JP5328432B2 - Digital broadcast receiving apparatus and program switching method - Google Patents

Description

  The present invention relates to a digital broadcast receiving apparatus having a function of receiving a digital television broadcast, and in particular, a main layer broadcast program (for example, a program for a fixed reception service using a full segment) and a sub layer broadcast program (for example, one The present invention relates to a method of switching to a mobile / mobile service program using segments.

  Terrestrial digital broadcasting divides the transmission band of one channel into 13 segments and adopts a different modulation method for each segment, so that broadcasting services for fixed receivers (so-called full segment broadcasting) and mobile / portable terminals Broadcast service (so-called one segment) broadcast for the same time.

  FIG. 1 is a diagram showing a segment structure of terrestrial digital broadcasting. Orthogonal frequency division multiplexing (hereinafter referred to as OFDM) is a method in which a plurality of narrow-band carriers are arranged on the frequency axis, and data is distributed to each carrier for transmission. However, only an error occurs in data transmitted using the frequency, and correction can be made with data from another carrier wave, which is resistant to multipath interference. In Japanese terrestrial digital broadcasting, the spectrum spectrum of OFDM is divided into 13 segments for each frequency. For example, the first to sixth segments and the eighth to thirteenth segments are assigned to full segment broadcasting, and these segments are: Modulated by 64 quadrature amplitude modulation (64QAM), the seventh segment is assigned to one-segment broadcasting, and modulated by QPSK or the like.

  QAM is a modulation scheme that combines phase change and amplitude change by performing quadrature phase modulation of a large number of amplitude shift key modulations, and can increase the amount of information per symbol, so that transmission efficiency is good. Although there is an advantage, a high CN ratio (Carrier to Noise ratio) is required. Therefore, full-segment broadcasting using QAM modulation cannot view the program unless the radio wave condition is good.

  On the other hand, phase shift keying (PSK) is performed by changing the phase of a carrier wave having a constant frequency, and the number of bits to be transmitted per modulation can be increased by increasing the types of phases. In particular, QPSK is for transmitting 2 bits with one modulation. QPKS has a small amount of information that can be transmitted compared to QAM, but has the advantage that it can transmit information and has high noise resistance even when the radio wave condition is poor and the CN ratio is low.

  In-vehicle terrestrial digital receivers perform inter-layer reception that automatically switches between full-segment broadcasting and one-segment broadcasting in order to expand the reception area. In other words, because the radio wave condition varies depending on the traveling position and reception environment of the vehicle, in a region where the reception condition is relatively good, a full segment broadcast with low noise resistance is received and output in high quality, and the reception condition is poor. In the region, it receives and outputs one-segment broadcasts with high noise resistance.

  Patent Document 1 relates to a digital broadcast receiver, and relates to a technique for detecting a difference in broadcast time between one-segment broadcast and full-segment broadcast and erasing a portion of sound that repeats for a period corresponding to the difference.

JP 2008-5255 A

  FIG. 2 is a diagram for explaining a switching operation between a one-segment broadcast and a full-segment broadcast in the conventional terrestrial digital broadcast receiver. The time periods T1, T2, and T3 indicate a state “x” in which the reception sensitivity of digital broadcasting is deteriorated, and the time periods T4, T5, and T6 indicate a state “o” in which the reception sensitivity is good. The terrestrial digital broadcast receiving apparatus performs switching control so that a full segment broadcast is output when the reception sensitivity is good, and a one segment broadcast is output when the reception sensitivity deteriorates. Accordingly, in the time periods T1, T2, and T3, the one segment broadcast is selected, and the full segment broadcast is switched after the time period T4.

  Due to the design of the digital broadcast receiver, the time from decoding the received digital broadcast transport (TS) data to starting playback is faster for full segment broadcast than for one segment broadcast due to data processing. . That is, as shown in FIG. 2, the TS data “1” of the full segment broadcast is reproduced in the period T1, while the TS data “1” of the one segment broadcast is reproduced in the period T2. Hereinafter, the difference in reproduction time between full segment broadcasting and one segment broadcasting is referred to as reproduction time difference D. Therefore, the audio signals of the one segment broadcast reproduced in the time periods T1, T2, and T3 in which the reception sensitivity is deteriorated are output in the time periods T2, T3, and T4 due to the reproduction time difference D, respectively. When the reception sensitivity transitions satisfactorily during the time period T4, switching to full segment broadcasting is performed. However, during the time period T4, the TS data 3 of one segment broadcasting is output as audio due to the reproduction time difference D. Then, in the time period T5, the TS data “5” of the full segment broadcast is reproduced and output as a sound, so that the TS data “4” skips. When a full-segment broadcast program and a one-segment broadcast program are the same, it is not noticed that a video data frame skips because it is a moving image, but skipping or sound interruption is easy to notice and it is easy to give a sense of incongruity.

