KR100225856B1 - Automatic tuning method of the settop box of a vod service system for short distance - Google Patents

Abstract

The present invention relates to a method of automatically tuning a set-top box of an NVOD service system capable of precisely tuning a broadcast program desired to be viewed by a user in an analog channel and a digital channel band.

The set-top box of the NVOD service system includes a step of inputting a channel number and a program identification code of a program to be watched by a user, an automatic channel tuning method, a step of detecting user data for automatic tuning from a received signal, Comparing the input channel number and the identification code, and checking whether the inputted channel number is an analog channel band, switching the channel selection channel to the input channel number, and setting a program identification code.

Description

How to auto-tune the set-top box of an on-demand local video service system

1 shows a channel allocation format of a CATV system;

FIG. 2 is a diagram for explaining an analog program service mode of an NVOD service system; FIG.

Figure 3 is a block diagram of an analog set top box of a typical NVOD service system;

FIG. 4 is a flow chart illustrating a conventional channel selection method using a real time counter. FIG.

FIG. 5 is a flow chart illustrating a conventional channel selection method using a control channel demodulator.

FIG. 6 is a view for explaining a digital program service mode of the NVOD system; FIG.

7 is a diagram for setting the transmitted MEPC-2 bitstream format of a digital NVOD system;

Figure 8 is a block diagram of a digital set-top box of a conventional NOVD service system.

FIG. 9 is a flowchart for explaining a method of automatically tuning a set-top box of a NOVD service system according to an embodiment of the present invention;

DESCRIPTION OF THE REFERENCE NUMERALS

10, 40: Tuner 12, 42: Analog channel processor

14, 50: CPU 16, 52: memory

18, 54: user relaying unit 20: RTC

22: control channel demodulator 44: data channel demodulator

46: data switching section 48: MPEC decoder

In a near-video-on-demand (NVOD) service system using a coaxial cable of the present invention, a set-top box (Set Top Box) for selecting and receiving a broadcast program via a coaxial cable from a broadcast program server and more particularly, to a method for automatically selecting a set-top box in which a user can precisely select and receive a desired broadcast program among broadcast programs from a server.

The conventional cable television (CATV) service system solves the problem of the conventional television broadcast messenger by providing the video and audio broadcast programs to the subscribers via the coaxial cable, Provide information. The CATV service system comprises a server for supplying video and audio broadcast programs to subscribers via a coaxial cable, and a set-top box connected to a coaxial cable for receiving broadcast programs from the server. The server divides the frequency band that can be transmitted on the coaxial cable and transmits various types of information to the set-top box. The frequency division format used by the server is divided into a control channel band, an analog channel band, and a digital channel band as shown in FIG. The control channel band occupies a frequency region within 50 MHz, the analog channel band is located in the frequency region of 50 to 450 MHz, and the digital channel band is located in the frequency region of 450 to 750 MHz. The CATV service system is divided into a VOD (Vedio On Demand) service system and a NOVD service system according to the transmission type of control information in the control channel band. VOD service system is transmitted to the server and the set-top box bidirectionally via the control information base control channel band. On the other hand, the NVOD service system is transmitted from the control information server through the control channel band to the set- . The analog channel band is divided into a plurality of subchannels in the frequency domain where analog CATV broadcasting programs can be transmitted. In addition, the digital channel band is divided into a plurality of detailed channel regions in a frequency region capable of transmitting a digital CATV program.

In the NVOD service system, the server provides the same broadcast program (e.g., movie) to subscribers at a predetermined time interval and services one broadcast program stream using one detailed channel. To this end, the detail channel has a bandwidth of 6 MHz. An important requirement of the server for the NVOD service system is to minimize the service interval of the same broadcast program, and the service interval is as shown in equation (1).

Ti = Ts / Nc Equation (1)

In equation (1), Nc is the number of channels, Ti is the service interval, and Ts is the service time of the broadcast program. For example, if the service time of the broadcast program is two hours and the detailed channel is four, the service interval is Ti = 2 hours / 4 = 30 minutes. Accordingly, the subscriber can select and watch a movie served at a predetermined time interval (Ti) using the set-top box. Due to this, the subscriber must wait for the highest service interval (Ti) in order to view a broadcast program (i.e., movie) from the beginning. During this waiting time, most users had to search for a channel in which a desired broadcast program is periodically started while watching another broadcast program. In order to solve such a problem, a set-top box has been proposed in which a start time and a broadcast channel information of a desired broadcast program are input from a user to automatically search for a channel. The set top box automatically selects a channel on which a broadcast program is broadcast at a desired time using a real time counter (RTC) or control information on a control channel band.

