WO2005081643A2

WO2005081643A2 - Recording medium and method and apparatus for reproducing and recording text subtitle streams

Info

Publication number: WO2005081643A2
Application number: PCT/KR2005/000479
Authority: WO
Inventors: Kang Soo Seo; Byung Jin Kim; Jea Yong Yoo
Original assignee: Lg Electronics Inc.
Priority date: 2004-02-26
Filing date: 2005-02-22
Publication date: 2005-09-09
Also published as: EP1721453A2; US20050191032A1; WO2005081643A3; KR20060129067A; US7558467B2; US20070122119A1

Abstract

A recording medium and method and apparatus for reproducing and recording text subtitle streams are disclosed. A PlayList file contains a set of PlayItems and a SubPlayItem. Each PlayItem is configured to reproduce at least one main AV stream, and the SubPlayItem is configured to reproduce at least one text subtitle stream. The PlayList file further contains synchronization information which indicates a presentation start time of the SubPlayItem within a playing time interval of one of the set of PlayItems. The PlayList file, main AV stream, and text subtitle streams are recorded on a recording medium. Each text subtitle stream includes a plurality of dialog presentation segments, each of which includes at least one region of dialog text.

Description

RECORDING MEDIUM AND METHOD AND APPARATUS FOR REPRODUCING A1 D RECORDING TEXT SUBTITLE STREAMS

Technical Field

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

medium and method and apparatus for reproducing and recording 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-DND"), 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 and method and

apparatus for reproducing and recording 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 recording text

subtitle streams in a recording medium, such as a blu-ray disc, and to provide a method and apparatus for reproducing the recorded text subtitle streams.

Another object of the present invention is to provide a method of creating style information

when recording text subtitle streams within a recording medium.

A further object of the present invention is to provide a method and apparatus for reproducing

text subtitle streams that can effectively reproduce the text subtitle streams.

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 first data area storing at least one PlayList file, each PlayList

file containing a set of Playltems and a SubPlayltem, each Playltem being configured to •

reproduce at least one main AV stream, the SubPlayltem being configured to reproduce at

least one text subtitle stream, the PlayList file further containing synchronization information

which indicates a presentation start time of the SubPlayltem within a playing time interval of

one of the set of Playltems, and a second data area storing the at least one main AV stream

and the at least one text subtitle stream. In another aspect of the present invention, a recording medium for reproducing text subtitle

streams includes a first data area storing a text subtitle stream including a plurality of dialog

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

dialog text and specifying presentation start and end times of the at least one region of dialog

text, wherein an initial value of a system time clock for the text subtitle stream is a

presentation start time of the first dialog presentation segment included in the text subtitle

stream.

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

includes reading a PlayList file recorded on a recording medium, reading a set of Playltems

and a SubPlayltem included in the PlayList file, each Playltem being configured to reproduce

at least one main AV stream recorded on the recording medium, the SubPlayltem being

configured to reproduce at least one text subtitle stream recorded on the recording medium-

reading synchronization information included in the SubPlayltem, the synchronization

information including a first data field indicating a Playltem identification value of one of the

set of Playltems and a second data field indicating a presentation start time of the

SubPlayltem within a playing time interval of the Playltem identified by the Playltem

identification value, and synchronizing presentation of the SubPlayltem with presentation of

the Playltem identified by the Playltem identification value.

includes reading a text subtitle stream recorded on a recording medium, reading a plurality of dialog presentation segments included in the text subtitle stream, each dialog presentation

segment containing at least one region of dialog text and specifying presentation start and end

times of the at least one region of dialog text, setting an initial value of a system time clock

for the text subtitle stream to a presentation start time of the first dialog presentation segment

included in the text subtitle stream, and presenting the at least one region of dialog text using

the presentation start and end times which are based on the system time clock.

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

includes a driver configured to drive an optical reproducing device to reproduce data

recorded on a recording medium, and a controller configured to control the driver to read at

least one PlayList file recorded on the recording medium, each PlayList file containing a set

of Playltems and a SubPlayltem, each Playltem being configured to reproduce at least one

main AV stream, the SubPlayltem being configured to reproduce at least one text subtitle

stream, the SubPlayltem including synchronization information which indicates a

presentation start time of the SubPlayltem within a playing time interval of one of the set of

Playltems.

