KR20050115656A - Method for changing channel in digital cable set top box - Google Patents

Abstract

The present invention relates to a channel switching method in an open cable type digital cable broadcast receiver. Particularly, the present invention extracts program information by parsing only one PAT / PMT that matches program_number described in the SVCT of the corresponding virtual channel when switching the channel, and based on the program information and the channel information extracted from the SVCT, Tune and decode to display. Therefore, the present invention can minimize the channel switching time even if the physical channel changes during the channel switching. In addition, since the physical channel is changed, unchanged, or only one PAT / PMT is parsed during channel switching, the channel switching time is almost similar to any channel switching.

Description

Method for changing channel in digital cable set top box

The present invention relates to a channel switching method in a digital cable broadcasting receiver, in particular, an open cable based digital set top box.

Korea decided the open cable system as the domestic digital cable broadcasting standard. The open cable method uses Dolby-AC3 as an audio compression method and MPEG-2 as a video compression method. In addition, the POD (Point Of Deployment) module, which is adopted for copy protection and limited access to high value-added broadcast contents, is separated from the main body of the digital cable set-top box, providing easy replacement of the security system and enabling retailing. Thus, there is an advantage that can supply a low-cost digital cable broadcast receiver. That is, by separating the POD module including the Conditional Access (CA) system that existed in the cable set-top box from the set-top box and defining a standard interface (I / F) between the set-top box and the POD module, only the POD I / F is matched. Anyone can make a set-top box. Therefore, when a consumer directly purchases the set-top box as a VCR, and a cable system operator (SO) gives the subscriber a POD module, the subscriber receives various cable broadcasts using the POD module and the cable set-top box body.

In the open cable method, the uplink band required for the bidirectional service uses a 5 to 42 MHz band, and the in-band downstream channel bandwidth is 6 MHz as in a domestic channel environment. In addition, the channel and broadcast program guide information uses an out of band (OOB) system information (SI) and in-band PSI (program specific information).

1 is a block diagram illustrating a general open cable type digital cable set top box, in which a cable set top box main body 100 and a POD module 200 separated from the main body 100 are provided.

The cable set-top box main body 100 is connected to a cable head-end, which is a kind of broadcasting station for sending a program for a digital cable, to receive an A / V broadcast program through an in-band among cable frequency bands, and out of band. (Out-Of-Band; OOB) makes bi-directional communication with the head-end.

That is, the A / V broadcast program transmitted through the in-band is tuned and demodulated through the tuner 111 and the demodulator 112 and then output to the POD module 200.

In addition, data information such as channel tuning and program guide transmitted through the OOB is output to the POD module 200 through the OOB transmitter / receiver 113.

The POD module 200 separates operations such as descrambling of the received broadcast signal and subscriber confirmation into a PCMCIA type card.

Therefore, the CA system in the POD module 200 descrambles the demodulated signal and outputs the descrambled signal to the transport (TP) demultiplexer 116 of the main body 100.

The demultiplexer 116 separates the multiplexed video, audio, and data packets and outputs them to the video decoder 117, the audio decoder 118, and the PSI parser 119, respectively. The video decoder 117 removes the overhead (various header information, start code, etc.) from the video packet, performs variable length decoding (VLD) on pure data information, and then dequantizes and inverse discrete cosine transform (VLD). IDCT) and motion compensation process using motion vectors to restore the pixel values of the original screen and output them to the monitor. The audio decoder 118 decodes the audio packet using the AC-3 algorithm and outputs the audio packet to the speaker.

Meanwhile, conventional terrestrial or satellite set-top boxes scan and store all channels that can be tuned first when the power is turned on. After that, when the user selects a channel, the stored scan information is read and the channel is tuned.

In contrast, open cable set-top boxes do not have a channel scan function. Instead, when the user selects a channel after the power is turned on, the VCT (Virtual Channel Table) received through the System Information (SI) is parsed in real time to obtain information about the channel, and the desired channel is selected from the channel information. Tune it. The VCT is also called a short-form VCT (SVCT) in the case of a cable set-top box, and is later referred to as an SVCT to distinguish it from terrestrial waves.

In other words, in digital cable broadcasting, information on channels and program guide information for each channel are provided so that a user can basically listen to the broadcasting.

