Information processing system, method and computer readable medium for determining whether moving bodies appearing in first and second videos are the same or not

1. An information processing system comprising:

a memory storing instructions; and

a processor configured to execute the instructions to:

receive inputs of videos captured by a plurality of imaging apparatuses;

detect a first moving body appearing in a first video captured by a first imaging apparatus among the plurality of imaging apparatuses and a second moving body appearing in a second video captured by a second imaging apparatus among the plurality of imaging apparatuses;

compute a feature value for both the first moving body and the second body;

derive, on the basis of similarity between the feature value of the first moving body appearing in the first video and the feature value of the second moving body appearing in the second video, a first probability indicating that both moving bodies are the same;

compute an elapsed time from a first time point when the first moving body disappears from the first video to a second time point when the second moving body appears in the second video;

derive a non-appearance probability indicating that the first moving body appearing in the first video does not appear in the second video at the second time point when the second moving body appears in the second video, based on a monotonically decreasing function with respect to time;

determine that the first moving body appearing in the first video and the second moving body appearing in the second video are the same when the first probability is larger than the non-appearance probability;

display the second video on a display device; and

change a display method, when the second moving body appearing in the second video is determined the same as the first moving body appearing in the first video, into a different display method from a display method used before the moving bodies are determined to be the same moving body.

2. The information processing system according to claim 1 , wherein the non-appearance probability is monotonously non-increasing with respect to the elapsed time after the first moving body disappears from the first video.

3. The information processing system according to claim 2 , wherein

the non-appearance probability decreases with time; and

the further the distance from the imaging range of the first imaging apparatus to the imaging range of the second imaging range of the second imaging apparatus, the lower the decrease rate of the non-appearing probability.

4. The information processing system according to claim 1 , wherein

when at least two first moving bodies appear in the first video and the processor determines that one of the first moving bodies is the same with the second moving body in the second video, the processor is further configured to execute the instructions to reduce the non-appearance probability, which represents another first moving body not yet appeared in the second video.

5. An information processing method comprising:

receiving inputs of videos captured by a plurality of imaging apparatuses;

detecting a first moving body appearing in a first video captured by a first imaging apparatus among the plurality of imaging apparatuses and a second moving body appearing in a second video captured by a second imaging apparatus among the plurality of imaging apparatuses;

computing a feature value for both the first moving body and the second body;

deriving, on the basis of similarity between the feature value of the first moving body appearing in the first video and the feature value of the second moving body appearing in the second video, a first probability indicating that both moving bodies are the same;

computing an elapsed time from a first time point when the first moving body disappears from the first video to a second time point when the second moving body appears in the second video;

deriving a non-appearance probability indicating that the first moving body appearing in the first video does not appear in the second video at the second time point when the second moving body appears in the second video, based on a monotonically decreasing function with respect to time;

determining that the first moving body appearing in the first video and the second moving body appearing in the second video are the same when the first probability is larger than the non-appearance probability;

displaying the second video on a display device; and

changing a display method, when the second moving body appearing in the second video is determined the same as the first moving body appearing in the first video, into a different display method from a display method used before the moving bodies are determined to be the same moving body.

6. The information processing method according to claim 5 , wherein the non-appearance probability is monotonously non-increasing with respect to the elapsed time after the first moving body exits and disappears from the first video.

7. The information processing method according to claim 5 , wherein the non-appearance probability exhibits a less decreased width with respect to the elapsed time when a distance from a imaging range of the first imaging apparatus to a imaging range of the second imaging apparatus is long than when the distance from the imaging range of the first imaging apparatus to the imaging range of the second imaging apparatus is short.

8. The information processing method according to claim 5 , further comprising:

determining whether or not any one of a plurality of moving bodies appearing in the first video at the same time is the same as a part of moving bodies appearing in the second video; and

lowering the non-appearance probability for a first moving body that is not associated with the second moving body appearing in the second video among the plurality of moving bodies when there is a first moving body determined to be the same as the second moving body appearing in the second video among the plurality of moving bodies.

9. A non-transitory computer readable storage medium recording thereon a program, when executed, causing a computer to perform a method comprising:

receiving inputs of videos captured by a plurality of imaging apparatuses;

detecting a first moving body appearing in a first video captured by a first imaging apparatus among the plurality of imaging apparatuses and a second moving body appearing in a second video captured by a second imaging apparatus among the plurality of imaging apparatuses;

computing a feature value for both the first moving body and the second body;

deriving, on the basis of similarity between the feature value of the first moving body appearing in the first video and the feature value of the second moving body appearing in the second video, a first probability indicating that both moving bodies are the same;

computing an elapsed time from a first time point when the first moving body disappears from the first video to a second time point when the second moving body appears in the second video;

deriving a non-appearance probability indicating that the first moving body appearing in the first video does not appear in the second video at the second time point when the second moving body appears in the second video, based on a monotonically decreasing function with respect to time;

determining that the first moving body appearing in the first video and the second moving body appearing in the second video are the same when the first probability is larger than the non-appearance probability;

displaying the second video on a display device; and

changing a display method, when the second moving body appearing in the second video is determined the same as the first moving body appearing in the first video, into a different display method from a display method used before the moving bodies are determined to be the same moving body.

10. The non-transitory computer readable storage medium according to claim 9 , wherein the non-appearance probability is monotonously non-increasing with respect to the elapsed time after the first moving body exits and disappears from the first video.

11. The non-transitory computer readable storage medium according to claim 9 , wherein the non-appearance probability exhibits a less decreased width with respect to the elapsed time when a distance from a imaging range of the first imaging apparatus to a imaging range of the second imaging apparatus is long than when the distance from the imaging range of the first imaging apparatus to the imaging range of the second imaging apparatus is short.

12. The non-transitory computer readable storage medium according to claim 9 , further comprising:

determining whether or not any one of a plurality of moving bodies appearing in the first video at the same time is the same as a part of moving bodies appearing in the second video; and

lowering the non-appearance probability for a first moving body that is not associated with the second moving body appearing in the second video among the plurality of moving bodies when there is a first moving body determined to be the same as the second moving body appearing in the second video among the plurality of moving bodies.