CN107396153B

CN107396153B - Channel switching method and device

Info

Publication number: CN107396153B
Application number: CN201710655413.7A
Authority: CN
Inventors: 汪桂兰
Original assignee: Hisense Visual Technology Co Ltd
Current assignee: Hisense Visual Technology Co Ltd
Priority date: 2017-08-03
Filing date: 2017-08-03
Publication date: 2020-05-12
Anticipated expiration: 2037-08-03
Also published as: CN107396153A

Abstract

The application provides a channel switching method and a channel switching device, which are applied to a digital television, wherein the digital television is connected with a CAM card for descrambling television programs, and the method comprises the following steps: when the digital television plays the scrambled program under a DTV channel, if the digital television is detected to be switched from the DTV channel to other channels, a descrambling stopping instruction is sent to the CAM card, and the descrambling stopping instruction is used for indicating the CAM card to empty descrambling information of the scrambled program. By applying the method, the problem that the user experience is poor due to the fact that a longer audio and video is in a mute state for a long time because the phenomenon of screen splash or screen flashing occurs when the digital television is switched from other channels to a DTV channel can be avoided.

Description

Channel switching method and device

Technical Field

The present application relates to the field of digital television technologies, and in particular, to a channel switching method and apparatus.

Background

A CAM (conditional Access Module) card is a special card with an intelligent card slot for a digital television, which is also called a conditional Access Module or a video card, and is used for connecting the digital television to process a data code stream sent by an external signal source. The basic function of the CAM card is filtering and descrambling, that is, the scrambled data code stream sent by the external signal source is converted into the television content and displayed on the digital television, so that the user can directly watch the ordered paid digital television content without a set-top box.

In the channel switching function commonly used in the digital television at present, the digital television needs to transmit a CA _ PMT table to the CAM card every time the channel is switched, so as to inform the CAM card of which channel data needs to be descrambled. After receiving the CA _ PMT table, the CAM card clears the descrambling information of the previous program, including the control word CW, etc., to start descrambling the new program again. With the diversification of television program signal sources, channel switching is becoming more and more common.

In some scenarios, when a user switches a Digital Television from a DTV (Digital Television) channel to another channel, for example, an HDMI (High Definition Multimedia Interface) channel, the Digital Television simply allocates resources such as a player to the other channel, but the CAM card still retains previous descrambling information and is ready to filter and descramble a received data stream at any time. Then, the subsequent user switches the digital television from another channel to the DTV channel, and if the channel before the channel switching (before the DTV channel is switched to another channel) continues to be played after the channel is switched to the DTV channel, because the channel is not changed, the CAM card immediately filters and descrambles the received data code stream based on the descrambling information retained before the channel switching, and the digital television starts to play the television content. However, in the related protocol, in order to avoid the problem that the CAM card cannot descramble the data stream due to the fact that the CA _ PMT table is not transmitted in some scenes, when the DTV channel is started or occupies the focus again, the digital television will transmit a CA _ PMT table corresponding to the current transmission code stream to the CAM card again, that is, when the digital television is switched from another channel to the DTV channel, the CAM card will receive a CA _ PMT table, and after the CAM card receives the CA _ PMT table, even if the channel corresponding to the CA _ PMT table is the channel played before the channel is switched, the CAM card will consider that the switching operation has occurred, so as to clear the current descrambling information, parse the CA _ PMT table, obtain new descrambling information, to filter and descramble the subsequently received data code stream according to the new descrambling information, and in the whole process, the CAM card receives the data code stream first, and receiving the CA _ PMT table, it can be seen that, after the digital television is switched from the DTV channel to another channel, and then switched back to the DTV channel by another channel, since the channel before switching is continuously played in most application scenes except for individual scenes after being switched back to the DTV channel, the digital television inevitably has a phenomenon that the television is suddenly stopped playing after playing the television content for a moment, and then continuously plays the television content again, that is, the digital television has a phenomenon of screen splash or screen splash.

In order to solve the above problems, in the related art, the audio and video of the digital television may be controlled to be in a mute state, i.e., a state of sound muting and image black screen, within a period of time after the digital television is switched back to the DTV channel from another channel, and after the CA _ PMT table processing to be sent down after being switched back to the DTV channel is finished, the mute state of the audio and video may be cancelled, so as to avoid the above-described screen splash or screen splash phenomenon.

