KR101694976B1 - Method and apparatus for transmitting conditional access message in DMB system - Google Patents

Abstract

The present invention relates to a method and apparatus for effectively transmitting a conditional access message for instructing conditional access to a broadcast service in a DMB system, and in a terrestrial DMB transmission system supporting limited reception, A conditional access system (CAS) server for generating information on a transmission period and an amount of an ECM (Entitlement Control Message) related to the authority, a stream (ECM) required for transmission of the ECM based on information on the transmission period and amount of the ECM and a DMB video encoder for generating a null packet as many as the calculated number of streams, wherein the DMB video scrambler comprises: a transport stream (transport stream) for the null packet; stream by inserting the ECM into a payload to generate an ECM packet. The.

Description

[0001] The present invention relates to a method and apparatus for transmitting a conditional access message in a DMB system,

The present invention relates to a method and apparatus for efficiently transmitting a conditional access message to instruct conditional access to a broadcast service in a DMB system.

As part of the profitability enhancement of terrestrial DMB service, provision of paid service for terrestrial DMB video service is becoming an issue. Accordingly, various discussions on the conditional access system for the video service are underway.

A conditional access system (CAS) is a system that modifies and delivers an original broadcast signal so that it can be normally viewed only by a receiver having a reception right for the broadcast program. The modification of the form of the original broadcast signal so that it can not be viewed by unauthorized receivers is referred to as scramble, and the apparatus for scrambling is referred to as a scrambler.

The limited reception method for video service has a focus on a method of transmitting a conditional access message rather than a method of applying a conditional access algorithm. An entitlement control message (ECM) and an entitlement management message (EMM) are the conditional access messages related to the reception right of the DMB service. The ECM encrypts a control word, which is a key used for scrambling, and transmits the encrypted control word to a receiver. The ECM is periodically transmitted for security, and a new control word is encrypted each time. The EMM functions to qualify or update the receiver.

As a conventional technique for transmitting such a conditional access message, a method of inserting ECM and EMM, which are conditional access messages, based on the amount of data input to the scrambler has been proposed. However, from the viewpoint of the scrambler, this method has a problem of adjusting the transmission period and amount of the ECM and the EMM depending on the amount of data to be input without considering the importance of the conditional access message.

Also, a method of transmitting an EMM having a large amount of data among restricted reception messages through a channel other than a channel for scrambling has been proposed. However, among the restricted reception messages, a method of efficiently transmitting an ECM having a relatively small amount of data and having a significant meaning is not addressed.

In a terrestrial DMB system in which standard specifications are limited compared to other broadcasting systems, it is required to present an effective transmission method of the ECM without deviating from the standard specifications.

The present invention also provides a method and apparatus for transmitting a conditional access message in a DMB system.

It is another object of the present invention to provide a method and apparatus for adjusting a transmission period and an amount of a conditional access message in a scrambler according to an independent criterion without depending on input data.

It is another object of the present invention to provide a method and apparatus for inserting an ECM in a scrambled video service channel.

According to an aspect of the present invention, there is provided a terrestrial DMB transmission system supporting conditional access. The transmission system includes a Conditional Access System (CAS) server for generating information on a transmission period and an amount of an ECM (Entitlement Control Message) related to a reception right of the DMB service, a transmission period and amount of the ECM, A DMB video scrambler for calculating the number of streams required for transmission of the ECM, and a DMB video encoder for generating a null packet by the number of the calculated streams, wherein the DMB video scrambler comprises: And inserts the ECM into a payload provided in a transport stream (TS) for a null packet to generate an ECM packet.

According to another aspect of the present invention, there is provided a terrestrial DMB receiving terminal supporting limited reception. The terminal includes a scrambled video stream by demultiplexing a multiplexed frame, an ECM packet generated by inserting an ECM into a payload provided in a transport stream for a null packet, and a demultiplexer A CAS client for generating descrambling control data based on the ECM packet; a descrambler for descrambling the scrambled video stream based on the descrambling control data; and a descrambler for decoding the descrambled video stream, Wherein the demultiplexer parses the PMT to extract the ECM packet.

