JP3172243B2 - Receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus for receiving a scrambled broadcast, and more particularly to a CATV (Community) for distributing a scrambled broadcast received by an antenna of a relay apparatus to individual receiving apparatuses via a cable. Ante
nna TV, CAble TV), relates to receiving apparatus that is used in the co-listening receiver systems.

[0002]

2. Description of the Related Art In recent years, pay broadcasting has started, and pay broadcasting apparatuses for receiving the pay broadcasting are becoming widespread. In pay broadcasting using such a pay broadcasting device, broadcasting is performed so that a person (hereinafter, simply referred to as a non-contractor) other than a viewer having a viewing contract (hereinafter, also simply referred to as a viewing contractor) cannot view. The station encodes or encrypts video and audio signals (hereinafter, simply referred to as scramble) and transmits them. In addition, the subscriber has to decode the scrambled signal back to the original video and audio signals (hereinafter, referred to as “decoding”).
It is possible to restore and view the signal using a decoder with a descrambler for simply descrambling), while non-subscribers cannot descramble and view.

An example of such a pay broadcasting system will be described with reference to a pay satellite broadcasting system in Japan. FIG. 5 shows the configuration of the transmitter 100 of the broadcasting station which is the transmitting side in the pay satellite broadcasting system, and FIG. 6 shows the configuration of the decoder 200 as the receiving side device.

[0005] First, referring to FIG. 5, a broadcast station scrambles video and audio signals using a scrambler 101 and a scrambler 105.

[0005] A scramble flag is used so that the receiving side can determine whether the program being received is a scramble broadcast or a non-scramble broadcast.
In the case of Japanese satellite broadcasting, the scramble flag includes the eighth bit of the range bit (hereinafter simply referred to as R # 8) and the twelfth bit of the control code (hereinafter simply referred to as b12) to be multiplexed into the audio signal. Using and sending.

The scramble flag is transmitted to the decoder 200
In the transmitter 100, the scramble flag is continuously transmitted a plurality of times, that is, so-called continuous transmission, so that the majority decision unit 217 can make a majority decision and protect against errors. In the transmitter 100, the scramble flag is input to the scramblers 101 and 107, and ON / OFF control of the scramble of the video and audio signals is performed.

In this pay broadcasting system, PN (P
The transmitter 1 does not need to transmit a pseudo-noise signal (so-called pseudo-random signal) itself from the transmitter 100 to the decoder 200.
00 and the decoder 200 generate the same PN signal.
The PN generators are provided with the same PN initial value KS (the PN initial value KS will be described later) at the same timing with respect to the video and audio signals so as to obtain exactly the same PN signal. .

As a timing signal for setting the PN initial value KS, there is a scramble timing TS. The transmitter 100 continuously transmits the scramble timing TS so that the majority decision judging section 215 of the decoder 200 can make a majority decision on the scramble timing TS to protect against errors. Also, the transmitter 10
0, the scramble timing TS is set to the PN generator 10
3, PN initial value KS is set.

As described above, in this pay broadcasting system, three types of encryption keys (so-called,
Key) to deal with unauthorized viewing. Next, the encryption key and the related information packet (program information described below,
Control information, individual information and message information are referred to as related information).

First, the PN initial value KS is an initial value given to the PN generators 103, 107, 237 and 241 used for scrambling and descrambling of video and audio signals. The PN generator is a pseudo-random data generator and is used to scramble video and audio signals at random to increase confidentiality.

If the PN initial value KS is always constant, it is possible to obtain the PN initial value KS by using a different means from the normal one and further apply it to the PN generators 237 and 241. For example, the PN initial value KS is updated every second to increase security. In the following description, the update cycle will be described as 1 second. This PN initial value KS is transmitted to the decoder 200 as a part of the program information. At this time, the program information and the control information are continuously transmitted so that the majority decision unit 221 of the decoder 200 can make a majority decision.

Next, the encryption key KW will be described. When the broadcasting station transmits program information and control information including the PN initial value KS only to the decoder 200 of the viewing subscriber, the encryption key KW is used to maintain the security of the PN initial value KS. This is an encryption key used when encrypting etc.

