Abstract:
A method of creating a thumbnail using luminance of a video sequence includes grouping the video sequence into predetermined frame groups and extracting basic frames of the groups; calculating a luminance difference between the extracted basic frames using the extracted basic frames; selecting motion prediction pixel frames using the calculated luminance differences between the basic frames; and calculating standard deviations of the selected motion prediction pixel frames and selecting a predetermined number of frames having great standard deviations as core frames to create thumbnails.

Description:
PRIORITY  
       [0001]     This application claims priority under 35 U.S.C. § 119 to an application filed in the Korean Intellectual Property Office on Dec. 1, 2005 and assigned Serial No. 2005-116133, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to a method and apparatus of creating and displaying a thumbnail, and in particular, to a method and apparatus of creating an animated thumbnail at a reduced cost using only luminance of each frame of a video sequence in a mobile communication terminal.  
         [0004]     2. Description of the Related Art  
         [0005]     With the development of multimedia technologies, the use of digital multimedia information is greatly increasing. Moreover, as recent mobile communication systems allow transmission of large-capacity data at a high rate, mass visual contents such as video data are being increasingly used in the mobile communication terminal. Therefore, research is ongoing on a method of facilitating search or management of the multimedia information.  
         [0006]     A “thumbnail” refers to a small image obtained by extracting a core frame of original data having a relatively large size in order to facilitate search or management of the multimedia information.  
         [0007]     The most commonly used techniques that extract a core frame for creating the thumbnail according to the conventional art include a technique that selects a first frame of each video shot as a core frame, and a technique that selects a core frame based on a frame quality factor.  
         [0008]     In the technique that selects a core frame according to the frame quality factor, the frame quality factor is represented by a weighted combination of an entropy and a standard deviation of color histograms, and a frame having the highest frame quality factor is selected as a core frame. That is, the core frame is selected by the use and analysis of visual criteria such as color properties of the video shot and a motion between video frames.  
         [0009]     The technique that selects the first frame as the core frame requires a low cost of calculation, but has problems in that conspicuous video contents of the video shot cannot be effectively captured. In contrast, the technique that selects the core frame according to the frame QoS can effectively capture visual contents because it takes the color properties of the video shot and the motion between the video frames into account, but disadvantageously requires a high cost of calculation.  
       SUMMARY OF THE INVENTION  
       [0010]     An object of the present invention is to substantially solve at least the above problems and/or disadvantages and to provide at least the advantages below. Accordingly, an object of the present invention is to provide a method and apparatus of creating and displaying a thumbnail, which reduces a thumbnail creation cost and captures conspicuous visual contents by taking the luminance of each frame of a video sequence into account.  
         [0011]     Another object of the present invention is to provide a method and apparatus of creating and displaying an animated thumbnail in consideration of only the luminance of each frame of a video sequence.  
         [0012]     According to an aspect of the present invention, a method and apparatus of creating and displaying an animated thumbnail includes creating an animated thumbnail using luminance of basic frames of a video sequence; creating a thumbnail list using the created thumbnails; and when one thumbnail is selected from the thumbnail list, displaying an animated video thumbnail of the selected thumbnail.  
         [0013]     According to another aspect of the present invention, a method of creating a thumbnail by using luminance of a video sequence includes grouping the video sequence into predetermined frame groups and extracting basic frames of the groups; calculating luminance a difference between the extracted basic frames using the extracted basic frames; selecting motion prediction pixel frames using the calculated luminance differences between the basic frames; and calculating standard deviations of the selected motion prediction pixel frames and selecting a predetermined number of frames having great standard deviations as core frames to create thumbnails. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:  
         [0015]      FIG. 1  is a block diagram of a mobile communication terminal for generating a thumbnail according to the present invention;  
         [0016]      FIG. 2  is a flowchart showing a process of displaying an animated thumbnail in a mobile communication terminal according to the present invention;  
         [0017]      FIG. 3  is a flowchart showing a process of generating an animated thumbnail in a mobile communication terminal according to the present invention; and  
         [0018]      FIG. 4  is a view illustrating a screen displaying a list of thumbnails in 3×3 configuration.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     Preferred embodiments of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail because they would obscure the present invention in unnecessary detail.  
         [0020]     A technique will be described below, which reduces a thumbnail creation cost by using the luminance of each frame of a video sequence, and creates a thumbnail by capturing conspicuous visual contents. Even though creating and displaying a thumbnail in a mobile communication terminal are described, the present invention is not limited thereto and may be applied to various fields that creates and displays the thumbnail.  
         [0021]      FIG. 1  is a block diagram of a mobile communication terminal according to the present invention. Examples of the mobile communication terminal may include cellular phones, Personal Communication System (PCS) terminals, Personal Data Assistants (PDAs), International Mobile Telecommunications-2000 (IMT-200) terminals, or the like. The following description will be made with a general structure of those examples.  
