KR20150023590A - method of transmitting a digital broadcast signal - Google Patents

Abstract

An embodiment of the present invention provides a method of transmitting a digital broadcast signal, which comprises the steps of: multiplexing auxiliary data including video data, audio data, an event information table (EIT), and a program map table (PMT) to MPEG-2 transport stream; and modulating and transmitting the multiplexed MPEG-2 transport stream to a broadcast signal. Regarding the multiplexing step, the EIT or the PMT includes a caption descriptor containing caption information. The caption descriptor includes the caption information exhibiting whether caption data included in the video data is the data providing a digital closed caption service according to electronic industry association (EIA)-708, or the caption data providing an analog closed caption service.

Description

[0001] The present invention relates to a method of transmitting a digital broadcast signal,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to caption data of a digital TV, and more particularly, to a method of transmitting closed caption data conforming to an open cable and a cable ready standard of digital cable broadcasting.

The US terrestrial broadcast standard for analog TV broadcasts closed captions such as English and Spanish using the 21st line of the VBI (Vertical Blanking Interval) section of the National Television System Committee (NTSC) broadcast signal And the related standard is EIA 608.

According to the EIA 608 standard, in the United States, there are eight types of services that can be transmitted for analog closed caption (CC) as shown in Table 1 below.

NTSC Field 1 Line 21 Caption NTSC Field 2 Line 21 Caption CC1 (main sync subtitle service) CC3 (Subtitle Subtitle Service) CC2 (Special Asynchronous Subtitles) CC4 (Special Asynchronous Subtitle) Text1 (first character information service) Text3 (third character information service) Text2 (second character information service) Text4 (fourth character information service)

In the case of analog captions in the United States, the user must determine eight settings as shown in Table 1. However, since the actual broadcast program does not have information on which of the above eight services is being performed, I had to change the settings to see what services were available.

In the case of analog TV broadcasting in Korea, due to the difference between Korean and English, there is a slight difference in the tables and detailed rules regarding the values of the actual characters and the commend set. However, in the US NTSC standard The caption information is transmitted using the 21st line of the VBI of FIG.

Meanwhile, as the broadcasting environment has been changed from analog to digital broadcasting, ATSC (Advanced Television System Committee) standards have been established as a terrestrial broadcasting standard in the United States. For this purpose, Digital TV Closed Caption (DTVCC ) (EIA 708) has been established and used.

The DTVCC will be described with reference to the accompanying drawings.

1 is a diagram of DTVCC caption data described in the EIA 708 standard in a bit stream of a general digital TV.

As shown in Fig. 1, the bit stream of the digital TV is composed of an audio data area, a video data area, and a control data area.

In the case of the DTVCC, the caption data itself is transmitted using a user data area included in a header of a picture constituting the video data area, and conforms to the MPEG-2 video standard and the ATSC standard (A53). At this time, the transmission amount can be transmitted up to 128 bytes in each user data area, and the total transmission amount can not exceed 9600 bps (bit per second).

This can be seen as a 10x increase in bandwidth compared to the analog closed caption based on EIA 608, which can not exceed 960 bps.

In the case of DTVCC based on EIA 708, a total of 63 caption services can be performed considering the extended bandwidth.

It is very unreasonable to let the user keep searching for the desired caption service by changing the setting like the analog closed caption that was mentioned above for the 63 possible caption services.

Therefore, when providing the DTVCC in the ATSC standard, the broadcasting station necessarily includes the caption_service_descriptor in the EIT (Event Information Table) or PMT (Program Map Table) in PSIP (Program and System Information Protocol).

This allows the DTV receiver to know what type of DTVCC is included in the program, the configuration of which is shown in FIG.

FIG. 2 is a diagram showing a syntax of a caption_service_descriptor defined in the ATSC standard (A65, Program and System Information Protocol for Terrestrial Broadcast and Cable).

Assuming, for example, that a broadcast station provides the following analog closed caption and six digital closed caption services to a program,

NTSC Field1 line 21 caption: 4 types

NTSC Field2 line 21 caption: 4 types

Caption Service 1: English

Caption Service 2: Spanish

Caption Service 3: English (with easy_reader flag)

Caption Service 4: Spanish (with easy_reader flag)

Caption Service 5: French

Caption Service 6: French (with easy_reader flag)

In this case, the above information is transmitted to the caption_service_descriptor in the PSIP in a table format as shown in FIG.

