JP2011124681A - Video editing device, video editing method, and video editing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically generate edited video while taking into consideration context of video to be generated. <P>SOLUTION: Video is divided into video sections (S202), the likelihood of each semantic content is given from the video feature of each video section and a likelihood model of a semantic content category dictionary (S204). The semantic likelihood is used to cluster the video sections (S205). A semantic change degree of the video is calculated from a connecting relationship as the video is calculated about a representative video section selected from each cluster (S206), a representative video section group to be used for edited video is selected from the semantic change degree of the entire candidate representative video sections (S207), and the edited video is generated (S209). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus and method for performing video editing in consideration of the context of a video section on an input video to be processed in a short processing time, and a video editing program used for realizing the video editing method. About.

  In recent years, distribution and sharing of video using communication has become active. Most of the videos distributed and shared here are created by general users, that is, non-professional people, and are consumer generated media (CGM) or user generated content (UGC). : User Generated Content). In the following, this paper will be referred to as CGM.

  It can be said that there are many CGMs that are not of high quality as compared to the images produced by professionals. The main cause is the equipment used by professional authors and general users (authors) who create CGM, and the skills to use them. Focusing on imaging equipment (video cameras), professionals have high-performance professional video cameras that can capture clear images, but for general users, use commercially available ones. ing. Since general users are not trained in shooting techniques such as camera work, there is a great difference in the quality of the shot images.

  Video editing is the biggest difference. Video is time-series data of images and sounds. In general, it is rare for a photographed video to be distributed as it is, and it is released through the following editing process.

・ Delete partial sections (select scenes)
・ Reorder time sequence ・ Insert another video (scene) The purpose of video editing is to organize unorganized video immediately after shooting into a form suitable for viewing. For example, in order to clarify the assertion point, there are cases where a redundant and useless scene is deleted, or the time order is intentionally changed to help understanding the content.

  The most important point when editing video is to make it easy for viewers to understand, organize, or enjoy. Since such editing requires a certain amount of specialized knowledge and judgment, the current situation is that it cannot be fully effective unless it is done by professionals such as trained video creators and editors. Therefore, it is difficult for general users to realize effective editing.

  Under these circumstances, there is an increasing demand for technology that can support editing by general users and can automatically perform high-level video editing.

  As prior art related to the present invention, the following Patent Document 1 analyzes video information, detects emotional sections, presents emotional sections to the user in an easy-to-understand manner, and supports editing. Video editing technology is disclosed.

JP 2009-1111938 A

  The video editing technology disclosed in Patent Document 1 presents an emotional section that is one of important video scenes in an easy-to-understand manner, thereby providing an editing support tool that is easy for the user to use. It was.

  However, this video editing technology only determines whether or not a scene is emotional, and selects a scene based on it. The “context” of the video generated as a result of editing is selected. "Is ignored. Video is a media with a time axis, and it is meaningful by playing it from the beginning and watching it in order along the timeline. In other words, it can be said that the video is a media having a context along the time direction. Of course, this should be taken into account when editing video.

  Here is an easy-to-understand example. For example, in the original video before editing, “(1): Man A is walking” “(2): Man B walking from the opposite side notices the baseball ball flying toward Man A. Let's say that “(3): Man B walking from the other side knocks out Man A when passing by”. Man B is a scene where he urgently jumps out so that Man A does not hit the ball. If there is no scene of (2) in the video generated as a result of editing, “(1): Man A is walking”, “(3): Man B walking from the opposite side passes. If it was a flow of “mushing man A”, it would seem that the content changed to something completely different.

  Even if it is not limited to cases that affect semantic content as described above, there is an important context. For example, suppose there was a very fun and funny scene. Immediately after that, if the scene was edited so that a scene that was sad and crying would come, it would be rare for viewers who watched the scene to feel sad or crying. Also, for example, if it was edited so that a much more enjoyable scene would continue, it would be speculated that the viewer will get bored gradually and the fun will fade.

  As described above, it is considered that considering the context is one of the most important issues in automatic video editing.

  In order to solve this problem, an object of the present invention is to provide a video editing technique for automatically generating and outputting an edited video for a processing target video in consideration of the context of the generated edited video. is there.

  In order to achieve this object, the present invention divides a video into small sections, and assigns a likelihood to each meaning content to each small section. Cluster the small intervals from their semantic likelihoods. For the representative small section of each cluster, the semantic change degree (context similarity) of the video is calculated according to a predetermined formula from the relationship of connection as video. If the average of the semantic change degree is taken, it becomes the semantic change degree of the whole image. When one cluster (representative section) is removed (a plurality of candidates for removal) are compared, and the cluster to be removed is determined according to preference (whether or not semantic change is desired). Thus, the target video editing is performed.

