JP2000165442A - Receiver and reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To output only substantial information data and to record only substantial information data to a storage medium or the like when the data are recorded in the storage medium or the like. SOLUTION: In a transmission system where null packets are inserted to an idle area not filled by packets of significant information in a frame and clock information is provided at a prescribed time interval for each unit frame, the title receiver is provided with a demodulation means 2 that demodulates a reception signal 1, a clock generating means 5 that obtains an output packet number (m) in a frame and an information packet number (n) with significant information in a frame from a signal demodulated by this demodulation means 2 and generates an n/m clock on the basis of the obtained values, and a data separate means 4 that extracts an information packet from the signal demodulated by the demodulation means 2 and outputs data of the information packet synchronously with the clock.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to satellite broadcasting (BS).
The present invention also relates to a receiving apparatus and a receiving method for controlling reception of a transmission packet used for digital terrestrial broadcasting and communication.

[0002]

2. Description of the Related Art In the past, analog broadcasting has been the zenith of television broadcasting and the like, but digital broadcasting has been attracting attention due to restrictions on the number of channels and transmission capacity as high image quality and multimedia are promoted. Broadcasting is gradually moving toward digitalization toward the 21st century.
With the transition from analog broadcasting to digital broadcasting, considering the fusion of various media,
Multiplexing of many information sources is being realized by information integration called DB.

[0003] In the ISDB, a large number of modulation methods and coding methods are defined in consideration of transmission characteristics, and a large number of information rates are defined by combinations thereof. However, the Japanese system stipulates that the output clock is fixed, and a null packet (empty information packet) that is not involved in information transmission is inserted to bridge the difference with the information rate to be transmitted. .

[0004] In digital broadcasting, moving pictures adopt the MPEG system, which is an international standard for moving picture compression.
The moving image signal compressed by the PEG method is transmitted as a packet.

However, when an encoding method requiring a low transmission rate is selected for an actual output MPEG signal packet, the output clock must be constant on a high-speed digital transmission path having a large transmission transmission capacity. To
As shown in FIG. 3, a null packet is inserted into most of the packets.

However, the null packet is an empty packet inserted to keep the output clock constant, and is a wasteful packet not used for information transmission. In other words, this means that in this state, the transmission rate is unnecessarily high for transmitting the packet of the output MPEG signal, and the communication resources are wasted, that is,
This is a waste of transmission capacity. In particular, when a broadcast program is recorded on a storage medium such as a DVD (Digital Video Disc) -RAM, if the received signal is recorded as it is, a situation in which an empty packet is recorded is inevitable. It is conceivable that waste such as a case occurs.

[0007]

In digital broadcasting in Japan, it is planned to multiplex a large number of sources by integrating information called ISDB.
Defines a large number of modulation schemes and coding schemes in consideration of transmission characteristics. A number of information rates are defined by the combination. However, in the Japanese method, a method is used in which the output clock is fixed and null packets that are not involved in information transmission are inserted to fill the difference with the transmitted information rate.
When a moving image signal compressed by the EG method is transmitted as a packet, and an encoding method requiring a low transmission rate is selected for the packet of the MPEG signal,
On a high-speed digital transmission path having a large transmission transmission capacity, a null packet is inserted into almost all packets in order to keep the output clock constant.

[0008] However, null packets are useless and do not contribute to information transmission. Therefore, the communication capacity is too large to be used for the packet transmission of the MPEG signal, and the communication resources are wasted, that is, the transmission capacity is wasted.
-When recording on storage media such as RAM,
Recording the received signal as it is is wasteful.

Therefore, the object of the present invention is to
In a transmission system in which null packets are inserted into empty areas that are not filled with significant information packets within a frame so that clock information is provided at predetermined time intervals for each unit frame, only the original information data is transmitted from the data separation unit. An object of the present invention is to provide a receiving apparatus and a receiving method that can output the data and, when recording the information on a storage medium or the like, can record only the original information data and can effectively use the storage medium. .

[0010]

In order to achieve the above object, the present invention is configured as follows. That is, a demodulation means for demodulating a received signal in a transmission system in which null packets are inserted into empty areas not filled with significant information packets in a frame so that clock information is provided at predetermined time intervals for each unit frame. From the signal demodulated by the demodulation means, the total number m of output packets per frame and the number n of information packets having significant information are obtained, and a clock generation for generating an n / m clock is performed based on the obtained values. Means for extracting an information packet from the signal demodulated by the demodulation means and outputting data of the information packet in synchronization with the clock.

