JP2008113139A - On-board receiving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an on-board receiving device 20 capable of preventing interruption of video when switching is made between a high quality video and a low quality video, while suppressing power consumption to low. <P>SOLUTION: The on-board receiving device 20 has a high quality video decoder 24 and a low quality video decoder 25. When an output source of video data is switched to the other decoder while the video data from one decoder are output to an external reproducing device 13, the other decoder is triggered to start decoding of video data. Then after a specified period has passed, the output source of video data is switched to the other decoder from one decoder, and that one decoder is stopped. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle-mounted receiving device that is mounted on a moving body such as a vehicle, receives digital broadcast radio waves, and outputs video and audio transmitted by the digital broadcast radio waves.

  In terrestrial digital broadcasting recently started, hierarchical transmission is performed in which a transmission band assigned to each broadcasting station is divided into a number of segments and a plurality of layers composed of one or more segments are transmitted simultaneously. Hierarchical transmission has the disadvantage that the higher the number of segments that make up a hierarchy, the higher quality video can be transmitted, but it is vulnerable to reception during movement. Therefore, for example, in the ISDB-T system that is compliant with Japanese digital broadcasting, the band for digital broadcasting of one channel is divided into 13 segments, and 12 segments among them are used for a fixed receiver. High quality video is provided, and the remaining one segment is used to provide low quality video using a transmission scheme that is highly resistant to transmission errors.

  As a result, a high-quality digital broadcast can be received by a fixed receiver installed in a home or the like, and a mobile receiver such as a mobile phone or a PDA can receive a stable digital broadcast even while moving, although the quality is low. It becomes possible.

  However, when a digital broadcast is received and displayed in a navigation device that is mounted on a mobile body and has a relatively larger screen than a mobile phone, PDA, or the like, as many as 12 segments are possible even during movement. There is a desire to display high-quality video using. In order to realize this, for example, in Patent Document 1, a high-quality video broadcast using 12 segments is decoded and displayed based on a reception situation such as a bit error, or one segment is displayed. It is determined whether to decode and display the low-quality video that is transmitted.

JP 2004-166173 A

  Incidentally, the high-quality video decoder and the low-quality video decoder are often implemented as separate ICs (Integrated Circuits) or are configured as different blocks within one IC. For this reason, when the output from one decoder is displayed, the output from the other decoder is not displayed. Therefore, from the viewpoint of reducing power consumption, it is preferable to stop the other decoder. However, the technique disclosed in Patent Document 1 stops the high-quality video decoder when decoding low-quality video, and stops the low-quality video decoder when decoding high-quality video. There is no statement to do so.

  In the technique disclosed in Patent Document 1, while the output from one decoder is being displayed, the other decoder is stopped, and at the time of switching, the active decoder is stopped and the stopped decoder is If it is activated, the power consumption can be reduced, but the video may be interrupted due to the switching of the decoder.

  For example, when one decoder that is operating is stopped and the other decoder that is stopped is started and decoding of the received signal is started, while the output from the decoder that was operating last time is in the buffer, If the output of the video data decoded by the other decoder is started, the video may not be interrupted. However, since a receiving device mounted on a vehicle is required to be small, light, and low in price, there are many cases where a large-capacity memory cannot be mounted, and before output of video data decoded by the other decoder is started. In addition, there is a case where the output from the decoder that was operating last time is lost from the buffer and the video is interrupted.

  In particular, when switching from receiving and displaying high-quality video to low-quality video, high-quality video has a large data size. I can't. Furthermore, although the decoder for low-quality video has a smaller data size than the decoder for high-quality video, the processing time is higher than that of the decoder for high-quality video in order to achieve advanced error correction and high compression ratio. Not so short. Therefore, before the output of the video data decoded by the low-quality video decoder is started, the output from the high-quality video decoder is lost from the buffer, and the video may be interrupted. .

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a video from being interrupted when switching between a high-quality video and a low-quality video while keeping power consumption low.

  In order to solve the above-described problem, the in-vehicle receiving device according to the present invention is configured such that, in two decoders that output video data, while the video data from one decoder is being output to the outside, the output source of the video data is the other. In the case of switching to the other decoder, after the other decoder is activated to start decoding the video data, the video data output source is switched from the one decoder to the other decoder after a predetermined period of time elapses. The one decoder is stopped.