  Details are as follows. The video editing apparatus according to the present invention probabilistically includes a semantic content category in which the meaning of video content is expressed by a predetermined specific word, and a video segment feature value including an image feature and / or a sound feature of the video segment. Semantic content category dictionary for storing likelihood model information indicating the relationship, video segment dividing unit for segmenting the input video into video segments, and video segment feature amount extracting unit for extracting video segment feature values from each video segment A semantic content likelihood calculating unit that refers to the semantic content category dictionary based on the extracted video segment feature and outputs the likelihood of each semantic content category for the video segment, and based on the likelihood A clustering unit that clusters the video segments and selects one or more representative video segments from each of the generated video segment clusters, and a combination of the selected representative video segments For a sequence of a plurality of candidate representative video sections obtained from the matching, a context similarity indicating a degree of semantic change in the connection of the video sections is calculated using at least the likelihood, and the whole is calculated based on the calculated context similarity. As a candidate representative video segment group used for editing video, either an arrangement of candidate representative video segments having a large degree of semantic change or a sequence of candidate representative video segments having a small degree of semantic change is selected. And an edited video output unit that generates and outputs an edited video by connecting video segments of the selected candidate representative video segment group.

  The video editing method of the present invention realized by the operation of each processing means described above can also be realized by a computer program, which is provided by being recorded on a suitable computer-readable recording medium, It may be provided via a network, and is installed when the present invention is implemented, and the present invention is realized by operating on a control means such as a CPU.

  In the video editing apparatus configured as described above, when a video to be processed is input, a video segment feature amount is extracted for each video segment from image information and / or sound information of the video to be processed, and a semantic content category is extracted. Calculate the likelihood. Examples of feature quantities include brightness features, color features, motion features, texture features, cut features, object features, image event features, pitch features, volume features, spectrum features, rhythm features, speech features, music features, and sound. There are event features and the like, and at least one of them is extracted as a feature amount.

  In addition, the degree of association with a certain semantic content category is calculated and stored for use in the context similarity calculation.

Subsequently, the following processing steps from [Process 1] to [Process 6] are repeated.
[Process 1]: Based on the likelihood, all video sections are clustered to generate a video section cluster, and one or more representative video sections are selected from each video section cluster.
[Process 2]: For each representative video segment position in the representative video segment sequence, meaning based on the video segment feature of the representative video segment position located in the past and the likelihood and the degree of association Calculate the predicted probability attributed to the content category.
[Process 3]: For each representative video segment position in the representative video segment sequence, the semantic content category based on the video segment feature of the representative video segment position located before and the likelihood and the relevance degree Calculate the posterior probability belonging to.
[Process 4]: The similarity between the prediction probability and the posterior probability is calculated as the context similarity.
[Process 5]: The average of the context similarity over the entire arrangement of the representative video sections is obtained, and the arrangement of the representative video sections such that the average becomes the maximum or the minimum is selected.
[Process 6]: If the end condition is not satisfied, the selected representative video segment group is regarded as a new video segment group, and the process returns to [Process 1]. If the end condition is satisfied, the obtained representative video sections are connected and output as an edited video.

  By calculating the semantic content attribution probabilities (predicted probabilities, posterior probabilities) and their similarities depending on the past contexts by the processing procedures of [Process 2] to [Process 4], the process matches the previous context. Video editing and video editing different from the previous context can be realized, and automatic video editing considering the context becomes possible.

  According to the present invention, a user can automatically execute video editing in consideration of a context simply by inputting a video. As a result, it is possible to realize highly edited video without the need for manual training for video creators and editors.

Also, when considering context in conventional video editing, processing time is required because video segment selection has to be performed in consideration of various video segment combinations. More specifically, for the number N of video sections, a calculation cost that is greater than or equal to the factorial order of N is expected, so that the problem does not end in polynomial time. In the processing procedure of the present invention,
(1) Narrow down the video section in stages,
(2) Cluster video segments with similar semantic content,
By introducing these two procedures, the procedure ends in polynomial time.

  Therefore, the user of the present invention can automatically obtain an edited video considering the context in a short time.

It is a figure which shows the structural example of the video editing apparatus which concerns on one Embodiment of this invention. It is a flowchart of the video editing process which a video editing apparatus performs. It is a figure which shows an example of clustering of a video section and representative video section extraction. It is a figure which shows an example which sifts a representative video area.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of a device configuration of a video editing device according to an embodiment of the present invention. In FIG. 1, a video editing apparatus 1 is an apparatus for inputting a video 10 to be edited and outputting an edited video 19 as a result of editing by computer hardware and software programs including a CPU, a memory, an external storage device, and the like. A video input unit 11, a video storage unit 12, a video segment dividing unit 13, a video segment feature quantity extracting unit 14, a semantic content likelihood calculating unit 15, a clustering unit 16, and an editing target video segment selection. Unit 17, edited video output unit 18, semantic content category dictionary 20, semantic content relevance calculation unit 21, and semantic content relevance storage unit 22.

  The editing target video segment selection unit 17 includes a similarity calculation unit 170 and a representative video segment screening unit 174. The similarity calculation unit 170 includes a context prediction probability calculation unit 171 and a context posterior probability calculation unit 172. And a context similarity calculation unit 173.

  The video input unit 11 inputs the video 10 to be edited and stores it in the video storage unit 12. The video segment dividing unit 13 divides the video to be processed into a plurality of video segments. The video section feature quantity extraction unit 14 extracts and outputs the feature quantity of each section based on the image information and sound information of the video section to be processed.