According to another aspect of the present invention, there is provided an ECM transmission method by a terrestrial DMB transmission system supporting limited reception. The method includes generating information on the transmission period and amount of the ECM related to the reception right of the DMB service, calculating the number of streams required for transmission of the ECM based on the transmission period and amount of the ECM, Generating a null packet by the number of the calculated streams, and inserting the ECM into a payload provided in the transport stream for the null packet to generate an ECM packet.

According to the present invention, it is possible to calculate the number of necessary packets without depending on the amount of the video stream input to the scrambler, request the DMB encoder, and efficiently insert the conditional access message based on the requested number of packets.

According to the present invention, an ECM can be inserted in place of the null packet generated by the encoder, and compatibility with the existing MPEG (Motion Picture Expert Group) -2 system standard is maintained.

FIG. 1 shows an embodiment of a DMB transmission system to which the present invention is applied.
2 shows an embodiment for inserting an ECM into a null packet according to the present invention.
FIG. 3 shows an embodiment of a DMB receiving terminal to which the present invention is applied.
4 shows a method of transmitting a conditional access message by the DMB transmission system according to the present invention.
5 shows a method of receiving a conditional access message by a DMB receiving terminal according to the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known configurations or functions will be omitted if it is determined that the gist of the present specification may be obscured.

FIG. 1 shows an embodiment of a DMB transmission system to which the present invention is applied.

Referring to FIG. 1, the DMB transmission system includes a DMB video encoder 110, a CAS server 120, a DMB video scrambler 130, and a DMB multiplexer 140.

The DMB video encoder 110 receives a video source and encodes the video source according to a predetermined standard to generate a video stream.

The CAS server 120 generates information on the transmission period and amount of the conditional access message and transmits the generated information to the DMB video scrambler. Information on the transmission period and amount of the conditional access message may be determined by the scrambling policy of the DMB video service.

The DMB video scrambler 130 calculates the number of MPEG-2 streams required for transmission of a conditional access message on the basis of information on the transmission period and amount of the received conditional access message and transmits the calculated number of streams to the DMB To the video encoder 110. [ In this case, the DMB video scrambler 130 calculates the number of streams in consideration of the output of the DMB video encoder 110. For example, the output of the DMB video encoder 110 is composed of an MPEG-2 stream in units of 204 bytes. The DMB video scrambler 130 receives the MPEG-2 stream in units of 204 bytes, The number of streams corresponding to the amount of messages (e.g., ECM) can be calculated in the same unit. At this time, the request of the stream may be performed automatically or manually.

The DMB video encoder 110 generates null packets for the number of streams requested from the DMB video scrambler 130 and transmits the null packets to the DMB video scrambler 130 together with the video streams. If the DMB video encoder 110 contains more null packets than the number of streams requested from the DMB video scrambler 130, the request can be ignored. However, if the DMB video encoder 110 includes fewer null packets than the number of streams requested from the DMB video scrambler 130, the DMB video encoder 110 additionally generates a missing null packet.

The DMB video scrambler 130 may insert a conditional access message into the null packet generated by the number of streams. Here, the conditional access message may be at least one of the EMM and the ECM described above. Since the amount of the stream of the DMB video is smaller than that of the other media, the space available as a null packet may be limited in this case. Therefore, the DMB video scrambler 130 may transmit only the ECM, It is possible to insert an ECM packet into a packet to generate an ECM packet. The DMB video scrambler 130 actively requests the number of packets required for inserting (and transmitting) the conditional access message without depending on the amount of the passively inputted video stream in the conditional access message delivery, (And transmit) a conditional access message. Hereinafter, the ECM will be described.

2 shows an embodiment for inserting an ECM into a null packet according to the present invention.

Referring to FIG. 2, one transport stream packet includes a header and a payload. Specifically, an MPEG-2 transport stream packet may include a 4-byte header and a payload of 184 bytes. The DMB video scrambler may modify the PID of the null packet to point to the ECM and segment the ECM into a payload of the packet. That is, the ECM packet may be generated by inserting the ECM into a payload provided in a transport stream (TS) for the null packet.

The header includes a payload unit start indicator, a packet identifier (PID), and a continuity counter field.

