FR2994786A1 - System for transmission of digital terrestrial broadcasting multimedia supporting conditional access, has digital multimedia broadcasting video scrambler generating entitlement control message packet by inserting payload in transport stream - Google Patents

Abstract

The system has a conditional access system (120) to generate a transfer cycle and an amount of entitlement control message (ECM) relative to access rights to a digital multimedia broadcasting (DMB) service. A DMB video scrambler (130) calculates the necessary number of streams to transmit the ECM based on the transfer cycle. A DMB video encoder (110) generates null packets as many as the number of streams, where the DMB video scrambler generates an ECM packet by inserting the ECM payload provided in a transport stream for the null packets. An independent claim is also included for a terminal for receiving digital terrestrial broadcasting multimedia supporting conditional access.

Description

FIELD OF THE INVENTION The present invention relates to a method and a device for efficiently transmitting a conditional access message so as to indicate an access to a conditional access message. conditional to a broadcasting service in a digital multimedia broadcasting system or DMB (for "Digital Multimedia Broadcasting"). 2. TECHNOLOGICAL BACKGROUND Recently, the provision of paid service for a terrestrial DMB video service has become a problem as part of the increased profits for terrestrial DMB. As a result, a conditional access system (CAS) for video service is being discussed in different ways. The CAS system is a system for modifying and delivering the original broadcast signal so that a corresponding broadcast program normally operates only in a receiver having access rights. The modification of the original broadcast signal so that an unauthorized receiver is unable to receive a corresponding broadcast program as described above is called scrambling and a device for scrambling the broadcast signal is called a scrambler. A conditional access method for video service is more focused on a method for sending a conditional access message than on a method using a conditional access algorithm. A conditional access message relating to access rights to the DMB service includes an access control message or ECM (for "Entitlement Control Message") and an access credential management message or EMM ( for "Entitlement Management Message"). The ECM works to encrypt a conditional word, that is, a key used to scramble, and send the encrypted conditional word to a receiver. The ECM is periodically transmitted for security and a new conditional word is encrypted each time the ECM is transmitted. The EMM works to allow a receiver or to update the access title.

As a method of sending conditional access messages, there has been proposed a method for inserting an ECM and an EMM, i.e., conditional access messages, based on the amount of data applied in entrance on a scrambler. However, this method is problematic in that the transfer cycle and the quantity of the ECM and the EMM are controlled according to the amount of input data without considering the importance of the conditional access messages. from a point of view of a scrambler. It has also been proposed a method of sending an EMM through another channel, not a channel in which the EMM having a large amount of data, among the conditional access messages EMM and ECM, is confuses. However, a method for efficiently sending the ECM with a relatively small amount of data and significance, among the EMM and ECM conditional access messages, has not been processed. There is a need for a method for efficiently sending the ECM while conforming to a standard in a terrestrial DMB system that is more conditionally configured than a broadcasting system having a different standard. SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for sending a conditional access message in a DMB system. Another object of the present invention is to provide a method and a device in which a scrambler controls the transfer cycle and the quantity of a conditional access message according to independent criteria without depending on received data. Still another object of the present invention is to provide a method and apparatus in which an ECM, among conditional access messages, is inserted into a video service channel in which the ECM is scrambled. According to one aspect of the present invention, a terrestrial DMB transmission system supporting conditional access is provided. The terrestrial DMB transmission system includes a conditional access system (CAS) server configured to generate a transfer cycle and a quantity of an Access Title Control (ECM) message relating to access rights to a DMB service, a DMB video scrambler configured to calculate a number of streams necessary to send the ECM based on information about the transfer cycle and the amount of the ECM, and a DMB video encoder configured to generate as many packets than the number of computed streams, in which the DMB video scrambler generates an ECM packet by inserting the ECM into a payload provided within a transport stream or TS (for "Transport Stream") for the null packet.

