Removing the background is a fairly common operation both when processing photos and when working with video materials. The main difference is that when working with video, you are not dealing with a single image, but with a sequence of frames that differ from each other.
Necessary
Adobe After Effects program
Instructions
Step 1
Import the video you want to remove the background from into After Effects. To do this, select the File option on the Import command on the File menu. Select the file for processing in the window that opens and click on the "Open" button. Use the mouse to drag the imported file into the Timeline palette.
Step 2
If the subject of your interest is shot against an evenly lit green background, remove the background with the Color Key effect. To do this, find the desired effect in the Keying group of the Effects & Presets palette. For a quick search, enter the full name of the effect or the word color in the search bar at the top of the palette. Drag the effect icon onto the processed video in the Timeline palette.
Step 3
Adjust the keying parameters. To do this, in the Effect Controls palette, click on the eyedropper image and use this tool to specify the color that you are going to remove from the video. If the background doesn't completely disappear, increase the Color Tolerance value, or use the Edge Thin and Edge Feather options for more fine-tuning. Increasing the value of the first parameter will make some pixels disappear at the edges of the remaining visible image, while increasing the value of the second parameter will create some number of semi-transparent pixels at the edges of the image. This is quite handy if the edges of the foreground object after keying are too sharp, but you shouldn't be too zealous with this parameter. By increasing the Edge Feather value, you run the risk of a flickering halo of translucent pixels around the image.
Step 4
Put a background under the video and see the result. To do this, import the background file or create a new layer by choosing the Solid option of the New command of the Layer menu. In the window that opens, select a background color and click on the OK button. Move the background layer under the effect layer with the mouse. Start video playback using the Space key.
Step 5
If you are satisfied with the result of applying the effect, import into the program the background on which you are going to overlay the video or save the file with the alpha channel if you are going to work with it in another editor. To do this, use the Add to Render Queue command from the Composition menu. In the Render Queue palette, click on the Lossless label to the right of the Output Module item. In the Output Settings window, select the RGB + Alpha channel from the Channels drop-down list. If you are going to output video with audio, check the Audio Output checkbox.
Step 6
Click on the caption to the right of the Output to field and specify the folder where the processed video will be saved. Click on the Render button and wait for the file to finish processing.