The packet identifier value included in the header of the null packet can be determined according to the standard, and can be set to, for example, OxIFFF. The DMB video scrambler modifies (or sets) the PID value of the null packet necessary for inserting the ECM data into the PID value for the ECM packet. May be referred to as a null packet if the PID of the transport stream packet indicates a null (i.e., OxIFFF), and may be referred to as an ECM packet if the PID of the transport stream packet indicates the ECM.

Also, in the null packet, the payload unit start indicator field indicating the start position of the payload is 0, and when the ECM packet is started for the first time in the DMB video scrambler, the payload unit start indicator field of the corresponding ECM packet is 1, and the payload unit start indicator field of the remaining ECM packet is set to zero. Based on this, the beginning of the ECM packet can be indicated.

In the case of an ECM packet, the DMB video scrambler defines a persistent counter field for each header of each ECM packet, and the persistent counter value is incremented by 1 for every ECM packet . Through this, it can be checked whether there is a packet lost in the middle. For example, the persistence counter field value of the first ECM packet is 1, the persistence counter field value of the second ECM packet is 2, the persistence counter field value of the nth packet is n, and the persistence counter field value of the next ECM packet Can be set to n + 1.

A method of inserting an ECM packet instead of a null packet can be performed by modifying or overwriting a null packet into an ECM packet by the DMB video scrambler as described above or by generating an ECM packet in the above format, It can be replaced with a packet.

The information (for example, the PID value) of the ECM packet inserted as described above is defined in the PMT (Program Map Table) according to the MPEG-2 system standard.

PSI (Program Specific Information) is used when transmitting and receiving a broadcast using MPEG-2. The PSI includes a program association table (PAT), a program map table (PMT), a network information table (NIT) ) And the like. Here, the PAT includes a PMT PID (Packet Identifier) of all programs, and the PMT includes a video PID and audio PID information of the corresponding program. The NIT contains information about the physical network parameters such as the FDM frequency or the number of transponders. The CAT includes the PID of the EMM for accessing and controlling the conditional access, and information on the conditional access parameters.

In the method in which the information of the ECM packet is defined in the PMT, the ECM packet is defined as a separate stream type, and the information may be described, or may be represented by the related data information in the video stream information.

Referring again to FIG. 1, the DMB video scrambler 130 scrambles the received video stream. In this case, the DMB video scrambler 130 can scramble the video stream based on the control word included in the ECM.

The DMB video scrambler 130 delivers the scrambled video stream and the ECM packet to the DMB multiplexer 140.

The DMB multiplexer 140 multiplexes the scrambled video stream and the ECM packet, and generates one multiplexed frame.

Meanwhile, the DMB video encoder 100 may generate a video stream as well as a data stream. That is, the DMB video encoder 100 may receive a data source and generate a data stream based on the received data source. In this case, the DMB video scrambler 130 can scramble the video stream and the data stream based on the control word included in the ECM. Also, the DMB video multiplexer 140 may multiplex the ECM packet, the scrambled video stream, and the scrambled data stream to generate one multiplexed frame.

The DMB transmission system may provide a video (broadcasting) service and a data (broadcast) service as separate services, and may provide a data service that is related to the video service or has a dependency on the video service, together with the video service. The ECM, which is a conditional access message, may be provided for video service and audio service, respectively. In this case, the DMB video scrambler 130 can scramble the video stream and the data stream, respectively, on the basis of the respective control words included in each ECM. Or the ECM may be provided publicly for video and data services. In this case, the DMB video scrambler 130 can scramble the video stream and the data stream, respectively, based on the control word included in one ECM. Accordingly, in this case, the DMB video scrambler 130 may not insert (and transmit) a separate ECM for the data service. For example, if a DMB transmission system provides a data service that is related to a video service or has a dependency on a video service, the DMB video scrambler 130 may generate a video stream based on control words included in one ECM, And the data stream, respectively.

FIG. 3 shows an embodiment of a DMB receiving terminal to which the present invention is applied.

Referring to FIG. 3, the DMB receiving terminal includes a demultiplexer 310, a CAS client 320, a DMB video descrambler 330, and a DBM video decoder 340.

The demultiplexer 310 demultiplexes the multiplexed frames to obtain a scrambled video stream and an ECM packet, and first extracts the ECM packet by parsing the PMT. That is, the demultiplexer 310 parses the PMT to separate the ECM packet and the scrambled video stream. Here, the ECM packet is generated by inserting an ECM into a payload provided in a transport stream for a null packet as described above, and the PMT defines (or includes) the information of the ECM packet.

