Method for creating caption-based search information of moving picture data, searching moving picture data based on such information, and reproduction apparatus using said method

[0002] 1. Field of the Invention

[0003] The present invention relates to a method of creating caption-based search information for a moving picture stream of a video title recorded on a disk storage medium and performing a search of the moving picture stream by using the caption-based search information in a video disk reproduction apparatus like a DVD player, and a reproduction apparatus using such a method.

[0004] 2. Description of the Related Art

[0005] Video reproduction systems with a caption display function like a video cassette recorder (VCR) are, in most cases, used to offer an effective means for studying foreign languages. For caption data in a VCR, video signals including character signals for caption are recorded on a video tape, and while the tape is reproduced, the character signals are selectively added to an image signal in the video signal so that the caption can be displayed in a superposed relationship to an image.

[0006] Meanwhile, several information storage media such as digital versatile disk (DVD) and DVD-ROM have been recently released in the market for use as multimedia optical disks. For example, a DVD-ROM that has a diameter of 120 mm and a storage capacity of around 4.7 GB on one side is suited for storage of several video titles in which multiple sub-picture channels and multiple audio channels are provided.

[0007] In DVD, caption data is recorded in the sub-picture channels in the form of bit-mapped image signals. While DVD is reproduced, the sub-picture data is read out and is then added to an image signal so as to display the caption.

[0008] While viewing a video title in foreign language audio mode, it often happens that a viewer wants to see a particular caption again. At this time, it is necessary for the viewer to manually perform searching of the moving picture stream which is reproduced with the caption by using search commands offered by the DVD reproduction apparatus and to resume the reproduction operation. The search is generally made by manually operating backward/forward movement keys or reproduction time search operation. Accordingly, it often takes many steps of pause-and-movement operations to precisely locate the moving picture data which is linked to the caption that the viewer wants to see, resulting in slow search time and the viewer's inconvenience.

[0009] It is a primary object of the present invention to provide a method of creating caption-based video search information, in which each caption information is linked to the location of its associated moving picture stream which is reproduced concurrently with the caption information, in a moving picture data storage medium like DVD.

[0010] It is another object of the present invention to provide a method of and apparatus for performing search of moving picture stream corresponding to caption data which is chosen by a viewer in a caption list display window with reference to the caption-based moving picture stream search information.

[0011] To achieve the object, the present invention provides a method of creating caption-based search information for moving picture data of a data storage medium, comprising the steps of: searching moving picture data recorded on the storage medium for data including caption information; obtaining the location of the moving picture data to be concurrently reproduced with the caption information discovered in said searching step; and storing link information including the caption information and the location of the corresponding moving picture data.

[0012] The method of performing a caption-based search for moving picture data of a data storage medium according to the present invention comprises the steps of: creating and storing link information including caption information and moving picture data to be reproduced concurrently with the caption information; displaying part of the stored caption information; searching the created link information for the location of moving picture data, which is correspondent to a particular caption information chosen by a viewer from a list of caption information displayed on a screen; and resuming reproduction of moving picture data of the storage medium from the location of moving picture data discovered by said searching step.

[0013] In the method and apparatus according to the present invention, all caption data are extracted while video titles recorded on a DVD are scanned, and they are stored together with location information of moving picture data, each of which is linked to its associated caption data in terms of reproduction time. When the DVD is reproduced, a list of parts of the caption data is displayed on a screen in which a viewer can choose a caption the viewer wishes to listen or see. Upon choosing of a particular caption, the location of moving picture data linked with the selected caption is obtained from the link information between caption data and moving picture data. The reproduction of the DVD is then resumed at the location of the moving picture data.

[0014] The accompanying drawings, which are included to provide a further understanding of the invention, the preferred embodiment of this invention, and together with the description, serve to explain the principles of the present invention.