The update period of the encryption key KW is, for example, 1
The broadcast is multiplexed to the broadcast wave from the broadcasting station and transmitted to the decoder 200 of a person who continues to have a viewing contract in the next month.
00 is not transmitted.

In the decoder 200, after decrypting the received encryption key KW, the individual information memory 235
In order to decode the program information including the PN initial value KS sent every second, as needed.
Read from 5 and use. Further, the encryption key KW is transmitted from the broadcasting station to each decoder 200 as a part of the individual information at each update cycle of the encryption key KW. The encryption key KW is not transmitted continuously.

Next, the encryption key KMi will be described.
This encryption key KMi is used when the broadcasting station transmits only the individual information including the encryption key KW to the decoder of the person who has subscribed to the viewing and the next month only to the decoder who has the viewing contract.
This encryption key is used when encrypting the encryption key KW and the like for maintaining the security of the encryption key KW.

The encryption key KMi is stored in the decoder 2
00 is written in the encryption key KMi memory 231 of the decoder 200 at the time of factory shipment, and differs for each decoder 200. Therefore, the transmission of the encryption key KW can be performed separately for each decoder 200. That is, the decoder 200 having a different encryption key KMi cannot decrypt the encryption.

The details of the program information, the individual information and the control information described above are described in the report of the Telecommunication Technology Council for Payable Satellite Broadcasting (see pages 48 to 57), and detailed description thereof will be omitted.

The program information and the control information are multiplexed with the individual information in the multiplexing section 119 and further added with the error correction code in the error correction code adding section 121, and then the scramble flag b12 and the scramble flag R # 8 are added. The multiplexing unit 123 performs time division multiplexing on the audio signal together with the scramble timing TS, and further, the multiplexing unit 125 performs frequency division multiplexing on the video signal and transmits the multiplexed signal.

Next, the decoder 200 will be described with reference to FIG. In the decoder 200, after the video and audio signals are separated by the separation unit 211, the separation unit 213 further separates the scramble flag b12, the scramble flag R # 8, the scramble timing TS, and the related information packet multiplexed on the audio signal.

Then, the scramble flag b12, R #
8. Scramble timing TS is determined by majority decision unit 21
After making a majority decision at 5,217, the PN generator 24
1, 237 and descramblers 239, 243.

The related information packet is separated in the separating section 219 into program information, control information and individual information according to the type identification in the data. Among them, the program information and the control information are inputted to the decoding unit 225 after the majority decision unit 221 makes a majority decision and the error correction unit 223 makes an error correction. The individual information is input to the decoding unit 233 after error correction is performed by the error correction unit 229.

Then, the program information and the control information are
At 25, the encryption is decrypted using the encryption key KW and P
The N initial value KS is input to the PN generators 237 and 241,
Other data is provided to the viewing permission / non-permission determining unit 227.
The individual information is stored in the individual information memory 35 after the encryption is decrypted by the decryption unit 233 using the encryption key KMi.

The viewability determining section 227 compares the program information with the data in the individual information memory 235 to determine the viewability. Then, according to this determination, the descrambler 2
Reference numerals 39 and 243 turn ON / OFF the descrambling operation. That is, a non-contractor without a decoder or a decoder for which the content of the individual information does not match the program and the result of the viewability determination is negative even if a contract is made cannot be descrambled and cannot be viewed.

[0024]

In the pay broadcasting system of the above-mentioned pay satellite broadcasting system in Japan, the scramble flag b12, R # 8, scramble timing T
S, the voice multiplexed related information packet is 5.727272MHZ
Is modulated and frequency-multiplexed with the video signal for transmission. However, in cable transmission such as reception by CATV and condominium co-listening, the bandwidth per channel is so narrow that this 5.727272 MHz audio subcarrier cannot be transmitted.

[0025] For this reason, necessary data cannot be transmitted to the decoder, and a repeater for receiving, remodulating, and re-modulating a pay satellite broadcast in a CATV or condominium co-listening system, and flowing it through a cable, a so-called head end, is not available. , Transmit descrambled signals to a cable, CAT
V and another scramble for condominium listening system are newly transmitted.