The demultiplexer 310 transfers the ECM packet to the CAS client 320 and delivers the scrambled video stream to the DMB video descrambler 330.

The CAS client 320 analyzes the ECM packet and generates descrambling control data. The CAS client 320 transmits the descrambling control data to the DMB video descrambler 330.

The DMB video descrambler 330 descrambles the scrambled video stream received from the demultiplexer 310 based on the descrambling control data received from the CAS client 320.

The DMB video descrambler 330 transmits the descrambled video stream to the DMB video decoder 340.

The DBM video decoder 340 decodes the descrambled video stream and obtains a video source.

Meanwhile, the demultiplexer 310 can demultiplex the multiplexed frame to obtain the scrambled video stream as well as the scrambled data stream. That is, the demultiplexer 310 can demultiplex the multiplexed frame to obtain a scrambled video stream, a scrambled data stream, and an ECM packet. In this case, the descrambler 330 can descramble the scrambled video stream and the scrambled data stream based on the descrambled control data, respectively. Also, the DMB video decoder 340 may obtain the video source by decoding the descrambled video stream, and may decode the descrambled data stream to obtain the data source.

4 shows a method of transmitting a conditional access message by the DMB transmission system according to the present invention.

Referring to FIG. 4, the DMB transmission system generates information on the transmission period and amount of the ECM, which is the conditional access message (S400).

The DMB transmission system calculates the number of streams required for transmission of the ECM based on information on the transmission period and amount of the ECM (S420).

The DMB transmission system generates a null packet by the number of the calculated streams (S440). The null packet consists of a header and a payload.

The DMB transmission system inserts the ECM into a payload provided in the transport stream for the null packet to generate an ECM packet (S460). The DMB transmission system divides the ECM into a payload of the null packet to generate the ECM packet. The header of the ECM packet includes a packet identifier (PID), a payload unit start indicator, and a continuity counter field. In this case, the packet identifier field may be set to a PID value for an ECM packet. In addition, the value of the payload unit start indicator field of the first ECM packet is set to 1, and the value of the payload unit start indicator field in the remaining ECM packets excluding the first ECM packet may be set to zero. Also, the persistent counter field may be set to increment by 1 in the order of each ECM packet.

Herein, the information (e.g., packet identifier) of the ECM packet may be defined in the PMT.

In addition, the DMB transmission system can generate a video stream. The DMB transmission system can scramble the video stream based on control words included in the ECM.

Thereafter, the DMB transmission system multiplexes the ECM packet and the scrambled video stream to generate a multiplexed frame. The PMT may be included in the multiplexed frame.

Meanwhile, the DMB transmission system may generate a data stream as well as a video stream, and may scramble the video stream and the data stream, respectively, based on a control word included in the ECM. In this case, the DMB transmission system may multiplex the ECM packet, the scrambled video stream, and the scrambled data stream to generate a multiplexed frame.

5 shows a method of receiving a conditional access message by a DMB receiving terminal according to the present invention.

Referring to FIG. 5, the DMB receiving terminal demultiplexes the multiplexed frames to obtain a scrambled video stream, an ECM packet, and a PMT (S500). Here, the ECM packet is generated by inserting an ECM into a payload provided in a transport stream for a null packet as described above, and the PMT defines (or includes) the information of the ECM packet.

The DMB receiving terminal may parse the PMT to distinguish the ECM packet from the scrambled video stream.

The DMB receiving terminal generates disclaimer control data based on the ECM packet (S520).

The DMB receiving terminal descrambles the scrambled video stream based on the descrambling control data (S540).

The DMB receiving terminal decodes the descrambled video stream and obtains a video source (S560).

Meanwhile, the DMB receiving terminal can demultiplex the multiplexed frame to acquire the scrambled video stream as well as the scrambled data stream. That is, the DMB receiving terminal can demultiplex the multiplexed frame to obtain a scrambled video stream, a scrambled data stream, and an ECM packet. In this case, the DMB receiving terminal can descramble the scrambled video stream and the scrambled data stream on the basis of the descrambled control data, respectively. The DMB receiving terminal may obtain the video source by decoding the descrambled video stream, and may decode the descrambled data stream to obtain the data source.