  For example, the present invention is a vehicle-mounted receiving device that is mounted on a vehicle and receives digital broadcasts, a high-quality video decoder that decodes signals included in radio waves for digital broadcasting and outputs high-quality video data; Either a low-quality video decoder that decodes signals contained in broadcast radio waves and outputs low-quality video data, and either a high-quality video decoder or a low-quality video decoder, depending on the reception quality of digital broadcast radio waves, It is determined whether to execute a video decoding process for decoding a signal included in a broadcast radio wave, and a determination unit that outputs a determination result and video data output from a high quality video decoder or a low quality video decoder Output means for outputting to the display device for display, and high quality video decoder or low quality depending on the judgment result from the judgment means A decoder switching means for causing the image decoder to execute a video decoding process and instructing the output means whether to output the video data from the high quality video decoder or the low quality video decoder to the display device; In the high-quality video decoder and the low-quality video decoder, when the determination unit outputs a determination result indicating that the other decoder executes the video decoding process while the first decoder executes the video decoding process. An output means for activating the other decoder to start the video decoding process, and switching the output source of the video data to be output to the display device from one decoder to the other decoder after a predetermined first period has elapsed. And an on-vehicle receiver characterized by stopping one of the decoders.

  According to the in-vehicle receiver of the present invention, it is possible to prevent the video from being interrupted when switching between the high quality video and the low quality video while suppressing power consumption.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a system configuration diagram illustrating the configuration of an in-vehicle reception system 10 according to an embodiment of the invention. The in-vehicle reception system 10 includes an antenna 11, a display device 12, a playback device 13, and an in-vehicle reception device 20. The in-vehicle receiving device 20 includes a demodulation unit 21, a determination unit 22, a DEMUX 23, a high quality video decoder 24, a low quality video decoder 25, a high quality audio decoder 26, a low quality audio decoder 27, an output unit 28, and a decoder switching unit 29. Have.

  The demodulator 21 receives the digital broadcast radio wave transmitted from the digital broadcast relay station via the antenna 11, demodulates the received radio wave, and performs processing such as deinterleaving, descrambling, and error detection / correction. The TS (Transport Stream) packet including high quality video data, the TS packet including low quality video data, the TS packet including high quality audio data, and the TS packet including low quality audio data are extracted and output to the DEMUX 23. .

  In the present embodiment, high quality video data and high quality audio data indicate video data and audio data that are broadcast using 12 segments of radio waves for digital broadcasting, respectively. The quality audio data indicates video data and audio data broadcast using one segment of digital broadcasting radio waves, respectively.

  The demodulator 21 generates data indicating the reception quality of the digital broadcast radio wave received via the antenna 11 and outputs the data to the determination unit 22. The data indicating the reception quality is, for example, the received electric field strength of the digital broadcast radio wave to be received, a CN ratio (Carrier to Noise Ratio) which is a noise level relative to the reception level of the carrier wave in the digital broadcast radio wave to be received, or demodulated This is data indicating the bit error rate of the data. The demodulator 21 generates data indicating the reception quality of the digital broadcast radio wave at intervals of several hundred milliseconds, for example, and outputs the data to the determination unit 22.

  The DEMUX 23 refers to the PID (Packet IDentifier) included in the TS packet output from the demodulator 21 and sends the TS packet including the high quality video data to the high quality video decoder 24 and the TS packet including the low quality video data. The TS packets including high quality audio data are distributed to the high quality audio decoder 26 and the TS packets including low quality audio data are distributed to the low quality video decoder 25, respectively.

  The high quality video decoder 24 and the low quality video decoder 25 construct a video PES (Packetized Elementary Stream) packet using the payload of the received TS packet, generate video data from the constructed video PES packet, and store it in the output buffer. Hold. The high quality audio decoder 26 and the low quality audio decoder 27 construct an audio PES packet using the payload of the received TS packet, generate audio data from the constructed audio PES packet, and hold it in the output buffer.

  Each of the high quality video decoder 24, the low quality video decoder 25, the high quality audio decoder 26, and the low quality audio decoder 27 extracts a PTS (Presentation Time Stamp) from the constructed PES packet, and the extracted PTS is decoded by the decoder. Output to the switching unit 29.

  The determination unit 22 predicts the reception quality after the first period (for example, 2 seconds) based on the reception quality of the digital broadcasting radio wave output from the demodulation unit 21, and the predicted reception quality is determined in advance. If the threshold value is equal to or higher than the threshold value Tha for switching the video decoder, a determination result indicating that the high-quality video decoder 24 is to decode the TS packet is output to the decoder switching unit 29. On the other hand, if the predicted reception quality is less than the threshold value Tha, the determination result indicating that the low quality video decoder 25 is to decode the TS packet is output to the decoder switching unit 29.

