JPH06303543A - Digital television broadcast receiver and broadcasting system - Google Patents

Abstract

PURPOSE:To display plural pieces of video information on the same screen simultaneously as plural slave screens without expanding the scale of a demodulation means in a multi-channel digital television broadcast receiver. CONSTITUTION:A transmission side transmits information required for the decoding of information as slave screen information by adding on additional data, or transmits the slave screen as the hierarchical information of a master screen seperately from master screen information. A reception side selects plural pieces of compression coding video information at a program selecting means 13, and decodes one of selected information as the master screen information and others as the slave screen information by a master screen video encoder 14A and a slave screen video encoder 14B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital television broadcast in which a plurality of sets of video information and audio information are compression-multiplexed, digitally modulated and transmitted, and more particularly, a plurality of sets of images based on the video information are provided on the same display screen. The present invention relates to a digital television broadcast receiver and a broadcast system suitable for multi-screen display simultaneously displayed on the top.

[0002]

2. Description of the Related Art In order to effectively utilize a limited number of channels such as terrestrial broadcasting, satellite broadcasting, and communication satellites, one program service is provided by one channel of conventional analog television broadcasting, while highly efficient digital image compression is performed. By using the technology and the digital modulation technology, multi-channel digital television broadcasting is planned in which a plurality of program services are provided in one channel of the analog transmission band.

Such a multi-channel digital television broadcasting system is disclosed in "(Interim Report of Study Group on Long-term Vision of Satellite Broadcasting Technology) of the Ministry of Posts and Telecommunications, December 1992.
An example is disclosed in "Month". The digital image compression is disclosed in the same document as "Configuration and elemental technology of typical digital compression encoding system".

FIG. 9 is a schematic diagram of the above disclosed example (multi-channel digital television broadcasting system). Figure 9
1, 1 is a transmitter, 2 (2A to 2n) is a video coding means, 3 (3A to 3n) is a voice coding means, 4 is a data coding means, 5 is a time division multiplexing means (TDM), 6 Is error correction coding means, 7 is digital modulation means, and 8 is frequency conversion / amplification means.

In addition, 9 is a receiver, 10 is amplification / channel selection means, 11 is digital demodulation means, 12 is error correction decoding means, 13 is program selection means, 14 is video decoding means,
Reference numeral 15 is a data decoding means, 16 is a voice decoding means, 10
0 (100A to 100n) is a video signal input terminal, 101
(101A to 101n) are audio input terminals, 102 is a data input terminal, 103 is a transmission output terminal, and 104 is a reception input terminal.

In FIG. 9, in the transmitter 1, a plurality of sets of video information are input from the video signal input terminals 100A to 100n, and are digitally image-compressed by the video encoding means 2A to 2n, respectively, to obtain a plurality of sets of compression-encoded video. Information becomes audio information, and audio information accompanying the video is audio input terminals 101A to 10A.
1n, and speech coding means 3A to 3n, respectively.
Then, the data is digitally compressed into a plurality of sets of compression-encoded voice information, and other related information is input from the data input terminal 102 and encoded by the data encoding means 4 to be additional data.

These pieces of information are, for example, interleave-multiplexed by the time division multiplexing means 5, subjected to error correction coding processing by the error correction coding means 6, digitally modulated by the digital modulation means 7, and subjected to frequency conversion. The frequency is converted and amplified by the amplifying means 8 and is transmitted from the transmission output terminal 103 as a digital modulation signal by radio wave, coaxial cable, optical cable or the like.

In the receiver 9, the digitally modulated signal is input from the reception input terminal 104, is tuned by the amplification / channel selection means 10, and is digitally demodulated by the digital demodulation means 11.
The error correction decoding means 12 performs error correction decoding, and the program selection means 13 releases interleaved multiplexing, and one of them (that is, one set) of compression encoded video information, compression encoded audio information, and additional data. Is selected, the video decoding means 14 decodes the compression coded video information, the data decoding means 15 decodes the additional data, and the audio decoding means 16 decodes the compression coded audio information. Image display and audio output can be obtained by digital signal processing means (not shown).

A conventional analog television broadcast receiver has a multi-screen display function of displaying two screens simultaneously on a common display screen as an additional function, for example, a child screen in which a program of another channel is reduced with respect to a main screen. A disclosure example of a technique for displaying a screen at the same time as the main screen (Japanese Patent Laid-Open No. 62-10267
(Japanese Patent Laid-Open No. 1) or a technique for reducing the program of different channels and displaying them simultaneously as a plurality of sub-screens (Japanese Patent Laid-Open No. Sho 6).
No. 2-13176).