However, controlling the mute state of the audio and video is only a means for avoiding the problem, and does not completely solve the problem of screen splash or screen splash, how to reasonably set the time length of the mute state is difficult to determine in practical application due to various factors, if the 'one-time-length' is short, the screen splash or screen splash described above cannot be avoided, and if the 'one-time-length' is long, namely the audio and video of the digital television is in the mute state for a long time, the user experience will be affected, therefore, in practice, considering various factors such as different types of CAM cards, different system platforms of the digital television, and the like, a long mute state time length is usually set, so that the user experience is very poor.

Disclosure of Invention

In view of this, the present application provides a channel switching method and apparatus, so as to avoid the problem that a longer audio/video mute state duration has to be set to cause poor user experience when a digital television is switched from another channel to a DTV channel, which causes a screen splash or screen flashing phenomenon.

Specifically, the method is realized through the following technical scheme:

according to a first aspect of the embodiments of the present application, there is provided a channel switching method, applied to a digital television to which a CAM card for descrambling a television program is connected, the method including:

when the digital television plays a first scrambled program under a DTV channel, if the digital television is detected to be switched from the DTV channel to other channels, a descrambling stopping instruction is sent to the CAM card, and the descrambling stopping instruction is used for indicating the CAM card to empty descrambling information of the first scrambled program.

According to a second aspect of the embodiments of the present application, there is provided a channel switching method applied to a CAM card for descrambling a television program, the CAM card being connected with a digital television, the method including:

receiving a descrambling stopping instruction, wherein the descrambling stopping instruction is sent when the digital television detects that the digital television is switched from a DTV channel to other channels when a first scrambled program is played under the DTV channel;

clearing descrambling information of the first scrambled program based on the suspend descrambling instruction.

According to a third aspect of the embodiments of the present application, there is provided a channel switching apparatus applied to a digital television to which a CAM card for descrambling a television program is connected, the apparatus including:

the first sending module is used for sending a descrambling stopping instruction to the CAM card if the digital television is detected to be switched from the DTV channel to other channels when the digital television plays a first scrambled program under the DTV channel, wherein the descrambling stopping instruction is used for indicating the CAM card to empty descrambling information of the first scrambled program.

According to a fourth aspect of the embodiments of the present application, there is provided a channel switching apparatus, which is applied to a CAM card for descrambling a television program, where the CAM card is connected with a digital television, the apparatus including:

a first receiving module, configured to receive a descrambling pause instruction, where the descrambling pause instruction is sent when the digital television detects that the digital television switches from a DTV channel to another channel when the digital television plays a first scrambled program in the DTV channel;

and the processing module is used for emptying descrambling information of the first scrambled program based on the descrambling stopping instruction.

It can be seen from the above embodiments that, when the digital television plays the scrambled program in the DTV channel, if it is detected that the digital television is switched from the DTV channel to another channel, the CAM card is sent a descrambling pause instruction, so that the CAM card clears descrambling information of the scrambled program according to the descrambling pause instruction, and it can be realized that, when the digital television is switched back to the DTV channel from the another channel, the CAM card does not store any descrambling information, so as not to descramble the received data code stream, until the CAM card receives the CA _ PMT table corresponding to the current transmission code stream sent by the digital television again, the CAM card descrambles the received data code stream according to the newly received CA _ PMT table, thereby avoiding the phenomenon of screen splash or screen splash when the digital television is switched from another channel to the DTV channel, and having to set a longer time length of the audio/video mute state, causing a problem of poor user experience.

Drawings

Fig. 1 is an exemplary embodiment of a conditional access system 100;

FIG. 2 is a flow chart of an embodiment of a channel switching method of the present application;

FIG. 3 is a flow chart of another embodiment of a channel switching method according to the present application;

FIG. 4 is a flow chart of another embodiment of a channel switching method according to the present application;

FIG. 5 is a block diagram of an embodiment of a channel switching device according to the present application;

fig. 6 is a block diagram of another embodiment of a channel switching device according to the present application.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.