[0011] In this system, a system is used in which a null packet is inserted into an empty area that is not filled with a packet of significant information in a frame so that clock information is provided at a predetermined time interval for each unit frame. In such a system, when a transmission frame is received, the transmission frame is demodulated by demodulation means, and the clock generation means derives the total number m of output packets per frame and significant information from the demodulated signal. Then, the number n of information packets having is obtained, and n / m clocks are generated based on the obtained value. Then, the data separating means separates and extracts the information packet from the signal demodulated by the demodulating means and outputs the data of the information packet in synchronization with the clock. As described above, the receiving side extracts (n−m) null packets from the received frame, extracts data of n significant information packets, and divides the data into n / m per frame interval. By outputting data from the data separating means in synchronism with the clock, it is not necessary to output null information from the data separating means, so that only the original information data is output from the data separating means. When recording on a storage medium or the like, only the original information data can be recorded, and the storage medium can be effectively used.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration. In the figure, 2 is a demodulator, 3 is an error correction unit, 4
, A data separation unit; and 5, a lock generation unit. In addition, 1 is a reception signal.

The demodulator 2 demodulates the received signal 1 to obtain hierarchical information and data. The error correction unit 3 receives the output from the demodulator 2 and performs error correction processing. is there. The data separation unit 4 extracts a data portion from the output corrected by the error correction unit 3 and outputs the data portion in synchronization with the clock from the clock generation unit 5. A clock is generated based on the hierarchical information of the output error-corrected by the unit 3 and is provided to the data separation unit 4.

Next, the operation of the present system having such a configuration will be described.

[0015] Significant data is inserted from a broadcasting station into a predetermined area in the hierarchical information, transmitted with a packet format after adding error correction information. Then, clock information is inserted at predetermined time positions in frame units so that the clock signal is at a constant interval. However, since the transmission capacity is large, in order to make the interval of the clock signal information constant, a null packet, which is an empty packet, is inserted and filled in a surplus portion of the frame.

The transmission signal is received on the receiving side. On the receiving side, received signal 1 is demodulated by demodulator 2
Is demodulated and output to the error correction unit 3. The demodulated signal after error correction processing by the error correction unit 3 is sent to the data separation unit 4 and the clock generation unit 5.

The clock generator 5 calculates the total number of data per frame (the total number of packets including empty packets) m and the number of data (the number of packets including information) n from the hierarchical information of the demodulated signal and the clock signal information. And from these, n
A clock having a division ratio of / m is generated and provided to the data separation unit 4.

The data separating section 4 selects desired information from the hierarchical information and outputs the selected information while synchronizing with the clock supplied from the clock generating section 5. This is the output signal 6.

The case of OFDM will be described as an example.

If it is assumed that the number of carriers is 2K (mode 1), guard bands are 1/8, and all 13 segments are transmitted by the modulation method QPSK and the coding rate r = 1/2, in this case, transmission is performed per frame. The number of packets m
152 ", and as many as" 1152 "packets are transmitted per frame, including empty packets. However, the number of significant information packets n actually transmitted is reduced because the transmission efficiency is reduced, such as encoding and guarding. Is only “156.” This is shown in FIG.

In FIG. 3, N is a null packet, and D is a significant information packet. A null packet is a packet that does not transmit insignificant information, in this case, information specified by MPEG.
It has D = 1FFF, and most of the contents are packets of “1”. In the digital terrestrial broadcasting system, since the transmission capacity is large and the output clock rate is constant, the clock remains high despite the fact that the actually output information rate is low.

Therefore, as shown in FIG. 3, it is necessary for the transmitting side to insert (nm) null packets for the purpose of adjusting the rate. Then, on the receiving side, (n−
m) Null packets are extracted from the received frame, and data of n significant information packets is extracted.
When data is output from the data separation unit 4 in synchronization with a clock divided by n / m per frame interval, null information is not required to be output from the data separation unit 4. Therefore, only the original information data can be output.

<Satellite Broadcasting> Next, the case of BS (satellite broadcasting) will be described. The BS outputs "48" as one frame, but when the modulation scheme is BPSK, the actual information rate is 1/4, and the total number m of packets per frame including empty packets is m = 48, and The number n of information packets actually transmitted is n = 12. At the receiving side, significant information is only a part of the reception output and almost null packet output.