According to another aspect of the present invention, a terrestrial DMB receiving terminal supporting conditional access is provided. The terrestrial DMB receiving terminal comprises a demultiplexer configured to obtain a scrambled video stream, an ECM packet generated by inserting an ECM into a payload provided within a transport stream, TS, for a null packet, and a program mapping table in which information about the ECM packet is defined by demultiplexing a multiplexed frame, a conditional access system client, CAS, configured to generate descrambling control data based on the ECM packet, a descrambler configured to descramble the scrambled video stream based on the descrambling control data, and a DMB video decoder configured to obtain a video source by decoding the descrambled video stream, wherein the demultiplexer retrieves the ECM packet by analyzing the mapping table. programs or PMT (for "a Program Map Table").

According to yet another aspect of the present invention, a method of sending an ECM by a terrestrial DMB transmission system supporting conditional access is provided. The method includes generating information regarding a transfer cycle and an amount of the ECM relating to access rights to a DMB service, calculating a number of flows necessary to send the ECM based on the information about the ECM transfer cycle and quantity, the generation of as many null packets as the number of calculated flows, and the generation of an ECM packet by inserting the ECM into a payload supplied to the ECM. inside a transport stream (TS) for the null packet. 4. LIST OF FIGURES FIG. 1 shows an embodiment of a DMB transmission system to which the present invention is applied; Fig. 2 shows an embodiment in which an ECM is inserted into a null packet according to the present invention; Figure 3 shows an embodiment of a DMB receiving terminal to which the present invention is applied; Fig. 4 shows a method of the DMB transmission system sending a conditional access message according to the present invention; and Fig. 5 shows a method of the DMB receiving terminal receiving a conditional access message according to the present invention. DETAILED DESCRITPTION Hereinafter, in this specification, some exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in assigning reference numbers to elements in the drawings, the same reference numbers designate the same elements in all the drawings, even in cases where the elements would be represented in different drawings. On the other hand, in the description of the embodiments of the present invention, a detailed description of the known functions and constitutions will be omitted if it is judged that it would render the essence of the present invention unnecessarily vague. Fig. 1 shows an embodiment of a DMB transmission system to which the present invention is applied. Referring to FIG. 1, the digital multimedia broadcasting transmission system, DMB, comprises a DMB video encoder 110, a conditional access system server, CAS, 120, a DMB video scrambler 130 and a DMB multiplexer 140. The DMB video encoder 110 receives a video source and generates a video stream by encoding the received video source according to a predetermined standard. The CAS server 120 generates information about the transfer cycle and the amount of a conditional access message and sends the generated information to the DMB video scrambler 130. Information about the transfer cycle and the amount of the message conditional access can be determined by the DMB video scrambling font.

The DMB video scrambler 130 calculates the number of MPEG-2 streams necessary to send a conditional access message based on the received information regarding the transfer cycle and the amount of the conditional access message and requests the number of MPEG streams. -2 in the DMB video coder 110. In this case, the video scrambler DMB 130 calculates the number of MPEG-2 streams taking into consideration the output of the DMB video coder 110. For example, the output of the DMB video coder 110 can understand an MPEG-2 stream of a unit of 204 bytes. The DMB video scrambler 130 may also calculate the number of streams corresponding to the amount of a conditional access message (e.g. ECM) in the same unit taking into account the MPEG-2 stream of a 204 unit. bytes. Here, the request for flows can be done automatically or can be done manually. The DMB video encoder 110 generates as many null packets as the number of MPEG-2 streams requested by the DMB video scrambler 130 and sends the null packets to the DMB video scrambler 130 together with a video stream. If the DMB video encoder 110 comprises null packets larger than the number of MPEG-2 streams requested by the DMB video scrambler 130, the DMB video encoder 110 may disregard the request. If the DMB video encoder 110 comprises null packets smaller than the number of MPEG-2 streams requested by the DMB video scrambler 130, the DMB video encoder 110 further generates insufficient null packets.