[0015] In the drawings:

[0016] FIG. 1 is a schematic diagram showing the sector area of a DVD;

[0017] FIG. 2 is a table showing volume structure and data fields;

[0018] FIG. 3 is a table showing file structure and data fields;

[0019] FIG. 4 is a schematic diagram showing the structure of a video object VOB;

[0020] FIGS. 5(A) and 5(B) are schematic diagrams showing the structure of a presentation pack;

[0021] FIGS. 6(A) and 6(B) are schematic diagrams showing the structure of a navigation pack;

[0022] FIGS. 7 and 8 are tables showing navigation information structure;

[0023] FIG. 9 is a schematic diagram of a reproduction apparatus implementing a method according to the present invention;

[0024] FIGS. 10 and 11 are flowcharts showing a method of creating link information between caption data and moving picture data according to the present invention;

[0025] FIG. 12 shows tables comprising caption-based moving picture search information according to the present invention;

[0026] FIG. 13 is a schematic diagram showing another embodiment of reproduction apparatus to implement the method according to the present invention;

[0027] FIG. 14 is a schematic diagram illustrating a caption list display window while reproducing a DVD title; and

[0028] FIG. 15 is a flowchart showing a method of searching moving picture data on the basis of the created link information between caption data and moving picture data.

[0029] The preferred embodiments of the present invention will be described hereinafter in detail referring to the accompanying drawings.

[0030] Before describing details of the method and apparatus according to the present invention, the data structure of video titles contained in DVD-ROM, one type of multimedia optical disks, is first described briefly below.

[0031] As shown in FIG. 1, the volume space of a DVD has the physical sector area (PSA) and the logical sector area (LSA), in which user data is recorded as 2048-byte logical sectors. The start location of the logical sector area, which is located by logical sector number (LSN) #0, is positioned outward away from the start location of the physical sector area by a predetermined distance. That is, the location of the sector of LSN #0 is the same as that of the physical sector number of 0x30000.

[0032] The volume space consists of a volume and file structure management area and a file data structure area As shown in FIG. 2, in the volume structure area, a “main volume descriptor sequence” containing a “volume recognition sequence”, a “volume ID”, a “date and time”, and a “logical volume integrity address” and a “reserved volume descriptor sequence” are stored in logic sectors LSN #0 to LSN #256. Information concerning the files stored in the file data structure area which includes a “file set descriptor” containing file names and their start location and size, a “file identifier descriptor”, and a “file entry” is stored in logic sectors LBN (logical block number) #0 to LBN #(q−1).

[0033] As shown in FIG. 3, the file structure area is made up of a video manager and a plurality of video title sets VTS #l−#K, where K is the number of video title sets. The video manager VMG stores the video manager information VMGI about the entire disk (denoted by VIDEO_TS.IFO) and information needed to build a volume menu which is used to set and change reproduction control of the entire volume (denoted by VIDEO_TS.VOB). Each video title set VTS comprises VTS information denoted by VTS_0k_0.IFO, where k is less than K, a VTS manager object denoted by VTS_0k_0.VOB and a plurality of VTS video objects VOB denoted by VTS_0k_n.VOB (where n=1, 2, . . . ).

[0034] The file data structure area stores a plurality of video object sets VOBS, each being made up of video objects VOB arranged in a time series, as shown in FIG. 4. Each VOB is made up of a plurality of cells, each containing playback sequence and playback control information. Each cell has information concerning a sequence of a plurality of video object units (VOBU), arranged in a time series. A VOBU is a multiplexed set of the various kinds of data, each of the multiplexed pieces having a reproduction time between 0.4 and 1.0 seconds. A VOBU comprises navigation data and presentation data which includes video data, audio data, and sub-picture data. Pieces of such data within a VOBU are respectively called video packs, audio packs, and sub-picture packs, each of which is 2048 Bytes in size and is the same size as a logical sector on the DVD. It is possible that no sub-picture data is provided in a VOBU.

[0035] The structure of a presentation pack is described with reference to FIGS. 5(A) and 5(B). The presentation packs comprise a “pack header”, a “packetized elementary stream (PES) header”, a “substream ID” for information on language as sub-picture data, and a “data area” in which audio, video, or sub-picture data are recorded. The pack header includes a “pack start code”, a “system clock reference” (SCR) defining the reference time for synchronized audio-visual data playback, and a “multiplex (MUX) rate”. The PES header includes “start codes” for audio, video, or sub-picture data. Here, the packetized elementary stream PES indicates a whole data stream exempting the pack header of 14 Bytes, as shown in FIGS. 5(A) and 5(B), and is considered as a data stream of common type.