With the development of digital televisions, users face more and more choices of digital television programs, and meanwhile, due to the increase of investment cost, broadcasters charge certain viewing fees to the users. A Conditional access system (CAS system for short) is a system for implementing access control for certain broadcast services, and its main function is to ensure that a user who pays or is about to pay a fee can watch a selected television program.

As shown in fig. 1, a conditional access system 100 is an exemplary embodiment of the conditional access system 100, and the conditional access system 100 illustrated in fig. 1 includes an external signal source 101, a digital television 102, and a CAM card 103 for descrambling television programs. The external signal source 101 may scramble an original data code stream by using a scrambling sequence, scramble data, and then send the scrambled data code stream to the digital television 102; the digital television 102 receives the data code stream, if the received scrambled code stream is detected, the CAM card 103 can be driven to work, a PMT table for describing program information is acquired from the scrambled code stream, the PMT table is analyzed to obtain a CA _ PMT table, the CA _ PMT table is sent to the CAM card 103, the CAM card 103 calls a decryption program according to the CA _ PMT table, the scrambled data is filtered and descrambled, and the original data code stream is recovered, so that the digital television 102 can display television content according to the original data code stream.

For the CA _ PMT table, it is mainly from a PMT (program map table) table in the codestream, and the PMT table is a table transmitted in the codestream for describing program information. One PMT table for each channel, the PMT tables for cctv1 and cctv2 being different. For the PMT table, detailed information of a channel is described in the table, but when a channel is played, the PMT table of the channel is first acquired from a code stream, contents such as pcrpid, audio/video pid, an encryption mode and the like of the channel are analyzed from the PMT table, and an audio/video data packet of the program is filtered according to the audio/video pid and is used for playing after decryption and decoding.

When the content of one channel is played, if the content is an encrypted program, the CAM card needs to be informed to descramble, and the CAM card needs to be informed of the program number, the audio/video pid, the encryption mode and the like of a specific channel during the informing. These information are all in the PMT table, but some information in the PMT table is irrelevant to the CAM card, so generally, the CA _ PMT table sent to the CAM card by the television system is a content format required for reconstructing the PMT table into the CAM card, and how to construct the CA _ PMT table is specific, which is a conventional technical means in the field and is not described in detail herein.

In an application scenario of channel switching of the digital television 102, assuming that the digital television 102 is currently in a DTV channel and is playing a scrambled program, if a user switches the digital television 102 from the DTV channel to an HDMI channel, the digital television 102 only allocates resources such as a player to the HDMI channel, and does not notify the CAM card 103 that the playing of the scrambled program is suspended, the CAM card 103 still retains descrambling information of the scrambled program, where the "descrambling information" may include a descrambling mode, a descrambling key, and the like.

Subsequently, if the user switches the digital television 102 from the HDMI channel back to the DTV channel and still plays the channel played before switching from the DTV channel to the HDMI channel, if the front-end operator does not modify the scrambling mode of the data code stream on the channel, the CAM card 103 descrambles the received data code stream immediately based on the retained descrambling information, so that the digital television 102 starts playing the television content. However, in the related protocol, in order to avoid the problem that the CAM card cannot descramble without transmitting the CA _ PMT table in some scenarios, when the DTV channel starts up or occupies the focus again, the digital television will re-transmit a CA _ PMT table corresponding to the current transmission code stream to the CAM card, that is, when the user switches the digital television 102 from the HDMI channel back to the DTV channel, the digital television 102 will re-transmit a CA _ PMT table to the CAM card 103. After the CAM card 103 receives the retransmitted CA _ PMT table, although the channel corresponding to the retransmitted CA _ PMT table is not changed, the CAM card still considers that the channel switching operation has occurred, so that the CAM card clears the current descrambling information and acquires corresponding descrambling information according to the retransmitted CA _ PMT table, so as to descramble the subsequently received data code stream.

