WO2012024921A1

WO2012024921A1 - Method and device for descrambling media data blocks

Info

Publication number: WO2012024921A1
Application number: PCT/CN2011/072116
Authority: WO
Inventors: 郭世亮; 肖龙安
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-08-23
Filing date: 2011-03-24
Publication date: 2012-03-01
Also published as: CN101917589A

Abstract

A method and device for descrambling media data blocks are provided, and the method includes the following steps: control words from a conditional access system are received by a descrambling module; the control words are saved by the descrambling module; media data blocks from a demultiplexing module are received by the descrambling module; and the media data blocks are descrambled by the descrambling module with the saved control words. The play of program stream is ensured by the present invention.

Description

The present invention relates to the field of communications, and in particular to a method and apparatus for media data block solution. BACKGROUND OF THE INVENTION In recent years, digital mobile multimedia broadcasting technologies, especially mobile TV technologies, have developed rapidly. Various television standards provide mobile multimedia broadcast terminal users with rich and colorful content, such as news, sports programs, variety shows, TV dramas, and movies. You can choose the service program of mobile multimedia broadcasting in your own hobby. Content operators often provide paid multimedia broadcast services in order to sustain the benefits of broadcast operations. This requires adding 4 special programs to the program stream. Only users who have been authorized to watch the program can watch the program. After the user is authorized, the program stream is received, and then the program stream is descrambled before being played. In order to use the mobile data service anytime and anywhere, the user needs to add a broadcast signal receiving chip to the receiving terminal (hereinafter referred to as the terminal), thereby realizing multimedia playback and being inexpensive, and is a popular receiving terminal. 1 is a schematic diagram of a mobile multimedia broadcast scheme (terminal) according to the related art. As shown in FIG. 1, a terminal supporting a mobile multimedia broadcast function includes at least a media broadcast module and a player module. The media broadcast module is composed of a receiving and demodulating chip, a demultiplexing module, a descrambling module, and a Conditional Access System (CAS). The player module generally refers to a player on a terminal such as a personal computer, a personal digital assistant (PDA), and a mobile phone. Specifically, the receiving and demodulating chip is responsible for receiving and demodulating the digital broadcast signal, and after obtaining the data frame, the demultiplexing module demultiplexes the media data block and the 4 authorized control information (Entitlement Control Message, referred to as ECM), then send the ECM to the CAS module, and send the scrambled media data block to the solution 4 module; · ί Entitlement Management Message (EMM) can be transmitted in the broadcast channel or through interaction Channel transmission (shown in Figure 1 is transmitted through the interactive channel) to the CAS, the CAS module calculates the control word (Control Word, referred to as CW) according to the EMM/ECM, and solves the media data block of the 4th module after obtaining the CW. De-scrambling is performed, and the stream is cleared and transmitted to the player module, and the player module decodes and plays the clear stream. Both the media data block and the ECM are delivered via the broadcast channel. For the purpose of key rotation, the key stream generally carries two keys at a time, that is, one ECM packet contains two CWs, one for solving the media data block of the current moment, and one for solving the solution. The media data block at the next moment. At present, the general policy of the terminal is: Save two keys at the same time, and update the local key in time as the key of the code stream is updated. After the descrambling module of the terminal obtains the CW, it first needs to synchronize the media data block and the CW to correctly solve the 4th. 2 is a schematic diagram of synchronization of a key stream and a media stream according to the related art. As shown in FIG. 2, a key stream is represented by a Key stream, and a media stream is represented by an A/V stream. Since the key synchronization mechanism of the terminal is synchronized with the code stream at any time, the Key stream is actually the key stream held by the terminal. Kl and Κ2 in the key stream respectively represent the first control word and the second control word, and are placed in a box to indicate that one ECM packet contains two CWs. K1 in the media stream indicates that the media block must be descrambled with the first control word, and descrambling with other control words will fail. However, in the actual system, the ideal situation in which the key stream shown in FIG. 2 is synchronized with the media stream is basically not seen. The reason is that the terminal uses the streaming media player, first buffers a certain media stream, and starts descrambling until before playing, which causes the key stream to be advanced compared to the media stream. 