[0036] The data construction of a navigation pack is shown in FIGS. 6(A) and 6(B). The navigation pack comprises a “pack header”, a “system header”, a “presentation control information (PCI)”, and “data search information (DSI)”. A navigation pack is placed at the beginning of each of video object units VOBU.

[0037] Two types of navigation information are provided in the DVD for playback control. One includes video manger information (VMGI) video title set information (VTSI) where program chain information (PGCI) is contained, as shown in FIGS. 7 and 8. The other navigation information is included in the PCI packet and DSI packet within the navigation packets, as shown FIGS. 6(A) and 6(B).

[0038] Hereinafter, the preferred embodiments of the present invention are described below in detail with reference to the accompanying figures.

[0039] FIG. 9 depicts a block diagram of the construction of an optical disk reproduction apparatus to which the method of the present invention is applied, comprising an optical pickup 2 for reading out information recorded in an optical disk by using a light beam irradiated from an LED; an radio-frequency (RF) demodulator 3 for demodulating the signal detected by the optical pickup into a binary signal; a digital signal processor 4 for processing the demodulated binary signal to obtain recorded digital data by utilizing a synchronized clock; an audio/video (A/V) signal processor 5 for decompressing the audio and video data stream and outputting them to an external device; a servo unit 7 for servo-controlling a driving unit of the optical disk on the basis of a focus error signal and a tracking error signal; a sled motor 13 for moving the optical pickup in the radial direction of the optical disk under control of the servo unit; a spindle motor 14 for rotating the optical disk under control of the servo unit; a sync clock generator 8 for generating the clock synchronized with the binary signal from the RF demodulator and outputting it to the digital signal processor 4; a microcomputer 11 for controlling the servo unit and the digital signal; a memory 12 for storing control data for the microcomputer and caption data; a display overlay unit 9 for displaying character signals in a caption display window in a superposed relationship to an image signal; and a mixing unit 6 for adding character signals to the image signal produced by the A/V signal processor 5.

[0040] A method of creating caption-based moving picture data search information embodied in the DVD player of FIG. 9 is described below in detail with reference to the flowcharts of FIGS. 10 and 11.

[0041] Upon loading of a DVD in the DVD player, the microcomputer 11 controls the servo unit 7 so that the DVD rotates at a constant rotation speed. Then, a volume structure search mode is set to read data stored in the volume structure area (S10). In the volume structure search mode, the optical pickup 2 is moved to the sector of LSN #256 to read out “main volume descriptor sequence address” which is stored in the “1st anchor point” (S11). By using the address, “main volume descriptor sequence” is read out and “logical volume integrity address” is obtained from a field of the “main volume descriptor sequence”.

[0042] Then “logical volume integrity” is read out by using the address and “file set descriptor address” is obtained from a field of the “logical volume integrity” and is then stored (S12, S13). The “file set descriptor” is then read in (S14), and names of all files recorded in the DVD, their sizes and start LSNs are read into the memory 12 (S15). Management information including the number of the video titles, start/end LSN thereof, the number of sub-picture of Part of Title (PTT) , and substream ID are also read and stored in the memory 12 (S16).

[0043] Upon completion of reading all information required, the DVD player is entered into an operation mode in which a caption-based moving picture data search information, or so-called sub-picture search table shown in FIG. 12 is created based on the data stored in volume structure, file structure, and navigation data (S17).

[0044] FIG. 11 shows a detailed flowchart of creating the sub-picture search table which is used for caption-based searching of moving picture data. In the sub-picture search table creation mode (S30), the number of video title sets VTS, K (the integer value ‘K’ of the video title set information VTS_0K_0.IFO ) is identified. Then, by using the number of the video title sets as well as the start locations and sizes thereof, a “video title set table (VTS table)” is created, as shown in FIG. 12 (S31).

[0045] The number of PTTs and the start locations and the number of sub-picture data thereof are extracted from the first video title set information VTS_01_0.IFO and are then used to create “PTT table” (S32). Sub-picture data belonging to each PTT are arranged in tabular form, i.e., a “sub-picture table” is created, as shown in FIG. 12. Then, a “sub-picture search table” is created in which sub-picture data belonging to each PTT is associated with the corresponding moving picture data. Note that if multiple languages are provided in video titles, the “sub-picture table” has multiple rows and “sub-picture search table” has multiple columns for each entry.

