Real-time feature extraction from video stream data for stream ...

ai.cs.uni.dortmund.de

Real-time feature extraction from video stream data for stream ...

7.1. Shot Boundary Detection

Prediction: true Prediction: false Total

Label: True 128 3 131

Label: False 51 23.276 23.327

Total 179 23.279 23.458

Table 7.2.: Resulting confusion matrix for the experiment shown in Figure 7.1

7.1.2. Analysis of reasons for misclassification

In order to understand in which setting misclassifications occur, figure 7.2 shows some

examples for misclassified frames. Each row shows one misclassified frame (in the middle),

plus the frames before and after. Having a look at the False Negatives (Figure 7.2 (a)),

we notice, that these images are all very similar in color and hence difficult to detect for

the used algorithm. For example in (a1) the background is unchanged, as both interviews

are recorded in front of the same wall. Furthermore the position of the microphones and

faces overlap, so that the difference between both images does not exceed the given

threshold.

(a) False Negatives

(b) False Positives

Figure 7.2.: Examples for misclassified frames.

False Positives occurred in frames 8816 ∗ , 8817 ∗ , 13089 ∗ , 13090 ∗ , 13153 ∗ , 13154 ∗ , 14350 ∗ ,

14351 ∗ , 14358 ∗ , 14359 ∗ , 14360 ∗ , 14363 ∗ , 14375 ∗ , 14382 ∗ , 14383 ∗ , 14385 ∗ , 14386 ∗ , 14390 ∗ ,

14396 ∗ , 14480 ∗ , 14481 ∗ , 14493 ∗ , 14496 ∗ , 14506 ∗ , 14531 ∗ , 14532 ∗ , 14586 ∗ , 14710 ∗ , 14711 ∗ ,

14733 ∗ , 14735 ∗ , 14736 ∗ , 14765 ∗ , 14766 ∗ , 14767 ∗ , 14768 ∗ , 15971, 15975, 15981, 17768,

20187, 20188, 20189, 20190, 20191, 20739 ∗ , 20740 ∗ , 20792 ∗ , 20793 ∗ , 20799 ∗ and 20800 ∗ .

Three examples for False Positive classified frames are shown in Figure 7.2 (b).

Obviously, the misclassifications in the first and third example of figure 7.2 (b) occur

due to overexposed frames. The reason for the occurrence of such frames are photographers

using flashlights whilst the shot is recorded. These photographic flashlights cause

large dissimilarity values of two adjacent frames, as every single pixel of the image get

significant brighter. In the above given enumeration of all false positive frames from the

”Tagesschau” show of September 11th, 2012, all frames that are misclassified due to photographic

flashes are marked with the symbol ∗ . As we see, photographic flashes are the

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