The DMB video scrambler 130 can insert a conditional access message into the generated null packets as numerous as the number of MPEG-2 streams. Here, the conditional access message may be at least one of the EMM and the ECM. Because the number of streams of a DMB video may be smaller than other media, spaces that can be blocked as null packets may be limited. As a result, the DMB video scrambler 130 can generate ECM packets by inserting in the null packets only the ECM which has a relatively small amount of data and significance. As described above, the DMB video scrambler 130 can actively request the number of packets necessary to insert (and send) a conditional access message without manually depending on the number of video streams received in the delivery of the message. conditional access and insert (send) the conditional access message. It is assumed hereinafter that a conditional access message is the ECM. Fig. 2 shows an embodiment in which an ECM is inserted into null packets according to the present invention. Referring to Figure 2, a transport stream packet (TS) includes a header and a payload. More particularly, the MPEG-2 TS packet can include the 4-byte header and the 184-byte payload. The DMB video scrambler 130 can change the Packet ID (PID) of a null packet so that the ECM is indicated, segment the ECM, and contain the segmented ECM in the load. useful of a corresponding package. Specifically, the DMB video scrambler 130 can generate an ECM packet by inserting the ECM into the payload provided within a transport stream (TS) for the null packet. The header includes a payload start indicator field, a PID field, and a continuity counter field. A PID value contained in the header of a null packet can be determined according to standards and can be determined for example as OxIFFF. The DMB video scrambler 130 modifies (or sets) the PID value of a null packet necessary to insert ECM data at (or at) a PID value for an ECM packet. If the PID of a TS packet indicates "null" (i.e. OxIFFF), it may be called a null packet. If the PID of a TS packet indicates an ECM, it can be called an ECM packet. On the other hand, in a null packet, a payload start indicator field indicative of the start position of a payload is set to 0. If an ECM packet starts first, the video scrambler DMB 130 sets the payload unit start indicator field of the ECM packet to 1 and sets the payload unit start indicator fields of the remaining ECM packets to 0. Accordingly, the beginning of the payload unit start flag fields of the ECM packets remains at 0. ECM packets can be indicated. Also, although a continuity counter field is not defined in the header of a null packet, in the case of an ECM packet, the video scrambler DMB 130 may define a counter field of Continuity in the header of each ECM packet and increase the continuity counter value by 1 for each ECM packet. As a result, it is possible to check whether a packet is lost or not halfway. For example, a value of the continuity counter field of the first ECM packet may be set to 1, a value of the continuity counter field of the second ECM packet may be set to 2, a value of the continuity counter field of a The umpteenth ECM packet can be set to n, and a value of the continuity counter field of a subsequent ECM packet can be set to "n + 1". The DMB video scrambler 130 may perform the method of inserting an ECM packet in place of a null packet by modifying (or overwriting) a null packet into an ECM packet as described above or may perform the method generating an ECM packet having the above format and replacing a null packet with the generated ECM packet. Information (eg, a PID value) about an ECM packet inserted as described above is defined in a Program Map Table (PMT) according to MPEG-2 system standards. If a broadcast is transmitted and received using MPEG-2, program-specific information (PSI) is used. PSIs include a Program Association Table (PAT), a Program Map Table (PMT), a Network Information Table (NIT), and a table. conditional access table (CAT). Here, the PAT includes the PIDs of all programs and the PMT includes information about the video PID and the audio PID of a corresponding program. The NIT includes information about a physical network parameter, such as an FDM frequency or the number of transponders. The CAT includes information regarding the PID of an EMM or conditional access parameters for control and conditional access. In a method of defining ECM packet information in the PMT, the ECM packet may be defined in an additional flow type and information about the ECM packet may be described or may be represented as related data in information of the ECM packet. video stream.

Referring again to FIG. 1, the DMB video scrambler 130 scrambles the received video stream. In this case, the DMB video scrambler 130 may scramble the video stream based on a conditional word contained in the ECM.

