JPH09312833A - Digital broadcast system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the digital broadcast system in which the configuration of a transmission center is simplified by adopting the configuration such that no superimposing processing is conducted at the transmission center but each reception terminal equipment conducts superimposing processing. SOLUTION: A transmission center 1 is provided with a character image processor 28 which generates data relating to characters and images subjected to be superimposing (on-screen) display. The transmission center 1 uses a data multiplex function of the Moving Picture Image Coding Experts Group 2(MPEG2) to send data relating to characters and images subjected to be superimposing display while being multiplexed onto an MPEG-TS (transport stream). A receiver terminal equipment 2 in a subscriber's home generates characters and images to be superimposing display based on the data relating to characters and images subjected to be superimposing display supplied from the transmission center to display them superimposingly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital broadcasting system using MPEG2, which is an image compression technique, and more specifically, using a data multiplexing function of MPEG2, characters to be displayed in superimpose (on-screen) display. -Data relating to an image is transmitted as an MPEG transport stream (MPEG-TS: MPEG-Transpo).
rt Stream) and send it from the sending center side, and intelligent receiver and decoder (IRD: Intelligent Rec
superimpose (on-screen) supplied from the sending center side on the receiving terminal side such as the user and decoder (STB: SetTop Box) and superimpose based on the data related to the character / image to be displayed. The present invention relates to a digital broadcasting system in which a character / image to be paused is generated and superposed and displayed.

[0002]

2. Description of the Related Art With the development of digital technology, the image compression technology MPEG2 has been put into practical use. For example, the DVB (Di
(Digital Video Broadcasting)
A digital broadcasting system based on MPEG2 is planned.

FIG. 7 is a block diagram showing the overall configuration of a conventional digital broadcasting system based on MPEG2. The digital broadcasting system includes a transmission center 100,
It is composed of a receiving terminal 200 such as an IRD (STB) installed in each subscriber's house, and a transmission path of satellite waves, terrestrial waves, cables and the like.

Various programs (programs) for broadcasting services supplied from program providers are encoded by MPEG2 encoders (ENC) 111a to 111d. The encoded program is an MPEG transport stream (MPEG-TS: MPEG-Transsp).
ort stream) as the MPEG server 112.
Sent to and accumulated. In addition, in FIG. 7, a program photographed by a camera such as a studio, a program received via a satellite, and a program received via a cable (wired) are respectively processed.
Compress and encode with the EG encoders 111a to 111c,
The program supplied to the MPEG server 112 and supplied on a tape or the like is reproduced by the VTR 113, and its reproduction output is MPEG.
An example has been shown in which the encoder 111d compresses and encodes the data and supplies it to the MPEG server 112.

Various programs accumulated in the MPEG server 112 are read by the integrated transmission controller 114 according to a program transmission table (playlist) created in advance. Each MPEG-TS related to each transmission program read from the MPEG server 112 according to the program transmission table
Are supplied to the respective MPEG2 decoders 115a to 115n, and the respective MPEG2 decoders (DEC) 115a
At ~ 115n, the baseband signal is restored. Each baseband signal is supplied to the router 116.

[0006] On the router 116, in addition to the baseband signals related to the program, the baseband signals of other sources related to commercials and promotions, as well as characters and images for displaying the company logo and characters by superimposing. Is supplied. Then, the router 116 creates a switch (switching) between the broadcast program read from the MPEG server 112 and the commercial or promotion, or a broadcast program in which the company logo, characters, etc. are superimposed. further,
The keyer 117 performs keying and voice over (replacement of voice).

Each baseband signal output from the keyer 117 and associated with each edited transmission program is re-encoded by each MPEG2 encoder 118a to 118n, multiplexed by the multiplexer 119, and each modulator (MOD).
It is supplied to 120a-120c. The modulator 120a is for satellite broadcasting, and signals relating to programs for a plurality of channels modulated by the modulator 120a are transmitted to the broadcasting satellite 127 via the broadcasting satellite parabolic antenna 121, and are transmitted to the broadcasting satellite 127. It is transmitted to each subscriber's home via 127. The modulator 120b is for terrestrial broadcasting, and the signals relating to the programs for a plurality of channels modulated by the modulator 120b are transmitted from the terrestrial broadcasting antenna 122 as terrestrial broadcasting. The modulator 120c is for cable broadcasting, and the signals related to the programs for a plurality of channels modulated by the modulator 120c are sent to each subscriber's house or the like via the cable 123.