However, in such a scramble system for CATV or condominium co-listening system, a portion for managing each decoder is provided in each head end, and each decoder is managed by this head end. Unlike a decoder that directly receives pay satellite broadcasting, a broadcasting station cannot directly manage each decoder by individual information or control information. So the broadcaster is C
Each decoder must be managed by entrusting management to an ATV station or forming a head end for condominium listening.

[0027] The present invention has been made in view of the above problems, and even when a scrambled broadcast is relayed through a narrow band CATV or condominium co-listening system, the broadcast station can use the individual information or control information. and to provide a receiving apparatus that can be managed decoders of each receiving device directly.

[0028]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
According to the first aspect of the present invention, the same signal used for descrambling is used.
Packetize a signal that contains multiple values,
Vertical identification of scrambled video signal
Multiplexing during scrambling and descrambling
A scrambled broadcast multiplexing the multiplexed audio signal
Through one of the two signals in the plurality of signals.
If the number of values is equal to or greater than the threshold value, one of the values is signaled.
The descrambler determines that the
A receiving device for determining a signal value used for the
The number of error bits of the packet type identification information is less than a predetermined value.
Sometimes the first threshold value is used for the signal determination, and the
The number of error bits of the type identification information of the packet is equal to or greater than the predetermined value.
, The second threshold larger than the first threshold
The gist is to use a low value.

In order to achieve the above object, the invention of claim 2 is provided.
2. The receiving device according to claim 1, wherein
Signal used for descrambling is pseudo-random
Scrambling indicating when to set the initial value of the signal
This is the gist of the timing signal.

To achieve the above object, the invention of claim 3
2. The receiving device according to claim 1, wherein
The signal used for scramble broadcasting or non-scramble
Summary that the signal is a scramble flag signal indicating broadcast
And

[0031]

According to the first aspect, the receiving apparatus is descrambled.
Packetizing a signal containing a plurality of identical values of a signal to be used,
Type identification information is added to this packet to scramble
It is multiplexed during the vertical blanking period of the image signal and
A scramble that multiplexes the unscrambled audio signal
Receiving the broadcast over a cable,
If the number of one of the binary values is equal to or greater than the threshold,
One of the values is determined to be a signal value by a threshold value determination.
Receiving device for determining a signal value used for the descrambling.
An error bit of the type identification information of the packet.
When the number is less than a predetermined value, a first threshold is used for the signal determination.
Using the value, the number of error bits of the packet type identification information
Is greater than or equal to the predetermined value, the first threshold value
Since a large second threshold was used, the packet
Of binary data due to encryption of data in
Also fails to receive the packet of the signal used for descrambling.
The probability of loss (loss rate)
Reducing the probability of capturing (false detection rate)
A signal used for descrambling can be transmitted.

[0032] The receiving apparatus according to claim 2 is the receiving apparatus according to claim 1.
In the communication device, the signal used for the descrambling is:
The initial value of the pseudo-random signal used for descrambling is
Scramble timing signal indicating the timing to cut
Therefore, the transmission error of the packet type identification information
To set the initial value of the pseudo-random signal even if
Ming can be received accurately.

[0033] The receiving apparatus according to claim 3 is the receiving apparatus according to claim 1.
In the communication device, the signal used for the descrambling is:
A screen indicating whether the broadcast is scrambled or non-scrambled.
Since the ramble flag signal was assumed, the scrambled
Accurately distinguish between broadcast and non-scrambled broadcasts
it can.

[0034]

An embodiment according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a scrambler for a receiving apparatus according to the present invention.
FIG. 2 is a block diagram showing a configuration of a head end 1 for relaying a broadcast broadcast , and FIG. 2 is a diagram illustrating a decoder corresponding to vertical section ranking period multiplexing (hereinafter, simply referred to as a VBI compatible decoder) which is an embodiment of a receiving apparatus according to the present invention. 3) is a block diagram showing a configuration of 3). The head end 1 transmits the scrambled broadcast received by the antenna to a plurality of Vs via a cable.
It is distributed to the BI-compatible decoder 3.