The DMB video scrambler 130 transfers the scrambled video stream and the ECM packet to the DMB multiplexer 140. The DMB multiplexer 140 generates a multiplexed frame by multiplexing the scrambled video stream and the ECM packet. At the same time, the DMB 100 video decoder can generate a data stream as well as the video stream. Specifically, the DMB video encoder 110 may receive a data source and generate a data stream based on the data source. In this case, the video scrambler DMB 130 may scramble each of the video stream and the data stream based on the conditional word contained in the ECM. On the other hand, the DMB video multiplexer 140 can generate a multiplexed frame by multiplexing the ECM packet, the scrambled video stream, and the scrambled data stream. A DMB transmission system may provide a video (broadcast) service and (broadcasting) service as separate services or may provide a data service, having a relationship with a video service or a video service dependency, together with a video service. The ECM, that is, a conditional access message, may be provided for each of the video service and the audio service. In this case, the video scrambler DMB 130 may scramble a video stream and a data stream based on respective conditional words contained in the ECMs. In some embodiments, the ECM may be provided jointly for a video service and a data service. In this case, the DMB video scrambler 130 may scramble a video stream and a data stream based on a conditional word contained in a single ECM. As a result, the DMB video scrambler 130 may not insert or send an additional ECM for a data service.

For example, if a DMB transmission system provides a data service having a relationship with a video service and a video service dependency in conjunction with the video service, the DMB video scrambler 130 may scramble a video stream and a data stream on a video service. the basis of a conditional word contained in an ECM.

Fig. 3 shows an embodiment of a DMB receiving terminal to which the present invention is applied. Referring to FIG. 3, the reception terminal DMB comprises a demultiplexer 310, a client CAS 320, a video descrambler DMB 330 and a video decoder DMB 340. The demultiplexer 310 obtains a scrambled video stream and an ECM packet by demultiplexing a frame 10 multiplexed and extracts an ECM packet by analyzing a PMT. Specifically, the demultiplexer 310 separates the ECM packet and the scrambled video stream from each other by analyzing the PMT. Here, the ECM packet, as described above, is generated by inserting an ECM into a payload provided in a packet transport stream (TS) and information about the ECM packet is defined or contained in the PMT. The demultiplexer 310 transfers the ECM packet to the CAS client 320 and transfers the scrambled video stream to the DMB video descrambler 330. The CAS client 320 parses the ECM packet and generates descrambling control data as a result of the analysis. 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 DMB video decoder 340 obtains a video source by decoding the descrambled video stream.

At the same time, the demultiplexer 310 can obtain both the scrambled video stream and a scrambled data stream by demultiplexing the multiplexed frame. Specifically, the demultiplexer 310 can obtain both the scrambled video stream, the scrambled data stream and the ECM packet by demultiplexing the multiplexed frame. In this case, the descrambler 330 may descramble each of the scrambled video stream and the scrambled data stream based on the descrambling control data. On the other hand, the DMB video decoder 340 can obtain a video source by decoding the descrambled video stream and obtain a data source by decoding the descrambled data stream. Fig. 4 shows a method of the DMB transmission system transmitting a conditional access message according to the present invention. With reference to FIG. 4, the DMB transmission system generates information about the transfer cycle and quantity of an ECM, i.e., a conditional access message, in step 5400. The DMB transmission calculates the number of streams necessary to send the ECM based on the information about the transfer cycle and the amount of the ECM in step 5420. The DMB transmission system generates as many null packets as the number. calculated stream in step 5440. The null packet includes a header and a payload. The DMB transmission system generates an ECM packet by inserting the ECM into a payload provided within a transport stream (TS) for the null packet in step 5460. The DMB transmission system segments the ECM and generates the ECM packet by inserting the ECM into the payload of the null packet. The ECM packet header includes a PID field, a payload start indicator field, and a continuity counter field. In this case, the PID field can be set as a PID value for the ECM packet. In addition, a value of the payload unit start indicator field of the first ECM packet may be set and payload unit start indicator field values of the remaining ECM packets, other than the first ECM packet can be set to 0. In addition, a value of the continuity counter field can be set so that it is increased by 1 according to the order of each ECM packet. Here, information (for example a PID) about the ECM packet can be set in the PMT.