At each subscriber's house, etc., an IRD (Intel
agent Receiver and Decode
r) or STB (Set Top Box) is installed. FIG. 7 shows a configuration in which the signal received by the satellite broadcast receiving antenna 124, the signal received by the terrestrial broadcast receiving antenna 125, and the signal from the cable 123 are all supplied to the receiving terminal 200. However, in practice, only one of them should be provided. Reference numeral 126 is a television receiver.

FIG. 8 is a block diagram of a receiving terminal of a conventional digital broadcasting system. The receiving terminal 200 is
A channel selection / demodulation unit 130, a descrambling unit 131,
MPEG2 decoder 132 and two D / A converters 13
It consists of 3,134. The tuning / demodulation unit 130 includes a tuner 135, a digital demodulation circuit 136, and error detection /
And a correction circuit 137. Descrambler 131
Includes a system controller 138 and a descrambling circuit 139.

Signals for a plurality of channels distributed from satellite waves, terrestrial waves or cables are supplied to a tuner 135, and the tuner 135 selects a channel desired by the user. The signal related to the selected channel is demodulated into a digital signal by the digital demodulation circuit 136. The demodulated digital signal is subjected to error detection and data correction at the detected error location by the error detection / correction circuit 137. The output of the error detection / correction circuit 137 is the descrambling circuit 139.
Supplied to

The key information for descrambling is supplied from the service provider to each subscriber by the IC card 140. The system controller 138
The key information supplied from the C card 140 is supplied to the descrambling circuit 139 for descrambling. The descrambled signal is MPEG2.
It is supplied to the decoder 132. When the distributed program is not scrambled, the descramble circuit 139 supplies the output of the error detection / correction circuit 137 to the MPEG2 decoder 132 without any processing.

The MPEG2 decoder 132 decodes the MPEG-TS signal output from the descrambler 131 and outputs a digital video signal 132a and a digital audio signal 132b. The digital video signal 132a is D / A converted by the D / A converter 133 on one side, and is supplied to the video terminal of the television receiver (TV) as an analog video signal. Digital audio signal 13
2b is D / A converted by the other D / A converter 134,
It is supplied to the audio terminal of the television receiver as an analog audio signal. As a result, the user can watch the digital broadcast on the television receiver 126 shown in FIG.

[0013]

However, in the conventional sending center 100 shown in FIG. 7, the company logo,
To require an operation to superimpose the station logo and characters on the screen,
Digital signals relating to various programs stored as MPEG-TS signals in the MPEG server 112 are once returned to baseband signals, and then the router 116 and the keyer 1 are used.
The superimposing process is performed by using 17, and the MPEG2 encoders 118a to 118n convert again to digital signals for digital transmission.

Therefore, the conventional sending center 100 is
In order to prevent the image quality from deteriorating even if the PEG-TS signal is decoded, superimpose processing is performed, and then re-encoded, the MPEG server 11
The bit rate of the MPEG-TS signal stored in 2 is
Bit rate at the time of transmission (for example, 3 to 4 megabits / second)
The image quality is sufficiently larger than that of the image to be actually transmitted so that an image having a higher image quality than that of the image actually transmitted is accumulated. Even though they are the same MPEG2, the bit rate of the MPEG-TS signal stored in the MPEG server 112 is set higher than the transmission bit rate.
12 requires more storage capacity.

Further, the conventional sending center 100 returns the MPEG-TS signal stored in the MPEG server 112 to the baseband signal in order to perform the superimposing operation in the state of returning to the baseband signal. The MPEG2 decoders 115a to 115n and the MPEG2 encoders 118a to 118n for re-encoding are required, and the system configuration must be redundant.

If the bit rate in the MPEG server 112 is twice the transmission bit rate, the capacity of the MPEG server 112 is required to be double. Moreover, since the bit rate is high, the number of inputs and outputs of the MPEG server 112 is halved. Also, a decoder and an encoder for decoding / re-encoding are required for each channel, which may result in a system with a poor cost performance ratio.

The present invention has been made to solve the above problems, and MPEG stored in an MPEG server is stored.
-MPE for transmitting the bit rate of the TS signal as a program
By making the bit rate of the G-TS signal the same, MP
The recording capacity of the EG server can be reduced, and the superimposing process is performed on each receiving terminal side without performing the superimposing process on the transmitting center side. It is intended to provide a simplified digital broadcasting system.

[0018]

In order to solve the above-mentioned problems, a digital broadcasting system according to the present invention provides data related to characters / images to be superimposed or on-screen displayed on a screen in an MPEG transport stream. A transmission center for time-division multiplexed transmission and MPE
Character / image to be displayed on the screen in superimpose display or on-screen based on the extracted character / image data extracted from the time-division multiplexed character / image data in the G transport stream And a receiving terminal device for displaying the generated characters / images in a superimposed display or on-screen display.