Accordingly, the digital TV notifies the user of the above information, allows the user to select a desired caption, or automatically selects a caption service corresponding to a language preset by the user.

At this time, it can be seen that, in the case of digital TV, pure DTVCC (native DTVCC) based on EIA 708 is not provided.

That is, the user data area including the DTVCC includes the analog closed caption of 2 bytes (byte) based on EIA 608 as well.

In this case, analog closed caption data loaded in the user data area is encoded in the VBI line 21 of S-VHS or Composite output. In this case, (C-VHS) or Composite is inputted, the caption display is performed through the analog closed caption decoder installed in the analog TV.

In addition, in the satellite broadcasting standard such as Direc TV, analog closed caption data loaded in the user data area instead of DTVCC is used for decoding purposes.

On the other hand, unlike terrestrial broadcasting, cable broadcasting has taken its own path in the nature of the market. The characteristics of the cable broadcasting are generally similar but somewhat different in terms of the broadcasting method depending on the region, the service company, or the supplier of the broadcasting equipment.

In particular, in the operation of closed caption, it is transmitted on the basis of a character value and a command set as defined in EIA 608, but it is the same as terrestrial analog broadcasting, but a VBI section other than the 21st line of VBI is used And is also transmitted.

That is, in some broadcasts, the caption is transmitted using the sixth line of the VBI, and in the case of some broadcasts, the caption is transmitted using the tenth line.

This characteristic of the analog cable broadcasting has made it possible to define the closed caption standard for digital broadcasting independently as the cable is converted into digital broadcasting.

The basic purpose of this standard, which is called SCTE 20 or DVS 157, is to convert the analog closed caption used in analog cable broadcasting to the user data area in the video data area of the digital TV.

The above specification does not refer to a new closed caption (DTVCC) such as EIA 708, but only the conventional analog closed caption is defined, and the form of the table is shown in FIG.

3 is a diagram showing the syntax of picture user data defined in SCTE 20 (DVS 157).

As mentioned earlier, in cable broadcasting, analog closed caption is transmitted on various lines including the 21st line of VBI.

Therefore, the caption data of the SCTE 20 or the DVS 157 as shown in the table of FIG. 3 includes information (caption data) indicating the caption to be transmitted through which field (even or odd) to each 2-byte caption data ), As well as information (line_offset expressed by 5 bits in FIG. 3) regarding the caption data transmitted through the second VBI line is also transmitted.

In the case of SCTE 20 or DVS 157, there is no definition of the new type of DTVCC as mentioned above.

In addition, the ATSC standard related to the DTVCC of FIG. 2, which has been described above, does not consider the closed caption according to SCTE 20 or DVS 157, which is a caption transmission standard used in cable broadcasting.

This is because, in the case of cable broadcasting in the closed market in the past, a cable broadcasting service company has distributed services to each user by distributing a cable set top box corresponding to its broadcasting, and a proper caption_service_descriptor Because cable broadcasting receiver developers have set up the broadcasting equipment setup of cable broadcasting service company and developed the receiver accordingly, there was no problem in digital cable broadcasting until before open cable.

However, in a new digital broadcast environment represented by open cable and cable ready, it has become necessary to view this problem from a different angle.

That is, in the open cable and cable ready environments, which are intended to allow a cable broadcasting receiver company to connect a cable to a device that is generally available in the market, rather than providing a receiver for a specific cable broadcasting company, Reception method is becoming a very complicated problem.

To be more specific, a digital television capable of receiving an open cable broadcast in accordance with the regulations of the Federal Communications Commission (FCC) must first be included in the DTVCC and analog CC defined in EIA 708 Closed caption).

You must also decode user data in other formats as defined in SCTE 20 or DVS 157, and encode the corresponding caption on the VBI line of the S-Video, Composite, 480i, Component output.

This requires the following operations for digital TV receiving open cable broadcasting.