[0010]

In the conventional analog television broadcast receiver, the demodulating means for obtaining the video signal from the modulated signal may be a simple analog demodulator. Even if a plurality of analog demodulators are required for multi-screen display of moving images, the circuit scale thereof is smaller than that of the entire analog television broadcast receiver, and the problem is that the simultaneous display as described in the above-mentioned prior art disclosed example. There was a screen display that started.

However, in the multi-channel digital television broadcasting receiver, in order to obtain the video signal from the modulated signal, as described in the above-mentioned prior art, after the digital demodulation, the error correction decoding is performed and the program selecting means 13 is performed. (FIG. 9), one compression-encoded video information is selected, and further the compression-encoded video information is decoded by the video decoding means 14 to obtain the circuit size. The circuit scale is a multi-channel digital television broadcasting receiver. It is large and expensive compared to the whole, and it is difficult to arrange all of these sets in plural in order to realize a multi-screen display function.

In the screen display, the information amount of the child screen is smaller than that of the parent screen. Therefore, if the compression-encoded video information that is the sub-screen is decoded by the same video high-efficiency decoding means as that of the main screen, information decoding means for further sub-screen conversion after decoding is required, and it becomes more and more complicated. , High price.

An object of the present invention is to solve the above-mentioned problems and, in a multi-channel digital television broadcast receiver, simultaneously display images of a plurality of sets of video information on a display screen without enlarging the scale of demodulation means. An object of the present invention is to provide a digital television broadcast receiver and a broadcast system that enable multi-screen display for display.

[0014]

The above object can be achieved as follows. That is, in the program selection means on the digital television broadcast receiver side, means for selecting a desired plurality of compression-encoded video information from a large number of compression-encoded video information constituting one channel after error correction decoding. Is provided, and one of the selected plurality of compression-encoded video information is decoded as parent screen information, and the other is decoded as child screen information, and multi-screen display is performed.

Further, screen related information, which is a type of additional data, for example, is displayed on the screen in accordance with the parent screen and the child screen. In addition, a plurality of pieces of compression-encoded video information are sequentially selected, sequentially decoded as child screen information, and displayed on multiple screens. In addition, the decoding of the child screen information is performed by a decoding means that is simplified with respect to the video decoding means of the parent screen, or by adding information related to the simplified decoding method such as information reduction in advance to the additional data on the transmission side. It is added and transmitted, and the child screen information is decoded based on the child screen decoding information in this additional data.

Further, since the child screen information is a small amount of information obtained by reducing the information from the parent screen information in advance, the child screen information is obtained on the transmitting side as information obtained by converting the parent screen into hierarchical information. Alternatively, the above object can be achieved by adopting a configuration in which the data is transmitted as a part of the additional data.

[0017]

With the means for selecting the compression-encoded video information of the program selection means, a desired plurality of compression-encoded video information obtained by deinterleaving the interleaved multiplexing is taken out, and one of them is used as the parent screen information, which is similar to the conventional one. The video decoding means (parent screen video decoding means) performs decoding, and the other simplified video decoding means (child screen video decoding means) performs decoding, so that the program selection means and the child screen video The decryption means is simplified.

Further, at this time, more information can be obtained by displaying the related information of the additional data, for example, the screen related information on the screen in accordance with the parent screen or the child screen. Further, the simplified decoding of the compression-coded video information serving as the sub-screen, which is performed based on the data included in the additional data, is the data included in the additional data by the data reduction method (that is, the simplified decoding method). Therefore, the sub-picture video decoding means is simplified.

The program selection means simplifies the program selection means by sequentially decoding the sub-picture video decoding means with the sequential information obtained by solving the interleaved multiplexing of the compression coded video information of each program. In addition, the video information on the transmitting side is hierarchical information consisting of the parent screen information and the child screen information, and the child screen information is associated with the child screen, so that the receiver side video decoding means It is simplified.

[0020]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a block diagram showing a digital television broadcast receiver as an embodiment of the present invention.
In FIG. 1, the same reference numerals are given to the same functional blocks as those in FIG.