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

recorded on a recording medium, and a controller configured to control the driver to read a

text subtitle stream recorded on the recording medium, the text subtitle stream including a

plurality of dialog presentation segments, each dialog presentation segment containing at least one region of dialog text and specifying presentation start and end times of the at least

one region of dialog text, wherein an initial value of a system time clock for the text subtitle

stream is a presentation start time of the first dialog presentation segment included in the text

subtitle stream. 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 data files recorded in a high density optical disc according to

the present invention;

FIG. 2 illustrates data storage areas of the high density 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 5C illustrate applications of the reproduction control information for reproducing

the text subtitle stream according to the present invention;

FIG. 6 illustrates a dialog, which forms a text subtitle stream according to the present

invention, and its relation with a presentation time;

FIG. 7 illustrates a structure of the text subtitle stream according to the present invention;

FIG. 8 illustrates a set of SubPath information among reproduction control file information

for controlling reproduction of the text subtitle stream according to the present invention;

FIG. 9 illustrates a method of synchronizing the text subtitle stream and a main AV stream

according to the present invention;

FIG. 10 illustrates a set of type information included in a general AV stream;

FIG. 11 illustrates a Cliphifo file among reproduction control file information for controlling

reproduction of the text subtitle stream according to the present invention; and

FIG. 12 illustrates 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. In 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". 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. Most particularly, by

synchronizing the text subtitle stream with the main data (AV stream), the present invention

proposes a method of providing to the users a text subtitle stream synchronized with the main

data (AV stream).

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 (CL1PINF), 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 (CL-PINF) 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. Accordingly, the Cliplnfo file (*.clpi) related to the text

subtitle stream according to the present invention will be described in detail in a later process

with reference to FIG. 11.

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 01000.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_Information_File_Name within the Playltem. Therefore, a PlayList file represents the

basic reproduction control information for one or more main AV clips. 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.

Accordingly, a main path refers to a path reproducing the main data by using at least one

Playltem included in a PlayList file, and a sub pat refers to a path reproducing the text

subtitle stream as the supplementary data. More specifically, a main path must be included in

a PlayList file, and at least one sub path for each attribute of a corresponding set of

supplementary data is included, when the supplementary data exist. Thus, a reproduction

using the main path and the sub path will be described in detail in a later process with

reference to FIG. 4, and more specifically, a sub path syntax for reproducing the text subtitle

stream according to the present invention will be described in detail with reference to FIG. 8.

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. Accordingly, the text subtitle stream must be

provided by being synchronized in the main data, and the method of synchronizing the text

subtitle stream with the main data will be proposed in the present invention.

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. More specifically, at

least one Playltem is included in the PlayList file as a main path for controlling reproduction

of the main data (i.e., main clip). And, when a corresponding text subtitle stream exists

within the main data, the text subtitle stream is controlled by a SubPlayltem as the sub path.

For example, referring to FIG. 4, a text subtitle clip 1 (English) and a text subtitle clip 2

(Korean) are each reproduced and controlled by a single SubPlayltem. And, each of the text

subtitle clip 1 and the text subtitle clip 2 is synchronized with the main data, thereby enabling

the text subtitle and the main data to be displayed on a display screen simultaneously at a

desired 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. Hereinafter, diverse information included in

the text subtitle stream will be described in detail with reference to FIG. 5 A to FIG. 7. And, the method of synchronizing the text subtitle stream with the main data will be described in

detail with reference to FIG. 8 to FIG. 11.

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, so as to facilitate reproduction control of the text subtitle stream, hi

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

(PTS). More specifically, a PTS section for reproducing one dialog includes a

"dialog_start_PTS" and a "dialog_end_PTS" for each dialog. Also, for example, presentation

of the dialog shown in FIG. 5 A starts at PTS (k) (i.e., dialog_start_PTS) and ends at PTS

(k+1) (i.e., dialog_end_PTS). Therefore, when 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), all of the text subtitle data is defined by the same dialog. Herein, 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.

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 blue background color is applied to Region 1, and a different region style with

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

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

applied to a particular portion of text 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.

FIG. 6 illustrates a method of creating each dialog applied to each presentation time (PTS)

section. For example, when 4 dialogs exist between PTS1 to PTS6, Dialog #1 is displayed as

text data Text #1 between PTS1 and PTS2. And, Dialog #2 includes 2 regions (Region 1 and

Region 2) between PTS2 and PTS3, wherein Region 1 is displayed as text data Text #1 and

Region 2 is displayed as text data Text #2. Further, Dialog #3 is displayed as text data Text

#2 between PTS3 and PTS4, and Dialog #4 is displayed as text data Text #3 between PTS5

and PTS6. Referring to FIG. 6, text subtitle data does not exist between PTS4 and PTS5. In

the method for creating each of the above-described dialog information, each of the dialogs

must include timing information (i.e., PTS set) for displaying the corresponding dialog, style

information, and actual text data (hereinafter referred to as "dialog data").

