JP4091236B2 - Digital broadcast receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital broadcast receiving apparatus that receives a plurality of digital broadcast waves.
[0002]
[Prior art]
In recent years, digital transmission of audio and video signals has been actively developed. Especially in terrestrial digital broadcasting, the OFDM (Orthogonal Frequency Division Multiplexing) method has been adopted as the most suitable method in Europe and Japan. It has come to be. In the OFDM method, modulation and demodulation are performed by allocating data to a plurality of carriers orthogonal to each other. By performing IFFT (Inverse Fast Fourier Transform) on the transmission side and FFT (Fast Fourier Transform) processing on the reception side, the frequency axis The above signal is converted into a signal on the time axis and transmitted.
[0003]
In this case, each carrier can use an arbitrary modulation method, and QAM transmission by synchronous detection, DQPSK transmission by delay detection, and the like are possible. Therefore, on the transmitting side, multiplexed information called TMCC (Transmission Mode Configuration Control) is transmitted together, and on the receiving side, TMCC is first demodulated and decoded to determine the transmission mode, and the main line system signal is determined based on the transmission mode. By performing demodulating and decoding, a plurality of types of modulation schemes can be used.
[0004]
In particular, the Japanese OFDM system has a great feature in that it enables layered transmission and concatenated transmission by narrowband broadcasting. This is done in consideration of the fact that the broadcasting band is limited and a sufficient band that can be allocated to many operators cannot be obtained. The broadcasting channel band of the television signal is 6 MHz. The width is divided into 13 segments and assigned to one broadcaster per 1 or 3 segments. In this case, a broadcasting service (program) can be provided by a maximum of 13 broadcasters in the 6 MHz band.
[0005]
[Problems to be solved by the invention]
By the way, in the digital broadcasting as described above, although a plurality of broadcasting services are provided within one reception band, since each broadcasting service can select a modulation method, the individual broadcasting services are the same. It is not always transmitted in the transmission mode. For this reason, even when switching broadcasting services within the same reception band, it is necessary to perform mode detection and switching, which takes a lot of time. When such a detection and switching process takes time, the viewer is very frustrated because he / she is accustomed to switching instantly with a conventional analog broadcast television receiver.
[0006]
On the other hand, it is also desired that multiple broadcast services can be played back simultaneously so that a multi-screen display or back recording can be performed.
[0007]
The present invention has been made in consideration of the above circumstances, and it takes only a very short time to detect and switch the mode of each broadcast service within the same reception band, and a comfortable broadcast service can be selected. It is another object of the present invention to provide a digital broadcast receiving apparatus that can simultaneously reproduce a plurality of broadcast services.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a digital broadcast receiving apparatus according to the present invention is for identifying a transmission system of each digital broadcast signal together with a plurality of digital broadcast signals according to an arbitrary transmission system within one or more broadcast bands. Receives a digital broadcast transmitted by multiplexing format information. The broadcast band signal extraction means extracts a signal in an arbitrary broadcast band of the digital broadcast, and the signal extracted by the broadcast band signal extraction means. Demodulating means for demodulating each digital broadcast signal and format information corresponding to each digital broadcast signal, format information accumulating means for accumulating format information of all the digital broadcast signals demodulated by the demodulating means, and demodulating means All digital broadcast signals to be demodulated are time-division multiplexed, and format information corresponding to each digital broadcast signal is sequentially taken from the format information storage means. And, characterized by comprising a division processing unit when performing time-divided reproduction processing of the digital broadcast signal based on the format information.
[0009]
That is, in the digital broadcast receiving apparatus according to the present invention, the format information of each of a plurality of digital broadcast signals within the same broadcast band is stored, and the time division processing of each digital broadcast signal is performed based on the stored format information. Thus, it is possible to receive a large number of broadcasts without causing a significant increase in circuit scale, and simultaneous decoding is possible.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
FIG. 1 is a block diagram showing the overall configuration of a digital broadcast receiving apparatus according to the present invention. Here, the case of digital terrestrial broadcasting in Japan will be described as an example.
[0012]
In FIG. 1, a received signal is input to a tuner unit 11 and selected. This channel selection is performed by matching the oscillation frequency of the local oscillator 12 with a desired channel frequency based on the channel selection information.
