WO2005091728A2

WO2005091728A2 - Recording medium, method, and apparatus for reproducing text subtitle streams

Info

Publication number: WO2005091728A2
Application number: PCT/KR2005/000829
Authority: WO
Inventors: Kang Soo Seo; Byung Jin Kim; Jea Yong Yoo
Original assignee: Lg Electronics Inc.
Priority date: 2004-03-26
Filing date: 2005-03-22
Publication date: 2005-10-06
Also published as: MY144414A; US8346050B2; RU2006137708A; JP4673885B2; TW200539126A; WO2005091728A3; US20050213942A1; US8437599B2; EP1730739A2; DE602005023285D1; ATE479987T1; US7848617B2; KR101053622B1; US20070280643A1; EP1730739B1; US20070280644A1; BRPI0509231A; KR20070007846A; TWI359410B; RU2378722C2

Abstract

A recording medium, method, and apparatus for reproducing text subtitle streams are disclosed. A buffer initially preloads a text subtitle stream including a dialog style segment defining a group of region styles and first and second dialog presentation segments. A text subtitle decoder initially presents a first region of dialog text included in the first dialog presentation segment in a graphics plane and reads a continuous presentation flag included in the second dialog presentation segment, which includes a second region of dialog text. The text subtitle decoder presents the second region of dialog text by preserving the presentation of the first region of dialog text in the graphics plane if the continuous segment indicates that continuous presentation is required between the first and second regions of the dialog text.

Description

[DESCRIPTION]

RECORDING MEDIUM, METHOD, AND APPARATUS FOR REPRODUCING TEXT SUBTITLE STREAMS

Technical Field

The present invention relates to a recording medium, and more particularly, to a recording

medium, method, and apparatus for reproducing text subtitle streams. Although the present

invention is suitable for a wide scope of applications, it is particularly suitable for recording

the text subtitle stream file within the recording medium and effectively reproducing the

recorded text subtitle stream.

Background Art

Optical discs are widely used as an optical recording medium for recording mass data.

Presently, among a wide range of optical discs, a new high-density optical recording medium

(hereinafter referred to as "HD-DVD"), such as a Blu-ray Disc (hereafter referred to as

"BD"), is under development for writing and storing high definition video and audio data.

Currently, global standard technical specifications of the Blu-ray Disc (BD), which is known

to be the next generation technology, are under establishment as a next generation optical

recording solution that is able to have a data significantly surpassing the conventional DVD,

along with many other digital apparatuses. Accordingly, optical reproducing apparatuses having the Blu-ray Disc (BD) standards applied

thereto are also being developed. However, since the Blu-ray Disc (BD) standards are yet to

be completed, there have been many difficulties in developing a complete optical reproducing

apparatus. Particularly, in order to effectively reproduce the data from the Blu-ray Disc (BD),

not only should the main AV data as well as various data required for a user's convenience,

such as subtitle information as the supplementary data related to the main AV data, be

provided, but also managing information for reproducing the main data and the subtitle data

recorded in the optical disc should be systemized and provided.

However, in the present Blu-ray Disc (BD) standards, since the standards of the

supplementary data, particularly the subtitle stream file, are not completely consolidated,

there are many restrictions in the full-scale development of a Blu-ray Disc (BD) basis optical

reproducing apparatus. And, such restrictions cause problems in providing the supplementary

data such as subtitles to the user.

Disclosure of Invention

Accordingly, the present invention is directed to a recording medium, method, and apparatus

for reproducing text subtitle streams that substantially obviate one or more problems due to

limitations and disadvantages of the related art.

An object of the present invention is to provide a method and apparatus for reproducing a text

subtitle stream that can record and reproduce a text subtitle stream file within a recording medium, such as a blu-ray disc (BD).

Additional advantages, objects, and features of the invention will be set forth in part in the

description which follows and in part will become apparent to those having ordinary skill in

the art upon examination of the following or may be learned from practice of the invention.

The objectives and other advantages of the invention may be realized and attained by the

structure particularly pointed out in the written description and claims hereof as well as the

appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the

invention, as embodied and broadly described herein, a recording medium for reproducing

text subtitle streams includes a data area storing at least one text subtitle stream, each text

subtitle stream including a dialog style segment defining a group of region styles and a

plurality of dialog presentation segments, each dialog presentation segment containing at

least one region of dialog text each of which is linked to a selected one of the group of region

styles, wherein a first region of dialog text included in a current dialog presentation segment

contains a continuous presentation flag which indicates that continuous presentation is

required between the first region of dialog text and a second region of dialog text included in

a previous dialog presentation segment.

In another aspect of the present invention, a recording medium for reproducing text subtitle

streams includes a data area storing at least one text subtitle stream, each text subtitle stream

including a dialog style segment defining a group of region styles and a plurality of dialog presentation segments, at least one of the plurality of dialog presentation segments containing

first and second regions of dialog text which are linked to first and second region styles

selected from the group of region styles, respectively, wherein the first and second region

styles define a same text flow.

In another aspect of the present invention, a method for reproducing text subtitle streams

includes reading a dialog style segment included in a text subtitle stream recorded on a

recording medium, the dialog style segment defining a group of region styles, the text subtitle

stream further including first and second dialog presentation segments, presenting a first

region of dialog text included in the first dialog presentation segment in a graphics plane, the

first region of dialog text being linked to one of the group of region styles, reading a

continuous presentation flag included in the second dialog presentation segment, the second

dialog presentation segment including a second region of dialog text which is linked to one of

the group of region styles, and presenting the second region of dialog text by preserving the

presentation of the first region of dialog text in the graphics plane, if the continuous

presentation segment indicates that continuous presentation is required between the first and

second regions of dialog text.

In a further aspect of the present invention, an apparatus for reproducing text subtitle streams

includes a buffer configured to preload a text subtitle stream, the preloaded text subtitle

stream including a dialog style segment defining a group of region styles and first and second

dialog presentation segments, and a text subtitle decoder configured to present a first region of dialog text included in the first dialog presentation segment in a graphics plane, and to read

a continuous presentation flag included in the second dialog presentation segment, the second

dialog presentation segment including a second region of dialog text, wherein the text subtitle

decoder presenting the second region of dialog text by preserving the presentation of the first

region of dialog text in the graphics plane, if the continuous presentation segment indicates

that continuous presentation is required between the first and second regions of dialog text.

It is to be understood that both the foregoing general description and the following detailed

description of the present invention are exemplary and explanatory and are intended to

provide further explanation of the invention as claimed.