  The semantic content likelihood calculation unit 15 includes each of one or more semantic content categories preset and registered in the semantic content category dictionary 20 based on the video segment feature extracted by the video segment feature extraction unit 14. On the other hand, the extent to which the video section belongs to the semantic content category is calculated as likelihood and output.

  The semantic content relevance calculation unit 21 receives as input any semantic content category registered in the semantic content category dictionary 20 in advance, calculates the degree of association between the semantic content category and other semantic content categories, Stored in the relevance storage unit 22.

  The semantic content category dictionary 20 and the semantic content relevance storage unit 22 are created in advance by learning about the semantic content category using the learning sample video or the like by the video editing device 1 or another device. I can keep it.

  The clustering unit 161 clusters video sections based on the likelihood output by the semantic content likelihood calculating unit 15. Further, one or more representative video sections from each cluster are output as representative video sections.

  The editing target video segment selection unit 17 selects a candidate representative video segment group used for the edited video. Therefore, the context prediction probability calculation unit 171 in the similarity calculation unit 170 displays the context prediction probability at each representative video section position when the representative video sections output from the clustering unit 16 are arranged in the playback time order. It is calculated based on the video segment feature at the representative video segment position and output.

  The context posterior probability calculation unit 172 converts the context posterior probability at each representative video segment position when the representative video segments output from the clustering unit 16 are arranged in the playback time order into the video segment feature at the previous representative video segment position. Calculate based on the output.

  The context similarity calculation unit 173 calculates and outputs the context prediction probability output by the context prediction probability calculation unit 171 and the similarity of the context posterior probability output by the context posterior probability calculation unit 172.

  The representative video section sieving unit 174 determines one or more representative video sections to be removed based on the similarity output from the context similarity calculation unit 173, and outputs the remaining representative video sections.

  When the end condition is satisfied, the edited video output unit 18 joins the representative video sections output by the representative video section sieving unit 174 and outputs them as the edited video 19.

  In this way, the video editing apparatus 1 performs processing so as to edit the video to be processed without intervention of the video creator or the editing section.

  FIG. 2 shows a flowchart of the video editing process executed by the video editing apparatus 1 configured as described above. An example of video editing processing performed by the video editing device 1 will be described in detail using this flowchart.

  In the video editing process described below, the semantic content category information stored in the semantic content category dictionary 20 created in advance and the semantic content relevance storage unit 22 calculated in advance by the semantic content relevance calculation unit 21 are used. The contents of the semantic content relevance stored in the above are used, and details thereof will be described in accordance with the description of the following processing procedure.

First, in step S201, a video to be processed is input, and in step S202, a video segmentation of the input video is performed. This video segmentation may be performed at predetermined intervals, for example, by a cut point that is a point at which the video is cut discontinuously, such as the method described in Reference 1 below. It is good also as what is divided | segmented.
[Reference 1]: Y. Tonomura, A. Akutsu, Y. Taniguchi, and G. Suzuki, “Structured Video Computing”, IEEE Multimedia, pp. 34-43, 1994.
Next, in step S203, video segment feature values are extracted from image / sound information in the video segment. Video segment feature values are extracted from images and extracted from sounds. In either case, for example, a statistic extracted from a minute section (frame) such as 50 ms is extracted by calculating within the section.

  For example, features extracted from an image include brightness features, color features, motion features, texture features, cut features, object features, and image event features.

  The brightness feature, color feature, motion feature, and the like can be obtained by calculating the brightness, RGB value, and motion vector for each pixel, respectively. As a texture feature, a statistic (contrast) of a density histogram, a power spectrum, or the like may be obtained. In addition, these may use statistics such as an average or variance for an entire image, or, for example, take a histogram for each small pixel region such as 8 × 8, 16 × 16, and extract it as a vector. It is good also as what to do.

  The cut feature is a feature quantity indicating the presence / absence of scene switching (cut) or the frequency. Strictly speaking, since it cannot be extracted from a single image, it is obtained using a neighboring image.

An object feature is an object contained in an image. In the present embodiment, object recognition for identifying what the object is is not performed, and local features used for object recognition are used as object features. As the local feature, for example, SIFT (Scale Invariant Feature Transform) described in Reference Document 2 below, SURF (Speeded Up Robust Features) described in Reference Document 3 below, or the like can be used.
[Reference 2]: DG Lowe, "Distinctive Image Features from Scale-Invariant Keypoints", International Journal of Computer Vision, pp.91-110, 2004.
[Reference 3]: H. Bay, T. Tuytelaars, and LV Gool, “SURF: Speeded Up Robust Features”, Lecture Notes in Computer Science, vol. 3951, pp. 404-417, 2006.
It is also conceivable to use a method of focusing and detecting a specific object as an object feature. For example, the approach of getting the appearance of a face and its expression is typical. As a method for detecting the face, for example, a method described in Reference Document 4 below may be used. Furthermore, when recognizing a facial expression, the method described in Reference Document 5 below may be used.
[Reference 4]: HA Rowley, S. Baluja, and T. Kanade, “Neural Network-based Face Detection”, IEEE Computer Society Conference on Computer Vision and Pattern Recognition, pp. 203-208, 1996.
[Reference 5]: I. Cohen, N. Sebe, A. Garg, LS Chen, and TS Huang, "Facial Expression Recognition from Video Sequences: Temporal and Static Modeling", Computer Vision and Image Understanding, vol.91, issues 1-2, pp.160-187, 2003.
An image event feature is an event that occurs in a video. For example, there are sudden camera work and the appearance of telop. For example, when a sudden camera work is used, it can be detected by using the method described in the above-mentioned Reference 1. Further, when using a telop, it can be detected by using a method described in Reference Document 6 below.
[Reference 6]: Hideo Kuwano, Masaharu Kurakake, Kazumi Odaka, “Telop Character Extraction Method for Video Data Retrieval”, IEICE Technical Report, PRMU, 96 (385), pp.39-46, 1996.
On the other hand, features extracted from sound information include pitch features, volume features, spectrum features, rhythm features, speech features, music features, sound event features, and the like.