  The determination unit 22 predicts the reception quality after the second period (for example, 1 second) based on the reception quality of the digital broadcasting radio wave output from the demodulation unit 21, and the predicted reception quality is determined in advance. When the predetermined threshold value is equal to or greater than the threshold value Thb for switching the audio decoder, a determination result indicating that the high-quality audio decoder 26 is to decode the TS packet is output to the decoder switching unit 29. On the other hand, if the predicted reception quality is less than the threshold value Thb, a determination result indicating that the low-quality audio decoder 27 is to decode the TS packet is output to the decoder switching unit 29.

  In this embodiment, the threshold value Tha for switching the video decoder is set to a value lower in reception quality than the threshold value Thb for switching the audio decoder. Accordingly, the determination unit 22 selects the high quality video decoder 24 even with lower reception quality for video, and selects the low quality audio decoder 27 for higher reception quality for audio. As another example, the threshold value Tha may be set to the same value as the threshold value Thb in reception quality.

  Here, the process performed by the determination unit 22 to predict the reception quality after the elapse of the first period or the second period based on the reception quality of the digital broadcast radio wave output from the demodulation unit 21 will be described below. explain in detail.

  For example, as illustrated in FIG. 2, the determination unit 22 stores a determination table 220 having m pieces of reference data 224 in advance. Each reference data 224 is associated with n pieces of reception quality data 221 indicating temporal variation in reception quality of radio waves for digital broadcasting and the reception quality data 221, and is included in the reception quality data 221. The first predicted quality 222 indicating the reception quality expected after the elapse of the first period from the last data, and the reception quality expected after the elapse of the second period from the last data included in the reception quality data 221 And second predicted quality 223.

  In the present embodiment, each reference data 224 in the determination table 220 is data measured in advance under different conditions. For example, the reception quality data 221 is the reception quality of radio waves for digital broadcasting measured n times every several milliseconds, and the first predicted quality 222 is obtained after the nth data of the reception quality data 221 is measured. The reception quality of the radio wave for digital broadcasting measured when the first period has elapsed, and the second predicted quality 223 is the second period after the n-th data of the reception quality data 221 is measured. It is the reception quality of radio waves for digital broadcasting measured at the time. As another example, each reference data 224 in the determination table 220 may include data calculated under different conditions by simulation or the like.

  The determination unit 22 collects n pieces of data indicating the reception quality output from the demodulation unit 21 in the output order at every predetermined timing (for example, every few seconds). Then, the reference data 224 having the reception quality data 221 indicating the closest variation to the temporal variation of the collected n reception qualities is specified.

  For example, the determination unit 22 uses the reference data 224 having the reception quality data 221 with the comparison value L calculated using Equation 1 below that is closest to 1 as close as possible to the time variations of the collected n reception qualities. It is specified as reference data 224 having reception quality data 221 indicating fluctuation.

ここで、Ｌ_ｍはｍ番目の比較値を示し、ｘ_ｉは復調部２１から収集したｉ番目の受信品質を示し、ａ_ｍｉはｍ番目の参照データ２２４内のｉ番目の受信品質データ２２１を示す。

Here, L _m represents the m th comparison value, x _i represents the i th reception quality collected from the demodulator 21, and a _mi represents the i th reception quality data 221 in the m th reference data 224. Show.

  Then, the determination unit 22 extracts the first predicted quality 222 included in the identified reference data 224 as a predicted value of the reception quality of the radio wave for digital broadcasting after the first period has elapsed, and the extracted predicted value and threshold value It is compared with Tha to determine which decoder is to decode the video, and the determination result is output to the decoder switching unit 29.

  Further, the determination unit 22 extracts the second predicted quality 223 included in the identified reference data 224 as a predicted value of the reception quality of the digital broadcast radio wave after the second period has elapsed, and extracts the predicted value and the threshold value. It is compared with Thb to determine which decoder is to decode the sound, and the determination result is output to the decoder switching unit 29.

  The decoder switching unit 29 controls the start or stop of the high quality video decoder 24, the low quality video decoder 25, the high quality audio decoder 26, and the low quality audio decoder 27 according to the determination result from the determination unit 22, and The output unit 28 is instructed to output a decoder for outputting video data to be output to the display device 12 and a decoder for outputting audio data to be output to the playback device 13.