However, the set-top box using the RTC can not select a desired program channel when there is a time difference from the server and when the start time of the broadcast program service of the server is changed. In addition, the set-top box that implements the control information has a disadvantage that a modulator for modulating the control information is added to the server and a demodulator for demodulating the modulated control information is additionally provided. Also, a set-top box having an automatic channel tuning function is used for selecting a broadcast program broadcast in an analog channel band, but can not be applied to a broadcast program broadcasted in a digital channel band. This is because information necessary for a bit stream of a broadcast program transmitted in a digital channel band is transmitted together. Problems of the conventional set-top box having the automatic channel tuning function will be described in detail with reference to FIGS. 3 to 5.

3, there is shown a tuner 10 for tuning a high frequency signal from a coaxial cable 11 and an analog channel processor 12 for processing a high frequency signal selected by the tuner 10 A set-top box is shown. The analog channel processor 12 inversely mixes the high frequency signal selected by the tuner 10 and generates a video signal and an audio signal of the original base band. The analog channel processor 12 then supplies the video signal and the audio signal to the television set either directly or by frequency-shifting to the channel frequency region of the television set.

The set-top box for analog NVOD includes a central processing unit (CPU) 14 for controlling the apparatus, a memory (not shown) for temporarily storing programs and data to be executed by the CPU 14 16, and a user relaying unit 18 for inputting information inputted by the user. The CPU 14 controls the analog set top box according to the program stored in the memory 16 via the user relay unit 18 to perform a function desired by the user. Further, the CPU 14 controls the tuner 10 to adjust the frequency band to be tuned by the tuner 10.

The set-top box for the analog NVOD may include an RCT 20 or a control channel demodulator 22 for counting an actual time. The RCT 20 or the control channel demodulator 22 may be configured such that when the user inputs a start time and a broadcast channel of a broadcast program to be viewed, the CPU 14 sets the channel selection channel of the tuner 10 at the start time of the broadcast program To change to a broadcast channel.

FIG. 4 is a flowchart illustrating a conventional channel selection method using the RCT, which is performed by the CPU 14 shown in FIG. 3, and will be described in detail.

The CPU 14 inputs the start time of the broadcast program desired by the user and the channel number of the broadcast program via the user relay unit 18 while receiving an NVOD program in operation 24. The CPU 14 maintains the channel selection channel of the tuner 10 so that the broadcast program currently being received is continuously received.

Then, the CPU 14 waits until the time counted by the RTC 20 becomes the start time of the inputted broadcast program (step 26). When the time counted by the RTC 20 matches the start time of the input broadcast program in step 26, the CPU 14 controls the tuner 10 to select the channel preset in the tuner 10 as the designated broadcast program (Step 28). At this time, the analog channel processor 12 restores the video signal and audio signal of the desired program from the high-frequency signal of the channel selected by the tuner 10, and outputs the restored video signal and audio signal to the output line 13, To the television set so that the broadcast program desired to be viewed by the user is outputted through the television set. In addition, the CPU 14 initializes the start time and the broadcast channel number of the inputted broadcast program (operation 30).

As described above, the automatic channel tuning method using the RTC 20 changes the tuning channel of the tuner 10 to the channel number specified by the user when the time counted by the RTC coincides with the start period of the program designated by the user, To watch the specified program. However, this automatic channel tuning method has a disadvantage that the user can not watch a desired program from the beginning if the time of the RCT does not coincide with the time on the server. This automatic channel tuning method prevents the user from watching a desired broadcast program when the program broadcast time of the server is changed.

FIG. 5 is a flowchart illustrating a conventional channel selection method using a control channel demodulator. The flowchart of FIG. 5 is performed by the CPU 14 shown in FIG. 3, which will be described in detail.

The CPU 14 inputs the channel number of the broadcast program that the user wants to view via the user relay unit 18 while receiving an NVOD program. (Step 32). The CPU 14 maintains the channel selection channel of the tuner 10 so that the broadcast program currently being received is continuously received.

