These techniques, however, do not work well for videos for two reasons: 1) most video transcripts are very short, as compared to a typical text collection; and 2) it is impractical to assume that there is a large video collection on a specific topic, due to the video production costs.
many keywords extracted from videos using traditional IR techniques are not really content-specific, and consequently, the video search results that are returned based on these keywords are generally unsatisfactory.