  More specifically, the decoder switching unit 29 is configured such that, in the high-quality video decoder 24 and the low-quality video decoder 25, while one of the decoders performs video decoding processing, the determination unit 22 sends the video to the other decoder. When the determination result indicating that the decoding process is to be executed is received, the other decoder is activated to start the video decoding process, and the video data output to the display device 12 is output after a predetermined first period has elapsed. The output unit 28 is instructed to switch the original from the one decoder to the other decoder, and the one decoder is stopped.

  Also, when switching the decoder that performs video decoding, the decoder switching unit 29 calculates the PTS value after the first period from the PTS value output from the active decoder, and the first period After the elapse, the output unit 28 is instructed to switch the video data output source decoder output from the video data corresponding to the calculated PTS value.

  With respect to the audio data, the decoder switching unit 29 causes the determination unit 22 to output the audio to the other decoder while the high-quality audio decoder 26 and the low-quality audio decoder 27 are executing the audio decoding process. When a determination result indicating that the decoding process is to be executed is received, the other decoder is activated to start the audio decoding process, and output of audio data to be output to the playback device 13 after a predetermined second period has elapsed. The output unit 28 is instructed to switch the original from the one decoder to the other decoder, and the one decoder is stopped.

  Also, when switching the decoder that performs audio decoding, the decoder switching unit 29 calculates the PTS value after the second period from the PTS value output from the active decoder, and the second period After the elapse, the output unit 28 is instructed to switch the audio data output source decoder to be output to the playback device 13 from the audio data corresponding to the calculated PTS value.

  The output unit 28 outputs the video data in the output buffer of either the high quality video decoder 24 or the low quality video decoder 25 to the display device 12 in accordance with an instruction from the decoder switching unit 29. When the decoder switching unit 29 is instructed to switch the decoder and the decoder switching unit 29, the output unit 28 refers to the video data in the output buffer of the switching destination decoder, and the video corresponding to the instructed PTS value. By outputting the data to the display device 12, the decoder that outputs the video data is switched.

  Similarly, for the audio data, the output unit 28 outputs the audio data in the output buffer of either the high quality audio decoder 26 or the low quality audio decoder 27 to the playback device 13 in accordance with an instruction from the decoder switching unit 29. To do. When the PTS value is instructed from the decoder switching unit 29 together with information on the switching destination decoder, the output unit 28 refers to the audio data in the output buffer of the switching destination decoder and corresponds to the instructed PTS value. The audio data output source decoder is switched by outputting the audio data to the playback device 13.

  FIG. 3 is a timing chart for explaining the operation of each video decoder when switching from high quality video to low quality video. This timing chart starts from a state in which the high quality video decoder 24 is operating, the low quality video decoder 25 is stopped, and video data from the high quality video decoder 24 is displayed on the display device 12.

  Based on the reception quality of the digital broadcasting radio wave, the determination unit 22 determines that the decoder that decodes the video data is the low-quality video decoder 25 after time 30. In response to the determination result from the determination unit 22, the decoder switching unit 29 activates the stopped low quality video decoder 25. Then, the decoder switching unit 29 calculates the PTS value after the first period based on the PTS value received from the high quality video decoder 24 and waits until the first period elapses.

  Then, at the time 31 when the first period has elapsed after the low-quality video decoder 25 is started up, the decoder switching unit 29 outputs to the output unit 28 that the video data output source decoder is switched together with the calculated PTS. The high quality video decoder 24 is stopped. The output unit 28 refers to the video data in the output buffer of the low quality video decoder 25 and switches the output source decoder from the video data corresponding to the instructed PTS value.

  FIG. 4 is a timing chart for explaining the operation of each video decoder when switching from low quality video to high quality video. This timing chart starts from a state in which the low quality video decoder 25 is operating, the high quality video decoder 24 is stopped, and video data from the low quality video decoder 25 is displayed on the display device 12.

  The determination unit 22 determines that the decoder that decodes the video data is the high-quality video decoder 24 after the time point 32 based on the reception quality of the digital broadcast radio wave. In response to the determination result from the determination unit 22, the decoder switching unit 29 activates the stopped high quality video decoder 24. Then, based on the PTS value received from the low quality video decoder 25, the decoder switching unit 29 calculates the PTS value after the first period has elapsed, and waits until the first period has elapsed.

  Then, at the time 33 when the first period has elapsed after the high-quality video decoder 24 is started up, the decoder switching unit 29 outputs to the output unit 28 that the video data output source decoder is switched together with the calculated PTS. Then, the low quality video decoder 25 is stopped. The output unit 28 refers to the video data in the output buffer of the high quality video decoder 24 and switches the output source decoder from the video data corresponding to the designated PTS value.