Then, the CPU 14 waits until the broadcast program start code for the input channel number is received from the control channel demodulator 22. (Operation 34). The CPU 14 controls the tuner 10 so that the channel selection channel of the tuner 10 is tuned to the designated broadcast channel in step 34. In step 34, To the channel number of the program (Step 26). At this time, the analog channel processor 12 restores the video signal and audio signal of the desired program from the high-frequency signal of the channel selected by the tuner 10, and outputs the restored video signal and audio signal to the output line 13, To the television set so that the broadcast program desired to be viewed by the user is output through the television set. In addition, the CPU 14 initializes the start time and the broadcast channel number of the inputted broadcast program (operation 38).

As described above, the automatic channel tuning method using the control channel demodulator changes the channel selection channel of the tuner 10 according to whether or not the program start code for the channel number designated by the user is received from the server, The channel on which the program is broadcast can be precisely tuned. As described above, this automatic channel tuning method can solve the disadvantage of the automatic channel tuning method using the RTC, but can not be used in the digital channel band. This is because not only the channel but also the program identification number must be set in the digital channel band so that the user can receive the desired broadcast program.

Accordingly, it is an object of the present invention to provide an automatic tuning method of a set-top box of an NVOD service system in which a user can precisely select a broadcast program to be viewed in an analog channel and a digital channel band.

In order to achieve the above object, an automatic channel tuning method of a set-top box of an NVOD service system according to the present invention is a set-top box of an on-demand type short-range video service system in which a channel number and a program identification code Detecting user data for automatic channel selection from the received signal; comparing the user data with the inputted channel number and identification code and checking whether the inputted channel number is an analog channel band; , Switching the channel selection channel to the input channel number, and setting the program identification code.

Other objects and advantages of the present invention will become more apparent from the following description of the preferred embodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

Before describing an embodiment of the present invention, the number of bit streams corresponding to the number of programs that can be transmitted in the digital channel band will be described. In the analog channel band, only one program per one channel of 6 MHz can be transmitted, whereas in the digital channel band, several programs (i.e., several bit streams) per channel of 6 MHz are transmitted depending on the digital modulation / Can be transmitted. For example, when using an MPEC-2 encoder with a transmission rate of 6 MHz and 64 right-angled amplitude modulation schemes of about 27 Mbps for the image data to be transmitted in the digital channel band, the number of transmittable programs (i.e., bit streams) 27 Mbps / 6 Mbps = 4.5, that is, four. In this case, if the number of channels of the digital frequency band is 2 and the service period of the program is 2 hours, the service interval Ti of the program is Ti = (2/4) / 2 = 15 minutes as shown in FIG. do. This is determined according to the following equation (2).

Ti = (Ts / Ns) / Nc - (2)

In Equation 2, Ns is the number of bitstreams that can be transmitted per channel.

Therefore, the user should wait for up to 15 minutes in order to watch the desired program from the beginning among the broadcasting programs started at regular intervals. Accordingly, the NVOD set-top box should automatically change the channel so that the user can view the program when he / she watches another broadcast program and a desired program starts to be transmitted.

The MEPC-2 bitstream transmitted in the digital channel band is transmitted in the form of a 188-byte transport packet as shown in FIG. 7, and the transport packet is composed of a synchronizer, a header, and a data portion. The data portion can be used as video, audio or user data depending on the content of the header.

In addition, when the server is used as user data to enable automatic channel tuning, the present invention automatically formats the start information of the automatic channel tuning data, the channel number of the program, the program identification number, and the end information of the automatic channel tuning data, I will.

8, a tuner 40 for tuning a high-frequency signal from a coaxial cable 41 and an analogue channel processor 42 for processing a high-frequency signal selected by the tuner 40 are provided. A digital set-top box of a service system is shown. The analog channel processor 42 inversely mixes the high frequency signal selected by the tuner 40 to generate a baseband video signal and an audio signal, which are original signals. The analog channel processor 12 supplies the baseband video signal and the audio signal to the television set as it is, or frequency-converts it to the channel frequency domain of the television set, and supplies the frequency-converted signal to the television set.