In FIG. 1, a head end 1 includes a separating unit 11 for separating a video signal and supplying the video signal to a VBI multiplexing unit 51, and a descrambler 39 connected to the separating unit 11 for separating an audio signal. The scramble timing TS is separated and the scramble flag b12 and the scramble flag R # 8 are separated and sent to the majority decision unit 17 to separate the scramble timing TS into the majority decision unit 17.
Separation unit 13 that separates related information including control information, individual information, and message information and outputs each to separation unit 19
And a majority decision unit 15 that majority decides the scramble timing TS and outputs the decision result to the PN generator 37 and the packetizing unit 45, respectively, a scramble flag b12, R #
8 and outputs the determination result to the descrambler 39 and the packetizing unit 45, respectively, the individual information is separated to the error correction unit 29, and the program information and the control information are separated to the majority determination unit 21. , A decoding unit 25 and an error correction unit 23 which outputs the result of the majority decision by the majority decision unit 21 to the decoding unit 25 and the buffer memory 41, and decodes the program information and the control information. A decoding unit 25 that outputs the PN initial value to the PN generator 37 and outputs the PN initial value to the PN generator 37; a viewing availability determination unit 27 that outputs the determination result to the descrambler 39; An error correction unit 29 that obtains the individual information separated by the separation unit 19 and corrects an error, and outputs the corrected information to the decoding unit 33 and the buffer memory 43; Encryption individual information key KMi memory 3
And a decryption unit 33 for decrypting based on the encryption key KMi read from No. 1 and outputting to the individual information memory 35.
3, an individual information memory 35 for storing and storing the individual information decoded in step 3, a PN generator 37 for generating pseudo-random noise based on the PN initial value output from the decoding unit 25,
A descrambler 39 for descrambling the audio signal from the demultiplexing unit 13 and outputting it to the frequency multiplexing unit 53, a buffer memory 41 for temporarily storing program information and control information from the error correction unit 23, Buffer memory 43 for temporarily storing the individual information of the packet, and packetizing section 45 for packetizing scramble flag b12, scramble flag R # 8, scramble timing TS, and the like.
Time multiplexing unit for multiplexing the program information, individual information and control information from the buffer memories 41 and 43 and the packet from the packetizing unit 45 (hereinafter, this packet is referred to as a TS packet) in a time division manner. 47, a bit synchronization / byte synchronization adding section 49 for adding bit synchronization and byte synchronization to the output signal, and a VBI multiplexing section 51 for multiplexing the output signal during the vertical blanking period of the video signal from the separation section 11. And a frequency multiplexing unit 53 for frequency multiplexing the output signal with the audio signal descrambled by the descrambler 39.

In FIG . 2 , VBI compatible decoder 3
Is a separation unit 61 for separating and outputting the descrambled audio signal, and a VBI multiplexing unit 5 of the head end 1.
1, a VBI separation unit 63 for separating the VBI-multiplexed video signal and outputting it to a descrambler 89, program information, individual information and control information, a scramble flag b12, a scramble flag R # 8, and a scramble timing TS
, An error correction unit 67, a separation unit 69, an encryption key KMi memory 71, and a decryption unit 73.
, An individual information memory 75, a decoding unit 77, a viewability judging unit 79, and the same value of a signal used for descrambling.
Signal decision using threshold from multiple packets
Signal determination unit 85, PN generator 87, VBI separation unit 6
3 is descrambled based on the scramble flag from the signal determination unit 85 and the pseudo-random (PN) signal from the PN generator 87.

Next, the operation of the head end 1 in this embodiment will be described with reference to FIG.

First, in the head end 1 shown in FIG. 1, after the video and audio signals are separated by the separation unit 11, the separation unit 13 further multiplexes the audio signal with the scramble flag b12.
Scramble flag R # 8, scramble timing T
S and the related information packet obtained by packetizing the related information. The separated scramble timing TS is determined by the majority decision unit 15, and the scramble flag b 12 and the scramble flag R # 8 are respectively determined by the majority decision unit 17. Then, the PN generator 37, the descrambler 39, and the packetizing unit 45 are both used. Is input to

Further, the related information packet is separated into program information, control information and individual information in the separating section 19 according to the type identification in the data. Among them, the program information and the control information are inputted to the decoding unit 25 after the majority decision unit 21 makes a majority decision and the error correction unit 23 corrects the error. The individual information is input to the decoding unit 33 after the error correction unit 29 corrects the error.

