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Multicam Roundup: Part 1

May 1, 2006 12:01 PM, By Jan Ozer

Putting NLE multicam features to the test.

Most video producers would agree — you can't be too skinny, too rich, or have too many camera angles. Though multicamera shoots can be a logistical challenge, the ability to switch to different angles while editing almost always justifies the effort.

It wasn't that long ago that you had to edit those multiple streams by hand — line up the tracks on the timeline, synchronize the streams, and cut away the video you didn't want. Today, most NLEs, including Adobe Premiere Pro, Apple Final Cut Pro, and Avid Xpress Pro HD, have native controls for handling multiple cameras, while Sony Vegas has a well proven third-party plug-in from VASST.

To a degree, the features are very similar. You capture and then synch your clips, usually via mark-in and mark-out markers on the timeline or timecode. Then you display the grouped sequences in some kind of multicam interface that lets you choose among the angles. The first time you use the tools, you'll be exhilarated by the time savings.

Then, inevitably, the questions start to arise: How many camera angles can I edit? What formats? How do I color-correct multiple streams? What are my audio options? Can I easily produce overlays and picture-in-picture effects?

In this article, I'll compare the multicam and related features of the four previously mentioned NLE programs. Then in a subsequent article, I'll compare the output quality of these programs, testing both HDV-to-SD downsampling and SD-to-HDV scaling for each one.

My test project is a four-camera shoot of the jazz band the Potluck Trio at the Old Courthouse in Independence, Va. The four cameras produced an eclectic mix of formats: HDV 1080i from the Sony HDR-FX1 and Canon XL H1, HDV 60p from the JVC GY-HD100, and plain old widescreen DV from my Sony DCR-VX2000. I produced the DVD for the group in SD widescreen mode, which was also the target output for most tests in this review.

To begin this analysis, I will start with the number of streams and types of formats each program can handle, and then describe how each one helps you color-correct your clips, a critical issue with multiple camera shoots.

Next, I will analyze several features ancillary to each application's multiple camera tool. First, since one of the benefits of shooting HDV for SD output is the ability to pan and zoom within the HDV stream while editing, I checked to make sure that all of these programs allowed this. Surprisingly, not all of them do.

In addition, when I was manually switching between cameras, I frequently employed overlay and picture-in-picture effects and assumed that automated tools would have these as well. Again, not all of them do.

Streams and formats

There are a couple of noteworthy limitations here. First, Premiere Pro 2.0 can handle only four camera angles, while all others can input as many as 128. In addition, though the multicamera tools offered by Premiere, Xpress, and Vegas could input all formats used in my shoot, Final Cut Pro couldn't. More specifically, Final Cut Pro's multicam tool can work only with clips that share the same resolution and codec.

If you're shooting with multiple formats and editing in Final Cut Pro, you have three options, none of which is perfect. First, you can upsample your lower-resolution streams (DV and 720p, in my tests) to the highest resolution (1080i), which takes time and disc space and can introduce distortion in the lower-resolution clips from the upsample and subsequent downsample for SD output.

Second, you can downsample your HDV streams (720p and 1080i, in my example) to your output resolution (16:9 DV). The negative here, besides time and disc space, is that you reduce video quality if you pan and zoom within the formerly HD streams during editing.

Or you can pan and zoom within the HDV streams to produce the optimal framing, and then downsample to DV resolution. However, since you can't tell which footage from each stream you'll actually use until you run the multicamera procedure, this means you'll have to deploy these time-consuming edits in footage that ultimately will never be seen by your audience, costing more time and disc space.

Operation

Multicam operation has two basic phases. In the first phase, you select and load the separate camera clips, which I call the source clips, into a group and then synchronize them. Then you use a separate interface to choose the audio and video angles to be included in the final multi-camera stream.

With Final Cut and Xpress, you group the source clips in the bin, create a Multiclip that contains all the angles, and then drag that clip to the timeline for editing. Both programs support automatic grouping via clip-naming conventions to streamline this process for repetitive projects, and can synchronize using timecode, in points, out points, or markers in the clips, as can Premiere Pro.

With Premiere Pro and Vegas, you synchronize the clips in a timeline (called a Sequence in Premiere). With Premiere, you drag this sequence into another sequence for camera selection, while the VASST tool for Vegas consolidates the camera angle changes in a master sequence atop the timeline (see Figure 4). VASST synchronizes the clips by placement on the timeline or via markers.

By grouping on a timeline, both Premiere Pro and Vegas make it simple to modify source clips and have all changes flow through to all instances of that source clip in the group. For example, with Premiere Pro or Vegas, if you color-correct or apply a 2D filter to the source clip, it automatically updates the multicam clip.

In contrast, Xpress can't apply filters to clips in the source bin, and though Final Cut can, effects applied to source clips after the grouping don't flow through to the group. That said, both applications can easily apply one effect to multiple clips on a timeline, so the inability to apply a filter to a source clip and have it flow through the final multicam clip is more of an administrative hassle than a serious feature deficit.