  An object of the present invention is to solve such a conventional problem and to provide a digital broadcast receiving apparatus and a program switching method capable of preventing sound skipping or interruption in program switching.

  A digital broadcast receiving apparatus according to the present invention divides one transmission band into a plurality of segments, a first program based on a first modulation method using at least one segment, and a segment different from the at least one segment. A receiving unit that can receive a digital broadcast including a second program in one channel using the second modulation method, a receiving unit that receives the digital broadcast, and a sensitivity detecting unit that detects the receiving sensitivity of the received digital broadcast; When it is determined that the reception means detected by the sensitivity detection means has deteriorated, the first program is selected and the reception sensitivity is good. Switching means for switching the program so as to select the second program when it is determined that there is a sound, and the sound reproduced by the reproducing means Audio output means for outputting a signal, and video output means for outputting the video signal reproduced by the reproduction means, wherein the audio output means switches from the first program to the second program by the switching means. When switching is performed, the audio signal of the second program is output at a higher speed than usual for a certain time.

  Preferably, the audio output means includes a memory that stores at least an audio signal of the second program, and outputs an audio signal of the second program stored in the memory after the audio signal of the first program is output. Reads and outputs voice at high speed for a certain time. Preferably, the audio output means determines the fixed time based on a difference between the reproduction time of the audio signal of the first program and the reproduction time of the audio signal of the second program by the reproduction means. The first program is a one-segment broadcast program, and the second program is a full-segment broadcast program. The memory can read and write data in synchronization with a clock signal, and the audio output means can change the frequency of the clock signal for a certain period of time so that the audio signal of the second program is faster than usual. You may make it read by.

  The program switching method of the digital broadcast receiving apparatus according to the present invention divides one transmission band into a plurality of segments, a first program based on a first modulation method using at least one segment, and the at least one program When it is determined that a digital broadcast including a second program based on the second modulation method using a segment different from the segment in one channel can be received and the reception sensitivity of the digital broadcast is deteriorated, the first program is selected. Selecting and switching the program so as to select the second program when it is determined that the reception sensitivity is good, and when switching from the first program to the second program, the audio signal of the second program is selected. After storing in the memory and outputting the audio signal of the first program, the audio signal read from the memory is read at a higher speed than usual for a certain period of time. And a step of voice output Te.

  According to the present invention, when switching from the second program to the first program, it is possible to suppress sound skipping or sound interruption due to a difference in the reproduction time between the audio signals of the first program and the second program.

It is a figure explaining the segment structure of terrestrial digital broadcasting. It is a figure explaining the program switching of the conventional full segment broadcast and one segment broadcast. It is a block diagram which shows the structure of the vehicle-mounted digital terrestrial television broadcast receiver which concerns on the Example of this invention. It is a block diagram which shows the internal structure of the audio | voice switching process part shown in FIG. It is a timing chart which shows the switching operation from the one segment broadcast in a present Example to a full segment broadcast. It is a flowchart which shows the switching operation of the program in the receiver of a present Example. It is a figure which shows the other structural example of a vehicle-mounted terrestrial digital broadcast receiver.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 3 is a block diagram showing the configuration of the in-vehicle digital television broadcast receiver according to the embodiment of the present invention. In the following description, “first” indicates one-segment broadcasting, and “second” indicates full-segment broadcasting. As shown in FIG. 3, the in-vehicle receiving device 100 is connected to the first antenna 102, the second antenna 103, the first tuner 104 connected to the first antenna 102, and the second antenna 3. Second tuner 105, first OFDM demodulator 106 that demodulates the signal received by first tuner 104, and second OFDM demodulator that demodulates the signal received by second tuner 5 107, a diversity combining unit 108 that combines the signals from the first and second OFDM demodulation units 106 and 107, an error correction unit 109 that detects and corrects an error that occurs during transmission of the received digital broadcast, A demultiplexer 110 that separates the multiplexed stream data to obtain an audio stream, a video stream, and a data stream, and an audio stream of the first program A first audio decoder 111 that decodes the stream and reproduces the digital audio signal, a second audio decoder 112 that decodes the audio stream of the second program and reproduces the digital audio signal, and a video stream of the first program A first video decoder 113 that decodes and reproduces the video signal; a second video decoder 114 that decodes the video stream of the second program and reproduces the video signal; a data decoder 115 that decodes the data stream; The audio switching processing unit 116 for switching the audio signal of the first program or the second program, the video switching processing unit 117 for switching the video signal of the first program or the second program, and the digital output from the audio switching processing unit 116 A D / A converter 118 that converts an audio signal into an analog audio signal, and a monitor that outputs the analog audio signal. 119, a rendering processing unit 120 for rendering the video signal output from the video switching processing unit 117 on a display, a display 121, a control unit 122, and an input unit 123 that receives input from the user. .