Brief Description of Drawings

The accompanying drawings, which are included to provide a further understanding of the

invention and are incorporated in and constitute a part of this application, illustrate

embodiments of the invention and together with the description serve to explain the principle

of the invention. In the drawings:

FIG. 1 illustrates a structure of the data files recorded in an optical disc according to the

present invention;

FIG. 2 illustrates data storage areas of the optical disc according to the present invention;

FIG. 3 illustrates a text subtitle and a main image presented on a display screen according to

the present invention; FIG. 4 illustrates a schematic diagram illustrating reproduction control of a text subtitle

stream according to the present invention;

FIGs. 5 A to 5 C illustrate applications of the reproduction control information for reproducing

the text subtitle stream according to the present invention;

FIG. 6 illustrates the structure of a text subtitle stream file according to the present invention;

FIG. 7 an example of the method for writing the reproduction control information within the

text subtitle stream according to the present invention;

FIGs. 8A to 8C illustrate examples of discontinuous presentation or continuous presentation

of the text subtitle stream according to the present invention;

FIG. 9 illustrates a syntax of the text subtitle stream file according to the present invention;

FIGs. 10A to IOC illustrate a detailed structure of a dialog_style_segment( ), which

represents a dialog style segment (DSS) according to the present invention;

FIGs. 11A and 1 IB a detailed structure of a dialog_presentation_segment( ), which represents

a dialog presentation segment (DPS) according to the present invention;

FIGs. 12A and 12B illustrate an optical recording and/or reproducing apparatus including a

reproduction of the text subtitle stream file according to the present invention.

Best Mode for Carrying Out the Invention

Reference will now be made in detail to the preferred embodiments of the present invention,

examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like

parts, hi addition, although the terms used in the present invention are selected from

generally known and used terms, some of the terms mentioned in the description of the

present invention have been selected by the applicant at his or her discretion, the detailed

meanings of which are described in relevant parts of the description herein. Furthermore, it is

required that the present invention is understood, not simply by the actual terms used but by

the meaning of each term lying within.

In this detailed description, "recording medium" refers to all types of medium that can record

data and broadly includes all types of medium regardless of the recording method, such as an

optical disc, a magnetic tape, and so on. Hereinafter, for simplicity of the description of the

present invention, the optical disc and, more specifically, the "Blu-ray disc (BD)" will be

given as an example of the recording medium proposed herein. However, it will be apparent

that the spirit or scope of the present invention may be equally applied to other types of

recording medium.

In this detailed description, "main data" represent audio/video (AV) data that belong to a title

(e.g., a movie title) recorded in an optical disc by an author. In general, the AV data are

recorded in MPEG2 format and are often called AV streams or main AV streams. In addition,

"supplementary data" represent all other data required for reproducing the main data,

examples of which are text subtitle streams, interactive graphic streams, presentation graphic

streams, and supplementary audio streams (e.g., for a browsable slideshow). These supplementary data streams may be recorded in MPEG2 format or in any other data format.

They could be multiplexed with the AV streams or could exist as independent data files

within the optical disc.

A "subtitle" represents caption information corresponding to video (image) data being

reproduced, and it may be represented in a predetermined language. For example, when a

user selects an option for viewing one of a plurality of subtitles represented in various

languages while viewing images on a display screen, the caption information corresponding

to the selected subtitle is displayed on a predetermined portion of the display screen. If the

displayed caption information is text data (e.g., characters), the selected subtitle is often

called a "text subtitle". In the present invention, an "MPEG-2 format" refers to an encoding

and decoding method in accordance with an international standard established as the ISO/IEC

13818 standard. According to one aspect of the present invention, a plurality of text subtitle

streams in MPEG2 format may be recorded in an optical disc, and they may exist as a

plurality of independent stream files. Each "text subtitle stream file" is created and recorded

within an optical disc. And, the purpose of the present invention is to provide a method and

apparatus for reproducing the recorded text subtitle stream file.

FIG. 1 illustrates a file structure of the data files recorded in a Blu-ray disc (hereinafter

referred to as "BD") according to the present invention. Referring to FIG. 1, at least one BD

directory (BDMV) is included in a root directory (root). Each BD directory includes an index

file (index.bdmv) and an object file (MovieObject.bdmv), which are used for interacting with one or more users. For example, the index file may contain data representing an index table

having a plurality of selectable menus and movie titles. Each BD directory further includes

four file directories that include audio/video (AV) data to be reproduced and various data

required for reproduction of the AV data.

The file directories included in each BD directory are a stream directory (STREAM), a clip

information directory (CLIPINF), a playlist directory (PLAYLIST), and an auxiliary data

directory (AUX DATA). First of all, the stream directory (STREAM) includes audio/video

(AV) stream files having a particular data format. For example, the AV stream files may be

in the form of MPEG2 transport packets and be named as "*.m2ts", as shown in FIG. 1. The

stream directory may further include one or more text subtitle stream files, where each text

subtitle stream file includes text (e.g., characters) data for a text subtitle represented in a

particular language and reproduction control information of the text data. The text subtitle

stream files exist as independent stream files within the stream directory and may be named

as "*.m2ts" or "*.txtst", as shown in FIG. 1. An AV stream file or text subtitle stream file

included in the stream directory is often called a clip stream file.

Next, the clip information directory (CLIPINF) includes clip information files that

correspond to the stream files (AV or text subtitle) included in the stream directory,

respectively. Each clip information file contains property and reproduction timing

information of a corresponding stream file. For example, a clip information file may include

mapping information, in which presentation time stamps (PTS) and source packet numbers (SPN) are in a one-to-one correspondence and are mapped by an entry point map (EPM),

depending upon the clip type. Using the mapping information, a particular location of a

stream file may be determined from a set of timing information (In-Time and Out-Time)

provided by a Playltem or SubPlayltem, which will be discussed later in more details. In the

industry standard, each pair of a stream file and its corresponding clip information file is

designated as a clip. For example, OlOOO.clpi included in CLIPINF includes property and

reproduction timing information of 01000.m2ts included in STREAM, and OlOOO.clpi and

O1000.m2ts form a clip.