In addition, the DMB transmission system can generate a video stream. The DMB transmission system may scramble the video stream based on a conditional word contained in the ECM. The DMB transmission system generates a multiplexed frame by multiplexing the ECM packet and the scrambled video stream. The PMT can be contained in the multiplexed frame. At the same time, the DMB transmission system may scramble a data stream in addition to the video stream and may scramble each of the video stream and the data stream based on a conditional word contained in the ECM. In this case, the DMB transmission system can generate a multiplexed frame by multiplexing the ECM packet, the scrambled video stream and the scrambled data stream. Fig. 5 shows a method of the DMB receiving terminal receiving a conditional access message according to the present invention. Referring to FIG. 5, the receiving terminal DMB obtains a scrambled video stream, an ECM packet, and a PMT by demultiplexing a multiplexed frame in step 5500. As described above, the ECM packet is generated by inserting the ECM in a payload provided in a packet transport flow (TS) 20, and ECM packet information is defined (or contained) in the PMT. The DMB receiving terminal can distinguish the ECM packet from the scrambled video stream by analyzing the PMT. The DMB receiving terminal generates descrambling control data based on the ECM packet in step 5520. The DMB receiving terminal descrambles the scrambled video stream based on the descrambling control data in step 5540.

The DMB receiving terminal obtains a video source by decoding the descrambled video stream in step 5560. At the same time, the DMB receiving terminal can obtain a scrambled data stream in addition to the scrambled video stream by demultiplexing the multiplexed frame. Specifically, the DMB receiving terminal can obtain the scrambled video stream, the scrambled data stream, and the ECM packet by demultiplexing the multiplexed frame. In this case, the receiving terminal DMB can descramble each of the scrambled video stream and the scrambled data stream based on the descrambling control data. On the other hand, the DMB receiving terminal can obtain a video source by decoding the descrambled video stream and obtain a data source by decoding the descrambled data stream. In accordance with the method described above, the DMB transmission system can calculate the number of packets needed and effectively insert an ECM based on the number of packets computed, without depending on the amount of video streams inputted to the scrambler. Furthermore, in accordance with the present invention, there is an advantage in that compatibility with the existing MPEG-2 (Motion Picture Expert Group) system standard is maintained because an ECM can be inserted instead of packets. nulls generated from an encoder.

While some exemplary embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art can change and modify the present invention in various ways without departing from the essential feature of the present invention. Accordingly, the embodiments described should not be construed as limiting the technical spirit of the present invention, but should be interpreted as illustrating the technical spirit of the present invention. The scope of the technical spirit of the present invention is not limited by the embodiments and the scope of the present invention is to be construed on the basis of the claims appended hereto. Accordingly, the present invention is to be understood as covering all modifications or variations arising from the meaning and scope of all the appended claims and their equivalents.

Claims (14)