- Determine what type of caption data (pure DTVCC of EIA 708, analog CC included in DTVCC, analogue CC according to SCTE 20 or DVS 157) is included in the digital cable broadcast being received.

- Select the appropriate caption from the captured caption data.

- Decode the selected caption.

Encode the transmitted caption in the appropriate VBI transmission interval of the analog output (S-Video, Composite, ...).

It is difficult to understand what kind of caption data is included in the digital cable broadcasting being received because of the data nature of caption. So, if you can not figure out what type of caption data is automatically included, you have to tell the user to choose, for example, to select the following options from the key or menu on the remote control .

- DTVCC, analog CC (EIA 708), analog CC (SCTE 20 or DVS 157)

It is a method of repeatedly selecting which of the above standards to decode the caption data of the standard so as to find out what is viewable. In fact, it is unreasonable to ask the user for the above matters, CC1, CC2, CC3, ...) must be selected again to view the caption. This inconvenience is greatly increased.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for simplifying a user's convenience and operation of a receiver in providing closed caption in accordance with an open cable and a cable ready standard, To be presented.

It is another object of the present invention to prevent the above-described method from causing malfunction of a cable broadcasting receiver according to the conventional ATSC standard.

An embodiment of the present invention is a method for multiplexing video data, audio data, and auxiliary data including an event information table (EIT) and a program map table (PMT) into an MPEG-2 transport stream, Wherein the caption descriptor includes tag information for identifying a type of the caption descriptor, the caption descriptor includes a field for identifying a length of the caption descriptor, a number of closed caption services And a caption descriptor included in the MPEG-2 transport stream, wherein the caption descriptor includes a caption data included in the video data, the caption data including a digital closed caption data according to an electronic industry association (EIA) Data that provides captioning services or electronic industry association (EIA) -708 Wherein the caption descriptor indicates whether the caption data is caption data for a 16: 9 aspect ratio, and the aspect ratio information indicating whether the caption data is caption data for a 16: 9 aspect ratio, Includes an identification number of a caption service provided by the caption data only when the caption data is data providing digital closed caption service according to electronic industry association (EIA) -708; And transmitting the multiplexed MPEG-2 transport stream as a broadcast signal.

The caption transmission / reception method in the digital broadcasting system according to the present invention has the following effects.

First, there is an effect of efficiently transmitting and receiving captions in a transmission environment based on open cable and cable ready standards.

Second, there is an effect that the present invention can be used for an open cable and a cable ready specification without significant deformation of a digital broadcast receiver conforming to the ATSC standard.

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 invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments but should be determined by the claims.

FIG. 1 is a block diagram of a DTV CC caption data related drawing
2 is a diagram showing a caption_service_descriptor syntax defined in the ATSC standard according to the prior art;
3 is a diagram showing the syntax of user data defined in SCTE 20 or DVS 157 according to the prior art
4 is a diagram showing a syntax of caption_service_descriptor according to the present invention;
5A to 5C are block diagrams showing a structure of a digital broadcast receiver according to the present invention

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

The open cable and cable ready standards comply with the ATSC standard. Therefore, the purpose of the present invention can be achieved by modifying the EIT on the PSIP or the caption_service_descriptor included in the PMT on the MPEG System Information as shown in FIG. 4, which is defined in the ATSC standard (A65, Program and System Information Protocol for Terrestrial Broadcast and Cable) .

4 is a view showing contents of a caption_service_descriptor modified according to the open cable and cable ready standards according to the present invention. The revised contents are shown in bold.

First, the caption_service_descriptor content of FIG. 4 will be described as follows.

descriptor_tag: It is expressed in 8 bits, and identifies the type of the descriptor.

descriptor_length: Represented by 8 bits, indicating the length of the entire structure.

number_of_services: Represents the number of total caption services, expressed in 5 bits.

language: Represents the language information of the corresponding caption such as English in service 1 or Spanish in service 2. As a 3-byte language code according to ISO 639.2 / B, each character is coded into 8 bits and inserted into a 24-bit field.

cc_type: 1 bit. If cc_type == 1, it is digital caption. If cc_type == 0, it is analog caption (analog caption included in EIA 708 standard or SCTE 20 (DVS157)).