3 is a schematic diagram of a key stream in advance according to a related art, in which a media block is desperately represented by a shadow, and the remaining parameters are defined in the same manner as in FIG. 2. As shown in FIG. 3, in the case where the key stream is advanced compared to the media stream, if the media data block is descrambled, the appropriate CW will not be found, that is, the key is out of synchronization. Loss of key will cause descrambling to fail, and will cause serious problems such as splashing, pause, and even play during playback. SUMMARY OF THE INVENTION The present invention has been made in view of the problem that the descrambling of a media data block caused by a key out of synchronization in the related art fails, which will result in the program stream being unplayable. Therefore, the main object of the present invention is to provide a media data block solution. In particular, methods and devices are used to solve the above problems. In order to achieve the above object, according to an aspect of the present invention, a media data block descrambling method is provided. The media data block descrambling method according to the present invention includes: the descrambling module receives the control word from the conditional receiving system; the descrambling module saves the control word; the descrambling module receives the media data block from the demultiplexing module; the descrambling module The media data block is descrambled using the saved control word. The descrambling module saves the control word including: The descrambling module saves the control word to the control word database in the descrambling module. The descrambling module uses the saved control word to descramble the media data block. The descrambling module searches the control word database for the presence of a control word corresponding to the media data block. If the search result is yes, the used control word is used. , descramble the media data block. Before the solution 4 receives the control word from the conditional receiving system, the method further includes: the demultiplexing module receiving the data frame from the receiving and demodulating chip; and the demultiplexing module demultiplexing the data frame to obtain the authorization control information The demultiplexing module transmits the authorization control information to the conditional receiving system; the conditional receiving system receives the authorization management information; and the conditional receiving system uses the authorization control information and the authorization management information to calculate the control word. Before the descrambling module receives the media data block from the demultiplexing module, the method further includes: the demultiplexing module receives the data frame from the receiving and demodulating chip; and the demultiplexing module demultiplexes the data frame to obtain the media data. Piece. After the descrambling module uses the saved control word to descramble the media data block, the method further includes: the descrambling module sends the descrambled media data block to the player module; and the player module pairs the descrambled media data The block is decoded and played. In order to achieve the above object, according to another aspect of the present invention, a media block descrambling apparatus is provided. A media data block descrambling apparatus according to the present invention includes: a first receiving unit configured to receive a control word from a conditional receiving system; a saving unit configured to save a control word; and a second receiving unit configured to receive from the demultiplexing module Media data block; descrambling unit, set to use the saved control word to descramble the media data block. The media data block solution 4 device further includes a control word database, and the saving unit comprises: a saving subunit, configured to save the control word to the control word database. The descrambling unit includes: a lookup subunit, configured to search in the control word database for whether there is a control word corresponding to the media data block; and a descrambling subunit, configured to use the searched control word when the search result is yes, Deblock the media data block. The media data block descrambling device further includes: a sending unit, configured to send the descrambled media data block to the player module, so that the player module decodes and plays the descrambled media data block. Through the invention, the descrambling module saves the control word, and uses the saved control word to descramble the media data block, thereby solving the problem that the descrambling failure is caused by the key out of synchronization in the related art, thereby ensuring the playback of the program stream. . BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set to illustrate,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, In the drawings: FIG. 1 is a schematic diagram of a mobile multimedia broadcast scheme (terminal) according to the related art; FIG. 2 is a schematic diagram of key stream synchronization with a media stream according to the related art; FIG. 3 is a key stream phase according to the related art. FIG. 4 is a schematic diagram of a mobile multimedia broadcast scheme (terminal) according to an embodiment of the present invention; FIG. 5 is a flowchart of a media data block descrambling method according to an embodiment of the present invention; FIG. 7 is a flowchart of a key synchronization method according to a preferred embodiment of the present invention; FIG. 8 is a flowchart of a key synchronization method according to a preferred embodiment of the present invention; FIG. A block diagram of a media block descrambling apparatus of an example; FIG. 9 is a block diagram showing the structure of a media block descrambling apparatus according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. The invention will be described in detail below with reference to the drawings in conjunction with the embodiments. FIG. 4 is a schematic diagram of a mobile multimedia broadcast solution (terminal) according to an embodiment of the present invention. As shown in FIG. 4, it includes two parts: a media broadcast module and a player module. Among them, the number of media broadcast modules The word broadcast signal receiving and demodulating chip, the demultiplexing sub-module, the descrambling sub-module, and the CAS sub-module are composed. The improvement of the scheme is that a control word