JP2001086494A - Digital broadcasting receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably present a signal of a best quality to a viewer corresponding to a receiving state when a service is presented for transmission as the signals of high and low hierarchies through different plural modulation systems of a required CN in order to improve the time rate of broadcasting or the like. SOLUTION: An area is divided into plural areas for each modulation system and further for each BER and the transition procedure of areas is predetermined from each area. Corresponding to each modulation system, on the other hand, a receiving state is successively measured and collated with a table and according to the transition procedure, the device is operated so as to extract and present or output only the signal of the best quality to external output equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital broadcast receiver, and more particularly, to the same program contents (video, audio, data) or a video and audio in a program for the purpose of improving a broadcast time rate. Can be suitably used in a digital broadcast receiver for receiving a broadcast service in which a plurality of modulation schemes having different required CNs are transmitted as high-layer and low-layer signals.

[0002]

2. Description of the Related Art In broadcasting media, it is an important mission to improve a broadcasting time rate (a rate at which a broadcast can be received at multiple points and a broadcast can be correctly received with respect to an entire broadcasting time). is there. For example, due to some factors such as the terrain, the surrounding environment, and the distance from the relay station, there are areas where the current analog terrestrial broadcast has a poor regular reception rate and extremely poor reception quality.

[0003] As a countermeasure for such a so-called difficult viewing area, satellite broadcasting is used. Satellite broadcasting covers the whole of Japan as a broadcasting range, and it is possible to obtain a certain quality by increasing the diameter of an antenna.

[0004] However, there is a phenomenon that the CN temporarily deteriorates depending on the receiving point, for example, due to rainfall. Current broadcasting satellites adopt the FM modulation method,
It exhibits a reception mode in which noise increases with the deterioration of the reception CN, and it is possible to receive even a video with considerably increased noise. The way to improve the correct reception rate is
If the performance of the tuner or the converter is constant, the only thing is to increase the antenna aperture and increase the gain.

[0005] On the other hand, digital broadcasting introduced from 2000 adopts the PSK modulation method. Among them, the 8PSK modulation method is a method in which the code transmission efficiency is increased so that frequency resources can be used as efficiently as possible.

In the 8PSK modulation method, the required CN is relatively high because the distance between codes is short. Further, there is shown a feature of the digital modulation system in which "very stable reception quality can be obtained up to a certain CN, but no reception can be performed at a time exceeding the CN".

From the above, in order to secure a correct reception rate in digital broadcasting more than in current analog broadcasting, for example,
The same program is transmitted using a modulation method (for example, 8PSK) that has high transmission efficiency but is fragile to CN deterioration while transmitting the same program with low image compression ratio and high quality, while low-resolution images and the like have high image compression ratio. Is planned to be simultaneously transmitted using a modulation scheme (eg, BPSK) which has low transmission efficiency but is resistant to CN degradation. This service is called a hierarchical transmission service.

Hierarchical transmission services cannot be provided unless signals can be transmitted simultaneously using a plurality of modulation schemes and the frame configuration for transmission does not employ an encoding scheme that can be flexibly organized.

[0009]

SUMMARY OF THE INVENTION Hierarchical transmission services such as those described above, for example, the same program is a modulation method (for example, a modulation method which has high transmission efficiency for high-quality images with a low image compression ratio but has a high transmission efficiency but is susceptible to CN deterioration). 8PSK) and a modulation scheme (eg, BPSK) that has a low image transmission rate and a low transmission efficiency but has a high image compression rate and a high resistance to CN degradation. The signal transmitted in the higher layer is transmitted with a large amount of information, and the signal transmitted in the lower layer is in a state with a small amount of information with a low resolution. In terms of video, high resolution (clear) and low-level signals have low resolution (blurred).

The high-layer signal has a high code transmission efficiency, but the transmission error of the code is low, for example, 8PSK, in which a transmission error due to the deterioration of the CN is likely to occur.
Transmission errors due to CN deterioration are less likely to occur, for example, BP
It is transmitted by SK.