In fact, after the CAM card receives the CA _ PMT table, the required data are filtered, and a CW control word is obtained through a certain mechanism, wherein the CW control word is used for scrambling audio and video data and can be used for descrambling the audio and video data. The CW control word is different in different frequency channels, the CW control word of the same frequency channel is continuously changed, for different encryption systems, the change period of the CW control word is different or is cyclically used, which mainly depends on the encryption system of an operator, but in the current common scrambling field, the scrambling information on the same frequency channel generally does not have large change. Therefore, when we switch from one channel and back, the same CW control word may also be used to descramble the data code stream, but in order to avoid that, in some scenarios, before and after channel switching, the CW control word actually available for descrambling changes, usually when the channel is switched back, a new CW control word is obtained again according to the currently received data code stream.

In the above-described whole process, the CAM card receives the data code stream first, and then receives the re-transmitted CA _ PMT table, so that in the process of switching the digital television 102 from the HDMI channel to the DTV channel, the digital television 102 suddenly stops playing after playing the television content for a moment, and then continues to play the television content again, that is, the digital television 102 appears a splash screen or a splash screen, thereby affecting the user experience.

It should be noted that the above-described switching of the digital television 102 between the DTV channel and the HDMI channel is only an example, and in practical applications, when the digital television 102 switches between the DTV channel and other non-DTV channels according to the above-described procedure, for example, the ATV channel, the AV channel, the component channel, and the like, a splash screen or a splash screen phenomenon occurs.

In order to solve the above problems, in the related art, the audio and video of the digital television can be controlled to be in a mute state, i.e., a state of sound muting and image black screen, within a period of time after the digital television is switched back to the DTV channel from other channels, and after the CA _ PMT table processing to be sent back to the DTV channel is finished, the mute state of the audio and video is cancelled.

Based on the above, the application provides a channel switching method and device, and by applying the method, the problem that the user experience is poor due to the fact that a longer audio/video duration in a mute state has to be set because the phenomenon of screen splash or screen splash occurs when the digital television is switched from other channels back to a DTV channel can be avoided.

As follows, the channel switching method proposed in the present application is described from the perspective of the digital television 102 and the CAM card 103, respectively, in conjunction with the conditional access system 100 illustrated in fig. 1:

first, description is made from the perspective of the digital television 102:

referring to fig. 2, a flowchart of an embodiment of a channel switching method according to the present application is shown, where the method may be applied to the digital television 102 illustrated in fig. 1, as shown in fig. 1, the digital television 102 is connected to a CAM card 103 for descrambling a television program, and the method may include the following steps:

step 201: when the digital television plays the scrambled program under the DTV channel, if the digital television is detected to be switched from the DTV channel to other channels, a descrambling stopping instruction is sent to the CAM card, and the descrambling stopping instruction is used for instructing the CAM card to clear descrambling information of the scrambled program.

In the embodiment of the present application, unlike the prior art, when the digital television 102 plays the scrambled program under the DTV channel, if it is detected that the digital television 102 switches from the DTV channel to another channel, for example, the HDMI channel, the digital television 102 may send a suspend descrambling instruction to the CAM card 103, where the suspend descrambling instruction is used to instruct the CAM card 103 to clear the current descrambling information, that is, the descrambling information of the scrambled program.

After receiving the descrambling pause instruction, the CAM card 103 may clear the current descrambling information. Through the processing, when the digital television 102 is subsequently switched back to the DTV channel from another channel, the CAM card 103 does not currently store any descrambling information, so that the received data code stream is not descrambled.

In a preferred implementation, the abort descrambling instruction may be a CA _ PMT table that does not carry a CA descriptor. Those skilled in the art can understand that the CA descriptor includes information such as CA _ system _ ID and CA _ PID, and the service key can be obtained through the information such as CA _ system _ ID and CA _ PID, and the ECM stream is further decrypted by the service key to obtain the control word CW, and the control word CW is filled into a corresponding register of a decoding chip of the CAM card, so that the CAM card can descramble the data stream to recover the original data stream.

Therefore, after the CAM card 103 receives the CA _ PMT table not carrying the CA descriptor, it can be considered that clear stream, that is, unscrambled data code stream, will be received subsequently, so that the current descrambling information is cleared, and descrambling operation is suspended.

In the preferred implementation manner, since a general CAM card can identify the CA _ PMT table, by modifying the CA _ PMT table, not only the function of suspending the descrambling instruction can be implemented, but also a manufacturer of the CAM card is not required to change the CAM card to identify the suspending descrambling instruction, and thus, in the embodiment of the present application, the CA _ PMT table not carrying the CA descriptor is better compatible as the suspending descrambling instruction.