The pitch feature may be a pitch, for example, and can be extracted using a method described in Reference Document 7 below.
[Reference 7]: Sadaaki Furui, “Digital Audio Processing, 4.9 Pitch Extraction”, pp.57-59, 1985.
As the volume feature, the amplitude value of the speech waveform data may be used, or a short-time power spectrum may be obtained and the average power in an arbitrary band may be calculated and used.

  As the spectral feature, for example, Mel-Frequency Cepstral Coefficients (MFCC) can be used.

As the rhythm feature, for example, a tempo may be extracted. In order to extract the tempo, for example, a method described in Reference Document 8 below can be used.
[Reference 8]: ED Scheirer, "Tempo and Beat Analysis of Acoustic Musical Signals", Journal of Acoustic Society America, Vol.103, Issue 1, pp.588-601, 1998.
The utterance feature and the music feature represent the presence or absence of utterance and the presence or absence of music, respectively. In order to find a section where speech / music exists, for example, a method described in Reference 9 below may be used.
[Reference 9]: K. Minami, A. Akutsu, H. Hamada, and Y. Tonomura, "Video Handling with Music and Speech Detection", IEEE Multimedia, vol.5, no.3, pp.17-25, 1998.
As sound event information, for example, emotional sounds such as laughter and loud voice, or occurrence of environmental sounds such as gunshots and explosion sounds may be used. In order to detect such a sound event, for example, a method described in Reference Document 10 (Patent Document) below may be used.
[Reference 10]: WO / 2008/032787
Subsequently, in step S204, the semantic content likelihood is calculated for all video segments based on the video segment feature value obtained in step S203.

  First, the semantic content category will be described here. The semantic content category represents the meaning of video content by a small number of words, and represents objects, events, concepts, emotions, and the like.

  For example, if a soccer goal scene is stored in the video section, the meaning content categories of the section are “ball (object)”, “goal (event)”, “soccer (concept)”, “joy ( Emotion) ”would be appropriate. In addition, “tree (object)”, “mountain (object)”, “walking (event)”, “hiking (concept)”, etc. are appropriate for the video section that shows hiking on a trip. .

  These objects, events, concepts, emotions, etc. are set in advance as semantic content categories and registered in the semantic content category dictionary 20. Also, likelihood model information indicating a probabilistic relationship between each semantic content category and video segment feature obtained by learning a large number of sample videos is registered in the semantic content category dictionary 20.

  The semantic content likelihood calculated in step S204 is a value obtained by probabilistically estimating the likelihood content belonging to each semantic content category as to which semantic content category this video section i seems to belong to. is there. The semantic content likelihood is calculated using a model (likelihood model) in which the relationship between the video segment feature value extracted in step S203 and each of the semantic content categories preset in the semantic content category dictionary 20 is set. This likelihood model may be obtained, for example, by modeling the video segment feature quantity of a video segment belonging to a certain semantic content category with a probability density function such as Gaussian distribution or Poisson distribution, or when the video segment feature is discrete. May be modeled by a conditional probability table or a multinomial distribution.

Since all of the above models are probability models, learning is performed based on, for example, a label of a semantic content category given in advance by hand. For example, it is assumed that a label “soccer” is manually assigned to a video section i in which a state of soccer is photographed. At this time, for the semantic content category “soccer”, the model is learned so that the video section feature amount x _i of the video section _i is likely to appear. For this learning, for example, a known method such as a maximum likelihood estimation method may be used. Even when a plurality of labels are given, the model may be learned for each label in the same manner.

  The obtained likelihood model is expressed by the following mathematical formula.

p (x _i | c _i ) (1)
Here, x _i is a video section feature amount of a video section i, c _i is a semantic content category of the video section i, and both are random variables. x _i takes the value of the feature amount calculated in step S203. c _i indicates each semantic content category. For example, c _i = “soccer” and c _i = “walk”.

When calculating the semantic content likelihood, an equation of p (x _i | c _i ) may be calculated for each semantic content category.