Since the transmission center has a structure for time-division-multiplexing and transmitting data relating to characters / images to be displayed in superimpose or on-screen in the MPEG transport stream, various programs stored in the MPEG server are transmitted. It is possible to make the bit rate of the signal relating to the same as the bit rate of the signal relating to the program to be transmitted.
Therefore, the recording capacity of the MPEG server can be reduced.

Since it is not necessary for the sending center side to generate and send a superimposed display or on-screen displayed image, an MPEG2 decoder for returning an MPEG2 encoded signal to a baseband signal and a superimposing M for re-encoding an image that has been subjected to pause display or on-screen display processing
There is no need to provide a PEG2 encoder, and the configuration on the sending center side is greatly simplified.

The receiving terminal device extracts the data relating to the characters / images which are time-division multiplexed in the MPEG transport stream, and displays the superimposed image on the screen based on the extracted data relating to the characters / images. Alternatively, a character / image to be displayed on-screen is generated, and the generated character / image is superimposed or displayed on-screen.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the overall configuration of a digital broadcasting system based on MPEG2 according to the present invention. The digital broadcasting system according to the present invention includes a transmission center 1, a receiving terminal 2 such as an IRD (STB) installed in each subscriber's house, and a transmission path for satellite waves, terrestrial waves, cables and the like.

Various programs (programs) supplied from program providers are MPEG2 encoded (ENC) 1
It is encoded with 1a to 11d. The encoded program (program) is an MPEG transport stream (MPEG-TS: MPEG-Transport).
Stream) is sent to and stored in the MPEG server 12. In FIG. 1, a program taken by a camera such as a studio, a program received via a satellite, and a program received via a cable (wired) are compression-encoded by the respective MPEG encoders 11a to 11c, and an MPEG server is provided. The program supplied to the recording medium 12 is reproduced by the video tape recorder (VTR) 13 and the reproduced output is compressed and encoded by the MPEG encoder 11d to obtain the MPEG.
An example of supplying to the server 12 is shown.

The sending center 1 according to the present invention is provided with a character / image processor 28 for generating data 28a relating to characters / images to be displayed by superimposing a company logo or characters. The data 28a relating to the character / image generated by the character / image processor 28 is M
Data PES packets are assembled by the PEG encoder 11e, and the MPEG server 1 as MPEG-TS.
It is sent to 2 and stored.

The various programs accumulated in the MPEG server 12 and the data PES packet of the data relating to the characters / images to be displayed by superimposing are prepared in advance by the integrated transmission controller 14 and the program transmission table (play table) is created. It is read according to the list). M
The MPEG-TS signals relating to the respective transmitted programs read from the PEG server 12 in accordance with the program transmitting table, and the data PES packets of the data relating to the characters / images to be displayed by superimposing are supplied to the router 16. It

The router 16 is provided with each MPEG-related program.
In addition to the TS signal, MPEG-TS signals of other sources related to commercials and promotions are supplied. Then, the router 16 switches the transmission program read from the MPEG server 12 to the commercial or promotion, and the data PES packet of the data relating to the characters / images to be superimposed on the company logo or characters. An MPEG-TS signal including the above is generated.

Each MPEG-TS signal output from the router 16 relating to each edited transmission program is edited by the multiplexer 1
The signals are multiplexed in 9 and supplied to the modulators (MODs) 20a to 20c, respectively. The modulator 20a is for satellite broadcasting, and signals related to programs for a plurality of channels modulated by the modulator 20a are transmitted to the broadcasting satellite parabolic antenna 21.
Is transmitted to the broadcasting satellite 27 via the
Is transmitted to each subscriber's home or the like via. The modulator 20b is for terrestrial broadcasting, and the signals relating to the programs for a plurality of channels modulated by the modulator 20b are transmitted from the terrestrial transmitting antenna 22 as terrestrial broadcasting. Modulator 2
0c is for cable broadcasting, and signals relating to programs for a plurality of channels modulated by the modulator 20c are sent to each subscriber's house or the like via the cable 23.

At each subscriber's house, etc., an intelligent receiver and decoder (IRD: Intellig
ent Receiver and Decoder)
And set top box (STB: Set Top)
A receiving terminal 2 such as a Box) is installed. FIG. 1 shows a configuration in which the signal received by the satellite broadcast receiving antenna 24, the signal received by the terrestrial broadcast receiving antenna 25, and the signal from the cable 23 are all supplied to the receiving terminal 2. However, in practice, only one of them should be provided. Reference numeral 26 is a television receiver.