It should be noted that, as described above, taking the CA _ PMT table not carrying the CA descriptor as the descrambling interruption command is only a preferred implementation manner, and in practical applications, there may be other manners, for example, an erroneous CA _ PMT table may be taken as the descrambling interruption command, where the "erroneous CA _ PMT table" may be a CA _ PMT table carrying an illegal CA _ PID value, and so on, so that when the CAM card receives the erroneous CA _ PMT table, it is considered that the station switching operation is currently performed, and thus the current descrambling information is cleared, but the information available for correct descrambling cannot be resolved according to the erroneous CA _ PMT table.

In addition, when the digital television 102 is switched back to the DTV channel from another channel, a corresponding CA _ PMT table may be obtained by parsing from a current transmission code stream, that is, a data code stream of a current scrambled program, and the corresponding CA _ PMT table may be sent to the CAM card 103, so that the CAM card 103 may descramble the current scrambled program according to the corresponding CA _ PMT table.

It should be noted that, in practical applications, when the channel that is played after the digital television is switched back from the other channel to the DTV channel is still the channel before the channel switching, the played scrambled programs may be the same or different, and the application does not limit this. No matter whether the channels are switched or not, the played scrambled programs are the same, obviously, by executing the method provided by the embodiment of the application, as the CAM card stops descrambling when the digital television is switched from the DTV channel to other channels, and subsequently, after the digital television is switched back from other channels to the DTV channel, even if the CAM card receives the data code stream first, the CAM card does not descramble the received data code stream due to lack of correct descrambling information, so that the digital television does not display television content, and the CAM card descrambles the received data code stream according to the CA _ PMT table until the digital television sends the correct CA _ PMT table to the CAM card again, and the digital television starts to display the television content. Therefore, by applying the method provided by the embodiment of the application, the situation that the digital television stops playing suddenly after playing the instant television content and continues to play the television content can not occur, namely, the digital television does not generate the phenomenon of screen splash or screen flashing. Meanwhile, the digital television sends the correct CA _ PMT table to the CAM card again, and the process that the CAM card obtains new descrambling information according to the CA _ PMT table is short in time, so that after the digital television is switched back to a DTV channel from other channels, the digital television does not display television contents only within a short time.

When the digital television is switched from the DTV channel to another channel and is switched back from another channel, if the channel changes, for example, the playing time on a certain channel reserved under the DTV channel reaches, after the user switches back, the user directly jumps to the reserved channel, and therefore, the channel changes before and after the channel is switched, at this time, because the channel is changed, descrambling data stored on one channel before the channel is switched cannot descramble code stream data on a new channel after the channel is switched, and therefore, only by obtaining a CA _ PMT table corresponding to the code stream data of the new channel after the channel is switched, descrambling and playing can be performed on the data of the new channel, that is, the problem of screen splash or splash screen described in the background art does not occur, in practice, such a scene is few, and when the digital television is switched back from another channel to the DTV channel, the channel where the digital television before the channel is switched back again, thus, the problems described in the background art basically occur.

As to how the digital television 102 parses the corresponding CA _ PMT table from the current transport stream, those skilled in the art can refer to the description in the prior art, and this application will not be described in detail.

It can be seen from the above embodiments that, when the digital television plays the scrambled program in the DTV channel, if it is detected that the digital television is switched from the DTV channel to another channel, the CAM card is sent a descrambling pause instruction, so that the CAM card clears descrambling information of the scrambled program according to the descrambling pause instruction, and it can be realized that, when the digital television is switched back to the DTV channel from the another channel, the CAM card does not descramble the received data code stream because the CAM card does not store any descrambling information, until the CAM card receives the CA _ PMT table corresponding to the current transmission code stream sent by the digital television again, the CAM card descrambles the received data code stream according to the newly received CA _ PMT table, thereby avoiding the phenomenon of screen splash or screen splash when the digital television is switched from another channel to the DTV channel, and having to set a longer time length of the audio/video mute state, causing a problem of poor user experience.