Referring back to FIG.l, the playlist directory (PLAYLIST) includes one or more PlayList

files (*.mpls), where each PlayList file includes at least one Playltem that designates at least

one main AV clip and the reproduction time of the main AV clip. More specifically, a

Playltem contains information designating In-Time and Out-Time, which represent

reproduction begin and end times for a main AV clip designated by

Clip_hιformation_File_Name within the Playltem. Therefore, a PlayList file represents the

basic reproduction file information, which performs reproduction of a combination of clips

desired by a combination of one or more Playltems. In addition, the PlayList file may further

include a SubPlayltem, which represents the basic reproduction control information for a text

subtitle stream file. When a SubPlayltem is included in a PlayList file to reproduce one or

more text subtitle stream files, the SubPlayltem is synchronized with the Playltem(s). On the

other hand, when the SubPlayltem is used to reproduce a browsable slideshow, it may not be synchronized with the Playltem(s). According to the present invention, the main function of

a SubPlayltem is to control reproduction of one or more text subtitle stream files.

Lastly, the auxiliary data directory (AUX DATA) may include supplementary data stream

files, examples of which are font files (e.g., aaaaa.font or aaaaa.otf), pop-up menu files (not

shown), and sound files (e.g., Sound.bdmv) for generating click sound. The text subtitle

stream files mentioned earlier may be included in the auxiliary data directory instead of the

stream directory.

FIG. 2 illustrates data storage areas of an optical disc according to the present invention.

Referring to FIG. 2, the optical disc includes a file system information area occupying the

inmost portion of the disc volume, a stream area occupying the outmost portion of the disc

volume, and a database area occupied between the file system information area and the

stream area. In the file system information area, system information for managing the entire

data files shown in FIG. 1 is stored. Next, main data and supplementary data (i.e., AV

streams and one or more text subtitle streams) are stored in the stream area. The main data

may include audio data, video data, and graphic data. And, the supplementary data (i.e., the

text subtitle) is independently stored in the stream area without being multiplexed with the

main data. The general files, PlayList files, and clip information files shown in FIG. 1 are

stored in the database area of the disc volume. As discussed above, the general files include

an index file and an object file, and the PlayList files and clip information files include

information required to reproduce the AV streams and the text subtitle streams stored in the stream area. Using the information stored in the database area and/or stream area, a user is

able to select a specific playback mode and to reproduce the main AV and text subtitle

streams in the selected playback mode.

Hereinafter, the structure of the text subtitle stream file according to the present invention

will be described in detail. First of all, the control information for reproducing the text

subtitle stream will be newly defined. Then, the detailed description of the method of

creating the text stream file including the newly defined control information, and the method

and apparatus of reproducing the text subtitle stream for reproducing the recorded stream file

will follow. FIG. 3 illustrates a text subtitle and a main image presented on a display screen

according to the present invention. The main image and the text subtitle are simultaneously

displayed on the display screen when a main AV stream and a corresponding text subtitle

stream are reproduced in synchronization.

FIG. 4 is a schematic diagram illustrating reproduction control of a main AV clip and text

subtitle clips according to the present invention. Referring to FIG. 4, a PlayList file includes

at least one Playltem controlling reproduction of at least one main AV clip and a

SubPlayltem controlling reproduction of a plurality of text subtitle clips. One of text subtitle

clip 1 and text subtitle clip 2, shown in FIG. A, for English and Korean text subtitles may be

synchronized with the main AV clip such that a main image and a corresponding text subtitle

are displayed on a display screen simultaneously at a particular presentation time. In order to

display the text subtitle on the display screen, display control information (e.g., position and size information) and presentation time information, examples of which are illustrated in FIG.

5A to FIG. 5C, are required.

FIG. 5A illustrates a dialog presented on a display screen according to the present invention.

A dialog represents entire text subtitle data displayed on a display screen during a given

presentation time. In general, presentation times of the dialog may be represented in

presentation time stamps (PTS). For example, presentation of the dialog shown in FIG. 5 A

starts at PTS (k) and ends at PTS (k+1). Therefore, the dialog shown in FIG. 5A represents

an entire unit of text subtitle data which are displayed on the display screen between PTS (k)

and PTS (k+1). A dialog includes a maximum of 100 character codes in one text subtitle. .

In addition, FIG. 5B illustrates regions of a dialog according to the present invention. A

region represents a divided portion of text subtitle data (dialog) displayed on a display screen

during a given presentation time. In other words, a dialog includes at least one region, and

each region may include at least one line of subtitle text. The entire text subtitle data

representing a region may be displayed on the display screen according to a region style

(global style) assigned to the region. The maximum number of regions included in a dialog

should be determined based on a desired decoding rate of the subtitle data because the greater

number of regions generally results in a lower decoding ratio. For example, the maximum

number of regions for a dialog may be limited to two in order to achieve a reasonably high

decoding rate. Accordingly, the maximum number of regions within a single dialog is

limited to 2 because of the decoding load, when the text subtitle stream is reproduced. In another embodiment of the present invention, a maximum of n number (wherein, n > 2 ) of

regions may exist within a single dialog.

FIG. 5C illustrates style information for regions of a dialog according to the present invention.

Style information represents information defining properties required for displaying at least a

portion of a region included in a dialog. Some of the examples of the style information are

position, region size, background color, text alignment, text flow information, and many

others. The style information may be classified into region style information (global style

information) and inline style information (local style information).

Region style information defines a region style (global style) which is applied to an entire

region of a dialog. For example, the region style information may contain at least one of a

region position, region size, font color, background color, text flow, text alignment, line

space, font name, font style, and font size of the region. For example, two different region

styles are applied to region 1 and region 2, as shown in FIG. 5C. A region style with

"position 1, size 1, and color = blue" is applied to Region 1, and a different region style with

"position 2, size 2, and color = red" is applied to Region 2.

On the other hand, inline style information defines an inline style information (local style

information) which is applied to a particular portion of text data strings included in a region.

For example, the inline style information may contain at least one of a font type, font size,

font style, and font color. The particular portion of text strings may be an entire text line

within a region or a particular portion of the text line. Referring to FIG. 5C, a particular inline style is applied to the text portion "mountain" included in Region 1. In other words, at

least one of the font type, font size, font style, and font color of the particular portion of text

strings is different from the remaining portion of the text strings within Region 1.

Accordingly, the above-described text data is recorded and described as a "text string" that is

applied to a specific inline style information (inline_styles).