[0013]
The output of the tuner unit 11 is converted into a digital signal by the A / D converter 13 and converted into a complex (I, Q) baseband OFDM signal by quasi-synchronous quadrature detection by the quadrature detection unit 14. This baseband OFDM signal is supplied to the FFT unit 15. The FFT unit 15 converts the input OFDM signal from a time domain signal to a frequency domain signal. The output of the FFT unit 15 is supplied to the demodulation unit 16. The demodulator 16 first decodes format information (TMCC) describing a transmission format such as a signal modulation method, and stores it in the format information storage units 17a and 17b. At that time, the format information storage units 17a and 17b store the format information of all broadcast services within the reception band. Although only two format information storage units 17a and 17b are shown in FIG. 1, the number is not limited.
[0014]
Based on the modulation scheme, the demodulator 16 uses the pilot signal inserted in the signal in the synchronous detection, detects the error of each carrier from the symbols before and after in the delay detection, and performs amplitude and phase equalization.
[0015]
The format information obtained by the demodulator 16 and the equalized signal are supplied to the error corrector 18. The error correction unit 18 determines the multiplexing mode, modulation scheme, interleave length, and coding rate from the format information, and performs deinterleaving processing and error correction processing based on the determination result. The output of this error correction unit 18 is a Moving Picture Experts Group (MPEG) 2 TSP (Transport Stream Packet), which is sent to the TS analysis unit 19 for MPEG depacket processing. The depacket output of the TS analysis unit 19 is restored to a signal such as video, sound, and data in the MPEG decoder 20 and output. Part or all of the format information is sent together with the demodulated signal.
[0016]
The operation of the above configuration will be described below while comparing with the conventional apparatus.
[0017]
First, in the conventional apparatus, only one format information is stored. Therefore, even if one channel is received by the tuner unit, one of the broadcasting services has to be selected. In the present invention, a plurality of format information can be stored, the local oscillation frequency is set to the center frequency of the reception channel, and after the FFT, a plurality of broadcast services in the signal developed in the frequency domain are time-divided and sequentially The main feature is that the demodulation and decoding processes are performed.
[0018]
Furthermore, here, narrowband OFDM, which is a Japanese terrestrial digital television broadcasting system, will be described.
[0019]
Television broadcasting is performed in units of one channel and 6 MHz band, but usually the band is divided into 13 segments and information is multiplexed for broadcasting. For this reason, the receiving device receives one wideband signal for 13 segments and demodulates and decodes it.
[0020]
Here, in order to enable broadcasting at a lower rate or a frequency band less than the 6 MHz band targeting voice, data, low-resolution broadcasting, etc., one or more broadcasting services are provided within one channel. Transmission in a narrow band of 3 segments is also specified. Generally, it is assumed that the above-described wideband broadcast receiving apparatus is configured to receive one or three segments of narrowband broadcast.
[0021]
For example, as shown in FIG. 2 (a), when there is a narrowband broadcasting service of A, B, and C by one or three of 13 segments in one channel, the frequency of the local oscillator 12 in FIG. By selecting according to the band of each broadcast service, the broadcast services A, B, and C are once converted into signals of the same intermediate frequency as shown in FIGS. The processing after the / D converter 13 can be performed in the same manner.
[0022]
Here, since the demodulated format information is transmitted with a frame structure in the A / D converter 15, the quadrature detection unit 14, the FFT unit 15, and the demodulation unit 16, a pull-in time in units of frames is required. Further, since the frequency of the local oscillator 12 does not exactly match the transmission frequency, there is an error. Therefore, the quadrature detection unit 14 and the demodulation unit 16 regenerate the clock and frequency from the received signal.
[0023]
Further, in order to avoid that the error correction unit 18 cannot partially decode beyond the correction capability when there is a time variation or frequency selective interference as a transmission condition, data arrangement called interleaving on the transmission side is performed. A replacement has been made.
[0024]
FIG. 3 shows the state of interleaving. FIG. 3 is a conceptual diagram of frequency axis interleaving. The frequency axis is taken in the row direction, the time axis is taken in the column direction, and different numbers of delay elements indicated by □ are connected in series to each row. The delay time is shifted. As described above, in interleaving, a large number of delay elements are arranged in the time axis direction to rearrange data. Therefore, it takes a long time until a signal is correctly output from a state where the signal is once interrupted. Cost.