analog_cc_type: corresponds to the case of the analog caption (analogue caption included in the EIA 708 standard or SCTE 20 (DVS157)), that is, when cc_type == 0, and when analog_cc_type == 1, the analogue caption is transmitted to the VBI line 21 according to the EIA 608 It means caption data. If analog_cc_type == 0, it means caption data that can be included in lines other than VBI line 21 according to SCTE 20 or DVS 157.

line_offset: It is represented by 5 bits, and it is the caption data according to SCTE 20 or DVS 157, that is, the caption included in the line of VBI when the analog_cc_type == 0.

line_field: Indicates whether the caption contained in the even field or the caption contained in the odd field. That is, if line_field == 0, the caption is included in the odd field, and if line_field == 1, the caption is included in the even field.

caption_service_number: Represented by 6 bits. In the case of digital caption, that is, when cc_type == 1, it represents 1 to 63 caption service numbers.

easy_reader: A flag indicating whether the user is an easy-to-read caption or not.

wide_aspect_ratio: Flag indicating whether caption is for 16: 9 screen.

Such a configuration is a method utilizing a reserved space in the configuration of the conventional caption_service_descriptor.

That is, the reserved 1 bit following cc_type shown in FIG. 2 is used as an information space for identifying the analog_cc_type, and the reserved 5 bits in the if statement are used as the information space representing the caption data included in the line of the VBI.

This will be described in more detail with reference to FIG. 4 showing the present invention.

First, when cc_type == 0, it means analog caption. As described above, there are analog captions according to the EIA 608 standard, analog captions included in the EIA 708 standard, and analog captions according to the SCTE 20 or DVS 157 standard. However, the analog captions according to the EIA 608 standard are pure It does not correspond to the closed caption of the digital TV mentioned in the present invention as an analog caption.

Accordingly, the analog caption corresponding to the cc_type == 0 means one of the analog captions included in the EIA 708 standard or the analog caption according to the SCTE 20 (DVS 157) standard.

Therefore, the process of selecting one of the two kinds of captions is one bit allocated to the analog_cc_type in FIG.

When the analog_cc_type is 0, it means that the corresponding caption is included in the video data area in the user data format according to the SCTE 20 or DVS 157 standard for digital cable broadcasting.

In this case, since it is not known whether the caption is the caption assigned to the second line of the VBI due to the nature of the cable broadcasting, the caption assigned to the second line of the VBI is expressed by 5 bits allocated to the line_offset.

When the analog_cc_type is 1, it means that the analog caption included in the EIA 708 standard is included in the video data area in the user data format.

In this case, since the caption is allocated to the 21st line of VBI, a line_offset value is not required. Therefore, five bits allocated to the line_offset are left as reserved bits, and one bit is assigned to the line_field indicating whether the caption included in the even field or the caption included in the odd field is expressed. If line_field == 0, the caption is included in the odd field, and if line_field == 1, the caption is included in the even field.

In this way, whether the caption data included in the digital cable broadcast is the analog caption or the digital caption through the information included in the caption_service_descriptor, whether it is the analog caption included in the EIA 708 standard or the standard of SCTE 20 or DVS 157 If the caption data is a caption according to the SCTE 20 or DVS 157 standard, it is determined whether the caption data is included in the second line of the VBI. If the caption data is a digital caption, So that the user can know the information of the user.

When the caption_service_descriptor information is transmitted through digital cable broadcasting, the operation on the receiver side will be described below.

FIG. 5A is a block diagram illustrating a configuration of a digital broadcast receiver based on closed caption data processing according to the present invention. FIG. 5B is a block diagram illustrating a configuration of a digital broadcast receiver, And FIG. 5C is a block diagram showing a configuration of a digital broadcast receiver centering on analog caption processing.

