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Guide to Defining Video Quality Requirements

Jump To: Use Cases | Use Classes | Generalized Use Class Aspects | GUC Questionnaire | GUC Example | Video System Tasks | Video System Functions | Recommendations Tool | Acknowledgments


Revised May 29, 2012
Section 9 of 9 of step 2 -- Generalize Use Cases into Use Classes -- in the bar chart highlighing the 4-step process for definfing video quality requirements.

Generalized Use Class Example

The following example demonstrates how by answering a few use case questions you can identify use classes from generalized use class aspects.

Use Case 1 and 2

Generalized use class aspects for use case 1 and 2.
While use case 1 and 2 demonstrate scene and task differences, these use cases belong to the same generalized use class. Click an Aspect in the figure for information.

The first two examples demonstrate how two seemingly different use cases may actually have the same video quality needs and belong to the same use class, because they share the same generalized use class aspects.

Use Case 1: Read license plates in real time

Application — real time or recorded. The scene is pursuit of a moving suspect car. Using a camera mounted in a patrol car, the task is to accurately read a license plate of a moving car from a moving vehicle, at speeds of up to 70 MPH using real-time video. The actors in this application are the patrol car officers, the dispatcher, and command and control officers. The patrol car follows the suspect car and video-captures the back of it. The officers attempt video acquisition of the license plate in real time. The alphanumeric characters of the license plate are the target. (Such recorded content might also be saved as forensic evidence.) The motion sources are the target and the camera. The lighting is variable.

Use Case 2: Recognize smoke features from small plumes in real time

Application — real time. The scene is a burning building. Using a camera mounted in a helicopter, the task is to determine color, velocity of small smoke plumes using real-time video. The actors are the firefighter in the air, and incident command and control. The helicopter circles the building looking for smoke plumes, and sends video back to command and control. The target is a section from a small plume of smoke. The motion sources are the target and camera. The lighting is variable.

Use Case 3

Generalized use class aspects for use case 3.
Use case 3 demonstrates scene and task differences from use case 1 and 2. But more importantly, use case 3 does not share generalized use class aspects with use case 1 and 2, so use case 3 belongs to a different use class. Click an Aspect in the figure for information.

This example demonstrates a different resulting use class. While the generalized use class aspects of use case 3 differ from those of use case 1 and 2, other use cases likely share the same generalized use class aspects of use case 3, and would thus fit in the same use class.

Use Case 3: Verify the number of people in a store aisle from recorded video

Application — recorded. The scene is a department store aisle. Using a mounted surveillance camera, the task is to verify the number of people in the scene using recorded video. The actors are forensic analysts. The sequence of events deals with the people that walk through a store during a period of two minutes. The target is the people. The motion sources are the people at walking speed. The lighting is indoor fluorescent lamps.