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Using the BCC Matchmove Filter in Avid Editing Systems

Media Used in this Exercise:

We're going to use the BCC Match Move filter to match the camera pan movement of one clip to that of a clip which was shot with a locked down camera and generate a seamless composite of the two clips making them appear as though they were shot with the same camera - all right within the Match Move filter. We'll start the project by importing the 2 clips that we need into a new project in Avid. Let's take a look at the two clips that we are using - one is a crane shot of a street scene of a clock taken on Fisherman's Wharf in San Francisco while the other is an underwater scene of a fish swimming near some coral along the California coast. In the crane scene, there is a clock on a post and we are going to comp the fish scene into the clock face. The fish clip has a circular alpha cut-out shape so that only the pixels within the circle are opaque.

avid plugin

To start, we create 2 video tracks in the timeline and then we drag foreground clip of the fish into the timeline on video 2 track, and drag the background clip with the clock into the Avid timeline in the video 1 track, directly below the fish track. Let's review the movement of the clip in the clock scene - there is a slow camera crane up that we will capture with the BCC Match Move filter. We'll set the current frame indicator to the start of the clip. Then we add the BCC MatchMove filter by selecting it from the effects bin and dragging it onto the fish clip in the timeline. We then select the clip with the filter, and click the effect mode button to access the filter parameters.

avid filter effects

Set the timeline quality to green mode and promote the effect to AVX 2 by clicking on the promote effect button in the Avid controls window. Twirl down the Title Matte group and enable the Apply to Title Matte button.

3rd party avid filters

Now let's track the background clip. Twirl down the motion tracker group in the BCC Match Move filter controls. By default the filter will set itself to track the clip to which it was applied and in this case that is not what we want to do, we want to track and recover the motion from the background clip with the crane and apply that to the fish shot. So, set the To set-up the tracker, enable the track-on-the-fly feature. Now set the Motion Tracking Source layer to First Below. Then enable the track-on-the-fly button. Drag the tracker center so that it is centered over the the bottom of the letter F on the sign. Then expand the target area (the inner box) to 15 pixels and leave the search at it's default value of 40.

matchmove

Now that the search and target regions have been set, we are ready to track. Just click on the play button in the Avid viewer window and the filter will analyze / track the feature. Tracking is complete when the clip has played through every frame in the comp. There are indicators at the bottom of the composite window that provide information regarding the integrity of the tracking process - a solid green bar indicates that all frames were tracked, while the color purple is used to indicate a non-tracked frame. A red bar is displayed to indicate the current time. When tracking has completed, you may want to monitor the tracker running through the frames to make sure that the tracker did not drift or move off target. Once satisfied with the tracking data, you can disable the track-on-the-fly feature.

editing system

So ... now that we have recovered the camera motion, we need to instruct the filter to use this motion to control the movement of the foreground clip in the composite, which in this case is the fish clip. Twirl down the Match Move parameter group and set the MM foreground to the shot of the fish. The fish will move correctly now to match the camera movement from the background clip, but it is not in the correct position over the clock face that we wanted to comp it onto.

special effects

Move the CTI to the middle of the clip. We'll reposition the fish so that it is positioned over the clock face. By using the offset parameters from the motion tracker group, we can change the relative position offset of the foreground clip to the recovered tracker data. Go to the Motion Tracker group and set the offset x to +0.020 and the offset y value to -0.354. This places the fish with alpha directly over the clock face. The fish will also move correctly now to match the camera movement from the background. But there is perspective distortion in the background shot that we need to apply to the foreground to make a convincing composite. To fix this, we let the filter do the work by using the built-in DVE controls to match the perspective in the background shot.

composting effects

Let's twirl down the Transform control group. This is where we apply transform operations to the foreground clip. First unlock the scale and set the scale x to 74 percent and the scale y to 84 percent. Observe now that we're getting close to a match. Set the Tumble parameter to -10 and the Spin parameter to + 34 degrees. Bingo - the foreground clip now sits right on top of the background clip with matching perspective distortion.

3rd party avx

Now we'll just go in and blend the edges of the foreground clip so that it looks like the two clips are one shot. The controls for this function are located in the Composite group. Twirl down the Composite group and set the Wrap Softness to 10 and the Wrap Width to 3. Play back the result and observe that the foreground clip is locked to the background clip in a seamless composite.

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