FIG. 2 is a block diagram of the receiving terminal of the digital broadcasting system according to the present invention. Receiving terminal 2
Is a channel selection / demodulation unit 30, a descrambling unit 31,
An MPEG2 decoder 32, a character / image generator 41,
It comprises a mixer 42 and two D / A converters 33 and 34. The channel selection / demodulation unit 30 includes a tuner 35, a digital demodulation circuit 36, and an error detection / correction circuit 37.
The descrambling unit 31 includes a system controller 38.
And a descrambling circuit 39.

Signals for a plurality of channels distributed from satellite waves, terrestrial waves or cables are supplied to a tuner 35, and the tuner 35 selects a channel desired by the user. The signal related to the selected channel is demodulated into a digital signal by the digital demodulation circuit 36. The demodulated digital signal is subjected to error detection and data correction at the detected error location by the error detection / correction circuit 37. The output of the error detection / correction circuit 37 is supplied to the descrambling circuit 39.

The key information for descrambling is supplied by the IC card 40 from the service provider to each subscriber. The system controller 38 supplies the key information supplied from the IC card 40 to the descrambling circuit 39 to perform descrambling. The descrambled signal is supplied to the MPEG2 decoder 32. If the distributed program is not scrambled, the descramble circuit 39 supplies the output of the error detection / correction circuit 37 to the MPEG2 decoder 32 without any processing.

The MPEG2 decoder 32 decodes the MPEG-TS signal output from the descrambling unit 31 to obtain a digital video signal 32a, a digital audio signal 32b, and data 32c relating to characters / images to be superimposed and displayed. And output. The data 32c relating to the character / image to be superimposed and displayed is supplied to the character / image generator 41. Character / image generator 4
1 produces | generates and outputs the television screen information data 41a which should be superimposed-displayed based on the data 32c regarding the character / image which should be superimposed-displayed.

The mixer 42 outputs the digital video signal 32a output from the MPEG2 decoder 32 and the television screen information data 41a output from the character / image generator 41.
And are mixed to generate and output a digital video signal 42a in which characters and images are superimposed.
Digital video signal 42a output from mixer 42
Is D / A converted by one of the D / A converters 33 and supplied as an analog video signal 33a to a video terminal of a television receiver (TV).

The digital audio signal 32b output from the MPEG2 decoder 32 is the other D / A converter 3
D / A conversion is performed at 4 and the analog audio signal 34a is supplied to the audio terminal of the television receiver. As a result, the user can watch the digital broadcast on the television receiver 26 shown in FIG.

FIG. 3 is a block diagram of the MPEG encoder, and FIG. 4 is an explanatory diagram showing the configuration of the MPEG transport packet. The MPEG encoder 11 includes a video interface 51 and an audio interface 52.
A data interface 53, a video compressor 54, an audio compressor 55, a primary multiplexer 56, an MPEG-TS buffer 57,
It is composed of a CPU 58.

The input video is supplied to the video compressor 54 via the video interface 51 and is compression-encoded by the video compressor 54.
The input audio is the audio interface 5
It is supplied to the audio compressor 55 via 2 and compressed and encoded by the audio compressor 55. Figure 4 for video, audio and data
The PES packet shown in (a) is generated. The PES packet is a packet of coded data of video and audio (elementary stream), a private stream, and the like, which have a variable length.

As shown in FIG. 4B, the TS packet is a fixed length packet of 188 bytes. The PID in the TS packet identifies the packet, and the identifier is used to identify the video, audio, and data (see FIG. 4C).

One PES packet is divided into payloads of a plurality of TS packets having the same PID number and transmitted. Here, enter text and image information in the data,
This data is included in MPEG-TS and transmitted together with video and audio, and is decoded in the receiving terminal 2 such as IRD or STB in the subscriber's house to generate character / image information from the data and generate the character / image. Superimposing display can be performed by superimposing information on the video.

As a result, the MPEG server 12 in the transmission center 1 can store various programs at the same rate as the transmission rate, which makes it possible to save storage and simplify the transmission system.

FIG. 5 is a flow chart showing the processing of the data PES packet in the receiving terminal. When there is the MPEG transport stream shown in FIG. 4 (b),
First, it is checked whether or not a TS packet with PID = 0 is received (step S1). The content of PAT (Program Association Table) is a correspondence table between programs and PIDs. According to the PAT,
Since m: PID = 20, it is recognized that the PMT (program map table) of the program can be obtained from the packet of PID = 20 (step S
2). Then, it is checked whether a TS packet with PID = 20 has been received (step S3). PID = 20
The PMT of the program is obtained from the TS packet of P
According to MT, Video: PID = 40, Audi
o: PID = 41, clock: PID = 42, dat
Since it is known that a: PID = 43, processing is performed for each packet number.