[0025]
Furthermore, in digital broadcasting, video, audio, and data are compressed, packetized, and transmitted, so that the processing cannot proceed unless the minimum unit data is prepared to some extent. For this reason, packet buffering is necessary on the receiving side, and then depacket and decompression processing is performed to reproduce video, audio, and data.
[0026]
From the above, in the conventional method, when switching between broadcast services even within the same processing band, it starts from changing the frequency of the local oscillator 12 and takes a great deal of time to complete the pull-in processing. It will take.
[0027]
In addition, a broadcast service such as A in a desired band is selected from the signal converted into the frequency domain after FFT, and only the part after A is processed after demodulation. Originally, this receiving apparatus has the capability of receiving broadband broadcasts and can process 13 segments, so that part of the capability is wasted.
[0028]
Therefore, in the present invention, as shown in FIGS. 4 (a) and 4 (b), the local oscillator 12 for the tuner unit 11 is processed so that it can be processed in a form including A, B, and C broadcast services at the time of channel selection. Is set to the center frequency of the channel band, and the tuner unit 11 extracts the entire channel band. The output of the tuner unit 11 is subjected to processing of the A / D converter 13, the quadrature detection unit 14, and the FFT unit 15 and developed in the frequency domain, and then A, B, and C modulation signals are extracted. Time division multiplexed and output to the demodulator 16.
[0029]
Here, the modulation signals A, B, and C are different broadcast service signals (hereinafter referred to as broadcast signals) and have different format information. For this reason, after demodulating each broadcast signal in the demodulator 16, the format information of each broadcast signal is once stored in the format information storage units 17a and 17b, and thereafter the format information corresponding to each demodulated signal of the broadcast signal is stored. The data is read sequentially and transferred to the subsequent processing system in accordance with the time division processing. Thereby, a plurality of broadcast signals can be processed. Further, it is possible to output a plurality of states restored to information such as video, audio and data broadcasting.
[0030]
Of course, in some cases, only one of them may be selected to receive a broadcast service. In this case, even if a broadcast service within the same processing band is switched, high-speed switching is possible.
[0031]
In this case, instead of selecting the output of the MPEG decoder 20 as shown in FIG. 1, as shown in FIG. 5, a selection unit 21 is provided at the subsequent stage of the error correction unit 10 so that an arbitrary broadcast service can be selected. You may make it share after TS analysis. Also with this configuration, it is possible to reduce the time for reproduction output after selection required for demodulation and correction. Of course, the selection unit 21 may be arranged anywhere after the error correction unit 10 and does not limit the switching position.
[0032]
Note that it is not the purpose of the present invention that the decoding process is performed up to the final stage, and the purpose is to process a large time delay element, so it goes without saying that it is particularly effective to perform time interleaving with a large delay. .
[0033]
Also, when broadcasting services at different frequencies can be received simultaneously, for example, reception by a double screen on a TV, reception of data broadcasting such as data broadcasting in the background, recording the signal to a hard disk or the like Accumulation and time shifting, and video backside recording can be realized without having multiple tuners.
[0034]
Therefore, according to the digital broadcast receiving apparatus having the above configuration, the frequency of the local signal generated by the local oscillator of the tuner unit is selected as the center frequency of the reception channel, and all the format information of the plurality of broadcast services in the reception channel is stored. In addition, since the processing after FFT is time-division multiplexed and demodulated and decoded based on the accumulated format information, it is possible to process multiple broadcasting services, which has conventionally taken nearly 1 second. Almost no time is required for switching. Also, simultaneous playback of a plurality of broadcast services can be realized.
[0035]
In addition, this invention is not limited to said embodiment. For example, the present invention is not limited to a narrow band and a wide band, and is also applicable to a case where a wider band processing such as a 30 MHz band including a plurality of 6 MHz wide bands is performed. In this case, broadcast services in a plurality of channels are simultaneously transmitted. It is possible to output or switch at high speed.
[0036]
In the above embodiment, OFDM has been mainly described. However, the present invention is not limited to OFDM, and can be extended to a plurality of separable broadcast waves.
[0037]
【The invention's effect】
As described above, according to the present invention, the time required for mode detection and switching of each broadcast service within the same reception band is very short, a comfortable broadcast service can be selected, and a plurality of broadcasts can be selected. It is possible to provide a digital broadcast receiver capable of simultaneously playing back services.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of an embodiment of a digital broadcast receiving apparatus according to the present invention.