Therefore, looking at the output of the system of the present invention, as shown in FIG. 2, according to the system of the present invention, the output clock is n / m, and in this case, 12/48 =
It is set to 1/4. In this way, the output clock is １ ／, and the output is sent from the data separation unit 4 at the ４ clock rate, so that the data separation unit 4 does not need to output null information. become. Therefore, only the original information data can be output. Therefore, the transmission rate can be used efficiently. <Clock Generation Method> Next, a clock generation method will be described. FIG. 4 is a timing chart showing the state of the generated clock.

In the clock generator 5, which divides the clock by n / m, if the total number of data per unit frame is m and the significant number of data per unit frame is n, The clock generation unit 5 is realized by using a frequency dividing circuit that divides a clock by n / m so that the number of clocks becomes n. Alternatively, when it is difficult to realize the n / m frequency dividing circuit, as shown in FIG.
Clocks are similarly generated by using a circuit configuration in which clocks are thinned out at appropriate intervals so that n clocks are generated per cycle, and clocks are thinned out so that only n out of m clocks remain. Note that the configuration for thinning out the clock may be an arithmetic processing circuit using a program or a configuration using a CPU. <Simpler Clock Generation Method> As a simpler method, as shown in FIG. 6, k is determined so as to satisfy n / m <1 / k, and the clock is divided by k. Generate. However, in this case, n / m = 1 / k
Therefore, it is necessary that the data separator 4 on the receiving side output data while inserting some nulls while outputting data in synchronization with the 1 / k clock.

Further, if k is selected so as to be a multiple of 2, the frequency divider only needs to extract a specific bit of the counter, so that the configuration of the clock generator 5 becomes very simple and easy to produce. . <Output> Next, the output 6 of the data separation unit 4 will be described.

When connecting to a serial IF (interface) called IEEE 1394, the clock rate needs to be constant to some extent, and from the viewpoint of transmission capacity, the use of unnecessary data (in this case, null packets) is minimized. I want to avoid transmission.

Therefore, as shown in FIG. 7, which is an example of the present invention, a serial IF
6 is adopted. As described above, by connecting the IEEE 1394 serial IF 6 to the output side of the data separation unit 4, the output of the data separation unit 4 conforms to the IEEE 1394 standard, and the insertion of a null packet becomes unnecessary.
Transmission efficiency can be maximized.

Further, in the present system, in order to extract (nm) null packets from the received frame and extract data of n significant information packets, the number of null packets is reduced to n / m per one frame interval. The data is output from the data separation unit 4 in synchronization with the circulated clock, and the data is output to the storage media recording unit 8, as shown in FIG.

In this way, it is not necessary to output null information from the data separation unit 4. Therefore, only the original information data can be output and recorded in the storage media recording unit 8.

That is, in the case of the configuration shown in FIG.
Storage media, for example, HDD, memory, DVD-RA
Since it is possible to record only significant data on recording media such as M, CD-R, CD-RW, magnetic tape, and MD, and not to record null packet information. Media usage can be reduced, and media can be used effectively. In addition, when retransmitting recorded data, it leads to effective use of a communication path, and effective use of communication resources can be achieved.

In consideration of a case where an output according to the ISDB standard is required, the present invention, as shown in FIG. 9, causes the clock generator 5 to "perform / not perform" the n / m clock division.
The switching function unit 5a is provided, and by performing a switching instruction of “performing / not performing” the n / m clock frequency division, the clock output from the clock generating unit 5 is set to m or n / m.
A configuration that allows selection of whether the number is m is adopted.

By adopting such a configuration, if there is a post-process in the original connection form, that is, in a restricted operation condition that the operation is performed only at the maximum rate, there is provided a mechanism for switching according to the connection. It is easy to realize a system that can flexibly respond.

Also, in the case where the above connection is performed while recording, etc., the problem can be solved by providing both outputs as shown in FIG.

In the above description, in the transmission by the OFDM system, the relative interval between information packets differs between broadband reception for receiving all data and partial reception for receiving only some data. The position of the PCR packet may be different.

The PCR packet is an OFDM frame.
By arranging them at predetermined positions, the relative relationship is maintained in both cases. By arranging the position in the first or last packet, no problem occurs even when clock conversion is performed according to the information rate as described above.

Also in the BS broadcast, a plurality of modulation schemes are mixed and a null packet is inserted for transmission at a higher coding rate.
By arranging the position of the R packet at a predetermined position such as the first or last position, even if a similar clock rate conversion is performed, the relative positional relationship is not broken, so that it is possible to prevent a failure. By reducing the output rate as described above, for example, in OFDM, the guard 1 /
4. In the case of QPSK, r = １ ／, 4 [Gb
The capacity that can be recorded on the HDD of [yte] is usually 16 minutes, but is 2 hours 16 minutes.