As shown in FIG. 5A, a digital broadcast receiver according to an embodiment of the present invention decodes an MPEG-2 transport stream transmitted through a digital cable broadcast and demultiplexes the received transport stream into video, audio, and control information An MPEG demultiplexer 501, a PMT buffer 502, an EIT buffer 503, the PMT buffer 502 or the EIT buffer 503 in which a PMT and an EIT in a PSIP belonging to the control information are separately stored, A user processor 504 for processing caption_service_descriptor information and caption information input by the user, parsing the video data decoded by the MPEG demultiplexer 501 to generate a user data area user_data () A video parser 505 for converting the video signal into MPEG-2 video data and a DTVCC decoder 505 for generating a digital caption through a signal processed through the user processor 504 and the video parser 505, An MPEG-2 video decoder 508 for decoding the MPEG-2 video data generated by the video parser 505 to generate a video program, an analog CC decoder 506 for generating an analog caption, A user graphic 510 for generating a GUI screen such as an OSD menu through information generated by the processor 504, a synthesizer 510 for synthesizing the generated analog or digital caption data, a video program, and an OSD menu, And a video reconstructor 309 for encoding the caption generated through the analog CC decoder 506 into the 21st line of the VBI.

The operation of the digital broadcast receiver according to the present invention will now be described.

First, an MPEG-2 transport stream transmitted through a digital cable broadcasting is demultiplexed into video, audio, and control information through an MPEG demultiplexer.

The PMT and the EIT in the PSIP belonging to the control information are separately stored in the PMT buffer 502 and the EIT buffer 503. The PSIP defines EPG (Electronic Program Guide) and SI (System Information) as one unit. The PSIP parses messages encoded by the MPEG-2 method and generates terrestrial waves and / ATSC standard for cable digital broadcasting (1997 DEC document A65).

That is, the PSIP transmits and receives A / V data made up of MPEG-2 video and AC-3 audio format, and has a plurality of tables so that information about channels of each broadcasting station and information about each program of the channel can be transmitted Information about the PMT (Program Map Table) is stored in the PMT buffer 502 and information about the EIT (Event Information Table) is stored in the EIT buffer 503.

According to the ATSC standard, the caption_service_descriptor must be included before the PMT or EIT. Therefore, the caption_service descriptor information is stored in the PMT buffer 502 or the EIT buffer 503.

Through the caption_service_descriptor information stored in the PMT buffer 502 or the EIT buffer 503, the user processor 504 finds the caption data included in the digital cable broadcasting based on the type of the caption service set by the user .

The service type of the found caption service may be DTVCC which is digital caption advanced information according to EIA 708 standard, that is, cc_type == 1 in FIG. 4, and the analog caption, cc_type == 0 Lt; / RTI >

In the case of the analog caption, analog caption according to the EIA 708 standard, that is, analog_cc_type == 1, and analog caption according to the SCTE 20 or DVS 157 standard, that is, analog_cc_type == 0.

For the sake of convenience of description, the types of the captions divided as described above will be described with reference to the accompanying drawings.

FIG. 5B is a block diagram showing a collection of corresponding blocks when the caption received in the digital broadcast receiver according to the present invention is digital.

If the user processor 504 shown in FIG. 5B determines that the digital information according to the EIA 708 is included in the caption_service_descriptor information (when cc_type == 1), the user selects the language information off (selects not to view the caption) , English, Spanish, and so on).

The caption information of the language uses 6-bit information (service ID) in caption_service_number.

And transmits the service ID of the found caption information to the DTVCC decoder 507.

The DTVCC decoder 507 extracts caption data corresponding to the service ID in the user data area of the picture header separated through the video parser 505.

The extracted caption data is combined with a video screen decoded by the MPEG-2 video decoder 508 and a video screen such as a TV menu screen generated in the user graphics unit 510 and a GUI screen using an OSD through a video synthesizer 509 And is output as an image.

5A, the output of the video synthesizer 509 is passed through a video reconstructor 511. Since the video reconstructor 511 is intended for analog captions, the output of the video synthesizer 509 The output is bypassed at the video reconstructor 511.

On the other hand, if cc_type == 0 in the user processor 504, based on the caption service type (off, cc1, cc2, cc3, ...) selected by the user, caption exists through line_field information corresponding to the caption service Field. As described above, if line_field == 0, there is an odd field, and if line_field == 1, there is a caption in an even field.

And caption information corresponding to the determined line_field is found in the caption_service_descriptor. That is, analog_cc_type information in the capton_service_descriptor is used.

(Analog_cc_type == 1) according to the EIA 708 standard, and analog caption according to SCTE 20 or DVS 157 (analog_cc_type == 0).

