JP4064771B2 - Digital broadcasting system and its receiving terminal device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital broadcasting system such as data broadcasting for mobiles and an image receiving terminal device thereof, and more particularly to a technique for shortening a viewing channel (program) switching time.
[0002]
[Prior art]
In digital broadcasting in Japan, system information necessary for receiving a program being broadcast and content data of the program itself are data called TS (Transport Stream) of the MPEG2 (Moving Picture Experts Group phase 2) system standard. It is supposed to be transmitted in the format. The system information includes PAT (Program Association Table), PMT (Program Mapping Table).
[0003]
In a receiving terminal device that receives such digital broadcasting, when switching viewing channels, system information (PAT, PMT) is first searched from the TS of the receiving channel, and the program itself is configured from this system information. Get information about the data. Next, based on the information obtained from the system information, the data itself constituting the program is extracted from the TS, so that the target program can be viewed.
[0004]
At this time, since the system information is transmitted from the broadcasting station with a certain period, the system information is not always obtained at the time of inputting the viewing channel switching (program switching) instruction on the receiving side. There is a waiting time of a period time at maximum to obtain system information. This directly affects the channel switching time.
[0005]
By the way, although the practical use of the S-band satellite digital broadcasting system for mobile bodies is currently underway, the above data format is also adopted in this digital broadcasting. Further, the TS is divided into a plurality of carriers and multiplexed and transmitted by a CDM (Code Division Multiplex) method.
[0006]
In the above-described digital broadcasting system for mobile units, a simple receiving terminal device cannot receive all of a plurality of carrier waves at the same time, so partial reception of TS is unavoidable. In this case, when retrieving system information from the TS, it is necessary to review the corresponding carrier wave every time.
[0007]
In the case of a mobile unit, data transmission processing called interleaving is generally performed on transmission data on a carrier wave. For this reason, the transmission data cannot be extracted unless there is a binding time for restoring the interleaving applied to the transmission data of the carrier when the carrier is captured.
[0008]
From the above, in the digital broadcasting system for mobile units, since the TS is divided into a plurality of carrier waves and transmitted by interleaving, the time required for capturing the carrier wave before extracting data from the TS and Interleaving constraint time after capture is necessary, and these times greatly affect the viewing channel switching time.
[0009]
Such a long viewing channel switching time cannot be accepted in the performance of the receiving terminal device. This problem is an important issue because PMT cannot be sent frequently in a relatively low-rate (for example, 256 kbps) broadcasting system such as digital broadcasting for mobiles.
[0010]
[Problems to be solved by the invention]
The present invention has been made under the circumstances described above, and the object of the present invention is to reduce the time required for acquiring system information necessary for receiving a program being broadcast, thereby switching the viewing channel. It is an object of the present invention to provide a digital broadcasting system and a receiving terminal device that realizes shortening of the time.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention divides a channel for regularly transmitting system information necessary for receiving a program being broadcast and a channel for transmitting content data of the program itself into a plurality of carrier waves. A digital broadcasting system that transmits a digital broadcast signal divided and multiplexed on the receiving side and extracts content data on the receiving side based on the system information. The receiving side holds the system information when acquiring the system information, and System information held at the time of acquisition of system information is allowed to be updated, and content data of a selection destination or a switching destination program is acquired with reference to the system information held at the time of selection or switching of the program It is characterized by.
[0012]
The receiving terminal device used in the digital broadcast system holds the system information when acquiring the system information, updates the system information held when acquiring new system information, and selects or switches the program Content data acquisition means for acquiring content data of a selection destination or switching destination program with reference to system information held in the holding means.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As an embodiment of the digital broadcasting system according to the present invention, an S-band satellite digital audio broadcasting system will be described as an example. In this system, CDM is adopted as a transmission method, and the MPEG2 system standard is adopted as a multiplexing method of system information (PAT, PMT, etc.) and program components. FIG. 1 shows the configuration of the receiving terminal apparatus of this system.