In FIG. 1, 14A is a parent screen image decoding means, 14B is a child screen image decoding means, 17 is a demultiplexer means, 18A is a parent screen image temporary storage means, 18
B is a child screen image temporary storage means, 19 is a data temporary storage means, 20 is a voice data temporary storage means, and 21 is a screen synthesis /
The image processing means, 22 is an image display means, 23 is a data processing means, 24 is an audio processing means, 25 is an audio output means, and a control system for controlling the whole which is generally considered necessary is omitted. .

Referring to FIG. The digitally modulated signal inputted from the reception input terminal 104 is amplified / tuned by the means 10
After channel selection, digital demodulation means 11 performs digital demodulation, error correction decoding means 12 performs error correction decoding to obtain multiplexed compression coded information, and program selection means 1
Input to 3.

The program selecting means 13 includes at least a demultiplexer means 17, a parent screen image temporary storage means 18A, a child screen image temporary storage means 18B and a data temporary storage means 19.
The demultiplexing means 17 deinterleaves the multiplexed compression-encoded information, and the demultiplexing means 17 decompresses the interleaving, and the parent screen image data selected on the parent screen and the child screen information selected on the child screen. The additional data and the audio data associated with are separated into the main screen video temporary storage means 18A, the child screen video temporary storage means 18B, the data temporary storage means 19, and the audio data temporary storage means 20, respectively.
Will be temporarily stored in.

The compressed coded video information of the parent screen video temporary storage means 18A is decoded by the parent screen video decoding means 14A, and the compressed coded video information of the child screen video temporary storage means 18B is decoded by the child screen video decoding means. 14B, and the screen synthesis / video processing unit 21 performs screen synthesis and video processing of the parent screen and the child screen to be displayed on the image display unit 22. The compression-encoded voice information in the voice data temporary storage means 20 is decoded by the voice decoding means 16, processed by the voice processing means 24, and the voice output means 25 outputs analog voice.

Conventionally, the video information is transmitted by the program selection means 13.
Although only one compression-encoded video information is solved by the demultiplexer means 17 by interleave multiplexing, in the present invention, the main-frame compression-encoded video information corresponding to one conventional compression-encoded video information and a new one. The demultiplexer means 17 deinterleaves both of the compressed and coded video information of the child screen, and the parent screen is decoded by the parent screen video decoding means 14A and the child screen is compressed by the child screen video decoding means 14B. Decryption is performed.

The child screen decoding means 14B can be simplified because it handles less information than the parent screen video decoding means 14A. The additional data in the data temporary storage means 19 is decoded by the data decoding means 15, the data processing means 23 extracts the relevant information of the parent screen and the child screen, and is input to the screen synthesizing / video processing means 21. The image is displayed on the image display means 22 after being combined with the small screen. This allows the viewer to know more program information. In the present invention, only one set of the child screen image temporary storage means 18B and the child screen image decoding means 14B is provided, but it is clear that more child screens can be displayed on the screen by providing a plurality of sets.

FIG. 2 is an explanatory view for explaining the operation of program selection in the program selection means 13 of FIG. An example of the transmission format of video information of digital television is
"Examination of ISDB Transmission System for 12 GHz Digital Satellite Broadcasting" Technical Report of Television Society Vol. 16,
No. 7, pp. There are disclosure examples in 13 to 18 (January 1992). FIG. 2 is a diagram illustrating selection of parent screen image data and child screen image data according to the present invention, taking the transmission format of the disclosure example as an example.

Referring to FIG. FIG. 2 is a diagram illustrating only video data, and audio data and additional data are omitted. The video information is transmitted by a bit stream including a frame in which m sectors are interleaved and multiplexed. On the receiver side, the interleaved multiplexing of this sector is canceled and only the target sector is read.

For example, sector No. Sector Nos. 1 and 2 are programs to be received as the parent screen, and the sector No. Assuming that programs 5 and 6 are desired to be received as sub-screens, the sector No. is selected from among the vertically interleaved signals. Only the data of 1 and 2 are read into the parent screen video temporary storage 18A, and the sector number. Similarly, only the data of 5 and 6 are read into the small screen video temporary storage 18B and decrypted by the decryption means 14A and 14B, respectively.

FIG. 3 is a block diagram showing a digital television broadcast receiver as another embodiment of the present invention. FIG. 3 is an embodiment in which a larger number of sub-screens are displayed as compared with the embodiment shown in FIG. 1, and a circuit for that is simplified. The same code | symbol is described about the functional block similar to that of FIG.