FIG. 6 illustrates a text subtitle stream file (e.g., 10001.m2ts shown in FIG. 1) according to

the present invention. The text subtitle stream file may be formed of an MPEG2 transport

stream including a plurality of transport packets (TP), all of which have a same packet

identifier (e.g., PID=0xl8xx). When a disc player receives many input streams including a

particular text subtitle stream, it finds all the transport packets that belong to the text subtitle

stream using their PIDs. Referring to FIG. 6, each sub-set of transport packets form a packet

elementary stream (PES) packet. One of the PES packets shown in FIG. 6 corresponds to a

dialog style segment (DSS) defining a group of region styles. All the remaining PES packets

after the second PES packet correspond to dialog presentation segments (DPSs)

In the above-described text subtitle stream structure of FIG. 6, each of the dialog information

shown in FIGs. 5A to 5C represent a dialog presentation segment (DPS). And, the style

information included in the dialog information represents a set of information that links any

one of the plurality of region style sets defined in the dialog style segment (DSS), which can

also be referred to as "region_style_id", and inline styles. A standardized limited number of

region style sets is recorded in the dialog style segment (DSS). For example, a maximum of 60 sets of specific style information is recorded, each of which is described by a

region_style_id. Therefore, is a text subtitle decoder (shown in FIG. 12B), the dialog

presentation segment (DPS) is read and decoded only one at a time.

FIG. 7 illustrates a method for creating a text subtitle stream according to the present

invention, wherein each dialog presentation segment (DPS) being applied to each

presentation time (PTS) section is defined. More specifically, referring to FIG. 7, DPS #n-l

is formed of two (2) regions (Region #1 and Region #2), wherein a specific Dialog text is

recorded in each region. The DPS #n-l is presented onto the screen within the PTSl_start ~

PTSl_end section. And, DPS #n is formed of one (1) region, wherein a specific Dialog text

is recorded in the corresponding region. The DPS #n is presented onto the screen within the

PTS2_start ~ PTS2_end section. Finally, DPS #n+l is formed of two (2) regions (Region #1

and Region #2), wherein a specific Dialog text is recorded in each region. The DPS #n+l is

presented onto the screen within the PTS3_start ~ PTS3_end section.

Accordingly, the characteristics of the DPS formed within one picture, as described above,

will now be described in detail with reference to FIGs. 8A to 8C. Firstly, either continuous

presentation or discontinuous presentation may be performed between neighboring DPSs.

FIG. 8 A illustrates the discontinuous presentation between the DPSs (i.e., the discontinuous

DPS), and FIG. 8B illustrates the continuous presentation between the DPSs (i.e., the

continuous DPS).

Referring to FIG, 8A, three (3) neighboring DPSs, i.e., DPS #n-l, DPS #n, and DPS #n+l, are all discontinuous. For example, the end PTS (= PTS2) of DPS #n-l is different from the

start PTS (= PTS3 > PTS2) of DPS #n. Similarly, the end PTS (= PTS4) of DPS #n is

different from the start PTS (= PTS5 > PTS4) of DPS #n+l. Therefore, each of the DPSs

shown in FIG. 8A is formed as DPSs that are independent from one another. Each

independent (or discontinuous) DPS includes a specific region style information

(region_style_id), and the position, background color, font size, font color, and so on, of the

dialog text within the DPS is decided in accordance with the corresponding region style

information. More specifically, "region_style_id = k" may be designated to DPS #n-l,

"region_style_id = k+1" may be designated to DPS #n, and "region_style_id = k+2" may be

designated to DPS #n+l. However, even though each DPS is independent from one another,

an identical region style information (region_style_id) may also be equally applied to each

DPS.

Referring to FIG. 8B, three (3) neighboring DPSs, i.e., DPS #n-l, DPS #n, and DPS #n+l,

are all continuous. For example, the end PTS (= PTS2) of DPS #n-l is identical to the start

PTS (= PTS2) of DPS #n. Similarly, the end PTS (= PTS3) of DPS #n is identical to the start

PTS (= PTS3) of DPS #n+l. Therefore, each of the DPSs shown in FIG. 8B is formed as

DPSs that are associated with one another. Each continuous DPS (DPS #n-l, DPS #n, and

DPS #n+l) includes an identical specific region style information (e.g., region_style_id = k).

And, thus, the position, background color, font size, font color, and so on, of the dialog text

within each of DPS #n-l, DPS #n, and DPS #n+l is equally decided in accordance with the corresponding region style information.

FIG. 8C illustrates a method for presenting (or reproducing) the discontinuous DPS and the

continuous DPS. More specifically, the text subtitle stream file includes a

continuous_present_flag, which indicate whether continuous presentation is performed

between each region of neighboring dialog presentation segments (DPSs), as shown in FIG.

8 A. Therefore, if the reproduction (or presentation) of the current DPS is continued from the

previous DPS, "continuous_present_flag=l" is assigned, and if reproduction is not continued,

"continuous_present_flag=0" is assigned. At this point, if at least one of the regions included

in the DPS is set to be continuously reproduced, the corresponding DPS is defined as a

"continuous presentation DPS". Thus, for example, DPS #2, DPS #3, and DPS #4, which are

continuous presentation DPSs, are grouped as "continuous presentation set #2". And, when

the above-described continuous presentation set #2 is reproduced (or presented), the first DPS

of the continuous presentation set #2 (i.e., DPS #2) is first reproduced. Thereafter, without

clearing the text data displayed onto the screen, the presentation is continued until the end of

the presentation, which is until the end of the display of DPS #4. Conversely, since DPS #1

and DPS #5 are discontinuous DPSs, DPS #1 and DPS #5 are presented (or reproduced)

independently regardless of their neighboring DPSs.

Furthermore, regardless of whether the DPS is a continuous DPS or a discontinuous DPS, the

Dialog text in each DPS should be newly defined. And, even two (2) regions exist in the

same DPS, the Dialog text flow within each region should be defined to be in the same direction. More specifically, each DPS should include a Dialog text information signifying

(or referring to) the corresponding DPS, and this rule equally applies to the continuous DPS.

In addition, when two (2) regions are included in one DPS, each region should have the same

text flow. In other words, a case in which the first region has a text flow direction of left-to-

right (left → right) and the second region has a text flow direction of top-to-bottom (top →

bottom) cannot be accepted or allowed, since the two text flow directions are different from

one another. Such condition should be apprehended as a forced condition in order to prevent

users from viewing disturbed images.

The syntax structure of the above-described dialog style segment (DSS) and the dialog

presentation segment (DPS) will now be described in detail with reference to FIGs. 9 to 1 IC.