REVENDICATIONS1. A terrestrial multimedia digital broadcast transmission system supporting conditional access, comprising: a conditional access system server (120) configured to generate a transfer cycle and a quantity of an access control message relating to rights of access to a digital multimedia broadcasting service; a multimedia digital broadcast video scrambler (130) configured to calculate a number of streams necessary to send the title check message based on information about the transfer cycle and the amount of the title control message; access; and a digital multimedia broadcast video encoder (110) configured to generate as many null packets as the number of calculated streams, wherein the multimedia digital broadcast video scrambler generates an access control message packet by inserting the access title control message in a payload provided within a transport stream for the null packet. A terrestrial digital multimedia broadcasting transmission system according to claim 1, wherein: the multimedia digital broadcast video encoder (110) generates a video stream, the multimedia digital broadcast video scrambler (130) scrambles the video stream on the basis of a conditional word contained in the access control message; and the transmission system further comprises a multimedia digital broadcast video multiplexer (140) configured to generate a multiplexed frame by multiplexing the access title control message packet and the scrambled video stream. The terrestrial multimedia digital radio transmission system according to claim 1, wherein: the multimedia digital broadcast video encoder (110) generates a video stream and a data stream, the multimedia digital broadcast video scrambler (130) scrambles each of the video stream and the data stream on the basis of a conditional word contained in the access control message; And the transmission system further comprises a multimedia digital broadcast video multiplexer (140) configured to generate a multiplexed frame by multiplexing the access control message packet, the scrambled video stream, and the scrambled data stream. . The terrestrial multimedia digital radio transmission system according to claim 1, wherein the multimedia digital broadcast video scrambler (140) defines information about the title check message packet in a program mapping table. . The terrestrial multimedia digital radio transmission system according to claim 1, wherein: the access control message packet contains a header and the payload, and the multimedia digital broadcast video scrambler ( 140) segments the control message of 10 access titles and inserts the segmented title control message into the payload. The terrestrial multimedia digital radio transmission system according to claim 5, wherein: the header contains a packet identifier field a payload start indicator field and a counter field continuity, and the digital multimedia broadcast video scrambler (140) sets the packet identifier as a value of the packet identifier for the access control message packet, sets a value of 1 to payload unit start indicator field in a first access control message packet, set at 0 payload start indicator field values in remaining packets of access title control message, other than the first access control message packet, and sets a value of the continuity counter field so that the value is increased by 1 depending on the order of each package uet access control message. 7. A terrestrial multimedia digital broadcast reception terminal supporting conditional access, comprising: a demultiplexer (310) configured to obtain a scrambled video stream, an access title control message packet generated by inserting a control message of access titles in a payload provided within a transport stream for a null packet, and a program mapping table in which information about the access control message packet is defined by demultiplexing a multiplexed frame; a conditional access system client (320) configured to generate descrambling control data based on the access control message packet; a descrambler (330) configured to descramble the scrambled video stream based on the descrambling control data; and a multimedia digital broadcast video decoder (340) configured to provide a video source by decoding the descrambled video stream, wherein the demultiplexer (310) extracts the access control message packet by analyzing the data table. mapping of programs. The terrestrial digital multimedia broadcasting receiving terminal according to claim 7, wherein: the demultiplexer (310) obtains a scrambled data stream by demultiplexing the multiplexed frame, the descrambler (330) descrambles the scrambled data stream on the base descrambling control data, and the multimedia digital broadcast video decoder (340) obtains a video source by decoding the descrambled data stream. A method of sending an access control message by a terrestrial multimedia digital broadcast transmission system supporting conditional access, the method comprising: generating (S400) information relating to a broadcast cycle; transfer and a quantity of the access control message relating to rights of access to a digital multimedia broadcasting service; Calculating (S420) a number of streams necessary to send the entitlement check message based on information about the transfer cycle and the amount of the access control message; Generating (S440) as many null packets as the number of calculated streams; and generating (S460) an access title control message packet by inserting the access control message into a payload provided within a transport stream for the null packet. . The method of claim 9, further comprising: generating a video stream; scrambling the video stream based on a conditional word contained in the access control message; and generating a multiplexed frame by multiplexing the access control message packet and the scrambled video stream. The method of claim 9, further comprising: generating a video stream and a data stream; scrambling each of the video stream and the data stream based on a conditional word contained in the access control message; and generating a multiplexed frame by multiplexing the access control message packet, the scrambled video stream, and the scrambled data stream. The method of claim 9, wherein the information about the access control message packet is contained in a program mapping table. The method of claim 9, wherein: the access control message packet contains a header and a payload, and the transmission system segments the access control message and inserts the segmented title control message segmented into the payload. The method of claim 13, wherein: the header of the access control message packet contains a packet identifier field a payload start indicator field and a continuity counter field, the packet identifier is set as a value of the packet identifier for the title control message packet, a value of the unit of charge start flag field useful in a first access control message packet is set to 1, payload start indicator field values in remaining access control message packets, other that the first access control message packet, are set to 0, and a value of a continuity counter field is set so that the value is increased by 1 according to the order of each access control message packet. 20