In FIG. 3, 18B1 to 18Bn are child screen image temporary storage means, and 26 is a sequential reading means. In response to the increase in the number of child screens, instead of providing a plurality of combinations of the child screen image temporary storage unit 18B and the child screen image decoding unit 14B, a plurality of child screen image temporary units corresponding to the number of child screens are provided. Storage means 18B1-18Bn
By providing one sequential reading means 26 and one small screen video decoding means 14B, the small screen video decoding means 14 is provided.
The required number of B is reduced.

Referring to FIG. Demultiplexer means 1
7, the compression-coded video information of a plurality of sub-screens for which interleaved multiplexing has been solved is stored in the sub-screen video temporary storage means 1.
8B1 to 18Bn for temporary storage and sequential reading means 26
By sequentially inputting to and decoding the child screen video decoding means 14B, a program list display including a plurality of child screens and program information from additional data can be easily displayed. By looking at this program list display, it is possible to decide which program to watch as the parent program.

FIG. 4 is an explanatory diagram of the program selection operation in FIG. Please refer to FIG. Frame n and frame n +
1, the sectors 1 and 2, the sector 3, the sector 4, the sector 5, and the frame 6 of the frame n are the video information of different programs, and the sectors 1 and 2, the sectors 3, and 4 of the frame n + 1 are the sector 1 of the frame n. Let 2, be the current parent screen. In this example, in order to display a plurality of sub-screens, only the video data of the corresponding sector out of the interleaved multiplexed images as in FIG.
18B5 is read into 18B5, and the child screen image temporary storage means 18B1
The contents of 18B5 are sequentially read by the reading means 26.
The sub-picture video decoding means 14B converter is transmitted.

FIG. 5 is an explanatory diagram showing a screen display in the case of this example. On the main screen, a child screen 2 with the same contents as the main screen
5 sub-screens including are displayed, and in the sub-screens,
Channels are displayed as related information, all programs can be viewed as a list, and programs can be easily selected.

FIG. 6 is a block diagram showing an embodiment of the digital television broadcasting system according to the present invention.
In FIG. 6, functional blocks similar to those in FIG. 1 and FIG. 9 are denoted by the same reference numerals, but speech coding-related is omitted.

In FIG. 6, reference numerals 2A1 to 2An are parent screen image coding means and 2B1 to 2Bn are child screen information extracting means. The data processing means 23 on the receiver side is connected to the small screen video decoding means 14B and the screen synthesis / video processing means 21.

In the transmitter 1, the child screen information extraction means 2
With B1 to 2Bn, when each parent screen is changed to a child screen, related information for performing a simplified decoding method such as how to change from the parent screen to the child screen when the amount of information is reduced is extracted. , Is added to the additional data, encoded by the data encoding means 4 and transmitted.

On the receiver side, the decoding of the small screen compression encoded video information is decoded on the basis of the small screen simplified decoding method information (related information) contained in this additional data. Data decoding means 15, data processing means 23, child screen video decoding means 1
4B is a means for performing such processing. In this way, by decoding the child screen based on the additional data (specifically, the related information included in the additional data),
Since the data reduction decoding method and other information are obtained in advance from the additional data, the child screen video decoding means 14B can be simplified.

FIG. 7 is a block diagram showing another embodiment of the digital television broadcasting system according to the present invention. In FIG. 7, the same functional blocks as those in FIG. 6 are designated by the same reference numerals. In FIG. 7, 2C1 to 2Cn are child screen image encoding means, respectively.

Referring to FIG. In the transmitter 1, the child screen image encoding means 2C1 to 2Cn perform encoding from each parent screen to the child screen compression encoded image information, and the image information (parent screen information and child screen information) is in a plurality of layers. It is transmitted as hierarchical information having a structure. Here, the sub-picture compression encoded video information is made to correspond to one of the hierarchical video information.
On the receiver side, the demultiplexer 17 temporarily stores the child screen compression encoded video information in the layered video information in the child screen video temporary storage means 18B, and the child screen video decoding means 1
The child screen is decoded by 4B.

By using the video information as layered information on the transmitting side and associating a part thereof with the child screen, the image decoding means 14B for the child screen on the receiver side is simplified, and the digital television with a simpler configuration. A John broadcasting receiver and a broadcasting system can be configured. Further, there is an effect that a receiver of a small screen display can be easily realized by using the hierarchical information of the small screen. Even if the hierarchized information of the child screen is transmitted as a part of the additional data, the gist of the present invention is not impaired. Further, although the present embodiment describes an example in which the layered information is transmitted by time division multiplexing, it is obvious that it can also be realized by a method of transmitting a plurality of carrier signals.