FIG. 9 illustrates a syntax of the text subtitle stream (Text_subtitle_stream( )) according to

the present invention. As described in FIG. 6, the Text_subtitle_stream( ) includes a

dialog_style_segment( ) syntax and a dialog_presentation_segment( ) syntax. More

specifically, the dialog_style_segment( ) syntax corresponds to a single dialog style segment

(DSS) defining the style information set, and the dialog_presentation_segment( ) syntax

corresponds to a plurality of dialog presentation segments (DPS) having the actual dialog

information recorded therein.

FIGs. 10A to IOC illustrate a detailed structure of the dialog_style_segment( ), which

represent the dialog style segment (DSS). More specifically, FIG. 10A illustrates the overall

structure of the dialog_style_segment( ), wherein a dialog_style set( ) defining diverse style information sets that are applied in the dialog is defined. FIG. 10B illustrates a dialog_style

set( ) according to the present invention, which is defined in the dialog_style_segment( ).

Apart from the region_styles, the dialog_style_set( ) includes a Player_style_flag, a

user_changeable_style set( ), and a palette( ). The Player_style_flag indicates whether

change in style information by the player is authorized. Also, the user_changeable_style

set( ) defines the range of change in style information by the player, and the palette( )

indicates color information and degree of transparency.

The region style information (region_styles) represents Global style information defined for

each region, as described above. A region_style_id is assigned to each region, and a style

information set corresponding to the specific region_style_id is defined. Therefore, when

reproducing a dialog by recording the region_style_id, which is applied to the corresponding

dialog, within the dialog presentation segment (DPS), style information set values defined by

identical region_style_id within the dialog_style set( ) are applied, so as to reproduce the

dialog. Accordingly, individual style information included in the style information set

provided to each region_style_id will now be described.

Herein, region_horizontal_position, region_vertical_position, region_width, and

regioη ieight are provided as information for defining the position and size of a

corresponding region within the screen. And, region_bg_color_index information deciding a

background color of the corresponding region is also provided. In addition, as information

defining an original (or starting) position of the text within the corresponding region, a text_horizontal_position and a text_vertical_position are provided. Also, a textjElow

defining the direction of the text (e.g., left→ right, right-* left, up→ down), and a

text_alignment defining the alignment direction of the text (e.g., left, center, right) are

provided. More specifically, when a plurality of regions are included in a specific dialog, the

text_flow of each region included in the corresponding dialog is defined to have the same

text_flow value, so as to prevent users from viewing disturbed images.

Furthermore, a line_space designating space between each line within the region is provided

as individual style information included in the style information set. And, a font ype, a font-

size, and a font_color_index are provided as font information for actual font information.

Meanwhile, the Player_style_flag recorded within the dialog_style set( ) indicates whether an

author may apply the style information provided to the player. For example, when

Player_style_flag=lb, as well as the style information defined in the dialog_style set( )

recorded in a disc, the player is authorized to reproduce the text subtitle stream by applying

the style information provided within the player itself. On the other hand, when

Player_style_flag=Ob, only usage of the style information defined in the dialog_style set( )

recorded within the disc is authorized.

FIG. IOC illustrates the user_changeable_style set( ) according to the present invention,

which is defined in dialog_style set( ). The user_changeable_style set( ) pre-defines the types

of style information that can be changed by the user and the range of change, and the

user_changeable_style set( ) is used for easily changing the style information of the text subtitle data. However, when the user is enabled to change all style information, which are

described in FIG. 10B, the user may more confused. Therefore, in the present invention, the

style information of only the font_size, the region_horizontal_position, and the

region_vertical_position may be changed. And, accordingly, variation in the text position

and the line space, which may be changed in accordance with the font_size, is also defined in

the user_changeable_style set( ). More specifically, the user_changeable_style set( ) is

defined for each region_style_id. For example, a maximum of 25 user_style_id within a

specific region_style_id=k may be defined in the user_changeable_style set( ) .

Also, each user_style_id includes region_horizontal_position_direction and

region_vertical_position_direction information, which designate the direction of the changed

position of each of the changeable region_horizontal_position and region vertical_position.

Each user_style_id also includes region_horizontal_position_delta and region_vertical

_position_delta information for designating a single position movement unit in each direction

as a pixel unit. More specifically, for example, when region_horizontal_position_direction=0,

the position of the region is moved to a right direction. And, when region iorizontal

_position_direction=l, the position of the region is moved to a left direction. Also, when

region_vertical_position_direction=0, the position of the region is moved to a downward

direction. Finally, when region_vertical_position _direction=l, the position of the region is

moved to an upward direction.

Furthermore, each user_style_id includes font_size_inc_dec information, which designates the changing direction each of the changeable font_size, and font_size_delta information for

designating a single position movement unit in each direction as a pixel unit. More

specifically, for example, font_size_inc_dec=0 represents an increasing direction of the

font_size, and font_size_inc_dec=l represents a decreasing direction of the font_size.

Similarly, the changed information (data field) related to the "text position" and the "line

space" may also be defined in accordance with the same principle

The characteristics of the user_changeable_style set( ) according to the present invention now

be described in detail. The number of user_control_style( ) defined in each region_style( )

included in the dialog style segment (DSS) is identical. In other words, the number of

user_control_styles that can be applied to each dialog presentation segment (DPS) is identical.

In addition, each user_control_style( ) is represented by a different user_style_id. And, when

the user selects a random user_style_id, the same order of user_control_style( ) is equally

applied to each region_style( ). Furthermore, all possible combinations of the changeable

styles are defined in a single user_control_style( ). In other words, the region_position and

the font_size are simultaneously defined in combination, instead of being defined separately.

And, finally, the moving direction (*_direction) or the increase/decrease indication

(*_inc_dec) is independently distinguished from each position movement unit (*_delta) and

recorded accordingly. More specifically, only the position movement unit (*_delta) is

defined without having the style value, which is the value that is actually being changed.

Subsequently, the defined position movement unit (*_delta) is added to the value defined in the region_style( ), thereby obtaining the final value of the style value that is actually being

changed.

FIG. 10D illustrates palette information (palette( )) according to the present invention, which

is defined in the dialog_style set( ). The palette( ) provides color changing information of the

text subtitle data recorded within the dialog. Herein, the palette( ) includes a plurality of

palette_entries, wherein each palette_entry is described by a palette_entry_id. And, each

palette_entry is provided with a specific brightness value (Y_value), a specific color value

(Cr_value, Cb_value), and a specific T_value, which designates the transparency of the text

data, for each palette_entry_id. Accordingly, one of the characteristics of the text subtitle

stream according to the present invention is that only one basic (or common) palette is

defined, the palette being applied to each dialog presentation segment (DPS) included in the

text subtitle stream file. More specifically, after defining a palette in the dialog style segment

(DSS), the defined palette is commonly used in each dialog presentation segment (DPS).