FIG. 5C shows a process of selecting the caption data included in the digital cable broadcasting in the case of the analog caption according to the SCTE 20 or DVS 157.

5C shows the blocks necessary for the analog caption according to SCTE 20 or DVS 157 in the configuration of FIG. 5A.

After confirming that the user processor 504 of FIG. 5C is an analog caption corresponding to SCTE 20 or DVS 157 through analog_cc_type, it checks the VBI line information indicating the position of the caption represented by 5 bits in line_offset.

The confirmed VBI line information and line_field information are input to the analog CC decoder 506. The analog CC decoder 506 finds analog caption data in the SCTE 20 or DVS 157 format using the VBI line information and the line_field information in the user data area in the video input from the video parser 505.

According to FIG. 5A, the user data input to the analog CC decoder 506 passes through the DTVCC decoder 507, which in this case is bypassed.

The detected analog caption data is combined with the video program decoded by the MPEG-2 video decoder 508 and the video screen such as the TV menu screen generated by the user graphic unit 510 and the GUI screen using the OSD through the video synthesizer 509 And then outputted through a video reconstructing unit 511. The video re-

The video reconstructor is responsible for reconstructing the caption by encoding the analog caption data generated by the analog CC decoder 506 into the VBI 21 line. This is to prevent an open caption when the generated image is stored in a storage medium such as a VCR.

Further, there may be a case where the result determined in the user data area is cc_type == 0 and analo_cc_type == 1, that is, analog caption according to the EIA 708 standard.

This is the case where 2 bytes of analog caption data is included in the user data area including the DTVCC for the analog receiver.

This case will be described with reference to FIG.

First, when the user processor 504 determines that cc_type == 0 through the caption_service_descriptor information, the corresponding line_field is determined based on the caption service types (off, cc1, cc2, cc3, ...) .

Based on the determined line_field information, if it is determined through analog_cc_type that it is an analog caption according to the EIA 708 standard, the line_field information is sent to the analog CC decoder 506. In this case, since the analog caption information is located on the VBI 21 line, the line_offset value is not required.

At this time, the DTV CC decoder 507 extracts 2 bytes of analog data from the user data area including the DTVCC separated from the video parser 505, and inputs the analog data to the analog CC decoder 506.

The analog CC decoder 506 finds analog caption data existing on the VBI 21 line from the 2-byte analog data based on the line_field information.

The detected analog caption data is combined with the video program decoded by the MPEG-2 video decoder 508 and the video screen such as the TV menu screen generated by the user graphic unit 510 and the GUI screen using the OSD through the video synthesizer 509 And then output through an image reconstructing unit 511. The image reconstructing unit 511 reconstructs the image.

In this case, the video reconstructor also reconstructs the caption by encoding the analog caption data generated by the analog CC decoder 506 into the VBI 21 line.

If both the analog caption according to EIA 708 and the analog caption according to SCTE 20 or DVS 157 are present, the analog caption according to EIA 708 takes precedence.

In addition, if both digital caption and analog caption according to EIA 708 are present, digital caption takes precedence.

501: MPEG demultiplexer 502: PMT buffer
503: EIT buffer 504: User processor
505: video parser 506: analog CC decoder
507: DTVCC decoder 508: MPEG-2 video decoder
509: Video synthesizer 510: User graphics section
511: Video reconstructor

Claims (1)

Multiplexing video data, audio data, and auxiliary data including an event information table (EIT) and a program map table (PMT) into an MPEG-2 transport stream,
Here, the EIT or the PMT may include a caption descriptor including caption information,
Wherein the caption descriptor includes:
A tag field for identifying the type of the caption descriptor, a length field for the caption descriptor, a field for indicating the number of closed caption services, and language information for the caption service included in the MPEG-2 transport stream ,
The caption descriptor provides the caption data included in the video data to provide digital closed caption service according to electronic industry association (EIA) -708 or analog closed caption service according to electronic industry association (EIA) -708 The caption information indicating whether the caption data is the caption data,
The video data including MPEG-2 video data and user data; And
And transmitting the multiplexed MPEG-2 transport stream as a broadcast signal.

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