The video clip you are seeking is a well-known test of perception.
Here are a few brief descriptions of this test:
"...In one study, perceivers are asked to watch a video tape of a
basketball game and they are asked to count the number of times one
team takes possession of the ball [Simons & Chabris, in press]. During
the film clip, which lasts a few minutes, a person in a gorilla suit
strolls onto the center of the court, turns and faces the audience and
does a little jig. The gorilla then slowly walks off the court. The
remarkable fact is that perceivers (including this author) do not
notice the gorilla. This is an example of what has been called
Perception, action,and nonconceptual content
"A demonstration of inattentional blindness goes something like this.
Viewers are asked to monitor three basketball players in white
T-shirts and count the number of times they pass the ball during a
video clip. Thirty-four seconds into this experiment, a person wearing
a gorilla suit walks through the game and even pauses to pound his
chest before moving on. Despite their vigilance, approximately half
the viewers never see the gorilla. Even after they are told about the
gorilla and shown the video, they refuse to believe it."
Aquatic Safety Research Group: A Matter of Perception
More on this test:
Charles Carver: A Gorilla In The Midst
The video can be viewed here by clicking on ["View the "basketball" video].
*Note: "This video is © 2004 by Daniel J. Simons. It is provided
solely so that individuals can view it. The video may not be
downloaded, saved, copied, reproduced, or used for any other purpose."
"video clip" basketball gorilla
"basketball video" gorilla
I hope the information provided is helpful.