FIG. 8 is an explanatory diagram showing an example of layering of video information. As can be seen in the figure, the original video information has at least the information necessary to compose the child screen (for example,
(Video information simplified to correspond to the pixels of the child screen)
In the layered transmission of video information, the rest of the video information is separated into the video information necessary for constructing the original video screen and transmitted as one video information.

On the receiving side, as the child screen, only the child screen information of the transmitted image information is stored in the child screen image temporary storage means 18B.
(FIG. 7), and the child screen image information decoding means 14B is read.
Then, the child screen is decrypted. In the case of the parent screen, all the video information is read into the parent screen video information temporary storage means 18A,
The parent screen image information decoding means 14A decodes the parent screen.

[0044]

According to the present invention, the means for selecting the compression-encoded video information of the program selection means on the receiver side takes out a plurality of the compression-encoded video information from which interleaved multiplexing has been canceled, and one of them is extracted. As the parent screen information, the same video decoding means (parent screen video decoding means) as the conventional one is used for decoding,
There is an advantage that the program selecting means and the sub-picture video decoding means can be simplified by performing the decoding by the video decoding means (sub-picture video decoding means) that is simplified otherwise.

Further, there is an advantage that more program information can be known by displaying the additional data, for example, screen related information on the screen in accordance with the parent screen or the child screen. In addition, the decoding means for simplifying the compression-encoded video signal which becomes the child screen based on the additional data is the data reduction method (the reduction method when the data is reduced from the parent screen to obtain the child screen). Since it is obtained from the additional data, there is an advantage that the child screen image decoding means can be simplified.

In the program selection means, the sub-picture video decoding means is sequentially decoded by the sub-picture video decoding means with the sequential information obtained by solving the interleaved multiplexing of the compression-encoded video information of each program, thereby simplifying the sub-picture video decoding means. For example, there is an advantage that the program list display including a plurality of child screens and program information from the additional data can be easily displayed.

Further, by making the video information (parent screen information and child screen information) the layered information on the transmitting side and associating some information constituting the layered information with the child screen, the child on the receiver side can be made. There is an advantage that a digital television broadcast receiver and a broadcast system can be configured with a simpler configuration by simplifying the screen image decoding means. Furthermore, there is an advantage that a small screen display receiver can be easily realized by using the hierarchical information of the child screen.

[Brief description of drawings]

FIG. 1 is a block diagram showing a digital television broadcast receiver as an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining a program selection operation in program selection means 13 of FIG.

FIG. 3 is a block diagram showing a digital television broadcast receiver as another embodiment of the present invention.

FIG. 4 is an explanatory diagram of a program selection operation in FIG.

5 is an explanatory diagram showing a screen display example in the embodiment of FIG.

FIG. 6 is a block diagram showing an embodiment of a digital television broadcasting system according to the present invention.

FIG. 7 is a block diagram showing another embodiment of the digital television broadcasting system according to the present invention.

FIG. 8 is an explanatory diagram showing an example of hierarchization of video information.

FIG. 9 is a schematic diagram showing a conventional example of a multi-channel digital television broadcasting system.

[Explanation of symbols]

2A1 to 2An ... Main screen image encoding means, 2B1 to 2B
n ... Child screen information extracting means, 2C1 to 2Cn ... Child screen video encoding means, 13 ... Program selecting means, 14A ... Parent screen video decoding means, 14B ... Child screen video decoding means, 18A ...
Parent screen video temporary storage means, 18B ... Child screen video temporary storage means, 21 ... Screen synthesis / video processing means.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ichio Nakagawa 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture

Claims (6)