FIG. 2 is a view for explaining a conventional technique corresponding to the reception process of the embodiment;
FIG. 3 is a view for explaining interleaving used as part of error correction according to the embodiment;
FIG. 4 is a view for explaining reception processing according to the embodiment;
FIG. 5 is a block diagram showing the configuration of another embodiment of the digital broadcast receiving apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Tuner part, 12 ... Local oscillator, 13 ... A / D converter, 14 ... Quadrature detection part, 15 ... FFT part, 16 ... Demodulation part, 17a, 17b ... Format information storage part, 18 ... Error correction part, 19 ... TS analysis unit, 20 ... MPEG decoder, 21 ... selection unit.

Claims (7)

In a digital broadcast receiving apparatus for receiving a digital broadcast transmitted by multiplexing format information for identifying a transmission method of each digital broadcast signal together with a plurality of digital broadcast signals by an arbitrary transmission method within the same broadcast band ,
Demodulation means for extracting and demodulating the plurality of digital broadcast signals and the format information from the reception output of the multiplexed signal transmitted in the broadcast band ;
Format information storage means for storing format information of all digital broadcast signals within the same broadcast band demodulated by the demodulation means;
Upon receiving the selection designation of any digital broadcast signal among all the digital broadcast signals within the same broadcast band demodulated by the demodulation means, the format information corresponding to the digital broadcast signal is extracted from the format information storage means And a playback processing means for performing playback processing of the designated digital broadcast signal based on the format information . When the digital broadcast signal has a TS (transport stream) packet structure,
The reproduction processing means includes
A time division multiplexing unit for time division multiplexing all digital broadcast signal packets demodulated by the demodulation means ;
An error correction unit for performing error correction processing in a time division manner on the basis of the corresponding format information from the format information storage means , respectively, for the packet of the time-division multiplexed digital broadcast signal ;
Packet separation means for analyzing the TS packet structure based on the format information and separating each packet with respect to the output of the error correction unit ;
For each packet separated by this packet separation means, a TS analysis unit that individually outputs a stream corresponding to a digital broadcast signal selected and designated among all digital broadcast signals within the predetermined band ; and
2. The digital broadcast receiving apparatus according to claim 1, further comprising: a reproduction processing unit that reproduces streams individually output by the TS analysis unit in a time division manner based on the format information. The TS analysis unit of the reproduction processing unit selects a digital broadcast signal in the same broadcast band by selecting a digital broadcast signal packet selected and designated from the packets separated by the packet separation unit. The digital broadcast receiver according to claim 2, further comprising: 3. The digital broadcast receiving apparatus according to claim 2, wherein the reproduction processing unit of the reproduction processing unit performs reproduction processing of an arbitrary plurality of streams in the stream output from the TS analysis unit .   3. The digital broadcast receiving apparatus according to claim 2, further comprising information recording means for recording any output after the error correction section. Multiplexed signal transmitted by the same broadcast band is an OFDM (Orthogonal Frequency Division Multiplexing) signal composed of a plurality of frequency segments, a plurality of digital broadcast signals in said multiplexed signal, one or more of each in the OFDM signal 2. The digital broadcast receiving apparatus according to claim 1, wherein the frequency segment is a transmission band. A digital broadcasting system which has a plurality of broadcast bands and multiplexes and transmits format information for identifying a transmission method of each digital broadcast signal together with a plurality of digital broadcast signals by an arbitrary transmission method within the same broadcast band. In the digital broadcast receiver used for
  A tuner for selecting an arbitrary broadcast band from the plurality of broadcast bands and receiving a multiplexed signal transmitted in the band;
  Demodulating means for extracting and demodulating the plurality of digital broadcast signals and the format information from the multiplexed signal selected and received by the tuner;
  Format information storage means for storing format information of all digital broadcast signals within the same broadcast band demodulated by the demodulation means;
  In response to the selection designation of any one of the digital broadcast signals within the same broadcast band demodulated by the demodulating means, the format information corresponding to the digital broadcast signal is extracted from the format information storage means. Reproduction processing means for performing reproduction processing of the designated digital broadcast signal based on the format information;
A digital broadcast receiver characterized by comprising:

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