Accordingly, as described above, the timing information (i.e., PTS set) being displayed is

recorded as "dialog_start_PTS" and "dialog_end_PTS". The style information is defined as

the above-described Global_Style_Info and Local_Style_Info. However, in the present

invention, the style information will be recorded as region_styles and inline_styles.

Furthermore, text data that is displayed on the actual display screen is recorded in the dialog

data. More specifically, since Dialog #2 includes 2 regions (Region 1 and Region 2), a set of style information and dialog data is recorded for each of Region 1 and Region 2.

FIG. 7 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 PEDs. Referring to FIG. 7, each sub-set of transport packets form a packet

elementary stream (PES) packet. One of the PES packets shown in FIG. 7 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. 7, each of the dialog information

shown in FIGs. 5A to 5C and FIG. 6 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.

FIG. 8 illustrates a syntax structure of a sub path and a SubPlayltem according to the present

invention. Herein, the sub path and the SubPlayltem are not used to control reproduction of the text subtitle stream only. Rather, an object of the sub path and the SubPlayltem is to

define and reproduce diverse supplementary data including the text subtitle stream,

depending upon the sub path type, which will be described in a later process. Therefore, a

specific field within the syntax structure of the sub path and the SubPlayltem will be defined

to have a specific value, when the specific field is irrelevant to the text subtitle stream or

when the specific field is used in the text subtitle stream.

More specifically, referring to FIG. 8, a SubPath( ) syntax designates a path of the

supplementary data that is associated with the main data included in a single PlayList. The

SubPath( ) syntax includes a SubPath_type field, an is_repeat_SubPath field, a

number_of_SubPlayItems field, and a SubPlayltem(i) field. Herein, the SubPath_type field

designates the type of a sub path. SubPath_type=2 represents a supplementary audio

browsable slideshow, SubPath_type=3 represents an interactive graphic presentation menu,

and SubPath_type=4 represents a text subtitle presentation. Therefore, the optical recording

and reproducing apparatus according to the present invention can determined which type of

clip is being controlled by each corresponding sub path through the SubPath_type field. Also,

the number_of_SubPlayItems field represents the number of SubPlayltems included within

the sub path. Herein, the optical recording and reproducing apparatus can verify the number

of SubPlayltems that are being controlled in the specific sub path through the number_of

_SubPlayItems field. The is_repeat_SubPath field represents a set of 1-byte flag information

for verifying whether the corresponding SubPath is to be used repeatedly. More specifically, when is_repeat_SubPath=Ob the SubPath is not used repeatedly, and when

is_repeat_SubPath=lb the SubPath is used repeatedly.

Accordingly, when controlling reproduction of the text subtitle stream by using the SubPath,

SubPath_type=4, number_of_SubPlayItems=l, and is_repeat_SubPath=Ob. In other words,

in the SubPath controlling the text subtitle stream, a single SubPlayltem controls

reproduction of a plurality of text subtitle streams (e.g., as shown in FIG. 4), and the SubPath

is not used repeatedly. Therefore, when reproducing the supplementary audio browsable

slideshow as SubPath^ype^, and when reproducing the interactive graphic presentation

menu stream as SubPath_type=3, the number_of_SubPlayItems field and the

is_repeat_SubPath field may be defined differently and used.

In addition, a detailed syntax of the SubPlayltem(i) field will now be described. A

Clip Jfoformation_file_name field is used as information designating a file name of a strea

that is controlled by the corresponding SubPlayltem, and a Clip_codec_identifier field

represents a coding format of the designated clip. As described above, since the text subtitle

information according to the present invention is encoded in an MPEG-2 format, the

Clip_codec_identifier field is defined as Cliρ_codec_identifier=M2TS. Also, a

SubPlayItem_IN_time field and a SubPlayItem_OUT_time field are used as information for

designating the reproduction begin time and reproduction end time within the designated clip.

Accordingly, as described in FIG. 1, the SubPlayItem_IN_time and the

SubPlayItem_OUT_time are changed to a set of address information (also referred to as a source packet number (SPN)) within the designated Cliplnfo file (*.clpi), so as to decide the

reproduction section within the actual clip. Further, a ref_to_STC_id field represents

information deciding a position of a seamless reproduction unit, which is applied to the

reproduction section, within the designated clip, a detailed description of which will be

described in detail with reference to FIG. 10.

