Matting Rotated QuickTime Videos
- Determine Image Size
In QuickTime, select Window -> Show Movie Info (Command-I) and make a note of the dimensions of your rotated video, both height and width.
- Do Math
Decide whether you want to matte your image in 4:3 or 16:9 format. Then round up the width to the nearest factor of 3 for 4:3 or 9 for 16:9. Hint: If the digits of a number add up to a multiple of 3, the height is divisible by 3. If a multiple of 9, it's divisible by 9. Here I round 320 (digit sum is 5) up to 321 (digit sum is 6, divisible by 3). Then multiply by the desired aspect ratio, in this case 4/3. The math tells me that my desired width is 428.
- Create the Matte
Create a new image in your favorite photo editor using the dimensions you just calculated, in this case 428 x 321.
- Save the matte to disk
Save the new matte to disk using any QuickTime readable format. Here, I use JPEG.
- Open the matte in QuickTime
In QuickTime, open the matte just as if it were a movie file. Then copy it to memory by choosing Edit -> Select All (Command-A), Edit -> Copy (Command-C) and then close it (File -> Close, Command-W).
- Scale the matte over the video
In QuickTime, scale the matte (currently in memory) over your rotated video as follows: Select the entire video (Edit -> Select All, Command A) and then add the scaled matte (Edit -> Add to Selection & Scale, Command-Shift-Option-V). The matte will cover most or all of your video.
- Open the Movie Properties window
Choose Window -> Show Movie Properties (Command-J) to open the movie properties window shown here. Notice that Video Track 2 uses an image format rather than a motion format. Select Video Track 2.
- Adjust the Matte Layer
Select Video Track 2 and click Visual Settings in the movie properties window. Locate the layer control at the bottom of the settings. Adjust the layer to increase its setting from a negative number to a positive one until the hidden video pops out in front of the matte.
- Do More Math
To center your image, you need to do some more math. Subtract the width of the rotated video (240 in this case) from the width of the matte (428) and divide that number by 2. This (94 in this case) is the offset you'll want to use.
- Adjust the offsets
Select Video Track 1, the movie track. Set its horizontal offset to the value you just calculated (here 94) and the vertical offset to 0. The video will now center on the matte.
Finish by exporting your matted and centered video to a new file.