[0011] Here, with the CN deterioration, the higher layer signal is
Many transmission errors occur.
The signal compressed by G or the like cannot be decoded, and the presentation stops. On the other hand, the low-layer signal is in a state where the high-layer signal cannot be presented, whereas the transmission error does not occur and can be presented in an error-free state.

[0012] From this aspect, if the high-layer signal is presented in a good CN state and the low-layer signal is presented in a degraded state, the picture quality changes, but the normal reception rate improves. There is a problem in appropriately switching between the presentation of the high-layer signal and the presentation of the low-layer signal.

[0013] Also, the high-layer signal and the low-layer signal are transmitted in the same transport stream. In the header of the transport stream, there are arranged a packet synchronization byte, an indicator indicating continuity of the packet, an error indicator indicating that the packet contains an error exceeding the correction capability of the correction code, and the like. When the CN deteriorates and reaches a threshold for switching to a lower layer, a transmission error that is considerably uncorrectable is present in the higher layer signal, and not only is there no use for the signal, but also the packet synchronization byte is lost or the packet is lost. However, there is a problem in that presentation of the receiver may be adversely affected due to a break in continuity of the data.

Further, when a hierarchical transmission service is supplied, a digital interface (compliant with IEEE1394)
In the case of outputting to an external device via a device or the like, since the external device often does not have a tuner, there is a problem that there is no means for measuring a current reception state and switching a reception signal.

An object of the present invention is to provide a digital broadcast receiver which solves the above problems.

[0016]

According to the present invention, the following means are provided in order to solve the above-mentioned problems.

That is, a multiplexed signal obtained by multiplexing a plurality of pieces of information is
A digital broadcast receiver for encoding by a plurality of encoding methods having different encoding rates, and receiving and decoding broadcast waves in which the encoded signals are transmitted hierarchically in the order of the encoding rate of the encoding method. In, the relationship between the carrier-to-noise ratio of the received signal and the data error rate of the decoded signal for the signal of each layer measured in advance is divided into a plurality of regions, and the received signal corresponding to the respective regions is A recording unit for recording whether it is appropriate to decode or output, and among the signals of the respective layers, a carrier of a received signal in order from a signal encoded by an encoding method having a high encoding rate. Measure the noise ratio or data error rate, apply the measured value to the area recorded in the recording unit, if the fitted area is not suitable for decoding or outputting the received signal, Decryption or It was so equipped and an output determination unit for switching the signal encoded by the sequence coding rate lower coding method to correspond to a region suitable for output.

A multiplex signal obtained by multiplexing a plurality of pieces of information is
A digital broadcast receiver for encoding by a plurality of encoding methods having different encoding rates, and receiving and decoding broadcast waves in which the encoded signals are transmitted hierarchically in the order of the encoding rate of the encoding method. In, the relationship between the carrier-to-noise ratio of the received signal and the data error rate of the decoded signal for the signal of each layer measured in advance is divided into a plurality of regions, and the received signal corresponding to each region is A recording unit that records whether it is appropriate to decode or output, and simultaneously measures the carrier-to-noise ratio or the data error rate of the received signals of all the layers in each of the layers, and calculates the measured value. Applying to the area recorded in the recording unit, a signal corresponding to an area suitable for decoding or outputting a received signal among the applied areas, and using a coding method having the highest coding rate. Sign An output judging unit for selecting a signal, may be provided with a.

Here, the output determination unit measures a carrier-to-noise ratio or a data error rate of the received signal, and applies the measured value to an area recorded in the recording unit. If the region is not suitable for decoding or outputting the received signal, it is preferable to delete or replace the signal encoded by the encoding method with a predetermined value.