Then, the program information and the control information are
At 5, the encryption is decrypted using the encryption key KW stored in the individual information memory 35. The PN initial value KS is input to the PN generator 37, and the other data is provided to the viewability determining unit 27. The individual information is stored in the individual information memory 35 after the encryption is decrypted by the decryption unit 33 using the encryption key KMi.

The audio signal separated by the separation unit 13 is subjected to a descrambler 39 to provide a scramble flag R # 8,
The signal is descrambled according to the scramble timings TS and PN, and is input to the frequency multiplexing unit 53.

Since the related information packets output from the error correction units 23 and 29 need to temporarily hold data and convert the data rate to be multiplexed during the vertical blanking period (VBI), the buffer memory 41 and the buffer memory 43
The program information and the control information packet are stored and stored in the buffer memory 41, and then the same data is read out a plurality of times for continuous transmission.

The program information and control information packet, the individual information packet and the packetization unit 45 packetize the scramble timing TS and the scramble flag b12 (hereinafter, this packet is referred to as the scramble timing TS packet). The multiplexed data is multiplexed by the multiplexing unit 47, and the same bit synchronization and byte synchronization as those of the teletext broadcasting are added by the bit synchronization byte synchronization adding unit 49 .

Further, this signal is multiplexed by the VBI multiplexer of the VBI multiplexing unit 51 in the vertical blanking period of the video signal which is not descrambled in the same manner as the teletext broadcasting.

Next, the details of the packet to be transmitted will be described. In the case of teletext broadcasting, according to Ordinance No. 77 of the Ministry of Posts and Telecommunications and Notice No. 803 concerning teletext broadcasting, 1
The number of bits of data that can be transmitted on the line is 272 bits including the prefix, and is 296 bits when bit synchronization and byte synchronization are added. The number of bits of the related information packet excluding the header is exactly 272 bits, and the packet configuration of the teletext broadcasting can be transmitted by exactly one line.

In the pay broadcasting system, the first 8 bits of the 272-bit data are used for type identification.
Used to identify program information, control information, and individual information.
The first 8 of 272-bit data in teletext broadcasting
The bits are used to identify a service mode and a transmission mode. In this manner, pay data and text multiplex broadcasts are similarly distinguished in that packets are identified on the receiving side by assigning different data to each packet using the first 8 bits of the 272-bit data as type identification. Can handle.

Therefore, in order to transmit the related information packet by VBI multiplexing, 272 bits obtained by removing the header from the related information packet have the same bit synchronization as in the text multiplex broadcasting.
By multiplexing the video signal after the byte synchronization, a signal processing IC for teletext broadcasting can be used on the receiving side, and an increase in cost due to the implementation of the present embodiment can be suppressed.

Next, the number of lines required for transmitting the related information packet by VBI multiplexing will be described.
In the pay broadcast system, the transmission interval of the related information packet is every 9 ms. For this reason, the packet transmission capacity is 111 packets / s. Also,
The transmission of the scramble timing TS packet is at most several packets per 1 s (assuming the interval of the scramble timing TS = 1 s) even if continuous transmission is considered. If two lines per field are used for transmitting these related information packets and scramble timing TS packets, the transmission capacity is 120 packets / s, so that the transmission is sufficient.

Next, a packetizer 4 for packetizing the scramble timing TS and the scramble flag b12.
5 will be described. In the packetizing unit 45, a type identification different from the program information, control information, and individual information in the first 8 bits in the 272-bit data area, for example, “11111”
111 "and the data of the scramble timing TS and the scramble flag b12 are transmitted with the remaining 264 bits. An example of the scramble timing TS packet is shown in FIGS. The type identification of the program information and the control information is “01111000”,
The type identification of the individual information is “10000111”.

FIG. 3 shows the scramble timing TS.
And transmitting data of the scramble flag b12 scramble timing TS and the scramble flag b12 in which transmit each 128-bit data is all 0 or all 1, the data threshold in the receiver side
Signal determination. The signal <br/> judgment using the threshold, for example, in 128-bit data, the threshold value
If data with a certain number of bits or more is one of two values
If it is less than this value, it is determined to be impossible
It is. For example, the scramble timing TS is regarded as the scramble timing TS if the data of 104 bits or more is 1, and the scramble flag b12 is scrambled if the data of 104 bits or more is 1.
If data equal to or greater than the number of bits is 0, non-scramble is set.