  The first and second tuners 104 and 105 receive a broadcast signal having a frequency of a selected channel in response to a user input from the input unit 123, and receive the broadcast signal with the first and second OFDM demodulation units 106, It outputs to 107. The first and second OFDM demodulation units 106 and 107 demodulate the received signal to generate a transport stream. Diversity combining section 108 combines phase shifter 108a that controls the phase of the transport stream from first OFDM demodulation section 106, and the transport stream that has been phase-controlled and the second OFDM demodulation section 107. The combiner 108 b is included, and the diversity combined transport stream is output to the error correction unit 109. Using diversity combining improves reception performance, but is not essential.

  The error correction unit 109 calculates an error rate during transmission of the digital broadcast received from the transport stream, and outputs a signal BER indicating the error rate to the control unit 122. The control unit 122 compares the error rate with a threshold value, and determines that the reception sensitivity is deteriorated when the error rate exceeds the threshold value, and determines that the reception sensitivity is good when the error rate is equal to or less than the threshold value. The threshold value is stored in a nonvolatile rewritable memory of the control unit 122, for example. In this embodiment, the error rate is used to determine the reception sensitivity. However, in addition to this, it is also possible to determine the reception sensitivity by monitoring the reception intensity of the first and second tuners 104 and 105. is there.

  The demultiplexer 110 separates the audio stream, the video stream, and the data stream multiplexed in the input transport stream, and outputs them to the respective decoders 111, 112, 113, 114, 115. Here, the data stream includes an information stream for data broadcasting, and further includes an EIT (Event Information Table). The EIT includes a program name, broadcast date and time, program contents, an event ID for identifying the program, and the like. By checking this event ID, it is possible to determine whether the full segment program and the one segment program are the same.

  The first audio decoder 111 decodes a one-segment broadcast program, that is, an audio stream of the first program, and outputs a reproduced digital audio signal. The second audio decoder 112 decodes a full segment broadcast program, that is, an audio stream of the second program, and outputs a reproduced digital audio signal. The first video decoder 113 decodes the video stream of the one-segment broadcast program, and the second video decoder 114 decodes the video stream of the full-segment broadcast program and outputs a video signal respectively. The data decoder 115 decodes the data stream and outputs the result to the control unit 122.

  The audio switching processing unit 116 selects the audio signal of the first program or the second program according to the control signal S from the control unit 122, and the video switching processing unit 117 is the first program or the second program. Select the video signal.

  The D / A converter 118 converts the audio signal output from the audio switching processing unit 116 into an analog audio signal, and the speaker 119 outputs the analog audio signal. The drawing processing unit 120 performs a scaling process or the like so that the video signal output from the video switching processing unit 117 is adapted to the display size of the display 121, and the display outputs this. The input unit 123 provides a user input interface such as a mouse, a keyboard, and a touch panel, and input information is output to the control unit 122.

  FIG. 4 is a block diagram showing an internal configuration of the voice switching processing unit 116. The audio switching processing unit 116 includes a one-segment audio output buffer 200 and a full-segment audio output buffer 210 that can store the audio signals L1 and L2 from the first and second audio decoders 111 and 112, and the audio output buffer 200. , 210 outputs a sound selection unit 220 that outputs one of the sound signals L1 and L2, and a buffer control unit 230 that controls the sound output buffers 200 and 210 based on the control signal S.