Further, if there is no signal encoded by the encoding method corresponding to an area suitable for decoding or outputting, of the signals of each layer, the output judging section stops the output. May further include an input / output unit with an external device, the output determination unit measures the carrier-to-noise ratio or the data error rate of the received signal, and the measured value is used as the Applying to the area recorded in the recording unit, if the applicable area is not suitable for decoding or outputting the received signal, delete the signal encoded by the encoding method or replace it with a predetermined value , From the input / output unit.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION In digital broadcasting using a broadcasting satellite (hereinafter referred to as BS digital broadcasting), configurations of a transmitter and a receiver for realizing a hierarchical transmission service will be described.

FIG. 1 is a diagram showing a configuration of a transmitter for BS digital broadcasting and a transmission path encoding method.

In FIG. 1, for example, video and audio encoded by MPEG, which is an international standard for encoding images and the like, are formed into a transport stream,
4,188) (RS: Reed-Solomon encoding)
After that, the plurality of transport streams are input to the frame generation unit 100.

The frame generation unit 100 replaces the MPEG synchronization byte with a synchronization and TMCC signal (transmission control signal) for BS digital broadcasting, and generates a transmission frame according to each modulation scheme to be transmitted. Here, the TMCC signal is a signal that defines the state and information of a signal to be transmitted.

Of the signals generated above, synchronization / TMCC
The main signal section other than the section is input to the energy spreading section 101 and the interleave section 102, while the synchronization / TMCC section is supplied to the RS (64, 48) coding section 103 and used for transmission path coding of BS digital broadcasting. Compliant signal processing is performed.

Thereafter, the main signal section and the synchronization / TMCC section are input to a mapping section 104 for performing mapping according to the respective modulation schemes, and after being subjected to convolution and mapping, are subjected to a time division multiplexing / orthogonal modulation section 105. Is modulated and output.

With the above configuration, signals can be transmitted in a time division manner using a plurality of modulation schemes having different CN tolerances. Further, a bit error rate per unit time can be detected in a Viterbi trellis decoding unit of the receiver described later. Furthermore, since the time and time at which the modulation scheme is switched can be detected by the BS frame configuration and the TMCC, the bit error rate for each modulation scheme can be detected.

Here, the definition of the TMCC signal will be briefly described. The TMCC signal is composed of a total of 384 bits, and the assignment of the signal is defined as shown in FIG. As shown in FIG. 1, this signal is transmitted by a modulation method having the strongest CN tolerance. Further, by decoding this signal, it is possible to detect the amount of transmission information allocated to each modulation scheme, which part is transmitted in which modulation scheme, and the like, in the transmission frame of the BS digital broadcast. Then, a receiver to be described later selects which TS to output from the frame configuration of the BS according to a request from a viewer and outputs the selected TS.

Next, the configuration of the receiver will be described.

FIG. 3 is a diagram showing a configuration of a BS digital broadcast receiver.

In FIG. 3, a broadcast wave is transmitted from an antenna and a converter (not shown) to the 1st. The signal down-converted to the IF is input to the channel selection unit 301. The input signal is the antenna gain, rain attenuation,
Due to various factors such as the converter NF, the CN ratio may dynamically change sequentially.

In the channel selector 301, the input signal is tuned to a desired channel (for example, BS1 channel) by a tuner. As a selection method, a program desired by a viewer is selected by a remote controller or the like, and tuning frequency information corresponding to the program is set in the channel selection unit 301.

The tuned IF signal is input to a demodulation unit 302 for demodulation into a digital signal. Demodulator 302
The apparatus has functions such as IF carrier recovery, basic clock recovery, synchronization acquisition, reference burst signal removal, absolute phase detection, and demapping according to the modulation method, and reproduces a stable digital signal.

Next, the digital signal is supplied to a trellis-Viterbi decoder 303. Here, the convolutionally coded signal and the like are decoded according to each modulation scheme and coding rate. Here, when decoding, the TMCC decoding unit 30 in the subsequent stage
4, since the configuration of each modulation scheme can be detected, an error state is held for each modulation scheme together with the decoding result of the trellis-Viterbi decoding unit 303, so that a BER (bit error rate) for each transmitted modulation scheme is maintained. Can be measured.