The digital set-top box of the NOVD service system includes a data channel demodulator 44 for demodulating bit streams from a high frequency signal from the tuner 40, a data switching unit 46 for inputting a bit stream from the data channel demodulator 44, And an MEPC decoder 48 for inputting data from the data switching unit 46. [ The data channel demodulator 44 demodulates the bit streams by quadrature amplitude demodulation or residual side band demodulation of the digitally modulated high frequency signal from the tuner 40 and supplies the demodulated bit streams to the data switching unit 46. The data switching unit 46 analyzes the switching data of the designated bit stream among the bit streams from the data channel demodulator 44 and supplies the MPEC video and audio data to the MPEC decoder 48 according to the result, To the line (45). The MPEC decoder 48 decodes MPEC video and audio data from the data switching unit 46 to generate a video signal (i.e., an NTSC or PAL video signal) and an audio signal, and outputs them to the output lines 47 and 49. [ To a television set not shown.

The digital set-top box of the NVOD service system includes a CPU 50 for controlling the box, a memory 52 for temporarily storing programs and data to be executed by the CPU 50, And a user relay unit 54 for inputting information. The CPU 50 controls the analog set top box according to the program stored in the memory 52 via the user relaying unit 54 to perform a function desired by the user. The CPU 50 also searches for the channel number and the image recognition code included in the user data input from the data switching unit 46 via the bus line 45 and displays the program on the digital channel band or the analog Adjusts the channel selection channel of the tuner 40 so that a program on the channel band is received, and changes the number of the bit stream to be input by the data switching unit 46.

FIG. 9 shows a flowchart of an automatic channel tuning method of a set-top box of an NVOD service system according to an embodiment of the present invention. The flowchart of FIG. 9 is performed by the CPU 50 shown in FIG. 8, which will be described in detail.

In operation 56, the CPU 50 inputs the channel number and the program identification code of the broadcast program that the user wishes to view via the user relay unit 54 while receiving an NVOD program. The CPU 50 maintains the tuning channel of the tuner 40 as it is so that the currently received broadcast program is continuously received.

The CPU 50 waits until the same channel number as the input channel number is input from the data switching unit 46 (operation 58). In operation 58, when a channel number identical to the input channel number is input from the data switching unit 46, the CPU 50 checks the channel number to determine whether the channel belongs to the analog channel band. If the channel number belongs to the analog channel band in operation 60, the CPU 50 controls the tuner 40 to change the channel selection channel of the tuner 40 to the channel number in operation 62. At this time, the analog channel processor 42 restores the video signal and the audio signal of the desired program from the high-frequency signal of the channel selected by the tuner 40, and outputs the restored video signal and audio signal to the output line 43. [ To the television set so that the user can watch the desired program.

On the other hand, if the channel number does not belong to the analog channel band in step 60, the CPU 50 compares the program identification code inputted by the user with the program identification code from the data diseased part 46 (step 64 ). If the program identification code input by the user does not match the program identification code from the data switching unit 46, the CPU 50 returns to step 58. [ On the other hand, if the program identification code entered by the user in step 64 matches the program identification code from the data switching unit 46, the CPU 50 sets the channel selection channel of the tuner 40 to the channel number input by the user And sets the program identification code entered by the user in the data switching unit 46 (operation 66). At this time, the data channel demodulator 44 demodulates the bit streams from the high-frequency signal from the tuner 40. The data switching unit 46 receives the bit stream corresponding to the set program identification code among the bit streams from the data channel demodulator 44 and outputs the MPEC video and audio data included in the bit stream to the MPEC decoder 48. [ . Then, the MPEC decoder 48 decodes the MPEC video and audio data from the data switching unit 46 to generate video and audio signals, and outputs the generated video and audio signals to the television So that the user can view a desired program. After step 62 or step 66, the CPU 50 initializes the channel number and the program identification code input by the user in operation 68.

As described above, according to the present invention, a channel number and a program identification code input by a user are automatically tuned to a channel of an analog channel band in comparison with a channel number and a program identification code transmitted from a server, Can be selected.

Claims (3)

A set-top box of a near-field video service system, comprising: inputting a channel number and a program identification code of a program to be watched by a user; detecting user data for automatic channel selection from the received signal; Comparing the input channel number and the identification code and checking whether the input channel number is an analog channel band; switching the channel selection channel to the input channel number and setting the program identification code; Wherein the automatic tuning method comprises: The automatic tuning method according to claim 1, further comprising the step of switching a channel selection channel to an input channel number when the inputted channel number is the analog channel band in the channel band inspecting step. The automatic tuning method according to claim 1, further comprising the step of initializing an input channel number and an identification code after the identification code setting step.