An is_multi_clip_entries field is a set of 1-byte flag information representing a number of

clip entries being controlled by the corresponding SubPlayltem. For example, referring to

FIG. 4, since a plurality of clips exists when 2 text subtitle clips are controlled by a single

SubPlayltem, is_multi_clip_entries=lb. Therefore, when is_multi_clip_entries=lb, at least 2

clip entries exist, and in this case, a subclip_entry_id is assigned to each clip entry, and a

specific Clip_Information_file_name field, Clip_codec_identifier field and a ref_to_STC_id

field for each subclip_entry_id are defined.

Finally, a set of information for a synchronization with the main data is included within the

SubPlayltem syntax, wherein the information includes a sync_PlayItem_id field and a

sync_start_PTS_of_PlayItem field. More specifically, the syncJPlayltein d field and the

sync_start_PTS_of_PlayItem field are used only when reproduction control of the text

subtitle stream is performed by using the SubPlayltem. Therefore, when reproducing the

supplementary audio browsable slideshow as SubPath_type=2, and when reproducing the

interactive graphic presentation menu stream as SubPath_type=3, the sync_PlayItem_id field

and the sync_start_PTS_of_PlayItem field become unnecessary information, and in this case, the corresponding field is set as 'OOh'.

In describing the sync_PlayItem_id field and the sync_start_PTS_of _PlayItem field, the sync

information for reproducing the text subtitle stream according to the present invention will

now be described with reference to FIG. 9. First of all, the text subtitle stream is

synchronized with the main data, and the reproduction begin time of the text subtitle stream

being synchronized with the main data is decided by the sync_PlayItem_id field and the

sync_start_PTS_of_PlayItem field. More specifically, the sync_PlayItem_id field is a set of

information designating a specific Playltem among at least one Playltems within the PlayList

file. And, the sync_start_PTS_of_PlayItem field is a set of information indicating the

reproduction begin time of the text subtitle stream as a Playltem PTS, within the designated

specific Playltem. For example, referring to FIG. 9, in the SubPlayltem for reproducing the

text subtitle stream, as information for deciding the reproduction begin time of the text

subtitle stream being synchronized with the main data, the sync_PlayItem_id field and the

sync_startJPTS_of_PlayItem field may be defined as syncJPlayItem_id=0 and

sync_start_PTS_of _PlayItem=tl. More specifically, reproduction of the text subtitle stream / using the SubPlayltem begins at a specific point of "tl(PTS)" within Playltem 1

(PlayItem_id=0).

Secondly, the text subtitle stream uses a counter of 90 kilohertz (khz) as a system time clock.

And, an initial value of the counter is the dialog_start_PTS within the first dialog presentation

segment (DPS #1), shown in FIG. 7. More specifically, unlike other streams, the text subtitle stream does not have a program clock reference (PCR) as the initial value. Accordingly, all

PTS (dialog_start_PTS and dialog_end_PTS) values within subsequent dialog presentation

segments (DPS) are decided by counting from the dialog_start_PTS within the first dialog

presentation segment (DPS #1).

Therefore, reproduction of the text subtitle begins starting from the time decided by the

sync_PlayItem_id field and the sync_start_PTS_of_PlayItem field. Afterwards, a system

time clock counter of 90 kilohertz (khz), having an initial value identical to that of the

dialog_start_PTS within the first dialog presentation segment (DPS #1), is used so as to

reproduce each dialog in accordance with the PTS (dialog_start_PTS and dialog_end _PTS)

value for each dialog defined within the dialog presentation segment (DPS) included in the

text subtitle stream. Thereafter, reproduction ends at dialog_end_PTS within the last dialog

presentation segment (last DPS) included in the text subtitle stream.

FIG. 10 illustrates a system time clock sequence (STC_sequence) and an arrival time clock

sequence (ATC_sequence) within the clip according to the present invention. Accordingly,

the STC_sequence refers to a continuous clip that is decided by a time reference. More

specifically, a new STC_sequence is created starting from a packet, which includes a

program clock reference (PCR) as the time reference, among the transport packets being

inputted. In the example shown in FIG. 10, a total of 3 STC_sequences (i.e., STC #0, STC

#1, and STC #2) exists. Therefore, a STC_discontinuity may occur between each

STC_sequence. Also, at least one STC_sequence (e.g., STC #0, STC #1, and STC #2) configures a single ATC_sequence. More specifically, each of the clips within the optical

disc is formed of an ATC_sequence including at least one STC_sequence.