Further, the digital signal is transmitted to the TMCC decoder 30.
4 is input to the frame reconstruction unit 305. The TMCC decoder 304 decodes and determines the state of the transmission signal described in the TMCC, the correspondence between the transport signal identification number and the relative number, and the like. As a result, it is possible to know which transport signal the main signal reconstructed into the BS digital broadcast frame configuration belongs to and which modulation scheme is being used.

The main signal (video, audio, data, program sequence information, etc.) part of the digital signal is deinterleaved, despread in energy,
The decoding process is performed, and the original MPEG transport stream is restored.

Since a plurality of transport streams, which are one of the features of BS digital broadcasting, are multiplexed in this signal, it is possible to determine on which transport stream a program desired by a viewer is multiplexed from program sequence information. The TS is decoded, and the only transport stream is separated by the TS separation unit 306.

The multiplex separation unit 307 separates program arrangement information, video, audio, and the like according to a viewer's request. That is, the demultiplexing unit 307 extracts the synchronization byte, the continuity index, and the error indicator of the only input transport stream, the error packet identification signal separately supplied from the RS decoding processing, the gate signal indicating valid data, and the like. It has a function of extracting valid data and separating program sequence information, video, audio, data, and the like.

The separated video and audio are MPEG De
The code is decoded by the code unit 308 and presented to the viewer.

In addition, the receiver has an external interface unit 309, for example, when a user uses a remote
A remote control interface for selecting a program to be viewed from the PG, an online shopping / questionnaire, and an interface with a public line for transmitting paid broadcast viewing information for collecting paid broadcast viewing fees, that is, a modem, an external device. (DVCR, etc.) and IEEE13
An external input / output terminal for exchanging signals according to a procedure conforming to 94 or the like is included.

When outputting an MPEG signal according to the IEEE 1394 procedure, it is necessary to change the program association table (PAT) and program map table (PMT) included in the MPEG output signal to contents that match the information of the output signal. is there. External devices are CN and BE
In the case of, for example, a hierarchical transmission service, there is no means for detecting the reception state such as R and there is no need to select on the external device side, it is reasonable to forcefully select and output only one of the services.

Here, FIG. 4 shows a typical modulation scheme of 8PSK (2
/ 3), C of QPSK (3/4), BPSK (1/2)
An example of an N-pair inner code error rate is shown.

The relationship between the modulation systems and the relationship between CN and BER in each modulation system show almost the same characteristics, although there are variations in the characteristics of the tuner section. Using this relationship,
It is possible to determine whether a single modulation scheme can maintain good quality even when presented, from the relationship between the error occurrence situation and the error correction capability.

Next, an embodiment according to the present invention of the digital broadcast receiver configured as described above will be described in detail.

In the receiver, the characteristics of the tuner and the inner code decoder are measured in advance, for example, as shown in FIG. This table is used as a reference for controlling all receivers.

A description will be given along the line segment of BPSK.
Is a boundary at which an error occurs from error free due to the effect of an outer code or the like from a bit error rate of each modulation scheme, a boundary b is a boundary at which an error is felt from a level at which the error does not matter in the evaluation of image quality, a boundary c is a boundary where the entire system is out of synchronization from an extremely bad image and cannot be presented.

As can be seen from FIG. 5, 8PSK (2/3)
In the signal transmitted by the above, an error occurs when the CN is about 11 dB, and the image quality reaches a bad level when the CN is about 9 dB. In this way, for example, four regions of the change axis of the error rate (region 1
To 4). When a similar program is transmitted by a plurality of modulation schemes (8PSK, QPSK, B
PSK), each area is divided into three (areas) as shown in FIG. As described above, in one or a plurality of modulation schemes, an area is determined for each image quality or modulation scheme, and a means for digitizing each range is provided.

