1. First, import the material into AE, and then drag the material to the lower panel of AE to automatically create composite material 2, as shown in the figure below, and then enter the next step.

2. Secondly, in the AE preview panel, you can view the uncut material size, as shown in the figure below, and then go to the next step.

3. Next, click the area icon indicated by the arrow at the bottom of the preview screen, as shown in the figure below, and then go to the next step.

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4. Then, after completing the above steps, you can draw the clipping area directly with the mouse. After trimming, you can also drag the trimming border with the mouse to adjust the trimming area, as shown in the figure below, and then proceed to the next step.

5. If you feel that the video image is not well cropped, you can click the area again to cancel the cropping, as shown in the figure below, and then proceed to the next step.

6. Then, if you think that the last cut was not accurate enough, you can right-click the upper material 2, click the composition settings, as shown in the figure below, and then go to the next step.

7. Finally, in the pop-up window, check the lock aspect ratio as 16:9, that is, the width and height are set in equal proportion, as shown in the figure below, and the problem is solved.