database for locally storing control words is added to the descrambling sub-module. The present invention provides a media data block descrambling method, which can be implemented based on the mobile multimedia broadcast scheme (terminal) shown in FIG. FIG. 5 is a flowchart of a method for descrambling a media block according to an embodiment of the present invention, including steps S502 to S508. Step S502, the descrambling module receives the control word from the conditional access system. In step S504, the solution 4 saves the control word. Step S506, the descrambling module receives the media data block from the demultiplexing module. Step S508, the descrambling module uses the saved control word to descramble the media data block. In the related art, the key out of synchronization will cause the descrambling of the media data block to fail. In the embodiment of the present invention, the control word used for decoding the media data block is saved, so that the media data block can be correctly decoded, thereby ensuring the play of the program stream. 6 is a schematic diagram of a key stream not causing a key out of synchronization in advance of a media stream according to an embodiment of the present invention. As can be seen from comparison with FIG. 3, since the key stream contains more keys, This ensures correct decoding of the media data blocks. Preferably, the descrambling module saves the control word comprising: the descrambling module saves the control word to a control word database in the descrambling module. In the preferred embodiment, a control word database for locally storing the control word is added, and the control word for decoding the media data block is saved in the control word database, which can further ensure that the media data block is correctly decoded. , in order to ensure the playback of the program stream. Moreover, the control word database is used to save the control word, and the implementation is simple and reliable. It should be noted that the number of locally saved control words should exceed the number of CWs (usually 2) included in one ECM in order to meet the descrambling requirements of the terminal. Preferably, the solution 4 uses a saved control word, and the solution 4 of the media data block includes: the descrambling module searches the control word database for whether there is a control word corresponding to the media data block; if the search result is yes, The media data block is descrambled using the lookup control word. The preferred embodiment describes a process for solving a block of media data using control words stored in a control word database. By finding the control word corresponding to the media data block, it is ensured that the media data block is correctly decoded, thereby ensuring the playback of the program stream. Preferably, before the descrambling module receives the control word from the conditional receiving system, the demultiplexing module receives the data frame from the receiving and demodulating chip; the demultiplexing module demultiplexes the data frame to obtain the authorization control information; The module transmits the authorization control information to the conditional receiving system; the conditional receiving system receives the authorization management information; and the conditional receiving system uses the authorization control information and the authorization management information to calculate the control word. The preferred embodiment describes a process for understanding a multiplexing module to calculate a control word, which is similar to the prior art, and can be used in various multimedia encryption protocols, various player applications without modification, and has good scalability. , debuggability and wide adaptability. Preferably, before the solution 4 module receives the media data block from the demultiplexing module, the demultiplexing module receives the data frame from the receiving and demodulating chip; the demultiplexing module demultiplexes the data frame to obtain the media data block. . The preferred embodiment describes a process for the multiplexing module to demultiplex a data frame to obtain a media data block. The implementation manner is similar to that in the prior art, and can be used in various multimedia encryption protocols and various player applications without modification. It has good scalability, debugability and wide adaptability. Preferably, after the descrambling module uses the saved control word to descramble the media data block, the descrambling module sends the descrambled media data block to the player module; and the player module performs the descrambled media data block. Decode and play. The preferred embodiment describes a process in which the player module decodes and plays the descrambled media data block, and the implementation manner is similar to that in the prior art, and can be used in various multimedia encryption protocols and various players without modification. In the application, it has good scalability, debugability and wide adaptability. The implementation process of the embodiment of the present invention will be described in detail below with reference to examples. FIG. 7 is a flowchart of a key synchronization method according to a preferred embodiment of the present invention. As shown in FIG. 7, the following steps S702 to S710 are included. Step S702, receiving and demodulating the chip to receive the signal to obtain a data frame, and sending the data frame to the demultiplexing module. Step S704, the demultiplexing module solves the ECM and sends the ECM to the CAS, and the decoded media data block is sent to the descrambling module. Step S706, the CAS calculates the CW according to the EMM of the outband transmission and the ECM that has been received, and then transmits the CW to the descrambling module. Step S708, the descrambling module first saves the CW to the CW DB, and then according to the media data block.