Although various embodiments have been described above, in short, the present invention provides null packets in empty areas that are not filled with significant information packets in a frame so that clock information is provided at predetermined time intervals for each unit frame. In a transmission system to be inserted, a demodulating means for demodulating a received signal, and a total number m of output packets per frame and a number n of information packets having significant information are obtained from the signal demodulated by the demodulating means. , Based on the obtained value, n /
clock generating means for generating m clocks; and data separating means for extracting an information packet from a signal demodulated by the demodulating means and outputting data of the information packet in synchronization with the clock. I do.

In this system, transmission is performed by inserting a null packet into an empty area that is not filled with a packet of significant information in a frame so that clock information is provided at a predetermined time interval for each unit frame. In such a system, when a transmission frame is received, it is demodulated by demodulation means,
The clock generation means obtains the total number of output packets m per frame and the number n of information packets having significant information from the demodulated signal, and based on the obtained values,
An n / m clock is generated, and the data separating means separates and extracts an information packet from the signal demodulated by the demodulating means and outputs data of the information packet in synchronization with the clock.

As described above, the receiving side extracts (n−m) null packets from the received frame, extracts data of n significant information packets, and reduces the data to n / m per one frame interval. In synchronization with the divided clock,
By outputting data from the data separating means, it is not necessary to output null information from the data separating means. Therefore, only the original information data can be output from the data separating means, and the data can be output to a storage medium or the like. When recording, only the original information data can be recorded, so that the storage medium can be effectively used.

[0041]

As described above in detail, according to the present invention, null packets are placed in empty areas not filled with significant information packets in a frame so that clock information is provided at predetermined time intervals for each unit frame. In a transmission system in which insertion is performed, only the original information data can be output from the data separation unit, and when recording on a storage medium or the like, only the original information data can be recorded. It is possible to provide a receiving apparatus and a receiving method that can effectively utilize the information.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing an output example of the present invention.

FIG. 3 is a diagram showing a conventional output example.

FIG. 4 is a timing chart showing one operation of the present invention.

FIG. 5 is a timing chart showing one operation of the present invention.

FIG. 6 is a timing chart showing the operation of the present invention.

FIG. 7 is a block diagram showing one embodiment of the present invention.

FIG. 8 is a block diagram showing one embodiment of the present invention.

FIG. 9 is a block diagram showing one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reception signal, 2 ... Demodulator, 3 ... Error correction part, 4 ... Data separation part, 5 ... Lock generation part.

Claims (6)

[Claims] 1. A transmission system in which a null packet is inserted into an empty area that is not filled with a packet of significant information in a frame so that clock information is provided at predetermined time intervals for each unit frame, and a received signal is demodulated. Demodulating means, and the total number m of output packets per frame and the number n of information packets having significant information are obtained from the signal demodulated by the demodulating means, and an n / m clock is generated based on the obtained values. Receiving means for extracting an information packet from a signal demodulated by the demodulation means and outputting data of the information packet in synchronization with the clock. . 2. The clock generating means according to claim 1, wherein when the number of output packets per unit frame is m and the number of information packets having significant information is n, an information ratio R = n
/ M, k calculating means for obtaining k satisfying R> 1 / k, means for dividing a clock synchronized with a unit frame by k,
The receiving device according to claim 1, comprising: 3. The receiving apparatus according to claim 2, wherein said k calculating means obtains k so as to be a multiple of two. 4. The receiving apparatus according to claim 1, wherein said clock generating means generates a clock by thinning out n clocks out of m output clocks. 5. The clock generating means outputs n / m frequency-divided clock when the number of output packets per unit frame is m and the number of information packets having significant information is n, 2. The receiving apparatus according to claim 1, further comprising: means for outputting a clock corresponding to m. 6. A demodulation of a received signal in a transmission system in which a null packet is inserted into an empty area not filled with a packet of significant information in a frame so that clock information is provided at a predetermined time interval for each unit frame. Demodulation step; from the demodulated signal, the total number m of output packets per frame and the number n of information packets having significant information
Generating an n / m clock based on the obtained value, extracting an information packet from the signal demodulated in the demodulation step, and outputting data of the information packet in synchronization with the clock. A data separation step.