  FIG. 5 is a timing chart for explaining the operation of each audio decoder when switching from high quality audio to low quality audio. This timing chart starts from a state in which the high quality audio decoder 26 is operating, the low quality audio decoder 27 is stopped, and audio data from the high quality audio decoder 26 is being reproduced by the reproduction device 13.

  The determination unit 22 determines that the decoder that decodes the audio data is the low quality audio decoder 27 after the time point 34 based on the reception quality of the digital broadcasting radio wave. In response to the determination result from the determination unit 22, the decoder switching unit 29 activates the stopped low quality audio decoder 27. Then, the decoder switching unit 29 calculates the PTS value after the second period has elapsed based on the PTS value received from the high quality audio decoder 26, and waits until the second period has elapsed.

  Then, at the time point 35 when the second period has elapsed after starting the low-quality audio decoder 27, the decoder switching unit 29 outputs to the output unit 28 that the audio data output source decoder is to be switched together with the calculated PTS. The high-quality audio decoder 26 is stopped. The output unit 28 refers to the audio data in the output buffer of the low quality audio decoder 27 and switches the output source decoder from the audio data corresponding to the instructed PTS value.

  FIG. 6 is a timing chart for explaining the operation of each audio decoder when switching from low quality audio to high quality audio. This timing chart starts from a state in which the low quality audio decoder 27 is operating, the high quality audio decoder 26 is stopped, and the audio data from the low quality audio decoder 27 is being reproduced by the reproduction device 13.

  Based on the reception quality of the digital broadcast radio wave, the determination unit 22 determines the decoder that decodes the audio data as the high-quality audio decoder 26 after the time point 36. In response to the determination result from the determination unit 22, the decoder switching unit 29 activates the stopped high quality audio decoder 26. Then, based on the PTS value received from the low quality audio decoder 27, the decoder switching unit 29 calculates the PTS value after the second period has elapsed, and waits until the second period has elapsed.

  Then, at the point 37 when the second period elapses after the high-quality audio decoder 26 is activated, the decoder switching unit 29 outputs to the output unit 28 that the audio data output source decoder is switched together with the calculated PTS. Then, the low quality audio decoder 27 is stopped. The output unit 28 refers to the audio data in the output buffer of the high quality audio decoder 26 and switches the output source decoder from the audio data corresponding to the instructed PTS value.

  FIG. 7 is a flowchart illustrating a video switching process executed by the in-vehicle receiving device 20. For example, at a predetermined timing such as when the power is turned on, the in-vehicle receiving device 20 starts the video switching process shown in this flowchart.

  First, the determination unit 22 predicts the reception quality after the first period based on the reception quality of the digital broadcasting radio wave output from the demodulation unit 21, and the predicted reception quality is equal to or higher than a predetermined threshold Tha. It is determined whether or not (S100). When the predicted reception quality is equal to or higher than the threshold Tha (S100: Yes), the determination unit 22 outputs a determination result indicating that the high-quality video decoder 24 is to decode to the decoder switching unit 29. Then, the decoder switching unit 29 activates the high quality video decoder 24 to start decoding (S101). The high quality video decoder 24 decodes the high quality video, holds the video data in the output buffer, and outputs the decoded PTS to the decoder switching unit 29.

  Next, the determination unit 22 determines whether or not the reception quality of the radio wave for digital broadcasting is less than the threshold value Tha (S102). When the reception quality is equal to or higher than the threshold value Tha (S102: No), the determination unit 22 repeats step S102 until the reception quality becomes less than the threshold value Tha. When the reception quality is less than the threshold value Tha (S102: Yes), the determination unit 22 outputs a determination result indicating that the low quality video decoder 25 performs decoding to the decoder switching unit 29. Then, the decoder switching unit 29 activates the low quality video decoder 25 to start decoding (S103).

  Next, the decoder switching unit 29 calculates the PTS value after the first period from the PTS value output from the high quality video decoder 24 (S104). Then, the decoder switching unit 29 determines whether or not the first period has elapsed since the start of the low quality video decoder 25 (S105). If the first period has not elapsed since the low-quality video decoder 25 is activated (S105: No), the decoder switching unit 29 repeats step S105 until the first period elapses.

  When the first period has elapsed since the low-quality video decoder 25 is activated (S105: Yes), the decoder switching unit 29 switches the video data output source to the low-quality video decoder 25 and calculates the calculated PTS. The value is sent to the output unit 28. The output unit 28 determines whether the video data corresponding to the PTS sent from the decoder switching unit 29 exists in the output buffer of the low quality video decoder 25 (S106).