However, the number of ATC_sequence is not limited to only one ATC_sequence, as

described in the example shown in FIG. 10. In other words, the clip may include a plurality

of ATC_sequences. Accordingly, in case of the text subtitle stream, the system time clock is

decided by using the dialog_start_PTS within the first dialog presentation segment (DPS #1)

as an initial value. Thus, the text subtitle stream is formed of an ATC_sequence including a

STC_sequence.

FIG. 11 illustrates a set of information recorded within a Cliplnfo file (*.clpi) according to

the present invention and, more specifically, illustrates information included in a

SequenceInfo( ) area. Referring to FIG. 11, a field for recording STC_sequence and

ATC_sequence information of each corresponding clip is included in the Sequencehιfo( )

area within the Cliplnfo file (*.clpi). More specifically, information on the number of

ATC_sequences is recorded in a number_of_ATC_sequences field. And, in the present

invention, one ATC_sequence is included in the text subtitle clip. Therefore, since only one

ATC_sequence is included in the text subtitle clip, only an ATC ID exists as atc_id=0.

Additionally, a number_of_STC_sequences(atc_id) field includes information on the number

of STC_sequences within the ATC_sequence (e.g., atc_id=0). And, as described above, only

one STC_sequence is included in the text subtitle clip according to the present invention.

Further, a stc_id is assigned to each STC_sequence, and each stc_id includes a PCR_PIC field, a SPN_STC_start field, a presentation_start_time field, and a presentation_end_time

field.

Herein, a set of information designating packet identification (PID) including a program

clock reference (PCR), which is a time reference of the STC_sequence, is recorded in the

PCR_PID field. And, a set of information designating a start source packet number (SPN) of

the STC_sequence is recorded in the SPN_STC_start field. Accordingly, since a PCR does

not exist in the text subtitle clip according to the present invention, either a dummy data

having no meaning is recorded in the PCR_PID field, or the PCR_PID field is set as 'OOh'.

Finally, a set of information designating the starting time and the ending time of each

corresponding clip is respectively recorded in the presentation_start_time field and the

presentation_end_time field. Accordingly, as described above, the presentation_start_time of

the clip becomes the dialog_start_PTS within the first dialog presentation segment (DPS #1),

and the presentation_end_time becomes the dialog_end_PTS within the last dialog

presentation segment (last DPS).

FIG. 12 illustrates a detailed view of an optical recording and/or reproducing apparatus 10

according to the present invention, including the reproduction of the text subtitle data. The

optical recording and/or reproducing apparatus 10 basically includes a pick-up unit 11 for

reproducing main data, text subtitle stream and corresponding reproduction control

information recorded on the optical disc, a servo 14 controlling the operations of the pick-up

unit 11, a signal processor 13 either recovering the reproduction signal received from the pick-up unit 11 to a desired signal value, or modulating a signal to be recorded to an optical

disc recordable signal and transmitting the modulated signal, and a microcomputer 16

controlling the above operations.

In addition, an AV decoder and text subtitle (Text ST) decoder 17 performs final decoding of

output data depending upon the controls of the controller 12. And, in order to perform the

function of recording a signal on the optical disc, an AV encoder 18 converts an input signal

into a signal of a specific fonnat (e.g., an MPEG-2 transport stream) depending upon the

controls of the controller 12 and, then, provides the converted signal to the signal processor

13. Accordingly, the AV decoder and text subtitle (Text ST) decoder 17 is included in the

present invention as a single decoder, for simplicity of the description. However, it is

apparent that only the text subtitle (Text ST) decoder can be independently included as an

element of the present invention.

A buffer 18 is used for preloading and storing the text subtitle stream in advance, in order to

decode the text subtitle stream according to the present invention. The controller 12 controls

the operations of the optical recording and/or reproducing apparatus. And, when the user

inputs command requesting a text subtitle of a specific language to be displayed. Then, the

corresponding text subtitle stream is preloaded and stored in the buffer 18. Subsequently,

among the text subtitle stream data that is preloaded and stored in the buffer 18, the controller

12 refers to the above-described dialog information, region information, style information,

and so on, and controls the text subtitle decoder 17 so that the actual text data are displayed with a specific size and at a specific position on the screen.