  As the audio output buffers 200 and 210, a DRAM or SRAM capable of reading and writing data in synchronization with a clock signal can be preferably used. The buffer control unit 230 supplies a read / write signal, a clock signal, an address signal, an enable signal, and the like to the audio output buffers 200 and 210 via the signal bus S2 based on the control signal S from the control unit 122. The enable signal allows the operation of the audio output buffers 200 and 210, and the audio signal can be accumulated only during the enable period. Furthermore, when switching the program from the one segment broadcast to the full segment broadcast, the buffer control unit 230 of the present embodiment stores the audio signal of the full segment broadcast in the audio output buffer in accordance with the reproduction time difference D. After the segment broadcast audio signal is output, the audio output buffer 210 is controlled such that the full segment broadcast audio signal is output at double speed.

  FIG. 5 is a timing chart showing the operation of the voice switching processing unit. It is assumed that the reception sensitivity is bad in the time periods T1 to T3, and the reception sensitivity is good in the time periods T4 to T6. When the program is switched to the one-segment broadcast program in the time period T1, due to the reproduction time difference D, the one-segment broadcast TS data 1 is read from the audio output buffer 200 in the time period T2 and output as audio. Subsequently, the TS data 2 and 3 of the one segment broadcast are output in the time periods T3 and T4.

  When it is determined that the reception sensitivity is good in the time period T4, the control signal S instructing switching to the full segment broadcast is supplied to the audio selection unit 220 in the time period T5 in consideration of the reproduction time difference D. In response to the control signal S, the audio selection unit 220 switches the input so that the audio signal from the audio output buffer 210 is output. In synchronization with this, the buffer control unit 230 supplies the address signal for reading out the TS data 4 and 5 to the audio output buffer 210, and the frequency of the clock signal when reading out the TS data 4 and 5 is 1.2 times, for example. Change to The period during which the frequency of the clock signal is varied is preferably substantially equal to the reproduction time difference D, so that in the time period T5, the audio of the TS data 4 and 5 of the full segment broadcast is output at double speed, and the reproduction time difference D Thus, skipping or interruption of sound of the TS data 4 is prevented. Then, in the time period T6, the audio signal of the TS data 6 is output, and the reproduction time difference D is eliminated.

  Next, the program switching operation in the present embodiment will be described with reference to the flowchart of FIG. First, it is assumed that a desired channel is selected by the user, and audio signals and video signals of a second program on the channel, that is, a full-segment program, are output from the speaker 119 and the display 121 (step S101).

  The error correction unit 109 calculates the error rate of the TS data of the selected channel and outputs a signal BER indicating the error rate to the control unit 122. The control unit 122 compares the error rate with a threshold value and determines whether the error rate is equal to or less than the threshold value (step S102). If the error rate is less than or equal to the threshold value, the reception sensitivity is good and the full segment broadcast program continues to be output. On the other hand, when the error rate exceeds the threshold value, the control unit 122 determines that the reception sensitivity has deteriorated, and sends the control signal S instructing switching to the one-segment broadcast program to the audio switching processing unit 116 and the video switching processing unit 117. (Step S103).

  In response to the control signal S, the audio selection unit 220 of the audio switching processing unit 116 switches the input of the audio signal, stops the output of the audio signal L2 from the second audio decoder 112, and the first audio decoder 111. The audio signal L1 from is output. The audio signal L1 output from the audio selection unit 220 is converted into an analog audio signal by the D / A converter 118, and the audio of the one segment broadcast is output from the speaker 119. Similarly, the video switching processing unit 117 selects the video signal of the one segment broadcast, and the video of the one segment broadcast is displayed on the display 121 (step S104).

  The control unit 122 monitors the error rate of the TS data of the selected channel (step S105), and if the error rate exceeds the threshold, the one-segment broadcast program continues to be output. On the other hand, if the error rate is equal to or lower than the threshold value, the control unit 122 determines that the reception sensitivity has transitioned satisfactorily, and transmits the control signal S instructing switching to a full segment broadcast program to the audio switching processing unit 116 and the video switching. The data is output to the processing unit 117 (step S106). The voice selection unit 220 switches input of a voice signal output in response to the control signal S. In addition, the buffer control unit 230 converts the audio signal of the full segment broadcast when the reception sensitivity is determined to be good for a certain period of time, preferably during the reproduction time difference D, to the audio output buffer 210 with a clock signal faster than usual. And the audio is output at double speed (for example, 1.2 times) (step S107). Thereby, when the program is switched from the one segment broadcast to the full segment broadcast, it is possible to prevent sound skipping or sound interruption due to the reproduction time difference D.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and various modifications can be made within the scope of the present invention described in the claims. Deformation / change is possible.

