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To create the master list of shots, the video was segmented. The results of this pass are called
subshots. Because the master shot reference is designed for use in manual assessment, a second pass
over the segmentation was made to create the master shots of at least 2 seconds in length. These
master shots are the ones to be used in submitting results for the feature and search tasks. In the
second pass, starting at the beginning of each file, the subshots were aggregated, if necessary,
until the currrent shot was at least 2 seconds in duration, at which point the aggregation began
anew with the next subshot.

The keyframes were selected by going to the middle frame of the shot boundary, then parsing left and
right of that frame to locate the nearest I-Frame. This then became the keyframe and was extracted.
Keyframes have been provided at both the subshot (NRKF) and master shot RKF) levels.

In a small number of cases (all of them subshots) there was no I-Frame within the subshot
boundaries. When this occured the middle frame was selected. (one anomally, at the end of the first
video in the test collection, a subshot occurs outside a master shot.)

The emphasis in the common shot boundary reference will be on the shots, not the transitions. The
shots are contiguous. There are no gaps between them. They do not overlap. The media time format is
based on the Gregorian day time (ISO 8601) norm. Fractions are defined by counting pre-specified
fractions of a second. In our case, the frame rate will likely be 29.97. One fraction of a second is
thus specified as "PT1001N30000F".

The video id has the format of "XXX" and shot id "shotXXX_YYY". The "XXX" is the sequence number of
video onto which the video file name is mapped, this will be listed in the "collection.xml" file.
The "YYY" is the sequence number of the shot. Keyframes are identified as by a suffix "_RKF" for the
main keyframe (one per shot) or "_NKRF" for additional keyframes derived from subshots that were
merged so that shots have a minimum duration of 2 seconds.

The common shot boundary directory will contain these file(type)s:

    * shots200* - a directory with one file of shot information for each video file in the
                  development/test collection
          o xxx.mp7.xml - master shot list for video with id "xxx" in collection.xml
    * collection.xml - a list of the files in the collection


Paul Over, over@nist.gov
National Institute of Standards and Technology
Jan 12, 2007
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