Through the above-described method, the DMB transmission system can calculate the number of required packets without depending on the amount of the video stream input to the scrambler, and insert the ECM efficiently based on the calculated number of packets. Also, according to the present invention, ECM can be inserted in place of a null packet generated in an encoder, so that compatibility with the existing MPEG (Motion Picture Expert Group) -2 system standard is maintained.

The foregoing description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (14)

In a terrestrial DMB transmission system supporting conditional access,
A Conditional Access System (CAS) server for generating information on the transmission period and amount of an ECM (Entitlement Control Message) related to the reception right of the DMB service;
A DMB video scrambler calculating a number of streams required for transmission of the ECM based on information on the transmission period and amount of the ECM; And
And a DMB video encoder for generating a null packet by the number of the calculated streams,
The DMB video scrambler generates an ECM packet by inserting the ECM into a payload provided in a transport stream (TS) for the null packet,
Wherein the DMB encoder further generates a null packet by an insufficient number for inserting the ECM if the number of null packets is less than the number of streams required for transmission of the ECM. The method according to claim 1,
The DMB video encoder generates a video stream,
Wherein the DMB video scrambler scrambles the video stream based on a control word included in the ECM,
Wherein the transmission system further comprises a DMB video multiplexer for multiplexing the ECM packet and the scrambled video stream to generate a multiplexed frame. The method according to claim 1,
The DMB video encoder generates a video stream and a data stream,
Wherein the DMB video scrambler scrambles the video stream and the data stream based on a control word included in the ECM,
Wherein the transmission system further comprises a DMB video multiplexer for multiplexing the ECM packet, the scrambled video stream and the scrambled data stream to generate a multiplexed frame. The method according to claim 1,
Wherein the DMB video scrambler defines information of the ECM packet in a PMT (Program Map Table). The method according to claim 1,
The ECM packet includes a header and the payload,
Wherein the DMB video scrambler segments the ECM into payloads of a plurality of ECM packets. 6. The method of claim 5,
The header includes a packet identifier (PID), a payload unit start indicator, and a continuity counter field,
Wherein the DMB video scrambler sets the packet identifier as a PID value for the ECM packet, sets the value of the payload unit start indicator field in the first ECM packet to 1, The value of the payload unit start indicator field is set to 0, and the persistent counter field is incremented by 1 in the order of each ECM packet. delete delete An ECM transmission method by a terrestrial DMB transmission system supporting limited reception,
Generating information on the transmission period and amount of the ECM related to the reception right of the DMB service;
Calculating a number of streams required for transmission of an ECM based on information on the transmission period and amount of the ECM;
Generating a null packet by the number of the calculated streams; And
Inserting the ECM into a payload provided in a transport stream for the null packet to generate an ECM packet,
Wherein the null packet is additionally generated in an insufficient number for insertion of the ECM if the number of streams required for transmission of the ECM is less than the number of streams required for transmission of the ECM. 10. The method of claim 9,
Generating a video stream;
Scrambling the video stream based on a control word included in the ECM;
Further comprising multiplexing the ECM packet and the scrambled video stream to generate a multiplexed frame. 10. The method of claim 9,
Generating a video stream and a data stream; And
Scrambling the video stream and the data stream, respectively, based on control words included in the ECM;
Further comprising multiplexing the ECM packet, the scrambled video stream, and the scrambled data stream to generate a multiplexed frame. 10. The method of claim 9,
Wherein information of the ECM packet is defined in a PMT (Program Map Table). 10. The method of claim 9,
The ECM packet includes a header and the payload,
Wherein the terrestrial DMB transmission system divides the ECM into payloads of a plurality of ECM packets and inserts the payload. 14. The method of claim 13,
The header of the ECM packet includes a packet identifier, a payload unit start indicator, and a persistent counter field,
The packet identifier is set to a PID value for the ECM packet, the value of the payload unit start indicator field in the first ECM packet is set to 1, the payload unit start indicator in the remaining ECM packets excluding the packet, The value of the field is set to 0, and the persistent counter field is set to increment by 1 in order of each ECM packet.

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