More specifically, the text subtitle decoder 17 reproduces the text subtitle stream preloaded in

the buffer 18. However, the text subtitle decoder 17 includes a counter 17a , so as to set the

dialog_start_PTS within the first dialog presentation segment (DPS #1) as an initial value, so

as to create the system time clock (e.g., by using a frequency of 90 khz). Furthermore, the

text subtitle decoder 17 verifies a synchronization point of the text subtitle stream with the

main data from the SubPlayltem within the PlayList file associated with the reproduction of

the text subtitle clip. For example, information included in the sync_PlayItem_id field and

the sync_start_PTS_of_PlayItem field within the above-described SubPlayltem is read, and

based upon the read information, the text subtitle stream is reproduced starting from a

specific time within a specific Playltem.

As described above, the recording medium and method and apparatus for reproducing and

recording text subtitle streams have the following advantages. The text subtitle stream is

synchronized with the main data, and therefore, the text subtitle stream and the main data are

reproduced simultaneously.

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 first data area storing at least one PlayList file, each PlayList file containing a set of

Playltems and a SubPlayltem, each Playltem being configured to reproduce at least one main

AV stream, the SubPlayltem being configured to reproduce at least one text subtitle stream,

the PlayList file further containing synchronization information which indicates a

Playltems; and a second data area storing the at least one main AV stream and the at least one text

subtitle stream.

2. The recording medium of claim 1, wherein each text subtitle stream includes a

plurality of dialog presentation segments, each dialog presentation segment including at least

one region of dialog text.

3. The recording medium of claim 2, wherein the each dialog presentation

segment specifies presentation start and end times of the at least one region of dialog text.

4. The recording medium of claim 1, wherein the synchronization information is

contained in the SubPlayltem.

5. The recording medium of claim 1, wherein the synchronization information comprises

a first data field indicating a Playltem identification value of the one of the set of Playltems,

and a second data field indicating the presentation start time of the SubPlayltem.

6. The recording medium of claim 1, wherein the SubPlayltem starts its presentation

when presentation of the Playltem has reached to the presentation start time of the

SubPlayltem.

7. The recording medium of claim 1, wherein the SubPlayltem includes a data field

specifying a name of a Clip information file which corresponds to each text subtitle stream.

8. The recording medium of claim 1, wherein the SubPlayltem includes a data field

indicating a presence of a multi-clip-entries structure.

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

comprising:

a first data area storing a text subtitle stream including a plurality of dialog presentation segments, each dialog presentation segment containing at least one region of dialog text and

specifying presentation start and end times of the at least one region of dialog text, wherein

an initial value of a system time clock for the text subtitle stream is a presentation start time

of the first dialog presentation segment included in the text subtitle stream.

10. The recording medium of claim 9, further comprising:

a second data area storing a Clip information file corresponding to the text subtitle stream, the

clip information file including a data field indicating a source packet number of a source

packet where a STC-sequence starts, the STC-sequence representing a sequence of source

packets that are continuous based on the system time clock.

11. A method of reproducing text subtitle streams, the method comprising:

reading a PlayList file recorded on a recording medium;

reading a set of Playltems and a SubPlayltem included in the PlayList file, each Playltem

being configured to reproduce at least one main AV stream recorded on the recording

medium, the SubPlayltem being configured to reproduce at least one text subtitle stream

recorded on the recording medium;

set of Playltems and a second data field indicating a presentation start time of the SubPlayltem within a playing time interval of the Playltem identified by the Playltem

identification value; and

synchronizing presentation of the SubPlayltem with presentation of the Playltem identified

by the Playltem identification value.

12. A method of reproducing text subtitle streams, the method comprising:

reading a text subtitle stream recorded on a recording medium;

reading a plurality of dialog presentation segments included in the text subtitle stream, each

dialog presentation segment containing at least one region of dialog text and specifying

presentation start and end times of the at least one region of dialog text;

setting an initial value of a system time clock for the text subtitle stream to a presentation

start time of the first dialog presentation segment included in the text subtitle stream; and

presenting the at least one region of dialog text using the presentation start and end times

which are based on the system time clock.

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

a driver configured to drive an optical reproducing device to reproduce data recorded on a

recording medium; and

a controller configured to control the driver to read at least one PlayList file recorded on the

recording medium, each PlayList file containing a set of Playltems and a SubPlayltem, each Playltem being configured to reproduce at least one main AV stream, the SubPlayltem being

configured to reproduce at least one text subtitle stream, the SubPlayltem including

synchronization information which indicates a presentation start time of the SubPlayltem

within a playing time interval of one of the set of Playltems.

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

recording medium; and

a controller configured to control the driver to read a text subtitle stream recorded on the

recording medium, the text subtitle stream including a plurality of dialog presentation

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

of the first dialog presentation segment included in the text subtitle stream.