However, if a new specific palette is to be used instead of the common palette in a specific

dialog presentation segment (DPS), the specific palette is newly defined by using the

palette_update_flag, the description of which will follow with reference to FIG. 11 A,

FIGs. 11A and 11B illustrate a detailed structure of the dialog_presentation _segment( ),

which represent the dialog presentation segment (DPS) according to the present invention.

FIG. 11A illustrates the overall structure of the dialog_presentation_segment( ), wherein a

dialog_start_PTS and a dialog_end_PTS are defined. The dialog_start_PTS and the dialog_end_PTS designate the presentation time of the corresponding dialog. Then, the

dialog_presentation_segment( ) includes a palette_update_flag, which indicates a change of

color information within the corresponding dialog. Herein, when palette_update_flag=lb, the

color and degree of transparency (T_value) are changed (or updated), and so the palette( )

information, which newly defines the color, is separately recorded. In this case, the palette( )

that is newly defined in the dialog presentation segment (DPS) must only be applied to the

corresponding dialog presentation segment (DPS). Assuming that palette_update_flag=Ob,

when presenting (or reproducing) the corresponding dialog presentation segment (DPS), the

above-described common palette, which has been defined in the dialog style segment (DSS),

as shown in FIG. 10A, should be restored (or preserved).

Subsequently, a dialog_region( ) that defines the region information is recorded in the

dialog_presentation_segment( ). In the present invention, a maximum of two regions is

provided within a single dialog, and therefore, dialog_region( ) information is provided to

each region. The dialog_region( ) includes region_style_id information and

continuous_present_flag information. The region_style_id information designates any one of

the region styles, as shown in FIG. 10B, and the continuous_present_flag information

identifies whether to perform a seamless reproduction with the previous dialog region, as

shown in FIG. 8C. More specifically, the continuous_present_flag is included in each region.

If two (2) regions are included in one DPS, and when at least one region is set to be

continuous_present_flag = lb, the corresponding DPS becomes the above-described continuous presentation DPS. Further, text data and region_subtitle( ) information are also

included in the dialog_region( ). The text data is included in the actual corresponding region,

and the region_subtitle( ) information defines the local style information.

FIGs. 11B and 11C illustrate an example of recording the region_subtitle( ), which includes a

text string and an identification information (i.e., data_type) identifying the inline style

information (i.e., inline_styles) applied to the text string. Also, a 1-byte information (i.e.,

escape_code) is recorded between the information being identified by the identification

information (i.e., data_type). More specifically, the text string and inline_styles are recorded

within the region_subtitle( ), so a s to include the text string and the identification information

(i.e., data_type) identifying the inline style information. Herein, when data_type=0b, the data

type is the inline style information (i.e., inline_styles), and when data_type=lb, the data type

is the text string. Therefore, when data_type=lb, the text string is recorded as a character

code within a specific field (i.e., char_data_byte) included in the text_string( ). In other

words, the char_data__byte is used to record text data, such as "Good morning" or "Good

afternoon", shown in FIGs. 8 A and 8B. And, the text data is recorded in each region within

each DPS, regardless of whether the DPS is a continuous presentation DPS or not.

Moreover, when data_type=0b, the inline style information (i.e., inline_styles) is recorded,

wherein the inline style information is configured to have at least one inline style type (i.e.,

inline_style_type). For example, inline_style_type=0x01 represents a change in the Font set,

and so a font ID value designated by the corresponding Cliplnfo is recorded in a specific field (i.e., the inline_style_data_byte), and inline_style_type^:=0x02 represents a change in the Font

style, and so a corresponding font style value is recorded in a specific field (i.e., the

inline_style_data_byte). Also, inline_style_type=0x03 represents a change in the Font size,

and a corresponding font size value is recorded in a specific field (i.e., the inline_style_data

_byte), and inline_style_type=0x04 represents a change in the Font color, and therefore, an

index value designated by the corresponding palette is recorded in a specific field (i.e., the

inline_style_data_byte). Further, inline_style_type=0x0A represents a line break. In this

case, data is not additionally recorded, except for that when the corresponding type (i.e.,

inline__style_type=^:OxOA) is read, one line should be changed upon decoding the text subtitle

stream prior to the reproduction (or presentation).

In addition, when data-type=0b, the inline style information (inline_styles) is recorded,

wherein information indicating the entire size of the inline_styles is recorded, which is the

inline_style_length. And, at least one inline_style_type and an inline_style _data_byte value,

which records the changed value for each type, are recorded within the corresponding size.

Therefore, the at least one inline_style_type included in the inline style information

(inline_styles) is continuously recorded as a single unit. Thereafter, when the recording of

the corresponding inline style information is completed, a 1-byte information (escape_code)

is inserted and recorded between the text string that is recorded by the succeeding (or

subsequent) identification information (i.e., data_type).

Hereinafter, the method and apparatus for reproducing the text subtitle stream recorded on the optical disc, as described above, will now be described in detail with reference to FIGs. 12A

and 12B. FIG. 12A illustrates the apparatus for reproducing the optical disc focusing on the

decoder according to the present invention and, more particularly, illustrates an example of a

text subtitle decoding part 40, which is separately included. More specifically, the apparatus

includes a packet identifier (PID) filter 5 for separating input streams into video streams,

audio streams, graphic streams, and text subtitle streams based on their packet identifiers, a

video decoding part 20 for reproducing the video streams, an audio decoding part 10 for

reproducing the audio streams, a graphic decoding part 30 for reproducing the graphic

streams, and a text subtitle decoding part 40 for reproducing the text subtitle streams.

The text subtitle streams may be extracted from an optical disc, or they could be inputted

from an additional external source, as shown in FIG. 12 A, For this reason, the apparatus

includes a switch 6 which selects an input data source. Therefore, if the text subtitle streams

in MPEG format are extracted from the optical disc, the switch 6 selects data line A

connected to the PID filter 5. On the other hand, if they are inputted through an additional

external source, the switch 6 selects data line B which is connected to the external source.

The video decoding part 20, audio decoding part 10, graphic decoding part 30 include a

transport buffer 21, 11, and 31, respectively, for storing a predetermined size of data streams

to be decoded. A video plane 23 and a graphic plane 33 are included in the video decoding

part 20 and graphic decoding part 30, respectively, for converting decoded signals into

displayable images. The graphic decoding part 30 includes a color look-up table (CLUT) 34 for controlling color and transparency levels of the displayable images.