  For example, in the above embodiment, the buffer control unit 230 supplies a clock signal for reading the audio signal at double speed to the audio output buffer. However, as shown in FIG. 4B, a PLL or DLL is used. Clock signals CLKOUT1 and CLKOUT2 having desired frequencies may be supplied from the clock generator 240 to the audio output buffers 200 and 210.

  In the above embodiment, the audio signals L1 and L2 from the first and second audio decoders 111 and 112 are supplied to the audio switching processing unit 116, and the audio signals L1 and L2 are selected there. In addition, as shown in FIG. 7, the first and second audio decoders 111 and 112 may be configured to operate or not operate according to the control signal S. For example, when switching to one segment broadcasting, the first audio decoder 111 is operated, the operation of the second audio decoder 112 is stopped, and when switching to full segment broadcasting, the opposite operation is performed. In this case, the voice switching processing unit 116 does not necessarily require the voice selection unit 220 as shown in FIG.

100: Terrestrial digital television receiver 109: Error correction unit 110: Demultiplexer 111: First audio decoder 112: Second audio decoder 113: First video decoder 114: Second video decoder 116: Audio switching processing unit 117: Video switching processing unit 122: Control unit 200, 210: Audio output buffer 220: Audio selection unit 230: Buffer control unit

Claims (6)

Dividing one transmission band into a plurality of segments, a first program using a first modulation method using at least one segment, and a second program using a second modulation method using a segment different from the at least one segment A digital broadcast receiving apparatus capable of receiving a digital broadcast containing the program in one channel,
Receiving means for receiving a digital broadcast;
Sensitivity detection means for detecting the reception sensitivity of the received digital broadcast;
Reproducing means for reproducing audio and video signals from the received digital broadcast;
When it is determined that the reception sensitivity detected by the sensitivity detection means is deteriorated, the first program is selected, and when it is determined that the reception sensitivity is good, the program is switched so that the second program is selected. Switching means to perform,
Audio output means for outputting the audio signal reproduced by the reproduction means;
Video output means for outputting the video signal reproduced by the reproduction means,
The audio output means is
A first buffer for storing an audio digital signal of the first program;
A second buffer for storing an audio digital signal of the second program;
A buffer control unit that controls the first buffer and the second buffer based on a switching result by the switching unit;
When switching is performed from the first program by the switching means to the second program, the buffer control unit, after the audio digital signal of the first program is output, the audio signal of the first program Reading out the digital audio signal of the second program stored in the second buffer based on the difference between the reproduction time and the reproduction time of the audio signal of the second program at a high speed for a predetermined time;
Digital broadcast receiver. 2. The digital broadcast reception according to claim 1, wherein the buffer control unit provides an enable signal to the first and second buffers and accumulates an audio digital signal in the first or second buffer during an enable period. apparatus. The digital broadcast receiving apparatus according to claim 1 or 2, wherein the first program is a one-segment broadcast program, and the second program is a full-segment broadcast program. The first and second buffers can read and write data in synchronization with a clock signal, and the audio output means can change the frequency of the clock signal for a certain period of time to change the audio of the second program. The digital broadcast receiver according to claim 1 , wherein the digital signal is read at a higher speed than usual. Dividing one transmission band into a plurality of segments, a first program using a first modulation method using at least one segment, and a second program using a second modulation method using a segment different from the at least one segment A program switching method of a digital broadcast receiving apparatus capable of receiving a digital broadcast including one program in one channel,
Selecting a first program when it is determined that the reception sensitivity of the digital broadcast is deteriorated, and switching the program so as to select a second program when it is determined that the reception sensitivity is good;
In response to switching of the switching step, switching the output of a first buffer for storing the audio digital signal of the first program and a second buffer for storing the audio digital signal of the second program;
After outputting the audio digital signal of the first program, the first program of the audio digital signal playback time and the second audio digital signals read out from the buffer based on the reproduction time difference between the audio digital signal of a second program normal and a step of voice output reading certain time faster than, the program switching method. 6. The program switching method according to claim 5 , wherein the first program is a one-segment broadcast program, and the second program is a full-segment broadcast program.

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