Here, normally, the reception state is in the area A / area 1, and a high quality signal rich in the amount of information is presented. When CN gradually deteriorates, the display shifts to region A / region 2. Although the presentation quality slightly deteriorates, 8P
SK signal is presented. When the CN further deteriorates, the region shifts to region A / region 3. However, since the presentation quality is extremely poor, the presentation signal is switched to a QPSK signal here.

As a result, it has been shifted to the area / area 1. Such a procedure is repeated as the CN deteriorates. For example, in the case of transition to region 3 / region 3, this means that a signal modulated by BPSK is presented with extremely poor quality. When the CN is further deteriorated, the area becomes the area / area 4, and the presentation stops after exceeding the synchronization limit point.

On the other hand, when the CN improves, on the other hand, first, when the CN is deteriorated and is in the area A / area 2, the CN shifts to the area A / area 3 due to the CN deterioration.
Here, the presentation signal is switched to shift to the area / area 1. Next, when CN improves and returns to the area, 8PS
The CN is converted from the BER of K, and is switched when good quality can be presented. That is, the processing shifts to area A / area 1.

In summary, the area is shifted in the order of area / area 1, area / area 2, area / area 1, area / area 1. By operating in such a manner as to provide hysteresis, a signal can always be presented with stable quality without errors. This operation is performed in response to a request from the viewer or performed automatically.

In the configuration of the TMCC shown in FIG. 2, any of the modulation schemes that can be transmitted at one time in BS digital broadcasting (maximum number 4) is used based on the transmission mode / slot information. Also, in the BS digital broadcast frame configuration, the number of slots (information transmission units) transmitted in each modulation scheme can be detected. Since the slot is assigned to the numbered slot, it is possible to detect which slot is transmitted by which modulation scheme.

Here, in the BS digital broadcast, a plurality of transport streams are multiplexed. It is necessary to select which transport stream the program that the user wants to view is transmitted, and which modulation scheme and which slot are being transmitted. that time,
Using a code obtained by converting the TMCC and the CN into two or more values, a signal transmitted in the same transport stream by a modulation method capable of presenting only a signal of poor quality is:
It detects which slot is being transmitted, and does not select the detected slot and does not output the stream to the subsequent stage.

However, the output rate is controlled in the same manner as when all the slots of the same transport stream are selected in a pseudo manner. On the other hand, when outputting all transport streams, etc., in all transport stream outputs, a signal transmitted by a modulation method that can only present a signal of poor quality is detected in which slot the signal is transmitted. The slot acts so as not to select and not output the stream to the subsequent stage.

In FIG. 5, 8PSK, QPS
In the case of transmission using three modulation schemes of K and BPSK, the respective reception states are sequentially updated from the bit error rates of the respective modulation schemes.

For example, initially, the CNs are located in the area A / area 1, the area A / area 1, and the area U / area 1, respectively, and the CN gradually deteriorates, and the area A / area 4, the area U / area 1, and the area U, respectively. In the case of shifting to / area 1, the output stream outputs only the stream of the modulation scheme QPSK, and does not output the stream transmitted by another modulation scheme without selecting it.

Further, initially, the CNs are located in the region A / region 1, the region U / region 1, and the region U / region 1, respectively, and the CN rapidly deteriorates, and the region U / region 4, the region U / region 4, and the region U. / If shifted to region 1, the output stream is the modulation scheme BP
Only the SK stream is output, and the stream transmitted by another modulation method is not selected and output.

As described above, by sequentially grasping the reception states of a plurality of modulation schemes, it is possible to present a signal of optimal quality for any change in CN.

In FIG. 5, 8PSK, QPS
8P when transmitted by 3 modulation schemes of K and BPSK
Based on the bit error rate of the SK, the reception state is sequentially updated. For example, initially, area A / area 1 respectively
When the CN gradually deteriorates and shifts to the area A / area 4, the output stream stops outputting only the stream of the modulation scheme 8PSK and shifts to the bit error rate measurement of the next modulation scheme QPSK. .