[0046] Each entry of the “sub-picture search table” has as many columns as the number of sub-picture channels for multiple languages and location information of the moving picture data which are concurrently reproduced with the sub-picture data. In order to create the entries of the “sub-picture search table”, while video title set objects (VTS_0X_M.VOB, M=0,1,2, . . . ) are scanned, sub-picture data located by identifying the sub-stream ID of packs (the sub-stream of sub-picture data packet ranges from 0x20 to 0x3F) and location information thereof is stored in a row of the “sub-picture search table” (S33). Therefore, sub-picture data and location information thereof are indicated by the same index value of the “sub-picture search table”. Specifically, the location information of a sub-picture data is represented by the logical block number of the start location of the navigation pack belonging to the video object unit VOBU including the sub-picture data.

[0047] After that, sub-picture data which has been stored in a DVD in the form of bit-mapped image data is converted into character data by using character recognition algorithms (S34). General optical character recognition (OCR) methods like artificial neural networks (ANNs)-based method can be applied. In case of ANNs-based character recognition algorithm, a training step is needed to determine the weights of ANNs and to map the output of the ANNs to the corresponding character code. To be specific, a training set of binary bit-mapped images of character samples is prepared and presented repeatedly to self organizing map (SOM), one of ANNs models, the function of which is to classify bit-mapped character samples. A mapping that maps the output of the SOM to one of distinct classes of character codes is then determined and used for a bit-mapped character classifier in a recognition step.

[0048] When it is applied, character images are extracted from sub-picture data of a bit-mapped image one after another. Each of a character images is converted into a black-and-white bit-mapped image and is then applied to the character classifier. In this way, caption images of sub-picture data are converted into character codes and are then stored in the memory and used for display. It is possible to display additional information by using character codes, for example, the meaning of words while the caption is displayed on a screen.

[0049] After creation of the “sub-picture table” and the “sub-picture search table” for a PTT is completed, the addresses pointing to the two tables are stored in the corresponding row of the “PTT table”, as shown in FIG. 12.

[0050] Once the scan of all PTTs in the video title sets VTS is completed through the loop formed by step S35,S36, and S37, the creation operation of the “sub-picture search table” is ended.

[0051] Without the character conversion operation, the caption images of sub-picture data can be directly stored in the memory 12 and used for display.

[0052] The three pointers of FIG. 12, P1x, P2x, and P3x, are used to point to the start point or range of captions listed in a caption display window that appear on a screen during playback, as shown in FIG. 14. To be specific, P1x, P2x, and P3x point to one entry of the PTT table, sub-picture table, and sub-picture search table, respectively, and they are updated when the video title is played back by the microcomputer 11.

[0053] FIG. 13 depicts a block diagram of another embodiment of the optical disk reproduction apparatus which is embodied in a personal computer to implement the present method according to the present invention. This embodiment comprises an optical disk driver 201 and a personal computer 202, both of which are connected to each other through a digital interference 100. The optical disk driver part comprises an optical pickup 2 for reading out information recorded in an optical disk; an RF demodulator 3 for demodulating the signal detected by the optical pickup; a digital signal processor 4 for processing the demodulated binary signal to obtain digital data; a servo unit 7 for servo-controlling a driving unit of the optical disk; a sled motor 13 for moving the optical pickup in the radial direction of the optical disk; a spindle motor 14 for rotating the optical disk; a sync clock generator 8 for generating a clock synchronized with the binary signal from the RF demodulator and outputting it to the digital signal processor 4; a microcomputer 11′ for controlling the servo unit and the digital signal processor 4, and communicating with an external device; a memory 12 for storing control data for the microcomputer. On the other hand, the personal computer part comprises a memory 22 for storing data transmitted from the optical disk driver through the digital interface 100; an A/V signal processor 25 for decompressing audio and video data stream read out from the memory; a display overlay unit 29 for displaying character signal in a caption display window in a superposed relationship to an image signal; a mixing unit 26 for adding a character signal of the display overlay unit to the image signal produced by the A/V signal processor 25; a video card 30 for outputting the mixed image signal to an external display unit; a central processing unit (CPU): 21 for controlling the mixing unit as well as above-mentioned components according to commands entered from keyboard 23 or pointing device; and a hard disk 40 for storing software programs.