Next, FIG. 4 shows the scramble timing TS.
And the scramble flag b12 are each transmitted with 128 bits of data, and are the same as in FIG. 3, except that the scramble timing TS and the scramble flag b12 are alternately transmitted, for example, separated by 1 bit or more, for example, every 7 or 8 bits. By doing so, the scrambling timing TS
And the error of the scramble flag b12 is reduced to １ ／.

Next, the VBI compatible decoder 3 shown in FIG. 2 will be described. The VBI compatible decoder 3 first separates the audio and video signals multiplexed by the FM in the separation unit 61,
The I multiplexing unit 63 separates the packets multiplexed during the vertical blanking period of the video signal. This VBI separation unit 63
In addition, a signal processing IC (waveform equalization IC, synchronization separation IC, character multiplex extraction IC, etc.) developed for receiving text multiplex broadcasting can be used. Then, the packet separated by the VBI separation unit 63 is used by the separation unit 65 to identify the related information packet and the same value of the signal used for descrambling by the type identification.
The packet is separated into scramble timing TS packets, which are packets including the same.

[0054] scramble timing TS packets separated by the separating unit 65 is the threshold in the signal determination unit 85
And a scramble timing TS and a scramble flag b12 are extracted. The scramble timing TS and the scramble flag b12 are input to a PN generator 87 and a descrambler 89 , respectively.

The related information packet separated by the separation unit 65 is subjected to error correction by the error correction unit 67,
In step 9, common information that is program information and control information is identified by type identification.
Information and individual information. Subsequent processing is the same as that of the decoder shown in FIG.

Next, protection against errors in the related information packet and the scramble timing TS packet will be described in detail.

In the pay broadcasting system, related information packets,
Scramble timing TS, scramble flag b1
2. If the scramble flag R # 8 or the like cannot be received correctly, descrambling becomes impossible, so that it is necessary to protect against errors taking into account the error rate that occurs on the transmission path.

Regarding the error rate occurring in this transmission path, according to the example of the data transmission rate and the bit error rate shown in FIG. 3 of the NHK Technical Monthly Report of July 1985, the evaluation of the TV picture quality is 3 or more. It is said that a bit error rate of about ^10.sup.-3 can be obtained at 5.73 Mb / s, which is the same transmission rate as teletext broadcasting, if the transmission path condition is as follows.

It is considered that the service limit of broadcasting for a fee is that the evaluation of television image quality is 3 or more. The CATV and pay broadcasting systems for condominium listening, which are the subject of this study, are also the data transmission methods described in the literature. For this reason, if protection against errors is performed so that the related information packet and the scramble timing TS packet can be correctly received at a bit error rate of 10 ⁻³ , it is considered that a pay TV system for CATV and condominium listening can also be provided.

Next, a method for protecting against errors will be described.
How to continuous transmission of the same packet to a method for correcting adds an error correction code, the same data to continuous transmission (e.g., such as all 0 or all 1) to the data at the receiving side
There is a method of determining a signal based on a threshold value . Therefore, the related information packet and the scramble timing TS packet are protected against errors as described below. However, the type identification of the scramble timing TS packet is as shown below. However, other data may be used as long as the inter-code distance between the program information packet and the control information packet is 4. Also, the scramble timing T
The transmission interval of the S packet is every 1 s.

Related information packet Program information packet Type identification = 0111000 Control information packet Type identification = 0111000 Individual information packet Type identification = 100000111 Scramble timing TS packet Type identification = 11111111 In this related information packet, the program information and control information packet are vertical. Using the two lines in the blanking period, the same packet is transmitted three times over two fields. Further, errors in identification of the type of the program information packet are allowed up to a 2-bit error.

That is, when considering a packet error,
The probability of failing to receive the packet = the loss rate and the probability of mistaking another packet = the false detection rate are increased. When a random error with a bit error rate of 10 ^-3 occurs,
If program information and control information packets are transmitted three times in a row, the loss rate and erroneous detection rate are as follows, and are sufficiently low.

