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

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

2. Video Segmentation and Tagging

anchorshot detection is the key challenge in order to analyze, segment, and browse news

video data.

2.3.3. Anchorshot Detection

First of all we have to define the term anchorshot.

Definition 5 (Anchorshot) Each shot within a news show showing one or more anchorperson(s)

is called anchorshot.

Anchorshots can vary in the number of anchorpersons

(mostly one or two), the absence or presence

of a news icon and title in the background, or a

labeling bar. If no news icon or title is present, the

anchorperson will usually be in the center. As soon

as the anchorshot shows one anchorperson and a

news icon, the anchorpersons’ position will be on

the right side and the news icon will be on the left

or vice versa. In case of two or more anchorpersons,

the anchorshot typically has no news icon.

This holds for most news shows world-wide.

Figure 2.11.: Example for an anchorshot.

As anchorshots are widely used to cut news shows

into meaningful segments, the detection of anchorshots

has been of great interest in the scientific community. Thus, shots in news shows

get typically classified into anchorshots and news report shots. First a given video data

gets segmented into shots. Afterwards one or more frames from each shot get selected as

key frames for this shot. Subsequently anchorshots get classified by either matching the

current key frame against a model for anchorshots (supervised) or by trying to recognize

similar shots that occur repeatedly during the news show (unsupervised). In the following

sections, some approaches get presented and their advantages and disadvantages will

be discussed.

Model matching

All approaches presented in this section try to classify anchorshot by taking benefit from

the a priori knowledge we have about anchorshots. Swanberg et al. [Swanberg et al., 1993]

propose a system that matches shots against a unique anchorshot model. As soon as the

current shot fulfills the characteristics of this model, it is labeled as an anchorshot. Their

method might work well as long as there are no variations between the anchorshots, but

Zhang et al. [Zhang et al., 1995b] have tested this model matching approach on news

videos broadcasted by the Singapore Broadcasting Corporation (SBC) and received poor

results due to the fact, that these news shows cover anchorshots with different spatial

structures. Hence, they have developed a system that matches each shot against a set

of models. Their matching is based on the pair-wise pixel difference and on color histograms.

Unfortunately, their approach still depends on the predefined models and does

not work on any news show. Hanjalic et al. [Hanjalic et al., 1999] have tried to overcome

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