Normally, when the CN gradually changes, it is located in the area / area 1, and the output signal is switched to QPSK. In this way, it works so that the measurement and the switching are performed from the one having the higher coding rate to the one having the lower coding rate. As for the output stream, the selection is sequentially stopped from the one with the poor quality and is not output.

As described above, the reception state of a single modulation method is sequentially grasped, and the operation is performed so as to sequentially switch from the modulation method having a high coding rate to the modulation method having a low coding rate.

In the above description, the presentation is stopped by not outputting the output signal. However, here, a method of forcibly controlling the sign by another method and eventually stopping the presentation will be described.

FIG. 6 shows the header configuration of the transport stream to be output. First, a synchronization byte (47h) for packet synchronization has 8 bits, an error indicator indicating that the packet contains an uncorrectable error has 1 bit, and finally, a continuity indicator 4 bits indicating packet continuity. There is.

Normally, the output transport stream is input to the demultiplexing section 307. The signals supplied to the normal demultiplexing unit 307 include a data, a clock, a data valid signal (a signal indicating valid data), an error signal (a signal indicating an uncorrectable packet), and the like. Demultiplexing unit 30
7 often has a function of extracting only a valid part of data from a data valid signal, a function of deleting an error packet from an error signal, and the like.

Further, by raising an error indicator signal in the header of the transport stream,
It may have a function to delete this packet. By using this function, the presentation can be stopped. Normally, these functions work to show only uncorrectable erroneous packets, but here, whether or not there are errors, the presentation is made by forcibly controlling the code based on the functions. Act to stop.

In the case of a receiver having a digital interface, if the output program is a hierarchical transmission service, a signal of a higher layer or a lower layer is forcibly selected and output according to the reception situation.

At this time, a function for changing the program association table and the program map table indicating the contents of the stream of the output signal is provided, and a function for outputting the program association table and the program map table together with the changed program association table and the program map table is provided.

The PAT (program association table) will be described with reference to FIG. The program association table has a header portion of 64 bits, followed by 16 bits of broadcast program number identification for identifying a program.
Next, an identification number indicating a PMT (program map table) is arranged for each broadcast program identification number. This indicates what broadcast program is included in the output stream.

Next, a PMT (program map table) indicating what identification numbers, for example, video and audio of a broadcast program have, will be described with reference to FIG.

The PMT identification number corresponding to the broadcast program is detected from the PAT, and the PMT corresponding to the only broadcast program is detected.
Describes a PCR identification number for synchronizing a system clock and an identification number (elementary identification number) for each video or audio.

As described above, when PAT and PMT are multiplexed into a stream, they must indicate the contents of the stream. When the layer transmission service is forcibly unified to one of the layers and output, it is necessary to change both the PAT and the PMT for output. On the other hand, outputting only one of the hierarchies means that the device at the output destination has no means for determining the reception state, and only outputs the same program at the same time even if the hierarchical transmission service is output. Simply wastes the output bit rate. Therefore, if the reception condition is good, only the high-layer signal is forcibly output, and if the reception condition is bad, only the low-layer signal is output.

[0072]

According to the present invention, when a hierarchical transmission service is provided for the purpose of improving the time rate of broadcasting, the resistance to CN for each modulation scheme is measured in advance, and the reception quality is always measured on the receiver side. , CN, the reception state can be easily grasped by assigning a numerical value, and the highest quality signal can be stably presented to the viewer according to the reception state. .

Further, since a signal that is unnecessary for presentation or has extremely poor quality does not need to be presented to the receiver, it is deleted to prevent malfunction and when outputting to an external output device, the output bit rate is reduced. Will be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a transmitter configuration of a BS digital broadcast and a transmission path encoding method.

FIG. 2 is a configuration diagram of a TMCC.

FIG. 3 is a configuration diagram of a BS digital broadcast receiver.

FIG. 4 is a diagram illustrating a CN versus BER characteristic of a Viterbi output.

FIG. 5 is a region division diagram of CN versus BER characteristics.

FIG. 6 is a structural diagram of a TS header.