In terms of camera selection, all applications let you choose the desired video angle during realtime playback or by manually dragging the edit line to a new location and switching cameras. All of them let you change camera angles on the timeline and use editing tools to slip and slide the edit points between the angles.

When selecting camera angles, I loved Final Cut's ability to display the file name in the multicam interface — the other applications used track numbers, which is less intuitive (see Figure 1). Figure 1 also shows the need for color matching, with the JVC clip looking better than the other clips. I'll take care of that in a second.

On the audio front, all the applications let you designate a master audio track or have the audio follow the video. Final Cut and Xpress users can switch audio and video independently in realtime, while Premiere Pro and Vegas users can do this later on the timeline.

Color correction

One critical issue in all my multicamera shoots is minimizing the color differences between the video from the different cameras. All four applications have excellent color-correction tools, and they're far too complicated to review in the context of this article. What is noteworthy is the color-correction interface and color-matching capability of Xpress Pro, both evident in Figure 2.

Xpress Pro is the only application that displays multiple clips in the color-correction interface, simplifying multicamera correction. In addition, its Match Color capability is the fastest, easiest, and most accurate way to match the colors from different cameras.

The matching feature is shown in the little box with two brown color clips in the middle right of Figure 2, beneath the third clip. The JVC clip I was attempting to correct is the middle clip in the top row. I clicked the floor in that clip, creating the dull brown color on the left in the little box, and then clicked the floor in the other two clips, creating the richer brown chip on the right. Then I clicked Match Color, and Xpress corrected the entire clip by using the two selected colors as a guide. If you compare the corrected middle clip in Figure 2 with the uncorrected clip in the bottom left of Figure 2, you'll be equally impressed.

Today, color matching is a fantastic capability unavailable in any other product, though VASST plans to release a color-matching plug-in for Vegas and Premiere Pro in mid 2006. Again, late-stage color corrections made to the source clip in Vegas and Premiere Pro automatically update the multicamera stream, while you'll have to do this manually with Final Cut and Xpress.

Pan and zoom

At this point, things get a bit wiggy. To help you understand why, let's discuss the pan and zoom process in detail. Remember that in my project, I produced the video at 720×480 widescreen resolution. In contrast, HDV 1080i video has an actual resolution of 1440×1080 and a display resolution of 1920×1080, more than four times the area of the 720×480 SD output.

In theory, this means I can pan and zoom around the high-definition image at up to 2X magnification with no quality loss because there is a pixel-to-pixel match with no actual zooming or interpolation. Certainly this is the case when editing HDV video for SD output outside the multicamera environment with all editors.

With Premiere Pro, however, once you group the clips, the source clips assume the project resolution, downsampling the HDV clips to SD resolution for SD projects. So if you zoom in to the source clip when setting up the source sequence, you can't pan across the clip when editing the multicamera clips. This is shown in Figure 3, where I'm editing video from the camera on the upper right of the four cameras, highlighted in yellow.

As you can see in the quad-cam view, there's room to the saxophone player's right in the actual HDV clip. However, when editing the multicamera sequence, if I try to pan that clip to the right, the balance of the frame isn't there, and I get the black bar shown on the left of the preview window.

There is a workaround. You can pan and zoom in the actual source clip, rather than in the multicamera sequence, but this is tedious and less intuitive. More to the point, in a competitive review, none of the other programs shares this restriction — all can access the full HDV frame in the multicamera sequence.

To be honest, in most of my productions, I don't pan and zoom much within the HDV stream; it's simply too time-consuming. So this isn't that much of a restriction for me. However, if you're shooting with plans to extensively pan and zoom around the footage, you'll find Premiere Pro's workflow below par compared to the other editors.

Overlays and PIPs

One of the joys of working with multiple cameras is the ability to display multiple views simultaneously, either via a full-frame overlay or in a picture-in-picture effect. I expected that all multicamera tools would park the selected clips in the timeline and let me edit them exactly as I could if I had selected them manually.

Specifically, if I wanted to drag one clip up and over the others and then blend them with PIP or overlay, I expected to be able to so, as I can in Vegas, as shown in Figure 4. Here, the VASST plug-in consolidated my camera selections in the second track from the top, labeled the Master Video track. On the left of the timeline, I dragged one of the clips up one track, filled in the gap below, and used Vegas' Event Pan/Crop and Track Motion tools to create the PIP shown in the preview window on the bottom right (which reminded me that more color correction is in order).

While I could do the same in Final Cut Pro and Premiere Pro, I couldn't in Xpress. I could drag the clip to a higher track, but I couldn't drag the edge to the left or right, or fill in the gap below. Of course, I could manually create the overlays in Xpress, but these operations are faster and easier in the other programs.

These are the mechanics of the multicamera tools. In the next article, I'll compare the video quality produced by the respective tools and summarize my views of ease of use and overall comparative functionality.

To comment on this article, email the Digital Content Producer staff at dcpfeedback@prismb2b.com.

© 2008 Penton Media, Inc.