Among these, the PSI includes information for displaying an A / V (audio / video) screen of a specific channel and is transmitted with a broadcast program through an in-band band. In other words, PSI is information that enables a digital cable set-top box to demultiplex and decode a particular stream within a multiplexed stream. The SI also contains information to tune the channel and is transmitted over the OOB band.

At this time, the PSI includes a Program Association Table (PAT), a Program Map Table (PMT), and the like, and the SVCT includes the SI.

The PAT describes the components of the program for each program number, which indicates the PID of the transport packet for transmitting the PMT. The PMT describes PID information of a transport packet in which individual bit strings such as video and audio constituting a program are transmitted, and PID information in which PCR information is transmitted.

The SVCT is one of the tables defined in the SI, and shows a general SVCT bitstream syntax structure for a cable in FIG. 2.

In FIG. 2, Virtual_channel_number is a virtual channel number indicating one of several virtual channels in a physical channel, and CDS_reference is a physical channel frequency of the virtual channel number. That is, several virtual channels exist in one physical channel, and one virtual channel corresponds to one broadcast program. For example, if five virtual channels exist in a physical channel, five broadcast programs exist in the physical channel.

program_number is a program number for connecting a virtual channel in which MPEG-2 PAT (Program Association Table) and PMT (Program Map Table) are defined. The program_number corresponds to a program number in the PAT / PMT.

MMS_reference represents modulation information. That is, it indicates a transmission method of a broadcast program corresponding to the virtual channel. For example, the open cable method uses 64 quadrature amplitude modulation (QAM) or 256 QAM for in-band, and uses QPSK transmission for OOB.

Therefore, when parsing the SVCT, a physical channel frequency, a virtual channel frequency assigned to the physical channel frequency, a modulation method, and the like can be known.

As described above, at least one virtual channel is allocated to the physical channel. For example, five virtual channels may be allocated to one physical channel, and 20 virtual channels may be allocated to another physical channel. As such, the number of virtual channels present in each physical channel is different for each physical channel.

At this time, if the user selects a specific channel using a numeric key such as a remote controller or switches a channel with a channel up / down key, the virtual channel changes every time the channel is changed. However, depending on the channel switching, the virtual channel may change but the physical channel may or may not change. For example, assume that there are 101,102,103 virtual channels in physical channel 10, and 106,108 virtual channels in physical channel 20. In this case, when the user watches a program of the virtual channel 101 and selects a program that is a virtual channel 103, the virtual channel is changed from 101 to 103, but the physical channel is 10 and does not change. However, when the program of the virtual channel 101 is selected while the program of the virtual channel 106 is selected, the physical channel also changes from 10 to 20.

Conventionally, when a physical channel is changed during channel switching, all virtual channels existing in the changed physical channel are parsed to configure channel map information, and then the corresponding channel is tuned using the channel map information. On the other hand, if the physical channel does not change during channel switching, since the channel map information for the physical channel is already configured, the corresponding channel is tuned using the existing channel map information without parsing the virtual channel.

As such, when channel switching occurs in the related art, in order to tune the switched channel, it is first checked whether the physical channel changes.

4 is a flowchart illustrating an example of a conventional channel switching method. When a user switches a channel while watching a specific program (step 401), the channel conversion engine 115 determines whether a physical channel changes according to channel switching. (Step 402).

If it is determined that the physical channel is changed, the SI parser 114 controls the SVCT of all virtual channels existing in the physical channel to configure and store channel map information (step 403). The SVCT is one of tables defined in the SI input through the OOB and the POD module 200.

In this case, since the actual video / audio / PCR PID in the channel is not in the SI, the channel conversion engine 115 outputs the channel information extracted from the SVCT to the PSI parser 119 again, and the PSI parser 119 transmits the channel. Based on the information, each PAT matching all virtual channels existing in the corresponding physical channel and all PMTs defined in each PAT are parsed and outputted to the channel conversion engine 115. The channel conversion engine 115 also stores the information parsed by the PAT / PMT in channel map information, and then controls the tuner 111 and the demultiplexer 116 based on the stored channel map information. Tun and demultiplex the A / V / PCR PID of the channel selected in step 404.