Find the correct CW in the CW DB, according to this CW 4 Baben data block solution 4 especially clear stream. Step S710, the player module decodes and plays the clear stream. It should be noted that the steps shown in the flowchart of the accompanying drawings may be performed in a computer system such as a set of computer executable instructions, and, although the logical order is shown in the flowchart, in some cases, The steps shown or described may be performed in an order different than that herein. The embodiment of the present invention provides a media data block descrambling device, and the media data block descrambling device can be used to implement the foregoing media data block descrambling method. FIG. 8 is a structural block diagram of a media block descrambling apparatus according to an embodiment of the present invention, including a first receiving unit 82, a saving unit 84, a second receiving unit 86, and a solution unit 88. The structure is described in detail below. a first receiving unit 82, configured to receive a control word from the conditional receiving system;

84, connected to the first receiving unit 82, configured to save the control word received by the first receiving unit 82; the second receiving unit 86 is configured to receive the media data block from the demultiplexing module; The saving unit 84 and the second receiving unit 86 are arranged to descramble the media data block received by the second receiving unit 86 using the control word held by the saving unit 84. In the related art, the key out of synchronization will cause the descrambling of the media data block to fail. In the embodiment of the present invention, the control word used for decoding the media data block is saved, so that the media data block can be correctly decoded, thereby ensuring the play of the program stream. 9 is a block diagram showing the structure of a media block descrambling apparatus in accordance with a preferred embodiment of the present invention. Preferably, the media data block solution device further includes a control word database, and the saving unit 84 includes a saving subunit 842 connected to the first receiving unit 82, and configured to save the control word received by the first receiving unit 82 to the control word database. In the preferred embodiment, a control word database for locally storing the control word is added, and the control word for decoding the media data block is saved in the control word database, which may be further Ensure that the media data block is correctly decoded to ensure the playback of the program stream. Moreover, the control word database is used to save the control word, and the implementation is simple and reliable. It should be noted that the number of locally saved control words should exceed the number of CWs (usually 2) included in one ECM in order to meet the descrambling requirements of the terminal. Preferably, the solution unit 88 includes: a lookup subunit 882 and a solution 4 subunit 884, the structure of which is described in detail below. The lookup subunit 882 is connected to the saving unit 84 and the second receiving unit 86, and is arranged to look up in the control word database held by the saving subunit 842 included in the saving unit 84 whether there is a corresponding corresponding to the media data block received by the second receiving unit 86. The control word; the solution 4 sub-unit 884, connected to the lookup sub-unit 882, is set to descramble the media data block using the searched control word if the lookup sub-unit 882 looks for a yes result. The preferred embodiment describes a process for solving a block of media data using control words stored in a control word database. By finding the control word corresponding to the media data block, it is ensured that the media data block is correctly decoded, thereby ensuring the playback of the program stream. Preferably, the media data block solution 4 device further includes a sending unit 89 connected to the solution 4 unit 88, and configured to send the media data block descrambled by the descrambling unit 88 to the player module, so that the player module pairs the solution 4 In particular, the media data block of the unit 88 is decoded and played. The preferred embodiment describes a process in which the player module decodes and plays the descrambled media data block, and the implementation manner is similar to that in the prior art, and can be used in various multimedia encryption protocols and various players without modification. In the application, it has good scalability, debugability and wide adaptability. It should be noted that the media data block descrambling device described in the device embodiment corresponds to the foregoing method embodiment, and the specific implementation process has been described in detail in the method embodiment, and details are not described herein again. In summary, according to the above embodiments of the present invention, a media data block descrambling method and apparatus are provided. The descrambling module saves the control word, and uses the saved control word to descramble the media data block, thereby solving the problem that the descrambling failure is caused by the key out of synchronization in the related art, thereby ensuring the playback of the program stream. It should be noted that the above methods are applicable to various terminal players and various descrambling algorithms.