Specifically, in step S4, the PMT is referred to by recognizing the PID = 43 of the data packet, and in step S5 it is checked whether or not the TS packet of PID = 43 is received, and in step S6. With data PES
The packet is read and a data PES packet is generated in step S7. Then, in step S8, based on the data generated in step S7, the characters shown in FIG.
Characters that should be superimposed on the image generator 41
Generate an image. Then, in step S9, the character / image and the video generated by the character / image generator 41 are displayed in FIG.
The mixer 42 shown in FIG.

FIG. 6 is an explanatory diagram showing an example of the structure of a data PES packet. The start address of the characters / images to be displayed superimposed on the TV screen is (a, b),
Let (x, y) be the size of the characters / images to be displayed by superimposing. The data PES packet has a start address: (a, b) and a size: next to the PES header.
(X, y), and subsequently, color information RGB is sequentially arranged. The character / image data to be superimposed and displayed on the MPEG-TS is IRD (ST).
In the MPEG2 decoder 32 (see FIG. 2) in the receiving terminal 2 such as B), the data PES packet shown in FIG. 6 is restored by processing in the reverse procedure of the encoding processing shown in FIG. The restored data PES packet is converted into television screen information by the character / image generator 41 shown in FIG. 2, mixed by the mixer 42, converted into the analog video signal 33a by the D / A converter 33, It is supplied to the video terminal of the TV.

As a result, the receiving terminal 2 receives the data relating to the characters / images to be superimposed and transmitted from the transmitting center 1, and the character / image generator based on the received data relating to the characters / images. 41 characters
Images can be generated and displayed in a superimposed manner.

Therefore, the transmission center 1 shown in FIG. 1 can be operated at the MPEG-TS level. M
Since the bit rate of the MPEG-TS signal stored in the PEG server can be made equal to the bit rate of the MPEG-TS signal transmitted as a program, the recording capacity of the MPEG server 12 can be reduced. Furthermore, the receiving center 2 does not perform superimposing processing on the receiving center 2 side.
Since the superimposing process is performed on the side, the configuration of the sending center 1 can be greatly simplified.

The router 16 in the transmission center 1 shown in FIG. 1 is a GOP (Group of Picture).
The program is switched in units of e).

[0046]

As described above, in the digital broadcasting system according to the present invention, the data relating to the characters / images to be superimposed displayed from the sending center side is time-division multiplexed in the MPEG transport stream and sent. On the receiving terminal side, data relating to characters / images which are time-division multiplexed in the MPEG transport stream is extracted,
Since the superimposing display is made on the screen based on the extracted character / image data, the bit rate of the signals relating to various programs stored in the MPEG server in the transmission center and the bit of the signals relating to the program to be transmitted. The rate can be the same. Therefore, the recording capacity of the MPEG server can be reduced.

Since it is not necessary for the sending center side to generate and send an image superposed or displayed on the screen, an MPEG2 decoder for returning a signal encoded by MPEG2 to a baseband signal, and a superimposition. M for re-encoding an image that has been subjected to pause display or on-screen display processing
There is no need to provide a PEG2 encoder, and the configuration on the sending center side is greatly simplified.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an overall configuration of a digital broadcasting system based on MPEG2 according to the present invention.

FIG. 2 is a block configuration diagram of a receiving terminal of the digital broadcasting system according to the present invention.

FIG. 3 is a block configuration diagram of an MPEG encoder.

FIG. 4 is an explanatory diagram showing the structure of an MPEG transport packet.

FIG. 5 is a flowchart showing processing of a data PES packet in the receiving terminal.

FIG. 6 is an explanatory diagram showing a configuration example of a data PES packet.

FIG. 7 is a block configuration diagram showing an overall configuration of a conventional digital broadcasting system using MPEG2.

FIG. 8 is a block configuration diagram of a receiving terminal of a conventional digital broadcasting system.

[Explanation of symbols]

1 sending center, 2 receiving terminals, 11, 11a-11
e MPEG2 encoder, 12 MPEG server, 2
8 character / image processor, 32 MPEG2 decoder, 41 character / image generator, 42 mixer

Claims (1)

[Claims] 1. A transmission center for time-division-multiplexing and transmitting data relating to characters / images to be superposed or on-screen displayed in an MPEG transport stream, and time-division-multiplexed in an MPEG transport stream. Extract the data related to the existing characters / images, generate the characters / images to be superimposed or on-screen displayed on the screen based on the extracted data related to the characters / images, and superimpose the generated characters / images. A digital broadcasting system consisting of a receiving terminal that displays an impose display or on-screen display.