On the other hand, if it is determined in step 402 that the physical channel does not change during channel switching, the channel map information for the physical channel is already configured and stored in the channel conversion engine 115. Therefore, in this case, the tuner 111 and the demultiplexer 116 are controlled based on the existing channel map information without parsing the virtual channel to tune and demultiplex the A / V / PCR PID of the channel selected by the user in step 401. (Step 405).

As described above, in the conventional method, when a physical channel changes during channel switching and there are several virtual channels in the physical channel, all of the multiple virtual channels are parsed. Therefore, in this case, there is a disadvantage that takes a long time when switching channels. In particular, the more virtual channels exist in the physical channel, the longer the channel switching time takes.

In addition, if the physical channel does not change during channel switching, channel map information already exists, so channel switching is performed without parsing the virtual channel. Since the virtual channels exist for each physical channel, if the physical channel changes during channel conversion, the channel switching time varies depending on the virtual channel present in the physical channel. Therefore, there is a disadvantage in that the channel switching time is inconsistent in some channels, such as channel switching very quickly, and some channels switching very slowly.

The present invention is to solve the above problems, an object of the present invention to provide a method for minimizing the channel switching speed in an open cable set-top box.

Another object of the present invention is to provide a method of making the channel switching time according to the change of the physical channel and the channel switching time according to the change of the virtual channel only in the open cable set-top box.

Channel switching method in a digital cable broadcast receiver according to an embodiment of the present invention for achieving the above object,

(a) extracting channel information by parsing a table (SVCT) of a virtual channel to be switched when channel switching is selected by a user;

(b) extracting program information by parsing only one PAT / PMT matching the program number among the channel information; And

(c) tuning and decoding a program of the channel selected in the step (a) based on the extracted channel and program information and displaying the same on a screen.

The channel switching method of the digital cable broadcast receiver according to another embodiment of the present invention,

(a) extracting channel information by parsing a table (SVCT) of a virtual channel to be switched when channel switching is selected by a user;

(b) extracting program information by parsing only one PAT / PMT matching the program number among the channel information;

(c) constructing and storing program map information using the extracted channel and program information, and simultaneously tuning, decoding, and displaying a program of a channel selected in the step (a) based on the program map information and displaying it on a screen;

(d) Subsequently, when the switching to the channel in the stored channel map information occurs in step (c), the program of the corresponding channel is tuned and decoded based on the channel and program information in the channel map information, and then output. Making the program invisible;

(e) parsing only one PAT / PMT matching the program number of the corresponding virtual channel read from the stored channel map information at the same time as step (d), extracting the program information, and then determining whether the program information matches the previously stored program information. step;

(f) if it is determined in step (e) that the two program information are identical, displaying the program decoded in step (d) so that the screen is visible; And

(g) if it is determined in step (e) that the two program information do not coincide, based on the program information parsed in step (e), newly tuning and decoding a program of a corresponding channel, and displaying the result on a screen; Characterized in that made.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, with reference to the accompanying drawings illustrating the configuration and operation of the embodiment of the present invention, the configuration and operation of the present invention shown in the drawings and described by it will be described as at least one embodiment, By the technical spirit of the present invention described above and its core configuration and operation is not limited.

The present invention constructs channel map information by parsing only one PAT / PMT that matches the program number in the SVCT of the virtual channel regardless of whether the physical channel is changed during channel switching, and configures the corresponding channel based on the channel map information. It features tuning, decoding, and display.

That is, since the desired program number (program_number) at the time of channel switching is already entered in the SVCT of FIG. 2, if it is transmitted to the PSI parser 119 and only one desired PAT / PMT is parsed, the channel switching to any channel is performed. Parsing time is about the same.

This requires much less time than parsing all virtual channels present in one physical channel frequency and the PAT of each virtual channel and all PMTs defined in the PAT. In addition, the channel switching time is almost the same no matter which channel is switched since the physical channel is changed, is not changed, or only one PAT / PMT is parsed.