When the text subtitle decoding part 40 receives one or more text subtitle streams from the

switch 6, all of these streams are initially preloaded into a subtitle preloading buffer (SPB) 41

at once. Assuming a typical size of a text subtitle stream file for a single language is about

0.5 megabytes, the size of the subtitle preloading buffer 41 should be determined based on

the total number of the text subtitle stream files. For example, in order to ensure seamless

presentation of a text subtitle when a user switches among subtitle stream files supporting

two languages, the size of the subtitle preloading buffer 41 should be greater than or equal to

1 megabytes. The size of the subtitle preloading buffer 41 should be large enough to preload

all the required text subtitle stream files at once.

The text subtitle streams are all preloaded in the buffer 41 and used, because the entire text

subtitle stream can be recorded within a small capacity, as described above. Therefore, the

text subtitle stream is recorded as a separate file, thereby facilitating the reading and usage of

the text subtitle data only. Moreover, since the entire text subtitle data is preloaded to the

buffer, the buffer can be controlled more easily, hi a specific type of optical recording and

reproducing apparatus, provided that a buffer underflow does not occur, the text subtitle

stream may be reproduced in combination with the main AV data, in real-time, without

preloading the text subtitle stream. Hereinafter, an example of the text subtitle stream being

preloaded according to the present invention will now be given and described in detail.

The text subtitle decoding part 40 further includes a text subtitle decoder 42 which decodes one or more text subtitle streams stored in the subtitle preloading buffer 41, a graphics plane

43 converting the decoded subtitle stream(s) into displayable images, and a color look-up

table (CLUT) 44 controlling the color information (Y, Cr and Cb values) and transparency / information (T value) of the converted images.

An image superi position part 50 included in the apparatus shown in FIG. 12A combines the

images outputted from the video decoding part 20, the graphic decoding part 30, and the text

subtitle decoding part 40. These combined images are displayed on a display screen. The

video images outputted from the video plane 23 of the video decoding part 20 are displayed

as a background of the display screen, and the images outputted from the graphic decoding

part 30 and/or the text subtitle decoding part 40 are superimposed over the displayed video

images. For example, if the output images of the graphic decoding part 30 are interactive

graphic images, the text subtitle images outputted from the text subtitle decoding part 40 are

initially superimposed over the video images by a first adder 52. Thereafter, the interactive

graphic images are further superimposed over the subtitle-superimposed images by a second

adder 53. The apparatus shown in FIG. 12A further includes a system decoder 4 for decoding

input transport streams (e.g., MPEG transport streams), and a microprocessor 3 for

controlling operations of all the mentioned components of the apparatus.

Reference will now be made in detail to a method for reproducing text subtitle streams

according to the present invention. When an optical disc is preloaded by an optical disc

player, an example of which is illustrated in FIG. 12 A, information required for reproduction of data recorded on the disc is initially extracted from the disc and stored in a memory (not

shown). When a particular title that associates with a PlayList is selected by a user, at least

one complete (entire) text subtitle stream file designated in the PlayList file .is initially

preloaded into the subtitle preloading buffer 41 and font files related to the subtitle stream file

is preloaded into the font preloading buffer 410.

For example, when a title that associates with the PlayList shown in FIG. 4 is selected by a

user, text subtitle files for text subtitle clip No. 1 (Korean) and text subtitle clip No. 2

(English) are initially preloaded into the subtitle preloading buffer 41. Also, font files related

to the text subtitle files, which may be designated in clip information files of the text subtitle

clips, are preloaded into the font preloading buffer 410. Thereafter, playback of the PlayList

is started. During the playback of the PlayList, AV streams of main AV clips No. 1 and 2 are

decoded by the audio decoding part 10 and the video decoding part 20, respectively, and

selected one of the preloaded text subtitle streams is decoded by the text subtitle decoder 42.

Then the decoded text subtitle images are superimposed over the decoded main video images,

and the entire images are displayed on a display screen.

As described above, when all operations are completed, and when the main video data that is

controlled by the Playltem is displayed onto the screen, the related text subtitle is

superimposed through the image superimposition part 50 (shown in FIG. 12A). And, as the

superimposed text subtitle is provided, the decoding of the text subtitle stream is initiated.

Meanwhile, in order to perform decoding of the text subtitle stream, a region style information and palette information within the dialog style segment (DSS), which configures

the first packet stream (PES), are separately read and stored for later usage when reproducing

the DPS. Most particularly, when the palette information is read, the palette information is

simultaneously provided to the CLUT 44, so as to provide the color and transparency desired

by the user, when displaying the text subtitle onto the screen.

FIG. 12B illustrates the text subtitle decoder 42, shown in FIG. 12A, in more details. The

decoding process performed by the text subtitle decoder 42 includes parsing, rendering, and

composition steps. In the parsing step, the text subtitle stream(s) stored in the subtitle

preloading buffer (SPB) 41 is parsed into composition information, rendering information,

and dialog text data, in accordance with the information included in the dialog presentation

segment (DPS). A dialog represents all the text subtitles that are displayed during a

predetermined period of time, which may be defined by a presentation time stamp (PTS).

Accordingly, the composition information corresponds to the information related to the

display time and display position of the text subtitle when displayed onto the screen, and also

to a new palette information that is newly defined by a palette information update

(palette_update_flag=lb). The rendering information corresponds to the information that

actually describe (or represent) the text of each region for each dialog. Such rendering

information includes "region width & height", "Background color", "Text Flow", "Text

Alignment", and "Font id/style/size". Furthermore, the dialog text information corresponds

to an inline style information that is applied to the actual text data and a specific text string recorded within the DPS.

Referring to FIG. 12B a text subtitle processor 421 included in the text subtitle decoder 42

parses the subtitle stream file(s) stored in the subtitle preloading buffer 41 into composition

and rendering information and dialog text data. The composition and rendering information is

then stored in a dialog composition buffer (DCB) 425, and the dialog text data are stored in a

dialog buffer (DB) 422. More specifically, a palette update information

(palette_update_flag=lb) is included in the composition information, which is parsed by the

parsing step. And, when palette_update_flag=Ob, the common palette information, which

was initially provided from the dialog style segment (DSS) to the CLUT 44, may be used

continuously without being updated. Conversely, when palette_update _flag=lb, the

common palette information within the DSS is ignored, and a new palette information is

newly defined within the corresponding DPS and is updated to the CLUT 44 and used.