  Here, a procedure for calculating the semantic content likelihood of a certain video section i will be described. For example, suppose that five semantic content categories are set. For example:

・ Meaning content category 1: "Soccer"
-Meaning content category 2: "Sports"
・ Meaning Category 3: “Sea”
・ Meaning Category 4: “Hiking”
Meaning content category 5: “Swimming”
First, in step S203, the video section feature amount x _i of the video section _i is obtained. In step S204, the semantic content likelihood is calculated for each of the semantic content categories 1 to 5 based on the video section feature amount x _i and p (x _i | c _i ) of the equation (1). is there. Let's assume that video section i is a picture of soccer. In the above category example, the semantic content likelihoods of p (x _i | c _i = soccer) and p (x _i | c _i = sports) are calculated to be high. On the other hand, soccer video rarely contains “sea” and is different from “hiking” and “swimming”, so p (x _i | c _i = sea), p ( The semantic content likelihood of x _i | c _i = hiking) and p (x _i | c _i = swimming) is calculated to be low. In this way, the likelihood of each semantic content category in a certain video section i is calculated.

Also, with respect to the expression p (x _i | c _i ), from the Bayes rule,
p (c _i | x _i ) = {p (x _i | c _i ) p (c _i )} / p (x _i ) (2)
Note also that

  Subsequently, in steps S205 to S208, the video segment used for generating the edited video 19 is selected by the editing target video segment selection unit 17, and the degree of association between the semantic content categories used for calculating the context similarity here. explain.

  The semantic content relevance calculation unit 21 calculates the degree of relevance between one or more predetermined semantic content categories and stores the calculated relevance level in the semantic content relevance storage unit 22. The degree of association between the semantic content categories is as follows.

Since the video sections are continuous, a video section i-1 exists immediately before a certain video section i. When I expressed these two semantic content category image segment c _i respectively, and c _i-1, the probability These conditional tables c _i | seeking c _i-1, the degree of association between the semantic content categories this .

This conditional probability table may be learned using the meaning content category label used when learning the semantic content likelihood. For example, assume that the meaning content category label assigned to video section i is “soccer” and the meaning content category label assigned to video section i−1 is “sports”. In this case, "when c _i-1 is" sports ", c _i is" soccer "" can be regarded as a frequency that there is one.

When multiple labels are given, the independence between each semantic content category is assumed for the calculation amount, and the frequency may be counted for each pair. For example, in the above example, it is further assumed that “sport” is given to the video section i and “ball” is given to the video section i-1. In this case, "when c _i-1 is" ball ", c _i is" soccer "", also "when c _i-1 is" ball ", c _i is" sports ""When c _i-1 is" sport ", each frequency of c _i is" sport "is also considered to be 1.

Such counting is performed over the entire video (section) where the label is obtained. As a result, the generated conditional probability table c _i | c _i-1 has the same number as the semantic content category in both the number of rows and the number of columns.

  The obtained conditional probability table is expressed by the following mathematical formula.

p (c _i | c _i-1 ) (3)
According to this conditional probability table, when a certain meaning content category c _i-1 is given, the degree of association (probability) with all other meaning content categories c _i can be calculated. For example, let c _i-1 = “soccer”. At this time, the probability of appearance of other categories, for example, c _i = “ball” or c _i = “sport” is p (c _i = ball | c _i−1 = soccer), p (c _i = sport) | C _i-1 = soccer).

  Information in the conditional probability table as described above is calculated by the semantic content relevance calculation unit 21 and stored in the semantic content relevance storage unit 22.

  Subsequently, in step S205, the video sections are clustered based on the semantic content likelihood calculated in step S204, and one or more representative video sections from each cluster are output as representative video sections.

  As an effect of this clustering process, when sieving the subsequent video section, it is only necessary to perform the calculation for the representative video section representing a small number of clusters without performing the calculation for all the video sections. A point is raised. Therefore, automatic editing can be executed in a short time.

  FIG. 3 shows an example of clustering and representative video segment extraction when the number of video segments is 15 and the number of clusters is 4.

  There are various known methods for clustering, such as K-means method, mean shift, hierarchical clustering, and affinity propagation. The elements necessary to use these methods are similar to any two video sections. Is to define gender. Therefore, here we describe the definition of similarity based on the semantic content likelihood and the semantic content relevance.

  From the viewer's point of view, it is preferable to perform clustering by judging similarity from the viewpoint of semantic content, because only the video sections having similar semantic content are bored. Therefore, the probability of the semantic content of each video section is calculated and defined as similarity.

For example, the probability p of meaning category c _i in a certain image segment i (c _i | x _i) can be calculated by Equation (2). Similarly, the probability p (c _i-1 | x _i-1 ) of the semantic content category c _i-1 in the video section i-1 can also be obtained by Expression (2). Therefore, the similarity between these two probability densities may be defined as the similarity between video sections.

  Typical examples of the similarity between probability densities include negative cullback-liver divergence or reciprocal of cullback-liver divergence. The reciprocal is expressed by, for example, the following mathematical formula.

s _{i, i-1} = 1 / {KL [p (c _i | x _i ) ‖p (c _i-1 | x _i-1 )]} (4)
However,
KL [p (x) ‖q ( x)] = Σ x p (x) log {p (x) / q (x)} ... (5)
It is (sigma _x is the sum of x). Cullback-liver divergence does not have symmetry. That is, if the two probability distributions p (x) and q (x) in the above equation (5) are exchanged, the output value changes. As the similarity used for clustering, it may be inconvenient that the symmetry is not established. Therefore, it is preferable to use negative Jensen-Shannon divergence or the inverse of Jensen-Shannon divergence.

s _{i, i-1} = 1 / {JS [p (c _i | x _i ) ‖p (c _i-1 | x _i-1 )]} Equation (6)
However,
JS [p (x) ‖q (x)]
= ΛKL [p (x) ‖q (x)] + (1−λ) KL [q (x) ‖p (x)] (7)
Here, when λ = 0.5, symmetry is established.

