarded, however, as the final videos proved overly jittery and artifact-laden.
With Xpress, to customize image stabilization, you select a section of the video that's supposed to remain stable (called "region of interest") and then click Auto Zoom to eliminate exposed edges. The tool's effectiveness varied by clip.
In the parade video, Xpress zoomed deeply into the clip to eliminate edges, which reduced the shakes but created some zooming artifacts. This was also apparent in the bus video, but the zooming (and associated artifacts) were not quite as severe. Premiere was the clear winner in both of these clips. In the concert video, however, which probably represents the most likely real-world use, the situation reversed, and Xpress zoomed in less and eliminated more shakes, producing the best looking, most stable video in the review (Figure 4).
Vegas bundles image stabilization tools from Boris FX Limited. As bundled, you use these tools as separate utilities, though you can pay more and get a plug-in that works within Vegas. Since most of our concerns are workflow and interface-related, that may make sense.
For example, to use the program, you have to export your videos from Vegas, stabilize in Boris, and then re-import the output from Boris. This takes time and adds a DV generation to the footage.
The Boris program itself is primitive and hard to use. For example, you can't just import a file and start working; you have to set duration, resolution, and field order, and then import. There is no DV preset for output, so you have to work through multiple encoding options to output your file.
Once you get started, Boris lets you choose a stable object once or track it with keyframes through the video, which we did with all test clips. There is a way to zoom into the finished frame to eliminate edges, but I never figured it out, and performed this manually in Vegas.
Boris produced a very stable image in the parade video, but the images in the other two were jerky with frequent interlacing artifacts, most likely because I chose the wrong field order or output parameters. While this utility shows great promise, usability needs to be vastly improved, and the function is infinitely better accessed as a plug-in rather than a standalone application.
In next month's final installment, we'll look at slideshow features and rendering, and draw some overall conclusions about which tools performed best in the ongoing Battle of the Software NLEs.
Previous Articles in the Battle of the Software NLEs Series
Companies Mentioned in This Article
Adobe Systems www.adobe.com
Apple Computer www.apple.com
Avid Technology www.avid.com
Pinnacle Systems www.pinnaclesys.com
Sony Media Software www.sonymediasoftware.com