  When the video data corresponding to the PTS sent from the decoder switching unit 29 exists in the output buffer of the low quality video decoder 25 (S106: Yes), the output unit 28 uses the low quality video decoder 25 from the video data. Is output to the display device 12 (S107). Then, the decoder switching unit 29 stops the high quality video decoder 24 (S109), and the determination unit 22 executes the process shown in step S112.

  When the video data corresponding to the PTS sent from the decoder switching unit 29 does not exist in the output buffer of the low quality video decoder 25 (S106: No), the output unit 28 starts from the PTS sent from the decoder switching unit 29. From the video data displayed at the closest timing, the video data from the low quality video decoder 25 is output to the display device 12 (S108), and the decoder switching unit 29 executes the processing shown in step S109.

  In step S100, when the predicted reception quality is less than the threshold value Tha (S100: No), the determination unit 22 outputs a determination result indicating that the low quality video decoder 25 is to decode to the decoder switching unit 29. Then, the decoder switching unit 29 activates the low quality video decoder 25 to start decoding (S111). The low quality video decoder 25 decodes the high quality video, holds the video data in the output buffer, and outputs the decoded PTS to the decoder switching unit 29.

  Next, the determination unit 22 determines whether or not the reception quality of the digital broadcast radio wave is equal to or higher than a threshold value Tha (S112). When the reception quality is less than the threshold value Tha (S112: No), the determination unit 22 repeats step S112 until the reception quality becomes equal to or higher than the threshold value Tha. When the reception quality is equal to or higher than the threshold value Tha (S112: Yes), the determination unit 22 outputs a determination result indicating that the high-quality video decoder 24 performs decoding to the decoder switching unit 29. Then, the decoder switching unit 29 activates the high quality video decoder 24 to start decoding (S113).

  Next, the decoder switching unit 29 calculates the PTS value after the first period from the PTS value output from the low quality video decoder 25 (S114). Then, the decoder switching unit 29 determines whether or not the first period has elapsed since the start of the high quality video decoder 24 (S115). If the first period has not elapsed since the high-quality video decoder 24 was activated (S115: No), the decoder switching unit 29 repeats step S115 until the first period has elapsed.

  When the first period has elapsed since the start of the high quality video decoder 24 (S115: Yes), the decoder switching unit 29 switches the video data output source to the high quality video decoder 24, and also calculates the calculated PTS. The value is sent to the output unit 28. The output unit 28 determines whether the video data corresponding to the PTS sent from the decoder switching unit 29 exists in the output buffer of the high quality video decoder 24 (S116).

  When the video data corresponding to the PTS sent from the decoder switching unit 29 exists in the output buffer of the high quality video decoder 24 (S116: Yes), the output unit 28 uses the high quality video decoder 24 from the video data. Is output to the display device 12 (S117). Then, the decoder switching unit 29 stops the low quality video decoder 25 (S119), and the determination unit 22 executes the process shown in step S102.

  When there is no video data corresponding to the PTS sent from the decoder switching unit 29 in the output buffer of the high quality video decoder 24 (S116: No), the output unit 28 starts from the PTS sent from the decoder switching unit 29. From the video data displayed at the closest timing, the video data from the high quality video decoder 24 is output to the display device 12 (S118), and the decoder switching unit 29 executes the processing shown in step S119.

  FIG. 8 is a flowchart illustrating an audio switching process executed by the in-vehicle receiving device 20. For example, at a predetermined timing such as when the power is turned on, the in-vehicle receiving device 20 starts the voice switching process shown in this flowchart.

  First, the determination unit 22 predicts the reception quality after the elapse of the second period based on the reception quality of the digital broadcasting radio wave output from the demodulation unit 21, and the predicted reception quality is equal to or higher than a predetermined threshold Thb. It is determined whether or not (S200). When the predicted reception quality is equal to or higher than the threshold Thb (S200: Yes), the determination unit 22 outputs a determination result indicating that the high-quality audio decoder 26 is to decode to the decoder switching unit 29. Then, the decoder switching unit 29 activates the high quality audio decoder 26 to start decoding (S201). The high quality audio decoder 26 decodes the high quality audio, holds the audio data in the output buffer, and outputs the decoded PTS to the decoder switching unit 29.