FIG. 5 is a flowchart illustrating an example of a channel switching method according to the present invention. When a user switches a channel while watching a specific program, the virtual channel changes (step 501). Then, the channel conversion engine 115 parses the SVCT of the virtual channel through the SI parser 114, extracts the program number (program_number) (step 502), and then outputs the program number to the PSI parser 119. . The PSI parser 119 parses only one PAT / PMT matching the program_number of the SVCT, extracts program information, and outputs the program information to the channel conversion engine 115. The channel conversion engine 115 configures and stores channel map information using channel information extracted from the SI parser 114 and program information extracted from the PSI parser 119 (step 503).

FIG. 3 shows a general PAT bitstream syntax structure. A table identifier (table_id) is composed of 8-bit fields and defines the value of table_id in ISO and ETSI. section_syntax_indicator indicates that it is compatible with PSI of MPEG-2 system standard, and section_length is used to indicate the length of the corresponding section.

In addition, the program guide or service information is inevitably changed according to time. In other words, as the program is aired, the contents of other programs must be guided as time passes, so a new version of service information must be transmitted. That is, the version_ number is used to inform that the information is different from the service information or the program guide information previously transmitted. current_next_indicator indicates whether the transmitted content is the content to be applied right now or the content to be applied next time. section_number represents a number of a section, and the digital cable broadcasting receiver may rearrange the received tables using the section number. last_section_number represents the number of the last section of the current table.

At this time, the loop for the 'for' loop of the PAT is used to describe program_number and PID (program_map_PID) of the PMT. The number of iterations (N) of the 'for' loop matches the number of PMTs assigned to the PAT.

Therefore, the PAT matching the program_number of the SVCT is parsed, and the PMT of the program_map_PID matching the program_number is again parsed from the PAT to extract program information.

Then, the channel conversion engine 115 configures and stores the channel map information with the channel information and the program information extracted from the SI parser 114 and the PSI parser 119, respectively, and based on the channel map information. The tuner 111 and the demultiplexer 116 are controlled to tune and demultiplex the A / V / PCR PID of the channel selected by the user in step 501 (step 504).

Therefore, the present invention can achieve a high-speed channel switching at the same time the physical channel is changed or unchanged or at about the same speed during the channel switching.

Then, when the user switches to a channel in the channel map information, the SVCT of the virtual channel is again parsed to extract channel information and program_number, and only one PAT / PMT matching the program_number is parsed by the PSI parser 119. You can get A / V / PCR PID of desired channel.

In another embodiment, when the user switches to the channel in the channel map information, the SVCT of the virtual channel is not parsed, but instead, the program_number of the corresponding virtual channel in the previously stored channel map information is transferred to the PSI parser 119. The program information is extracted by parsing one PAT / PMT matching the program_number. The program information of the extracted program information and the pre-stored channel map information are compared with each other. At the same time, the program of the corresponding channel is tuned and decoded using the pre-stored channel map information and output to the screen, but the program is not visible on the screen. That is, the screen is black or a specific pattern is displayed on the screen.

In this case, when it is determined that the newly parsed and extracted program information and the previously stored program information match the PSI parser 119, the program displayed after being tuned and decoded by the previously stored channel map information is normally displayed on the screen.

On the other hand, if it is determined that the two program information does not match, the program of the corresponding channel is tuned and decoded based on the newly parsed information and displayed on the screen. At the same time, the channel map information is updated and stored with the parsed information.

However, since the A / V / PCR PID hardly changes during actual broadcasting, the latter method can save SI parsing time, thereby making the channel switching speed faster.

Meanwhile, the present invention has been described with reference to an embodiment of an open cable set-top box in which the POD is separated from the main body. However, in another embodiment, the present invention may be applied to a digital cable broadcasting receiver in which the POD is integrated into the set-top main body.

Terminologies used in the present invention are terms defined in consideration of functions in the present invention and may vary according to the intention or custom of a person skilled in the art, and the definitions refer to the overall contents of the present invention. It must be laid down.

In addition, since the present invention has been described through the preferred embodiment of the present invention, in view of the technical difficulty aspects of the present invention, those having ordinary skill in the art can easily and other embodiments of the present invention. Other variations can be made. Therefore, it is apparent that all of the embodiments and variations cited in the above description belong to the claims of the present invention.