  In this example, an example of similarity calculation for two adjacent video sections i and i-1 is described. However, equations (4) and (6) can be calculated without being limited to adjacent video sections. It is.

Based on the similarity s _{i, i−1} obtained by these equations, clustering may be performed by the above-described known clustering method, for example, affinity propagation described in Reference Document 11 below. There are three advantages of using affinity propagation, especially compared to the K-means method.
(1) In the case of K-means, it is necessary to set the number of clusters before clustering. In affinity propagation, it is not necessary to give the number of clusters in advance.
(2) In the case of K-means, the center of the generated cluster is not necessarily a certain video section. In the case of affinity propagation, it always indicates a certain video section. Therefore, the representative video section can be determined as the cluster center.
(3) In the case of K-means, the clustering result largely depends on an initial value that is normally selected at random, and therefore, it is necessary to devise such as obtaining the best clustering result after a plurality of trials. In the case of affinity propagation, the clustering result does not depend on the initial value, so only one trial is required.
[Reference 11]: BJ Frey, and D. Deuck, “Clustering by Passing Messages Between Data Points”, Science, vol. 315, pp. 972-976, 2007.
Also, a method of applying Time-Constrained Clustering described in Reference Document 12 may be taken.
[Reference 12]: MM Yeung, and B.-L. Yeo, “Time-Constrained Clustering for Segmentation of Video into Story Units”, International Conference on Pattern Recognition, vol.3, pp.375-380, 1996.
Subsequently, in step S206, the context similarity is calculated based on the context prediction probability and the context posterior probability, and in step S207, one or more representative video sections to be removed are determined based on the context similarity, and the rest The representative video section is output.

  Let S be the original representative video segment group. FIG. 4 shows an example of sieving the representative video space when the original number of representative video sections is four. In this process, one cluster including the representative video section in which the average f of the context similarity is highest or lowest is removed. Since zero or more video sections having semantic contents similar to the representative video section are stored in the cluster, these video sections are removed from the edited video.

First, the representative video sections of each cluster are arranged in the order of playback time. Now, when if the number of representative video section was M, _{which, K 1, K 2, K} 3 time order, ..., and be expressed as K _M. In the example of FIG. 4, the number of representative video sections is four. Let this original representative video section group be S.

Next, a candidate representative video segment group is generated by removing only one representative video segment from the representative video segment group S. In the example of FIG. 4, since there are four representative image segment from K ₁ to K _4, four candidate representative image interval from S / K ₁ except for K ₁ to S / K ₄ except K ₄ A group is generated.

Next, an average context similarity f is calculated for each candidate representative video section group. Here, among the four candidate representative image segments, shown in FIG. 4 shows an example of obtaining a mean context similarity f (S / K ₂₎ for the S / K ₂ was removed K _2. It goes without saying that other candidate representative video section groups can be similarly calculated.

In order to calculate the average context similarity f (S / K ₂ ), it is necessary to calculate the context similarity t ₁ , t ₃ , t ₄ of each representative section K ₁ , K ₃ , K ₄ . Since there is no K ₂ now, for convenience, K ₁ will be replaced with K ′ ₁ , K ₃ will be replaced with K ′ ₂ , and K ₄ will be replaced with K ′ ₃ . First, a method for calculating each context similarity t _j will be described.

A context prediction probability and a context posterior probability in the representative video section K ′ _j are calculated. For this purpose, it is necessary to use past context prediction probabilities and context posterior probabilities calculated up to previous representative video sections K ′ ₁ ,..., K ′ _j−1 .

The video section feature amount of the representative video section K ′ _{j is} represented as x _j and the semantic content category is represented as c _j . First, the context prediction probability is calculated based on the following equation (8).

p (c _j | x ₁ , x ₂ ,..., x _j-1 )
= Σp (c _j | c _j−1 ) p (c _j−1 | x ₁ , x ₂ ,..., X _j−1 ) (8)
(Where Σ is the sum of c _j-1 )
Here, p (c _j−1 | x ₁ , x ₂ ,..., X _j−1 ) appearing on the right side is the context posterior probability of K ′ _j−1 .

  Subsequently, the context posterior probability is calculated based on the following formula.

p (c _j | x ₁ , x ₂ ,..., x _j )
= {P (x _j | c _j ) p (c _j | x ₁ , x ₂ ,..., X _j-1 )} / Σ {(p (x _j | c _j ) p (c _j | x ₁ , x ₂ , ..., x _j-1 )} ... (9)
(Where Σ is the sum of c _j )
Here, p (c _j | x ₁ , x ₂ ,..., X _j-1 ) is the context prediction probability obtained by the equation (8).