ISMACryp (Internet Streaming Media Alliance Encryption and Authentication), Secure Real-time Transport Protocol (SRTP), and IPsec (IP Security) are all effective. Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general-purpose computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device, such that they may be stored in the storage device by the computing device, or they may be separately fabricated into individual integrated circuit modules, or they may be Multiple modules or steps are made into a single integrated circuit module. Thus, the invention is not limited to any particular combination of hardware and software. The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the scope of the present invention are intended to be included within the scope of the present invention.

Claims

A media data block solution method includes: a descrambling module receives a control word from a conditional access system;

The descrambling module saves the control word;

The descrambling module receives a media data block from the demultiplexing module;

The descrambling module descrambles the media data block using the saved control word. The method according to claim 1, wherein the descrambling module saves the control word includes:

The descrambling module saves the control word to a control word database in the descrambling module. The method according to claim 2, wherein the descrambling module uses the saved control word to descramble the media data block, including:

The descrambling module searches the control word database for whether there is a control word corresponding to the media data block;

If the result of the search is yes, the media data block is solved using the searched control word. The method according to any one of claims 1 to 3, wherein before the descrambling module receives the control word from the conditional access system, the method further comprises: the demultiplexing module Receiving data frames from the receiving and demodulating chip;

The demultiplexing module demultiplexes the data frame to obtain authorization control information; the demultiplexing module sends the authorization control information to the conditional receiving system; and the conditional receiving system receives the authorization management information;

The condition receiving system calculates the control word using the authorization control information and the authorization management information.

The method according to any one of claims 1 to 3, wherein, before the descrambling module receives the media data block from the demultiplexing module, the method further includes: The demultiplexing module receives the data frame from the receiving and demodulating chip; the demultiplexing module demultiplexes the data frame to obtain the media data block.

The method according to any one of claims 1 to 3, wherein after the descrambling module performs the solution 4 on the media data block by using the saved control word, the method further includes :

The descrambling module sends the descrambled media data block to the player module; the player module decodes and plays the descrambled media data block.

7. A media data block descrambling device, comprising:

a first receiving unit configured to receive a control word from the conditional receiving system; a saving unit configured to save the control word;

a second receiving unit, configured to receive a media data block from the demultiplexing module; and a descrambling unit configured to descramble the media data block using the saved control word.

The media data block descrambling device according to claim 7, wherein the media data block descrambling device further comprises a control word database, and the saving unit comprises:

A save subunit is arranged to save the control word to the control word database.

9. The media block descrambling apparatus according to claim 8, wherein the descrambling unit comprises:

Locating a subunit, configured to look in the control word database whether there is a control word corresponding to the media data block;

The descrambling subunit is arranged to descramble the media data block using the searched control word if the search result is YES.

The media data block descrambling device according to any one of claims 7 to 9, further comprising: The sending unit is configured to send the descrambled media data block to the player module, so that the player module decodes and plays the descrambled media data block.