[0014]
In FIG. 1, an antenna 11 captures an S-band satellite broadcast signal. The captured broadcast signal is selected by a tuner unit 12 of a front end unit FE, and is subjected to CDM demodulation and decoding processing by a demodulation / decoding unit 13. A baseband signal is acquired, and a TS is further extracted by the baseband processing unit 14. The extracted baseband signal is descrambled as necessary by a CA (Conditional Access) module 15 of the back-end unit BE, and sent to an MPEG2 decode separation unit (DEMUX) 16. The MPEG2 decode separation unit 16 extracts system information from the input TS, decodes a multiplexed bit stream necessary for the selected program from the TS based on the system information, and generates a data bit stream, a video bit stream, and an audio bit stream. Are output separately.
The decode separation unit 15 sends the multiplexed bit stream to a recording / reproducing apparatus (not shown) for recording / reproducing, and takes in the multiplexed bit stream from the recording / reproducing apparatus, and performs the same processing as the received data. .
[0015]
The data bit stream is input to the data decoder unit 16, and EPG (Electric Program Guide), basic data, and data broadcast program data are decoded and reproduced. The video bit stream is input to the video decoding unit 17, the video signal is decoded and reproduced, and the audio bit stream is input to the audio decoding unit 18, and the audio signal is decoded and reproduced. The decoded video signal is combined with the video of the data content obtained by the data decoder unit 16 by the combining unit 19 and becomes a video output.
[0016]
Each processing block is connected to the control system CPU 20, the memory 21, and the external input interface unit (I / F) 22 through the control bus BUS. The control system CPU 20 executes a series of reception / reproduction processes by controlling the process of each block in accordance with an instruction input from the external input interface unit 22 according to a program registered in the memory 21 in advance. Here, it is assumed that the maximum number of CDM reception channels is 2, and the transmission contents are multiplexed and controlled by the MPEG4 system. Further, the memory 21 has an area for registering and sequentially updating system information such as the latest acquired pilot, PAT, and PMT.
[0017]
Here, in the present broadcasting system, a CDM channel for transmitting PAT and a CDM channel for transmitting PMT and program components are multiplexed. In this case, in the conventional operation, a method for extracting the PAT and the PMT in the system information every time in the receiving terminal device has been considered.
[0018]
In the case of such a conventional operation method, the time required for switching the viewing channel in the receiving terminal apparatus directly affects the time required for capturing the PAT and PMT.
Therefore, in the present invention, the receiving terminal device side holds the PAT and PMT information at the time of the previous operation and sequentially updates when new information is acquired. This time is shortened.
[0019]
The reception sequence that characterizes the present invention will be described below in comparison with the conventional one. FIG. 2 shows a time chart of a reception sequence according to a conventional method, and FIG. 3 shows a time chart of a reception sequence according to the present invention. In FIG. 2 and FIG. 3, the physical layer processing time, CPU processing time, and the like are not considered in order to simplify the description.
[0020]
Here, in this system, configuration information is allocated to CDM channel 0 (pilot channel), NIT / PAT / CAT / PMT / EMM-S / ECM-S / etc. Are allocated to CDM channel 1 (CAS channel), SDT / EIT is assigned to CDM channel 2 (EPG channel), and PMT / ES is assigned to CDM channel 3 (content channel).
[0021]
In the conventional method, as shown in FIG. 2, first, when the power is turned on, the pilot channel (CDM0) is selected, AFC (Auto Frequency Control) is locked to the same channel, and the head of the frame is detected by detecting the unique word (UW). Is detected. At this time, pilot information is acquired.
[0022]
Subsequently, the CAS channel (CDM1) and the EPG channel (CDM2) are selected, the interleaving of the respective reception outputs is canceled, and the PAT (0.5 sec cycle) from the CAS channel, as well as CAT to EMM-S (10 sec cycle). ) And obtain an EPG from the EPG channel. Thereby, initial reception (channel selection) is completed.
[0023]
Next, the content channel (CDM3) is selected, the interleaving of the reception output is canceled, and the PMT (0.5 sec cycle) is acquired again. By referring to this PMT, ECM-S (2 sec period) is acquired from the CAS channel, a content channel (CDM3) is selected based on this ECM-S, and a reception ES is set.
After setting the reception ES, reception demodulation of the AAC stream is started, decoding processing is performed, and audio output is started. Since AAC buffering takes about 0.2 sec, the maximum time from channel selection to audio output time is 5.7 sec.