[0054] The reproduction operation in the optical disk reproduction apparatus of FIG. 13 is as follows. The microcomputer 11′ receives control commands from an personal computer and controls the digital signal processor 4 and the servo unit 7 according to the commands, so that data stored in the optical disk is reproduced and sent to the personal computer through the digital interface 100. The data is stored in the memory 22 temporarily and is then input to the A/V signal processor 25.

[0055] These operations such as control of the optical disk driver 201 and data communication through the digital interface 100 are performed by loading a program stored in the hard disk 40 into the memory 22 and executing the program on the CPU 21.

[0056] The method of creating caption-based moving picture rig data search information in the embodiment of FIG. 13 is the same as that of the foregoing embodiment of FIG. 10 except that, after the caption-based moving picture data search information is created, it is stored in the hard disk 40 as a file in order to avoid a redundant creation operation that takes place when the same optical disk is inserted in the optical disk driver. To do this, once an optical disk is loaded, the volume ID on the disk is identified. It is then checked whether or not a file which contains the caption-based moving picture data search information corresponding to the volume ID has been stored on the hard disk 40. If the corresponding file does not exist, a new caption-based moving picture data search information is created and stored in the hard disk 40. Otherwise, the corresponding file is read into the memory and used to perform caption-based search of moving picture data.

[0057] Once the caption-based search table for moving picture data such as the sub-picture search table of FIG. 12 is created in this way, when a viewer selects a particular caption data, the location of the video object unit VOBU which is linked to the selected caption data is obtained with reference to the corresponding entry of the sub-picture search table.

[0058] FIG. 14 illustrates a caption display window according to the present invention, which is displayed at the corner of the main image display window (optionally in full-size window). The caption display window has a scroll bar by which a viewer can choose any caption included in video titles.

[0059] By selecting a particular caption on the caption display window, the viewer can search for any moving a picture data linked to the selected caption and resume to reproduce the video title at the located moving picture data. The operations for caption selection on the caption display window and the resulting search of the corresponding moving picture are described below in detail with reference to a flowchart of FIG. 15.

[0060] On specifying a video title set, VTS (S50), a file containing video title set information corresponding to the specified VTS, say, VTS_0N0.IFO is read out to obtain the start/end location of the VTS, attributes of video/audio/sub-picture data, and PTT (S51). Then, the video objects VOB belonging to the specified VTS begins to be reproduced (S52). Meanwhile, among the caption data which have been stored as text data in the memory 12 by application of character recognition algorithm, the caption data which are linked to moving picture data falling into a predetermined period of time centering the moving picture data being reproduced are output to the display overlay 9, so that they are superimposed on the image data by the mixing unit 6 and displayed on the caption display window (S53).

[0061] After that, if a viewer chooses a caption among captions listed in the caption display window (S54), the logical block number LBN of the corresponding video object unit VOBU is retrieved from the sub-picture search table which was already made (S55), and then the optical pickup is jumped to the location of the corresponding VOBU. At this time, three pointers for PTT table, sub-picture table, and sub-picture search table of FIG. 12, P1x, P2x, and P3x are updated in accordance with the jump.

[0062] Video and audio packs in the located VOBU is are read and then processed to be presented in accordance with playback control information contained in the navigation pack in the VOBU (S56). In this way, it is possible to search and display moving picture data which is linked to the selected caption on the caption display window.

[0063] Meanwhile, if the captions are scrolled up or down in the caption display window and thus the captions to be listed fall outside of the current entry of the PTT table, P1x is changed, that is, P1x points to the next entry of the PTT table, and the two pointers of the PTT table point to another sub-picture table and sub-picture search table in accordance with the PTT pointed by the updated P1x, respectively., In this way, captions on the caption list window are scrolled and displayed smoothly.

[0064] The present invention explained above provides a rapid, exact, and automatic way of searching for moving picture data which is reproduced concurrently with a caption chosen by a viewer, so that it is very useful for a person to practice listening and speaking a foreign language repetitively while viewing the title of a disk.

[0065] The foregoing is provided only for the purpose of illustration and explanation of the preferred embodiments of the present invention, so changes, variations and modifications may be made without departing from the spirit and scope of the invention.