Next, description is made from the perspective of the CAM card 103:

referring to fig. 3, a flowchart of another embodiment of the channel switching method of the present application is shown, the method may be applied to the CAM card 103 illustrated in fig. 1, as shown in fig. 1, the CAM card 103 is connected to the digital television 102, and the method may include the following steps:

step 301: and receiving a descrambling stopping instruction, wherein the descrambling stopping instruction is sent when the digital television detects that the digital television is switched from the DTV channel to other channels when the digital television plays the scrambled program under the DTV channel.

Step 302: descrambling information of the scrambled program is cleared based on the suspend descrambling instruction.

The detailed description of step 301 and step 302 can refer to the above description of the embodiment shown in fig. 2, and will not be described in detail here.

It can be seen from the above embodiments that, when the digital television plays the scrambled program in the DTV channel, if it is detected that the digital television is switched from the DTV channel to another channel, the CAM card is sent a descrambling pause instruction, so that the CAM card clears descrambling information of the scrambled program according to the descrambling pause instruction, and it can be realized that, when the digital television is switched back to the DTV channel from the another channel, the CAM card does not descramble the received data code stream because the CAM card does not store any descrambling information, until the CAM card receives the CA _ PMT table corresponding to the current transmission code stream sent by the digital television again, the CAM card descrambles the received data code stream according to the newly received CA _ PMT table, thereby avoiding the phenomenon of screen splash or screen splash when the digital television is switched from another channel to the DTV channel, and having to set a longer audio/video in the mute state, causing a problem of poor user experience.

Referring to fig. 4, a flowchart of another embodiment of the channel switching method of the present application is shown, where the method shown in fig. 4 focuses on the processing procedure of the CAM card 103 after switching the digital television from other channels back to the DTV channel based on the method shown in fig. 3, and may include the following steps:

step 401: and when the digital television is switched back to the DTV channel from other channels, analyzing the current transmission code stream to obtain a corresponding CA _ PMT table.

The detailed description of step 401 can refer to the related description of the embodiment shown in fig. 2, and will not be described in detail here.

Step 402: and analyzing the corresponding CA _ PMT table to obtain descrambling information.

Step 403: and descrambling the current scrambled program according to the descrambling information.

How the CAM card 103 parses the CA _ PMT table to obtain descrambling information of the scrambled program currently played by the digital television 102, and descrambles the scrambled program currently played by the digital television 102 according to the parsing information may refer to the description in the prior art, which is not described in detail in this application.

Corresponding to the embodiment of the channel switching method, the application also provides an embodiment of a channel switching device.

Referring to fig. 5, a block diagram of an embodiment of a channel switching apparatus according to the present application, the apparatus may be applied to the digital television 102 illustrated in fig. 1, as shown in fig. 1, the digital television 102 is connected to a CAM card for descrambling a television program, and the apparatus may include: a first transmission module 51.

The first sending module 51 may be configured to, when the digital television broadcasts the scrambled program in the DTV channel, send a descrambling pause instruction to the CAM card if it is detected that the digital television is switched from the DTV channel to another channel, where the descrambling pause instruction is used to instruct the CAM card to clear descrambling information of the scrambled program.

In one embodiment, the abort descrambling instruction comprises:

CA _ PMT table that does not carry conditional access CA descriptor.

In an embodiment, the apparatus may further comprise (not shown in fig. 5): a second sending module 42.

The second sending module 52 may be configured to trigger, when the digital television is switched back to the DTV channel from another channel, to obtain a corresponding CA _ PMT table from a current transmission code stream by parsing, and send the corresponding CA _ PMT table to the CAM card, so that the CAM card descrambles a current scrambled program according to the new CA _ PMT table.

Referring to fig. 6, which is a block diagram of another embodiment of the channel switching device of the present application, the device may be applied to the CAM card 103 illustrated in fig. 1, as shown in fig. 1, the CAM card is connected with a digital television 102, and the device may include: a first receiving module 61 and a processing module 62.

The first receiving module 61 may be configured to receive a descrambling pause instruction, where the descrambling pause instruction is sent when the digital television detects that the digital television switches from a DTV channel to another DTV channel when the digital television plays a scrambled program in the DTV channel;

the processing module 62 may be configured to clear descrambling information of the scrambled program based on the suspend descrambling instruction.