  Next, the determination unit 22 determines whether or not the reception quality of the digital broadcasting radio wave is less than the threshold Thb (S202). When the reception quality is equal to or higher than the threshold Thb (S202: No), the determination unit 22 repeats Step S202 until the reception quality becomes less than the threshold Thb. When the reception quality is less than the threshold Thb (S202: Yes), the determination unit 22 outputs a determination result indicating that the low-quality audio decoder 27 performs decoding to the decoder switching unit 29. Then, the decoder switching unit 29 activates the low quality audio decoder 27 to start decoding (S203).

  Next, the decoder switching unit 29 calculates the PTS value after the second period has elapsed from the PTS value output from the high quality audio decoder 26 (S204). Then, the decoder switching unit 29 determines whether or not the second period has elapsed since the start of the low quality audio decoder 27 (S205). When the second period has not elapsed since the low-quality audio decoder 27 was activated (S205: No), the decoder switching unit 29 repeats step S205 until the second period elapses.

  When the second period has elapsed since the start of the low quality audio decoder 27 (S205: Yes), the decoder switching unit 29 switches the audio data output source to the low quality audio decoder 27, and also calculates the calculated PTS. The value is sent to the output unit 28. The output unit 28 determines whether or not the audio data corresponding to the PTS sent from the decoder switching unit 29 exists in the output buffer of the low quality audio decoder 27 (S206).

  When the audio data corresponding to the PTS sent from the decoder switching unit 29 exists in the output buffer of the low quality audio decoder 27 (S206: Yes), the output unit 28 uses the low quality audio decoder 27 from the audio data. Is output to the playback device 13 (S207). Then, the decoder switching unit 29 stops the high quality audio decoder 26 (S209), and the determination unit 22 executes the process shown in step S212.

  When there is no audio data corresponding to the PTS sent from the decoder switching unit 29 in the output buffer of the low quality audio decoder 27 (S206: No), the output unit 28 starts from the PTS sent from the decoder switching unit 29. The audio data from the low quality audio decoder 27 is output from the audio data reproduced at the closest timing to the reproduction device 13 (S208), and the decoder switching unit 29 executes the process shown in step S209.

  In step S200, when the predicted reception quality is less than the threshold Thb (S200: No), the determination unit 22 outputs to the decoder switching unit 29 a determination result indicating that the low quality audio decoder 27 is to decode. Then, the decoder switching unit 29 activates the low quality audio decoder 27 to start decoding (S211). The low quality audio decoder 27 decodes the high quality audio, holds the audio data in the output buffer, and outputs the decoded PTS to the decoder switching unit 29.

  Next, the determination unit 22 determines whether or not the reception quality of the digital broadcasting radio wave is equal to or higher than the threshold Thb (S212). When the reception quality is less than the threshold Thb (S212: No), the determination unit 22 repeats Step S212 until the reception quality becomes equal to or higher than the threshold Thb. When the reception quality is equal to or higher than the threshold Thb (S212: Yes), the determination unit 22 outputs a determination result indicating that the high-quality audio decoder 26 performs decoding to the decoder switching unit 29. Then, the decoder switching unit 29 activates the high quality audio decoder 26 to start decoding (S213).

  Next, the decoder switching unit 29 calculates the PTS value after the second period has elapsed from the PTS value output from the low quality audio decoder 27 (S214). Then, the decoder switching unit 29 determines whether or not the second period has elapsed since the start of the high quality audio decoder 26 (S215). If the second period has not elapsed since the high quality audio decoder 26 was activated (S215: No), the decoder switching unit 29 repeats step S215 until the second period elapses.

  When the second period has elapsed since the start of the high quality audio decoder 26 (S215: Yes), the decoder switching unit 29 switches the output source of the audio data to the high quality audio decoder 26 and the calculated PTS. The value is sent to the output unit 28. The output unit 28 determines whether there is audio data corresponding to the PTS sent from the decoder switching unit 29 in the output buffer of the high quality audio decoder 26 (S216).

  When the audio data corresponding to the PTS sent from the decoder switching unit 29 exists in the output buffer of the high quality audio decoder 26 (S216: Yes), the output unit 28 uses the high quality audio decoder 26 from the audio data. Is output to the playback device 13 (S217). Then, the decoder switching unit 29 stops the low quality audio decoder 27 (S219), and the determination unit 22 executes the process shown in step S202.

  When there is no audio data corresponding to the PTS sent from the decoder switching unit 29 in the output buffer of the high quality audio decoder 26 (S216: No), the output unit 28 starts from the PTS sent from the decoder switching unit 29. From the audio data reproduced at the closest timing, the audio data from the high-quality audio decoder 26 is output to the reproduction device 13 (S218), and the decoder switching unit 29 executes the process shown in step S219.