         [0022]     Referring to  FIG. 1 , a controller (e.g., a microprocessor unit (MPU))  100  controls an overall operation of the mobile communication terminal. For example, the controller  100  processes and controls voice communication and data communication. In addition to the general functions, the controller  100  serves to create and display an animated thumbnail of a video sequence using luminance according to the present invention. The general functions of the controller  100  will be omitted for conciseness.  
         [0023]     A communication module  102  processes a radio data signal received/transmitted through an antenna. For example, during a transmission operation, the communication module  102  channel-codes and spreads transmission (TX) data to output an RF signal. During a reception operation, the communication module  102  converts a received RF signal into a baseband signal and recovers a data by despreading and channel-decoding the baseband signal.  
         [0024]     A camera module  104  includes an image sensor, a camera lens, a signal processor, and an image processor. The camera module  104  converts captured image data into digital data to obtain a moving image or a still image, and then outputs the moving or still image to a display unit  106 .  
         [0025]     The display unit  106  displays status information generated during operations of the mobile communication terminal, numerals and characters, moving images and still images under control of the controller  100 . A color liquid crystal display (LCD) may be used for the display unit  106 .  
         [0026]     A memory unit  108  includes a read only memory (ROM), a random access memory (RAM), and a flash ROM. The ROM stores microcodes of a program and various reference data for processing and controlling the controller  100 . Particularly, the ROM stores a program for creating and displaying an animated thumbnail using luminance of a video sequence according to the present invention. The RAM is a working memory of the controller  100 , which stores temporary data generated during operations. Also, the flash ROM stores various updateable data such as a phone book, outgoing messages, incoming messages, or the like. Also, the flash ROM stores an animated thumbnail of each video sequence generated by the thumbnail creating program.  
         [0027]     A keypad  110  includes numeric keys of digits 0-9 and a plurality of function keys, such as a Menu key, a Cancel (Delete) key, a Confirmation key, a Talk key, an End key, an Internet connection key, and Navigation keys (▴/▾/         /         ) to provide key input data that corresponds to keys pressed by a user to the controller  100 .  
         [0028]     An audio processor  112  is called a CODEC and inputs and outputs an audio signal through a microphone  114  and a speaker  116 . For example, the audio processor  112  converts digital data received from the controller  100  into analog audio signals to output the analog audio signals through the speaker  116 , and converts audio signals received through the microphone  114  into digital data to output the digital data to the controller  100 .  
         [0029]      FIG. 2  is a flowchart showing a process of creating an animated thumbnail in a mobile communication terminal according to the present invention.  
         [0030]     Referring to  FIG. 2 , the controller  100  searches a video sequence existing in the mobile communication terminal in step  201 . The video sequence may be captured through the camera module of the mobile communication terminal, or may be received from the outside through an interface connection or communication module.  
         [0031]     When the video sequence is searched in step  201 , the controller  100  creates animated video thumbnails using luminance of each frame of the searched video sequence in step  203 , which will be described later in further detail with reference to  FIG. 3 .  
         [0032]     When the video thumbnails are created in step  203 , as illustrated in  FIG. 4 , the controller  100  creates a thumbnail list (e.g., 3×3 thumbnail list) using the created thumbnails, and displays the list on the display unit  106  in step  205 . The thumbnails included in the displayed thumbnail list display first frames of images, respectively.  
         [0033]     In step  207 , the controller  100  checks whether one thumbnail from the displayed thumbnail list is selected by a user&#39;s key manipulation.  
         [0034]     When one thumbnail is selected, the controller  100  displays animation thumbnail information of the selected thumbnail in step  209 . Other thumbnails that are not selected display the first frames of the images, respectively.  
         [0035]     Thereafter, the controller  100  terminates the algorithm.  
         [0036]      FIG. 3  is a flowchart of a process of creating an animated thumbnail in the mobile communication terminal according to the present invention.  
         [0037]     Referring to  FIG. 3 , the controller  100  checks whether a thumbnail creating mode is performed in step  301 . That is, the controller  100  checks whether a new video sequence is input to the mobile communication terminal and thumbnails of the video sequence are created.  
         [0038]     When the thumbnail creating mode is performed, the controller  100  groups the entire input video sequence into groups of pictures (GOPs) by a predetermined number of frames, and then extracts I frames, a reference frame, from the GOPs in step  303 . The “I frame” refers to a random access point to allow desired contents to be easily checked from the GOPs.  
         [0039]     After the I frame is extracted from the GOP, the controller  100  creates a group of I frames (GOIF), a stream combination of the I frames extracted from the individual GOPs in step  305 .  
         [0040]     In step  307 , the controller  100  calculates a picture difference (hereinafter, referred to as PD) between matching pixels of a previous I frame and a current I frame with respect every pixel of each frame using Equation (1):  
                 PD   ⁡     (     x   ,   y     )       =         ∑     i   =   0     M     ⁢       ∑     j   =   0     N     ⁢       F   pre     ⁡     (       x   +   i     ,     y   +   j       )           -       F   current     ⁡     (       x   +   i     ,     y   +   j       )           ,     0   ≤   x   &lt;   M     ,     0   ≤   y   &lt;   N             (   1   )             
 