In one embodiment, the abort descrambling instruction comprises:

CA _ PMT table that does not carry conditional access CA descriptor.

In an embodiment, the apparatus may further comprise (not shown in fig. 6): the second receiving module, the analysis module and the descrambling module.

The second receiving module may be configured to receive a corresponding CA _ PMT table obtained by parsing a current transmission code stream when the digital television is switched back to the DTV channel from another channel;

the analysis module can be used for analyzing the corresponding CA _ PMT table to obtain descrambling information;

the descrambling module can be used for descrambling the current scrambled program according to the descrambling information.

The implementation process of the functions and actions of each unit in the above device is specifically described in the implementation process of the corresponding step in the above method, and is not described herein again.

For the device embodiments, since they substantially correspond to the method embodiments, reference may be made to the partial description of the method embodiments for relevant points. The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of the application. One of ordinary skill in the art can understand and implement it without inventive effort.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A channel switching method based on a digital television is applied to the digital television, and is characterized by comprising the following steps:

when the digital television is switched from a DTV channel to other channels, sending a descrambling pause instruction to a conditional access Card (CAM) card, wherein the descrambling pause instruction is used for indicating the CAM card to empty the current descrambling information;

when the digital television is switched back to the DTV channel from the other channels, a CA _ PMT table of a specified channel is sent to the CAM card, so that the CAM card descrambles the received data code stream of the specified channel according to the CA _ PMT table of the specified channel, and the specified channel is a channel played before the digital television is switched from the DTV channel to the other channels.

2. The method of claim 1, wherein the abort descramble instruction comprises:

CA _ PMT table that does not carry conditional access CA descriptor.

3. A channel switching method based on a digital television is applied to a conditional access Card (CAM) card and is characterized by comprising the following steps:

receiving a descrambling pause command, wherein the descrambling pause command is sent when the digital television is switched from a DTV channel to other channels;

clearing the current descrambling information based on the descrambling stopping instruction;

receiving a CA _ PMT table of a specified channel, wherein the CA _ PMT table of the specified channel is transmitted when the digital television is switched from the other channels to the DTV channel, and the specified channel is a channel played before the digital television is switched from the DTV channel to the other channels;

analyzing the CA _ PMT table of the appointed channel to obtain descrambling information of the appointed channel;

and descrambling the received data code stream of the appointed channel according to the descrambling information of the appointed channel.

4. The method of claim 3, wherein the abort descramble instruction comprises:

CA _ PMT table that does not carry conditional access CA descriptor.

5. A channel switching device based on a data television is applied to a digital television, and is characterized by comprising:

the first sending module is used for sending a descrambling stopping instruction to a conditional access Card (CAM) card when the digital television is switched from a DTV channel to other channels, wherein the descrambling stopping instruction is used for indicating the CAM card to empty the current descrambling information;

and the second sending module is used for sending a CA _ PMT table of a specified channel to the CAM card when the digital television is switched back to the DTV channel from the other channel, so that the CAM card descrambles the received data code stream of the specified channel according to the CA _ PMT table of the specified channel, and the specified channel is a channel played before the digital television is switched from the DTV channel to the other channel.

6. The apparatus of claim 5, wherein the abort descramble instruction comprises:

CA _ PMT table that does not carry CA descriptor.

7. A channel switching device based on digital television is applied to a conditional access Card (CAM) card, and is characterized by comprising:

the first receiving module is used for receiving a descrambling pause instruction, wherein the descrambling pause instruction is sent when the digital television is switched from a DTV channel to other channels;

the processing module is used for clearing the current descrambling information based on the descrambling stopping instruction;

a second receiving module, configured to receive a CA _ PMT table of a specific channel, where the CA _ PMT table of the specific channel is sent when the digital television is switched from the other channel to the DTV channel, and the specific channel is a channel played before the digital television is switched from the DTV channel to the other channel;

the analysis module is used for analyzing the CA _ PMT table of the appointed channel to obtain descrambling information of the appointed channel;

and the descrambling module is used for descrambling the received data code stream of the specified channel according to the descrambling information of the specified channel.

8. The apparatus of claim 7, wherein the abort descramble instruction comprises:

CA _ PMT table that does not carry conditional access CA descriptor.