[0024]
On the other hand, for the video system, after the reception SE is set, descrambling is performed, ES reception is started, MPEG4-I is acquired from the content channel (CDM3) (2 sec), the MPEG4 stream is received, and the video signal is received. Perform decoding and start video output. At this time, buffering of MPEG4 data takes 0.5 sec. Therefore, the maximum time from channel selection to video output time is 8 sec.
[0025]
On the other hand, in the present invention, as shown in FIG. 3, after deinterleaving by selecting the CAS channel (CDM1) and the EPG channel (CDM2), CAT to EMM-S (10 sec period) are acquired from the CAS channel. The PAT / PMT obtained from the channel is stored, and when a new PAT / PMT is obtained, it is updated.
[0026]
As a result, there is no need to acquire the PMT from the content channel (CDM3), and ECM-S (2 sec) can be acquired immediately after the completion of interleaving of the content channel reception data. It can be shortened.
[0027]
As is clear from comparison between FIG. 2 and FIG. 3, it takes a maximum of 5.7 sec from the channel selection to the audio output time in the past, but in the present embodiment, it is shortened to 4.7 sec. Conventionally, it takes 8 sec at the maximum from the channel selection to the audio output start time, but in the case of the present embodiment, it is shortened to 7 sec at the maximum.
[0028]
In addition, by adopting the same method as described above, it is possible to reduce the time required for re-reception processing in the case of significant degradation of the temporary reception environment during continuous reception on a mobile object. . FIG. 4 shows a time chart in a conventional re-receiving process sequence, and FIG. 5 shows a time chart in a re-receiving process sequence according to the present invention. In FIGS. 4 and 5, the physical layer processing time, CPU processing time, and the like are not taken into account for the sake of simplicity.
[0029]
In the conventional method, as shown in FIG. 4, first, when receiving is possible, the pilot channel (CDM0) is selected, the AFC is locked to the same channel, and the head of the frame is detected by unique word (UW) detection. At this point, pilot information is reacquired and resynchronization is established.
[0030]
Subsequently, the CAS channel (CDM1) and the EPG channel (CDM2) are selected, the interleaving of the respective reception outputs is canceled, and the CAT to EMM-S (10 sec cycle) in addition to the PAT (0.5 sec cycle) from the CAS channel. ) And obtain an EPG from the EPG channel.
[0031]
Next, the previous reception channel is selected, the interleaving of the reception output of the content channel (CDM3) is canceled, and the PMT (0.5 sec cycle) is acquired again. By referring to this PMT, an ECM-S (entitlement control message for S-band) (2 sec cycle) is acquired from the CAS channel, a content channel (CDM3) is selected based on this ECM-S, and the received ES Set.
After setting the reception ES, reception demodulation of the AAC stream is started, decoding processing is performed, and audio output is started. Since AAC buffering requires about 0.2 sec, the maximum time from tuning to audio output time is 9.2 sec.
[0032]
On the other hand, for the video system, after the reception SE is set, descrambling is performed, ES reception is started, MPEG4-I is acquired from the content channel (CDM3) (2 sec), the MPEG4 stream is received, and the video signal is received. Perform decoding and start video output. At this time, buffering of MPEG4 data takes 0.5 sec. Therefore, the maximum time from channel selection to video output time is 11.5 sec.
[0033]
On the other hand, in the present invention, as shown in FIG. 5, after re-synchronization is established, the pilot information is reacquired by selecting the previous reception channel using the stored pilot, PAT, and PMT information, The NIT / PAT / CAT / PMT / EMM-S is received again from the CAS channel (CDM1), and the information at the time of change is updated. In parallel with this, the received ES is reset from the stored information, and after deinterleaving by selecting the EPG channel (CDM2), CAT to EMM-S (10 sec period) is acquired from the CAS channel, and the content channel (CDM3) ) Receive output is deinterleaved. Thereafter, the ECM-S is acquired from the CAS channel (CDM1), and based on this ECM-S, the audio decoding and the video decoding are executed as described above, and the respective reproduction signals are output.
[0034]
As described above, according to the present embodiment, it is not necessary to acquire the PMT from the content channel (CDM3), and after selecting the reception channel based on the stored system information, the interleaving of the content channel reception data is completed. As a result, ECM-S (2 sec) can be acquired immediately, and the time required to complete the reception ES setting can be reduced accordingly.