FIG. 7 is a structural diagram of a PAT.

FIG. 8 is a structural diagram of a PMT.

[Explanation of symbols]

 Reference Signs List 100 frame generation unit 101 energy spreading unit 102 interleave unit 103 Reed-Solomon coding unit 104 convolution coding unit 105 time division multiplexing / orthogonal modulation unit 301 channel selection unit 302 demodulation unit 303 trellis-Viterbi decoding unit 304 TMCC decoding unit 305 frame reconstruction Unit 306 TS separation unit 307 Multiplex separation unit 308 MPEG Decode unit 309 External interface unit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // H04L 27/32 F term (reference) 5C025 AA28 BA08 BA18 BA25 BA27 BA30 DA01 DA04 DA05 DA08 5C059 KK00 MA00 RA04 RB01 RD03 RD05 RD07 SS02 TA17 TA73 TC21 TD11 UA05 5C063 AA01 AB03 AB07 AC01 AC05 CA34 5C064 BA01 BB05 BC16 BC20 BD08 5K004 AA07 HA03

Claims (5)

[Claims] 1. A multiplexed signal obtained by multiplexing a plurality of pieces of information is encoded by a plurality of encoding methods having different encoding rates, and the encoded signals are hierarchically arranged in the order of the encoding rate of the encoding method. In a digital broadcast receiver that receives and decodes a transmitted broadcast wave, the relationship between the carrier-to-noise ratio of the received signal and the data error rate of the decoded signal, which is measured in advance for the signals of each layer, is stored in a plurality of areas. A recording unit for classifying and recording whether it is appropriate to decode or output a received signal corresponding to each of the regions; and a coding method having a high coding rate among the signals of each layer. In order from the signal coded in, the carrier-to-noise ratio or the data error rate of the received signal is measured, and the measured value is applied to the area recorded in the recording unit. Decode received signal Or an output judging unit for sequentially switching to a signal coded by a coding method having a low coding rate until it falls into an area suitable for decoding or outputting when the signal is not suitable for output. A digital broadcast receiver, characterized in that: 2. A multiplexed signal obtained by multiplexing a plurality of pieces of information is encoded by a plurality of encoding methods having different encoding rates, and the encoded signals are hierarchically arranged in the order of the encoding rate of the encoding method. In a digital broadcast receiver that receives and decodes a transmitted broadcast wave, the relationship between the carrier-to-noise ratio of the received signal and the data error rate of the decoded signal, which is measured in advance for the signals of each layer, is stored in a plurality of areas. A recording unit for classifying and recording whether it is appropriate to decode or output a received signal corresponding to each of the regions, and a carrier-to-noise ratio of the received signals of all the layers in each of the layers Or, simultaneously measure the data error rate, apply the measured value to the area recorded in the recording unit, and, among the fitted areas, correspond to an area suitable for decoding or outputting a received signal. Faith A, the digital broadcast receiver characterized by comprising an output determining unit that selects a signal encoded in the highest code rate encoding method, the at. 3. The output determination unit measures a carrier-to-noise ratio or a data error rate of a received signal, and applies the measured value to an area recorded in the recording unit.
2. The method as claimed in claim 1, wherein when the corresponding area is not suitable for decoding or outputting the received signal, the signal encoded by the encoding method is deleted or replaced with a predetermined value. Item 2. A digital broadcast receiver according to item 2. 4. When there is no signal encoded by an encoding method corresponding to an area suitable for decoding or outputting, among the signals of each layer, the output determining unit stops outputting. The digital broadcast receiver according to any one of claims 1 to 3, wherein: 5. An input / output unit with an external device, wherein the output determination unit measures a carrier-to-noise ratio or a data error rate of a received signal, and stores the measured value in the recording unit. If the applied area is not suitable for decoding or outputting the received signal, the signal coded by the coding method is deleted or replaced with a predetermined value, and The digital broadcast receiver according to claim 1, wherein the digital broadcast is output from an output unit.