[Claims] 1. When three sets of compression-encoded video information, compression-encoded audio information, and additional data are combined to form one set of program information, the plurality of sets are multiplexed and then error-correction encoded, Further, it is digitally modulated and transmitted as a broadcast signal of 1 channel, and a channel selection means for receiving multiple channels of such a broadcast signal and selecting 1 channel from the multiple channels, In a digital television broadcast receiver including digital demodulation means for performing digital demodulation on one channel and error correction decoding means for performing error correction decoding on one channel after digital demodulation, the error correction decoding Number for arbitrarily selecting a plurality of desired program information from a plurality of sets of program information forming one channel after error correction decoding by means. Selection means, and compression-encoded video information belonging to one specific program information from the plurality of selected program information as parent screen information, and compression-encoded video information belonging to the remaining program information as child screen information A video decoding means for respectively decoding, and an image display means for respectively displaying on the same screen, after the video decoding, the obtained parent screen information as a parent screen and the child screen information as a child screen,
A digital television broadcast receiver, further comprising: 2. The digital television broadcast receiver according to claim 1, wherein the video decoding unit decodes compression-encoded video information as main screen information, and a decoding unit for a main screen, each of which is a child screen. The plurality of compression-encoded video information selected as the information is composed of a sub-picture decoding unit common to plural sub-picture information which is sequentially selected and decoded one by one. Broadcast receiver. 3. The digital television broadcast receiver according to claim 1, wherein a specific one or a plurality of pieces of program information is selected from the plurality of pieces of program information selected by the program selecting means and belongs to the selected piece of program information. Digital television broadcasting characterized by further comprising data decoding means for taking out additional data and decoding it, and said image display means for displaying the decoded additional data together with the parent screen and the child screen on the same screen. Receiving machine. 4. The digital television broadcast receiver according to claim 1, 2, or 3, wherein the child screen information is
A digital television broadcast receiver characterized by comprising screen information obtained by decoding compression-encoded video information originally used for decoding parent screen information, the information having a reduced amount of information. 5. When the compression-encoded video information, the compression-encoded audio information, and the additional data are combined into one set of program information, the plurality of sets are multiplexed by a multiplexing means, and then the error-correcting code is added. A transmitter for performing error correction coding by the encoding means, digitally modulating it by the digital modulating means, and transmitting it as a broadcast signal for one channel, and at the time of the transmission, the compression encoded video information is transmitted to the parent side by the receiving side. It is used for screen information, and the child screen information is created by processing the compression-encoded video information for the parent screen information, and the processing-related information indicating the processing method and the data used for the processing is added to the additional screen information. A television transmitter that transmits the data included in the data and a multi-channel portion of the broadcast signal that is transmitted and transmitted and receives one channel from the multi-channel. In addition to a channel selection unit for selecting a channel, a digital demodulation unit for performing digital demodulation on the selected channel, and an error correction decoding unit for performing error correction decoding on the channel after digital demodulation A program selection means for selecting any desired plurality of program information from a plurality of sets of program information constituting one channel after error correction decoding by the error correction decoding means, and a program selected by the program selection means A data decoding means for decoding additional data belonging to the information, and a parent for decoding, as parent screen information, compression coded video information belonging to one specific program information from the plurality of program information selected by the program selecting means. The video decoding means for the screen and the compression coded video information belonging to the remaining program information are added to the additional data decoded by the data decoding means. A sub-screen video decoding means for generating and decoding sub-screen information by processing using the processing-related information included in the sub-screen information; A digital television broadcasting system comprising: a digital television receiver further comprising image display means for displaying screen information as child screens on the same screen. 6. The compression-encoded video information and the simplification information thereof have a hierarchical relationship, and when both of them are collectively referred to as hierarchical information, the hierarchical information, the compression-encoded audio information, and the additional data are included. The three are combined to form one set of program information, the multiple sets are multiplexed by the multiplexing means, error correction coding is performed by the error correction coding means, and digital modulation is further performed by the digital modulation means. A television transmitter for transmitting as a broadcast signal for channels, and a channel selection means for receiving multiple channels of the broadcast signal transmitted and transmitted and selecting one channel from the multiple channels. And digital demodulation means for performing digital demodulation on the selected channel, and error correction for performing error correction decoding on the channel after digital demodulation. And a program selecting means for selecting any desired plurality of program information from a plurality of sets of program information constituting one channel after the error correction decoding by the error correction decoding means, and the program. Main screen video decoding means for decoding, as main screen information, compression-encoded video information in the hierarchical information belonging to one specific program information from the plurality of program information selected by the selection means, and the rest. Sub-screen video decoding means for decoding simplified information in the hierarchical information belonging to the program information as sub-screen information, and the sub-screen information obtained after video decoding as the main screen, the sub-screen information A digital television receiver further comprising: image display means for displaying each as a sub-screen on the same screen, and a digital television receiver.