By calculating the above from K ′ ₁ to K ′ _{3 in} order, the context prediction probabilities and context posterior probabilities in all the representative video sections can be calculated. Note that the context prediction probability of K ′ ₁ cannot normally be calculated because there is no past context posterior probability. Therefore, the K ′ ₁ context prediction probability may be given an arbitrary probability distribution such as a uniform distribution.

Subsequently, the context similarity t _j of each representative video section is obtained. Context similarity t _j of the representative video section j is defined as the similarity of context prediction probability and context posterior probability. Since both are probability distributions, the similarity is obtained using Eqs. (4) and (6).

_{t j = Σ {p (c} j | x 1, x 2, ..., x j) log {p (c j | x 1, x 2, ..., x j) / p (c j | x 1, x 2 , ..., x _j-1 )}} ... (10)
(Where Σ is the sum of c _j )
The context similarity t _j is the context similarity of the representative video section K ′ _j , but can be calculated similarly for other representative video sections by calculating in order from K ′ ₁ .

Finally, the average context similarity f (S / K ₂ ) is calculated for the candidate representative video segment group S / K ₂ . This may be simply an arithmetic average of the representative video section similarity t _j or a weighted average.

  As described above, the average context similarity f for all candidate representative video section groups is calculated.

  After the average context similarity of all candidate representative video section groups is calculated, the candidate representative video section group that becomes the maximum / minimum among them is selected, and adopted and output as a new representative video section group S ′.

  At this time, whether to maximize or minimize depends on what kind of edited video you want to create. If you want to create edited videos with the same context (consistent context), the average should be low. If you want to create edited videos with various contexts, the average should be high. That's fine.

  Of the processing steps described above, steps S205 to S207 are repeatedly executed until the end condition is satisfied (step S208). The end condition may be, for example, when the time length of the edited video is equal to or less than a certain video section, or may be when the average value of the context similarity is greater than or equal to a certain value.

  The effect of this iterative process can be mentioned as follows. Usually, when generating an edited video in consideration of context, it is necessary to generate an edited video from all possible combinations of video sections, which causes a problem of so-called combination explosion. More specifically, when the number of video sections is N, a calculation amount exceeding O (N!) Is required as a calculation order, and the calculation cannot be completed in a realistic time.

  On the other hand, in the iterative processing according to the present embodiment, the edited video can be generated from the more promising representative video section groups that are reduced in stages, so that the polynomial time is dramatically shorter, The edited video can be generated in consideration of the context.

  The clustering process in step S205 may normally be performed only once, and even in the example of this embodiment, the process consistency is not lost. However, there is an effect by including it repeatedly, and this can be described as follows.

  In the clustering process, the number of clusters to be generated is usually determined adaptively according to the number of target data (can be automatically determined when using affinity propagation). To give a simple example, if there are only 10 data, it would not make much sense to generate 9 clusters, for example, 2 or 3 should be set. Also, when the number of data is 1 million, an excessively rough cluster is generated with two or three clusters, so it will be necessary to set a few more clusters.

  In this embodiment, the video segments to be clustered are reduced step by step. By including this clustering process in the iteration, it is possible to determine the number of meaningful clusters according to the number of video segments in each step. become.

  In the above processing example, only the case where one candidate representative video section group is deleted from the original representative video section group is handled. However, as a processing method, the candidate representative video segment group may be generated not only by deleting the video segment as described in FIG. 4 but also by adding the video segment or changing the time order. One of the notable effects is that the use of this embodiment can support not only the editing of deleting a video section but also a more general editing action.

  Finally, when the end condition is satisfied in step S209, the representative video sections output in step S207 are connected and output as the edited video 19.

  The above is the description of the video editing method in the example of the embodiment of the present invention. It goes without saying that the processing process executed by the video editing apparatus can be described as a computer-readable program.

  The video editing apparatus according to the exemplary embodiment of the present invention has been described in detail above. The present invention is not limited to the example of the embodiment described, and various modifications can be made within the technical scope described in the claims.

  For example, the present invention can be used for various video distribution / communication services such as IPTV, digital signage, and VOD (Video on Demand). Specifically, it is possible to realize application services such as an arrangement for enhancing the effect of video advertisement and automatic generation of a video playlist.

DESCRIPTION OF SYMBOLS 1 Image | video editing apparatus 10 Image | video 11 Image | video input part 12 Image | video memory | storage part 13 Image | video area division | segmentation part 14 Image | video area feature-value extraction part 15 Semantic content likelihood calculation part 16 Clustering part 17 Editing object image | video area selection part 170 Similarity degree calculation part 171 Context Prediction probability calculation unit 172 Context posterior probability calculation unit 173 Context similarity calculation unit 174 Representative video section sieving unit 18 Edit video output unit 19 Edit video 20 Semantic content category dictionary 21 Semantic content relevance calculation unit 22 Semantic content relevance storage unit

Claims (7)