First, the loss rate will be described.

(1) Occurrence rate of 3-bit error resulting in type identification detection error 5.7 × 10 ⁻⁸ (2) Occurrence rate of 9-bit error where SDSC error cannot be corrected 1.5 × 10 ⁻¹¹ (1) (2) ) The total common information packet loss rate is 5.7 × 10 ^−8, so if three consecutive transmissions are performed, the common information packet loss rate is 1.7 × 10 ⁻²² . SDSC is used in pay broadcasting systems. (272, 190) Abbreviation of shortened difference set cyclic code.

Next, the erroneous detection rate will be described.

The probability that the type identification (= 11111111) of the TS packet is erroneously (2 errors) and regarded as a common information packet 2.8 × 10 ^-5 This is the frequency of occurrence once per hour. However, even if the type identification of the TS packet is erroneously (two errors) and is regarded as a common information packet, the error correction unit 67 of FIG. 2 drops the SDSC error as uncorrectable, and the decoding unit 77 of FIG. This does not pose a particular problem, because it falls upon detection of tampering in encryption / decryption.

As shown in FIGS. 3 and 4, the TS packet includes a scramble timing (TS); (128 bits, all 1) and a scramble flag (b12) ; (128 bits, all 0/1), an error of the type identification of the packet is allowed up to a 3-bit error, and the threshold for signal determination is 104/1.
He was 28. This packet is transmitted twice.

When a random error having a bit error rate of 10 ^-3 occurs, the loss rate and the false detection rate of the scramble timing data are as follows. The loss rate and the erroneous detection rate of the scramble flag packet data can be considered in the same manner.

First, the loss rate will be described.

(1) Rate of occurrence of 4-bit error causing type identification detection error 1.0 × 10 ⁻¹⁰ (2) Rate of occurrence of 24-bit error resulting in signal determination error 5.4 × 10 ⁻⁴⁷ (1) (2) If two consecutive transmissions are performed based on the total TS packet loss rate of 1.0 × 10 ^{−10, the} TS packet loss rate becomes 1.0 × 10 ⁻²⁰ .

Next, the erroneous detection rate will be described.

[0072] Conversely incorrectly common information packet type identification (1 performs error), it is considered a TS packet, further threshold
The probability that the signal determination using a small value is also OK is when 1 and 0 are offset in the 128 bits of the common information packet.

However, the common information packet is encrypted, and there should be little deviation between 1 and 0 in the data.
Even if there is a bias of about 88:40, (1) the type identification 1-bit error occurrence rate 7.9 × 10 ⁻³ (2) the 16-bit error occurrence rate erroneously detected by signal determination 7.4 × 10 ^{− 29} (1) (2) Erroneous detection rate of total TS data According to 7.1 × 10 ⁻³¹ , the erroneous detection rate of TS data after two consecutive transmissions is 1.4 × 10 ⁻³⁰ (where TS is Scramble timing).

Next, another embodiment of the signal judgment using the threshold value will be described. The above-described embodiment is based on the assumption that there is little deviation between 1 and 0 in data due to encryption.
This is an example in which even if there is a deviation, the ratio is set to about 88:40. In this embodiment, a case where the amount of deviation is large will be described. That is, in the case of an encryption scheme with more bias, the threshold used for signal determination is changed according to the type identification error as described below.

When the type identification is 0 or 1 bit error: 104/128 threshold value When the type identification is 2 or 3 bit error: 112/128 threshold value, ie, the error in the type identification code is 0 or 1 bit , The threshold is set to 1 out of 128 bits.
When the probability that the packet is a common information packet is low, the threshold value for signal determination is lowered. When the error in the type identification code is 2 or 3 bits, the threshold value is set to 128 bits. When the packet is 112 bits and the probability that the packet is a common information packet is high, the signal determination threshold is increased.

As described above, in each of the above embodiments, only the audio signal is descrambled at the head end, and the video signal is passed as it is. Therefore, a new video scrambler is unnecessary, and the related information packet is retransmitted as it is. The broadcaster can directly manage each decoder.