 where x and y denotes locations of a pixel, and M and N denote horizontal and vertical resolutions, respectively. For example, in the case of a common intermediate format (CIF), M is 288 and N is 360. In the case of quarter CIF (QCIF), M is 144 and N is 180. 
 
         [0041]     To reduce computation quantity, only a luminance (Y) value of a YUV image format is used when the PDs are calculated using Equation (1). Because human eyes are insensitive to changes in a chrominance information value of an adjacent pixel rather than luminance changes, only the use of the luminance may contribute to find a visually conspicuous core frame. The YUV is aimed at the fact that the human eyes are sensitive to luminance rather than chrominance, in which the color is divided into a Y component, the luminance, and U and V components, the chrominance.  
         [0042]     In step  309 , after the PD of each I frame is calculated, the controller  100  selects a motion prediction pixel (PF) frame using Equation (2):  
               PF   n     =       [         ∑     i   =   0     M     ⁢       ∑     j   =   0     N     ⁢       PD   pre     ⁡     (       x   +   i     ,     y   +   j       )           -       PD   current     ⁡     (       x   +   i     ,     y   +   j       )         ]     &gt;   T             (   2   )             
 
 where x and y denotes locations of a pixel, M and N is horizontal and vertical resolutions, and n denotes a location of an I frame set as the PF frame. 
 
         [0043]     When a difference between the previous PD and the current PD obtained using Equation (2) is greater than a critical value (T), the corresponding I frame is selected as a PF frame.  
         [0044]     After the PF frames are selected in such a manner, the controller  100  calculates standard deviations of the selected PF frames in step  311 . In step  313 , the controller  100  determines, as core frames, P number of frames having relatively large standard deviations of the calculated standard deviations of the selected PF frames.  
         [0045]     In step  315 , the controller  100  creates an animated thumbnail using the P number of core frames and then terminates the algorithm.  
         [0046]     According to the present invention, an animated thumbnail is created using only luminance of a video sequence. Because only a luminance (Y) value of the YUV image format is used, a thumbnail can be created by capturing conspicuous visual contents at a creation cost reduced by ⅓. Also, the animated thumbnail allows for convenient searching for a video file.  
         [0047]     While the present invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.