However, when the presentation (or reproduction) of the corresponding DPS is completed,

the palette update is cleared, and the common palette information initially provided from the

CLUT 44 is used once again. At this point, the update of the CLUT 44 should be completed

before the presentation (or reproduction) of the subsequent DPS.

In the rendering step, the parsed dialog text data are rendered into bitmap data using the

rendering information, which represents style information required for rendering the dialog

text data. A text renderer 423 renders the dialog text data stored in the dialog buffer 422 into

bitmap data under control of a dialog presentation controller 426. In order to perform the rendering function, the text renderer 423 receives font data associated with the dialog text

data from the font preloading buffer 410, receives rendering information and inline style

information from the dialog presentation controller 426, and renders the dialog text data into

bitmap data using the rendering information and inline style information, which is applicable

for each text string of the dialog text data. Thereafter, the rendered text data are then stored

in a bitmap object buffer (BOB) 424 as a bitmap object. Accordingly, the "Object" being

recorded in the BOB buffer 424 corresponds to the text data of each region within each dialog,

which is converted to a bitmap object. Therefore, a maximum of 2 objects for each region is

parsed and stored within the BOB buffer 424.

Finally, in the composition step, the rendered text data are added into the graphics plane (GP)

43 according to the composition information, which represents information indicating time

for displaying a text subtitle within the display screen. Finally, the bitmap object stored in

the bitmap object buffer 424 is transferred (added) to the graphics plane 43 according to the

composition information provided by the dialog presentation controller 426. The color look-

up table 44 uses palette information included in the composition information to adjust color

and transparency levels of an output of the graphics plane 43.

Accordingly, in presenting (or reproducing) continuous DPS #2, DPS #3, and DPS #4 that

configure the continuous presentation set #2, as shown in FIG. 8C, the leading DPS #2 is

presented by using all of the above-described presentation processes. Thereafter, in

presenting DPS #3 and DPS #4, the region enabling the continuous presentation with DPS #3 and DPS #4 uses the same region style as that of the previous DPS #2. And so, in this case,

the rendering process is omitted, and the information related to the previous DPS #2 within

the graphic plane (GP) is preserved and used. More specifically, the graphic plane (GP) is

preserved until the dialog_end_PTS of the DPS #$, wherein the continuous presentation is

completed. However, when a discontinuous presentation of DPS #5 begins, the information

within the graphic plane (GP) is entirely reset. Even though the DPS is a continuous

presentation DPS within the continuous presentation set, a discontinuous region may be

included, and in this case, the independent region should configure a bitmap object through a

separate rendering process.

Industrial Applicability

It will be apparent to those skilled in the art that various modifications and variations can be

made in the present invention without departing from the spirit or scope of the inventions.

Thus, it is intended that the present invention covers the modifications and variations of this

invention provided they come within the scope of the appended claims and their equivalents.

Claims

[CLAIMS]

1. A recording medium for reproducing text subtitle streams, the recording

medium comprising: a data area storing at least one text subtitle stream, each text subtitle stream including

a dialog style segment defining a group of region styles and a plurality of dialog presentation

segments, each dialog presentation segment containing at least one region of dialog text each

of which is linked to a selected one of the group of region styles, wherein a first region of

dialog text included in a current dialog presentation segment contains a continuous

presentation flag which indicates that continuous presentation is required between the first

region of dialog text and a second region of dialog text included in a previous dialog

presentation segment.

2. The recording medium of claim 1, wherein each one of the first and second regions

of dialog text includes at least one pair of an inline style and a text string.

3. The recording medium of claim 2, wherein the pairs of an inline style and a text

string included in the first and second regions of dialog text, respectively, are identical to

each other.

4. The recording medium of claim 1, wherein at least one of the plurality of dialog presentation segments includes two regions of dialog text, which are linked to first and

second region styles specifying a same text flow.

5. The recording medium of claim 1, wherein the first and second regions of dialog text

are linked to a same region style selected from the group of region styles defined in the dialog

style segment.

6. The recording medium of claim 1, wherein the first region of dialog text included in

the current dialog presentation segment is presented in a graphics plane by preserving

presentation of the second region of dialog text included in the previous dialog presentation

segment in the graphics plane.

7. A recording medium for reproducing text subtitle streams, the recording medium

comprising:

a data area storing at least one text subtitle stream, each text subtitle stream including a dialog

style segment defining a group of region styles and a plurality of dialog presentation

segments, at least one of the plurality of dialog presentation segments containing first and

second regions of dialog text which are linked to first and second region styles selected from

the group of region styles, respectively, wherein the first and second region styles define a

same text flow.

8. The recording medium of claim 7, wherein the same text flow indicates at least one

of character progression and line progression.

9. A method for reproducing text subtitle streams, the method comprising:

reading a dialog style segment included in a text subtitle stream recorded on a recording

medium, the dialog style segment defining a group of region styles, the text subtitle stream

further including first and second dialog presentation segments;

presenting a first region of dialog text included in the first dialog presentation segment in a

graphics plane, the first region of dialog text being linked to one of the group of region styles;

reading a continuous presentation flag included in the second dialog presentation segment,

the second dialog presentation segment including a second region of dialog text which is

linked to one of the group of region styles; and

presenting the second region of dialog text by preserving the presentation of the first region

of dialog text in the graphics plane, if the continuous presentation segment indicates that

continuous presentation is required between the first and second regions of dialog text.

10. The method of claim 9, wherein the first and second regions of dialog text are linked

to a same region style selected from the group of region styles defined in the dialog style

segment.

11. The method of claim 9, wherein a presentation start time of the second dialog

presentation segment is identical to a presentation end time of the first dialog presentation

segment, if the continuous presentation flag indicates that continuous presentation is required

between the first and second dialog presentation segments.

12. The method of claim 9, further comprising preloading the text subtitle stream into a

buffer.

13. An apparatus for reproducing text subtitle streams, the apparatus comprising:

a buffer configured to preload a text subtitle stream, the preloaded text subtitle stream

including a dialog style segment defining a group of region styles and first and second dialog

presentation segments; and

a text subtitle decoder configured to present a first region of dialog text included in the first

dialog presentation segment in a graphics plane, and to read a continuous presentation flag

included in the second dialog presentation segment, the second dialog presentation segment

including a second region of dialog text, wherein the text subtitle decoder presenting the

second region of dialog text by preserving the presentation of the first region of dialog text in

the graphics plane, if the continuous presentation segment indicates that continuous

presentation is required between the first and second regions of dialog text.