As described above, according to the channel switching method in the digital cable broadcasting receiver according to the present invention, when only one PAT / PMT matching the program_number described in the SVCT of the corresponding virtual channel is parsed at the time of channel switching, it is based on the parsing information. Tune, decode and display the program for that channel. Therefore, the present invention can minimize the channel switching time even if the physical channel changes during the channel switching. In addition, since the physical channel is changed, unchanged, or only one PAT / PMT is parsed during channel switching, the channel switching time is almost similar to any channel switching.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

1 is a block diagram of a general open cable type digital cable broadcast receiver

2 illustrates a general SVCT bitstream syntax structure

3 illustrates a general PAT bitstream syntax structure.

4 is a flowchart illustrating an example of a channel switching method in a conventional digital cable broadcasting receiver.

5 is an operation flowchart showing an example of a channel switching method in a digital cable broadcast receiver according to the present invention.

Explanation of symbols for main parts of the drawings

100: cable set-top box body 111: tuner

112: demodulation unit 113: OOB transmitter / receiver

114: SI parser 115: channel conversion engine

116: demultiplexer 117: video decoder

118: audio decoder 119: PSI parser

200: POD module

Claims (6)

In the channel switching method of the digital cable broadcast receiver in which at least one virtual channel exists in one physical channel, and receives the channel and program guide information, (a) extracting channel information by parsing a table (SVCT) of a virtual channel to be switched when channel switching is selected by a user; (b) extracting program information by parsing only one PAT / PMT matching the program number among the channel information; And and (c) tuning, decoding, and displaying the program of the channel selected in the step (a) based on the extracted channel and program information and displaying the same on a screen. . The method of claim 1, wherein when the digital cable broadcast receiver is an open cable method in which the POD module is separated from the main body, In step (a), the SVCT is a channel switching method in a digital cable broadcasting receiver characterized in that parsing in the SI received through the out of band (OOB) and the POD module. The method of claim 1, wherein when the digital cable broadcast receiver is an open cable method in which the POD module is separated from the main body, In the step (b), the PAT / PMT channel parsing method in the digital cable broadcasting receiver characterized in that the parsing in the PSI received by the main body through the in-band. The method of claim 1, wherein step (c) (c-1) constructing and storing channel map information using the extracted channel and program information; (c-2) After the switching to the channel in the stored channel map information occurs, the program of the corresponding channel is tuned and decoded based on the channel and program information in the channel map information, and then outputted. Making it invisible, (c-3) The program information is extracted by parsing only one PAT / PMT matching the program number of the corresponding virtual channel read from the stored channel map information at the same time as the step (c-2), and matching with the previously stored program information. Determining whether or not, (c-4) if it is determined in step (c-3) that the two program information are identical, displaying the program decoded in step (c-2) so as to be displayed on the screen; (c-5) If it is determined in step (c-3) that the two program information do not match, the program of the corresponding channel is tuned and decoded based on the program information parsed in step (c-3) and displayed on the screen. Channel switching method in a digital cable broadcast receiver, characterized in that further comprising the step of. In the channel switching method of the digital cable broadcast receiver in which at least one virtual channel exists in one physical channel, and receives the channel and program guide information, (a) extracting channel information by parsing a table (SVCT) of a virtual channel to be switched when channel switching is selected by a user; (b) extracting program information by parsing only one PAT / PMT matching the program number among the channel information; (c) constructing and storing program map information using the extracted channel and program information, and simultaneously tuning, decoding, and displaying a program of a channel selected in the step (a) based on the program map information and displaying it on a screen; (d) Subsequently, when the switching to the channel in the stored channel map information occurs in step (c), the program of the corresponding channel is tuned and decoded based on the channel and program information in the channel map information, and then output. Making the program invisible; (e) parsing only one PAT / PMT matching the program number of the corresponding virtual channel read from the stored channel map information at the same time as step (d), extracting the program information, and then determining whether the program information matches the previously stored program information. step; (f) if it is determined in step (e) that the two program information are identical, displaying the program decoded in step (d) so that the screen is visible; And (g) if it is determined in step (e) that the two program information does not match, tuning and decoding the program of the corresponding channel based on the newly parsed program information in step (e), and displaying the result on the screen. A channel switching method in a digital cable broadcast receiver, characterized in that made. The method of claim 5, wherein step (g) And if it is determined that the two program information does not match, updating and storing the channel map information with the program information parsed in the step (e).