Further, since the scramble timing TS and the scramble flag b12 are packetized, time-division transmission can be performed on the same video line as the related information packet.
Only the line needs to be used for this system, and the vertical blanking period can be effectively used.

Further, even when there is a deviation between 1 and 0 in the data of the encrypted related information packet, the signal used for descrambling is determined according to the type identification error.
By changing the threshold value , pay satellite broadcasting can be received by CATV or condominium listening system.

[0079]

According to the present invention as described above, according to the present invention, de
A signal containing multiple identical values of the signal used for scrambling
Packetize and add type identification information to this packet
Multiplexing during vertical blanking period of scrambled video signal
Multiplex the unscrambled audio signal
Received the scrambled broadcast via a cable,
A threshold value is a number that is one of two values in the plurality of signals.
If the value is equal to or greater than the value, it is determined that the one value is a signal value.
The signal value used for the descrambling is determined by the threshold value judgment.
A receiving device for determining the type of the packet.
When the number of error bits in the report is less than a predetermined value,
Using a first threshold value, and identifying the type of the packet
When the number of error bits is equal to or greater than the predetermined value,
Use a second threshold greater than the threshold of
Therefore, binary data is encrypted by encrypting the data in the packet.
Even if there is an offset, the signal packet used for descrambling
The probability of missing a packet (loss rate) and other packets
Reducing the probability of mistaking a packet (false detection rate)
And transmit the signal used for descrambling,
A receiver that allows the broadcaster to directly manage each decoder
Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a head end according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of an embodiment of a VBI compatible decoder corresponding to FIG. 1;

FIG. 3 is a diagram illustrating an example of a configuration of a scramble timing TS packet corresponding to FIG. 1;

FIG. 4 is a diagram illustrating an example of a configuration of a scramble timing TS packet corresponding to FIG. 1;

FIG. 5 is a block diagram showing a schematic configuration of a transmitter for pay satellite broadcasting.

FIG. 6 is a block diagram showing a schematic configuration of a decoder for pay satellite broadcasting.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Head end 3 VBI compatible decoder 11 Separation unit 13 Separation unit 15 Majority decision unit 17 Majority decision unit 19 Separation unit 21 Majority decision unit 23 Error correction unit 25 Decryption unit 27 Viewing availability determination unit 29 Error correction unit 31 Encryption key KMi memory 33 Decoding Unit 35 Individual Information Memory 37 PN Generator 39 Descrambler 41 Buffer Memory 43 Buffer Memory 45 Packetizing Unit 47 Time Division Multiplexing Unit 49 Bit Synchronization / Byte Synchronization Adding Unit 51 VBI Multiplexing Unit 53 Frequency Multiplexing Unit 61 Separation unit 63 VBI separation unit 65 Separation unit 67 Error correction unit 69 Separation unit 71 Encryption key KMi memory 73 Decryption unit 75 Individual information memory 77 Decryption unit 79 Viewing availability determination unit 85 Signal determination unit 87 PN generator 89 Descrambler

Claims (3)

(57) [Claims] The same value of a signal used for descrambling is determined.
Packetize a signal that contains multiple
Vertical blanking of scrambled video signal with additional information
Is multiplexed during the scrambling period and the scramble is released.
Multiplexed audio signals into a scrambled broadcast
Through one of the two signals in the plurality of signals.
If a certain number is equal to or greater than a threshold value, the one value is represented by a signal value.
The descrambling is performed according to a threshold value determination that there is
A signal value used for the packet type identification information , wherein the number of error bits in the packet type identification information is less than a predetermined value.
When it is full, the first threshold value is used for the signal determination,
The number of error bits of the packet type identification information is equal to the predetermined value.
In the above case, the second threshold value larger than the first threshold value is set.
A receiving device using a threshold value. 2. The signal used for descrambling is descrambled.
Set the initial value of the pseudo-random signal used for scrambling.
With a scramble timing signal
The receiving device according to claim 1, wherein the receiving device is provided. 3. The signal used for descrambling is
A scramble indicating whether the broadcast is scrambled or non-scrambled.
2. The signal according to claim 1, wherein the signal is a flag signal.
Receiving device.