[0035]
As apparent from the comparison between FIG. 4 and FIG. 5, it takes up to 9.2 sec from the establishment of resynchronization until the audio output time in the prior art, whereas in the present embodiment, it is shortened to 5.2 sec. Conventionally, it takes a maximum of 11.5 sec from the channel selection to the audio output start time, but in the case of the present embodiment, it is shortened to a maximum of 7.5 sec.
[0036]
In the above embodiment, the case where CDM is adopted as the transmission method has been described. However, the present invention is not limited to this, and other transmission methods can be similarly implemented.
In the receiving terminal device of the embodiment described above, the PMT inserted in the content channel (CDM3) is not used after all. For this reason, in the broadcasting system, it is not necessary to assign system information such as PMT to the content channel by performing an operation that allows the receiving terminal apparatus to hold the previous system information, and the transmission area is reduced accordingly. It becomes possible to do.
[0037]
【The invention's effect】
As described above, according to the present invention, it is possible to shorten the time required to acquire system information necessary for receiving a program being broadcast, and thereby to reduce the viewing channel switching time. A system and its receiving terminal device can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a receiving terminal device when an S-band satellite digital audio broadcasting system is taken as an example of an embodiment of a digital broadcasting system according to the present invention.
FIG. 2 is a time chart showing a reception sequence at the time of initial setting according to a conventional method for the embodiment.
FIG. 3 is a time chart showing a reception sequence at the time of initial setting according to the method of the present invention in the embodiment.
FIG. 4 is a time chart showing a reception sequence when resynchronization is set according to the conventional method for the embodiment.
FIG. 5 is a time chart showing a reception sequence when a resynchronization period is set according to the method of the present invention in the embodiment.
[Explanation of symbols]
FE ... front end unit BE ... back end unit 11 ... antenna 12 ... tuner unit 13 ... demodulation / decoding unit 14 ... baseband processing unit 15 ... CA module 16 ... MPEG2 decoding separation unit 17 ... data decoder unit 18 ... video decoding unit 19 ... Speech decoding unit 20 ... synthesis unit 21 ... control system CPU
22 ... Memory 23 ... External input interface

Claims (3)

The first channel for transmitting broadcast data configuration information, the second channel for transmitting PAT ( Program Association Table : program association table information), the PMT ( Program Mapping Table : program mapping table information), and the contents of the program itself Digital that transmits a digital broadcast signal multiplexed with a third channel for transmitting data by a CDM ( Code Division Multiplex ) method and extracts content data on the receiving side based on system information including the PAT and PMT. A broadcasting system,
A transmission-side apparatus for generating the digital broadcast signal by allocating system information including a PMT together with the PAT to the second channel;
After selecting the first channel and performing a reception process based on the configuration information, the second channel is selected to acquire the system information and hold the system information. Based on the system information, the first channel A receiving side device for extracting content data of the program when selecting three channels,
The receiving-side apparatus allows updating of system information held when new system information is acquired from the second channel, and selects with reference to system information held when the program is selected or switched A digital broadcasting system characterized by acquiring content data of a destination or switching destination program.   2. The digital broadcasting system according to claim 1, wherein the system information and the content data are generated in a TS (Transport Stream) data format of MPEG2 (Moving Picture Experts Group phase 2) system standard. A first channel for transmitting broadcast data configuration information, a second channel for transmitting PAT ( Program Association Table : program association table information), a PMT ( Program Mapping Table : program mapping table information), and content data of the program itself. It is used in a digital broadcast system that transmits a digital broadcast signal that is multiplexed with a third channel to be transmitted by a CDM ( Code Division Multiplex ) method,
When assigning system information including PMT together with the PAT to the second channel on the transmission side,
Receiving processing means for selecting the first channel and performing receiving processing based on the configuration information;
After the reception processing based on the configuration information, the second channel is selected to acquire the system information, hold the system information, and update the system information held when new system information is acquired from the second channel. Holding means to
A digital broadcasting system comprising: content data acquisition means for acquiring content data of a selection destination or switching destination program with reference to system information held in the holding means at the time of selection or switching of the program Receiving terminal device.

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