A video editing device that automatically generates and outputs an edited video from an input video,
A likelihood model that shows the stochastic relationship between a semantic content category that expresses the meaning of video content by a specific word and a video segment feature that consists of image features and / or sound features of the video segment. A semantic content category dictionary for storing information;
A video segmentation unit that divides the input video into video segments;
A video segment feature value extraction unit that extracts a video segment feature value from each of the video segments;
A semantic content likelihood calculation unit that refers to the semantic content category dictionary based on the extracted video segment feature and outputs the likelihood of each semantic content category for the video segment;
Clustering the video segments based on the likelihood, and a clustering unit for selecting one or more representative video segments from each generated video segment cluster;
For the arrangement of a plurality of candidate representative video sections obtained from the selected representative video section combination, at least the likelihood is used to calculate the context similarity indicating the degree of semantic change in the connection of the video sections. As a candidate representative video segment group that uses either an arrangement of candidate representative video segments with a large degree of semantic change or a sequence of candidate representative video segments with a small degree of semantic change as a whole based on the context similarity A video segment selection section to be selected,
A video editing apparatus comprising: an edited video output unit configured to generate and output an edited video by connecting video segments of the selected candidate representative video segment group. The video editing apparatus according to claim 1,
For each semantic content category stored in the semantic content category dictionary, a semantic content relevance storage unit that stores the degree of association with other semantic content categories obtained by learning the sample video,
The editing target video section selection unit
For each video segment position in the list of candidate representative video segments, input the video segment feature of the video segment position located in the past, the likelihood, and the degree of association stored in the semantic content relevance storage unit A context prediction probability calculation unit for calculating a context prediction probability using an expression for calculating a prediction probability that the video section at the position belongs to each semantic content category;
For each video segment position in the candidate representative video segment sequence, the video segment feature of the previous video segment position, the likelihood and the degree of association stored in the semantic content relevance storage unit are input. A context posterior probability calculation unit for calculating a context posterior probability using an expression for calculating a posterior probability that the video segment of the position belongs to each semantic content category;
A context similarity calculation unit that calculates the similarity between the context prediction probability and the context posterior probability as a context similarity indicating the semantic change degree;
For each arrangement of the candidate representative video sections, an average of the similarities calculated by the context similarity calculation section is obtained, and a representative video section sieving section for selecting an arrangement of candidate representative video sections having the maximum or the minimum A video editing apparatus characterized by comprising: The video editing apparatus according to claim 1 or 2,
The video section included in the candidate representative video section group selected by the editing target video section selection section is set as a video section to be clustered by the clustering section, and the processing by the clustering section and the editing until a predetermined end condition is satisfied. A video editing apparatus characterized by repeating the processing by the target video section selection unit. A video editing method in which a video editing device automatically generates and outputs an edited video from an input video,
A likelihood model that shows the stochastic relationship between a semantic content category that expresses the meaning of video content by a specific word and a video segment feature that consists of image features and / or sound features of the video segment. Using a semantic content category dictionary that stores information,
Video segmentation processing for dividing the input video into video segments;
Video segment feature value extraction processing for extracting video segment feature values from each of the video segments;
A semantic content likelihood calculation process for referring to the semantic content category dictionary based on the extracted video segment feature and outputting the likelihood of each semantic content category for the video segment;
Clustering the video segments based on the likelihood, and a clustering process for selecting one or more representative video segments from each generated video segment cluster;
For the arrangement of a plurality of candidate representative video sections obtained from the selected representative video section combination, at least the likelihood is used to calculate the context similarity indicating the degree of semantic change in the connection of the video sections. As a candidate representative video segment group that uses either an arrangement of candidate representative video segments with a large degree of semantic change or a sequence of candidate representative video segments with a small degree of semantic change as a whole based on the context similarity A selection process for selecting a video segment to be edited;
A video editing method comprising: executing an edited video output process of generating and outputting an edited video by connecting video segments of the selected candidate representative video segment group. The video editing method according to claim 4,
For each semantic content category stored in the semantic content category dictionary, the degree of association with other semantic content categories obtained by learning the sample video is stored in the semantic content relevance storage unit,
In the video segment selection process for editing,
For each video segment position in the list of candidate representative video segments, input the video segment feature of the video segment position located in the past, the likelihood, and the degree of association stored in the semantic content relevance storage unit A context prediction probability calculation process for calculating a context prediction probability using an expression for calculating a prediction probability that the video section at the position belongs to each semantic content category;
For each video segment position in the candidate representative video segment sequence, the video segment feature of the previous video segment position, the likelihood and the degree of association stored in the semantic content relevance storage unit are input. A context posterior probability calculation process for calculating a context posterior probability using an expression for calculating a posterior probability that the video segment of the position belongs to each semantic content category;
A context similarity calculation process for calculating a similarity between the context prediction probability and the context posterior probability as a context similarity indicating the semantic change degree;
For each arrangement of the candidate representative video sections, an average of the similarities calculated by the context similarity calculation processing is obtained, and a representative video section sieving process for selecting an arrangement of candidate representative video sections having the maximum or the minimum The video editing method characterized by performing. The video editing method according to claim 4 or 5,
The video section included in the candidate representative video section group selected by the editing target video section selection process is set as a video section to be clustered by the clustering process, and the clustering process and the editing target video are satisfied until a predetermined end condition is satisfied. A video editing method characterized by repeating the section selection process.   A video editing program for causing a computer to execute the video editing method according to claim 4, 5 or 6.

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