  The embodiment of the present invention has been described above.

  As is clear from the above description, according to the in-vehicle receiving device 20 of the present invention, it is possible to prevent the video from being interrupted when switching between the high quality video and the low quality video while keeping the power consumption low.

  In addition, this invention is not limited to said embodiment, Many deformation | transformation are possible within the range of the summary.

  For example, in the above-described embodiment, switching of video data and switching of audio data has been described. However, the present invention can also be applied to a case where a data broadcast is received and displayed. For example, the in-vehicle receiving device 20 receives data broadcasts transmitted using 12 segments and receives data broadcasts transmitted using one segment according to the reception quality of radio waves for digital broadcasting. When one data broadcast is switched to the other data broadcast during display, the data broadcast before switching is displayed until decoding of the other data broadcast is completed and display is possible.

  As a result, for example, as shown in FIG. 9, in a screen display 40 having a video display area 41 and a so-called L-shaped data broadcast display area 42, high quality using 12 segments in the video display area 41. When a video is displayed and a data broadcast using 12 segments is displayed in the data broadcast display area 42, the video displayed in the video display area 41 when the reception quality of radio waves for digital broadcasting is deteriorated Is switched to a low-quality video using one segment after the first period has passed, but the data broadcast displayed in the data broadcast display area 42 is transmitted as a data broadcast using one segment by carousel transmission. Until then, data broadcasts using 12 segments are displayed as they are.

  Further, when the reception quality further deteriorates and the low quality video using one segment cannot be normally displayed, for example, as shown in FIG. 10, the entire screen display 40 is replaced with the data broadcast display area 46. You may make it do. Thereby, it is possible to prevent the viewer from feeling uncomfortable due to flickering of the video or the like.

  Further, in the above-described embodiment, the in-vehicle receiving device 20 switches the video data and the audio data between high quality and low quality at any time according to the reception quality of the digital broadcasting radio wave. As a form, for audio data, when the low quality audio decoder 27 is once selected as a decoder for decoding the audio data, the decoder switching unit 29 receives the digital broadcasting radio wave until the vehicle engine is stopped. A decoder that decodes audio data regardless of quality may be fixed to the low-quality audio decoder 27.

  The driver often obtains information by voice because it is difficult to see the screen while driving even if it is important information. However, if the voice quality changes frequently, the voice may be difficult to hear. . On the other hand, by fixing the output source of the audio data to the low quality audio decoder 27 regardless of the reception quality of the digital broadcasting radio wave, it is possible to provide audio information that is more easily heard by the driver.

  Further, in the above-described embodiment, the determination unit 22 predicts the reception quality of radio waves for digital broadcasting after a predetermined period has elapsed, and determines whether to switch the video decoder or the audio decoder according to the predicted reception quality. As another form, it is possible to determine whether or not to switch between the video decoder and the audio decoder by comparing the reception quality of the digital broadcasting radio wave at that time with a threshold value at predetermined time intervals. .

  Further, in the above-described embodiment, the decoder switching unit 29 instructs the output unit 28 to switch the decoder together with the PTS of the data to be switched after a predetermined period of time has elapsed since starting the stopped decoder. After receiving the instruction from the decoder switching unit 29, it is determined whether or not there is data corresponding to the instructed PTS in the buffer of the switching destination decoder. However, the present invention is not limited to this. As another example, the decoder switching unit 29 instructs the output unit 28 to switch the decoder without waiting for the elapse of a predetermined period after starting the stopped decoder. The decoder may be switched when data corresponding to the data from the active decoder is stored in the buffer. In this case, the output unit 28 notifies the decoder switching unit 29 that the decoder has been switched, and the decoder switching unit 29 receives the notification and stops the switching source decoder.

  In the above-described embodiment, the determination unit 22 uses the determination table 220 to predict the reception quality of radio waves for digital broadcasting after a predetermined period has elapsed, but the present invention is not limited to this. For example, the determination unit 22 may predict the reception quality ahead of a predetermined period from a certain point in time by causing the neural network to learn an actual measurement value of the reception quality of the digital broadcast radio wave. In addition, the determination unit 22 uses the quality of the digital broadcasting radio wave being received from a certain point of time by a predictive genetic algorithm, tabu search method, least squares method, linear programming method, regression analysis, statistical method, or the like. The reception quality ahead of a predetermined period may be predicted.

1 is a system configuration diagram illustrating the configuration of an in-vehicle reception system 10 according to an embodiment of the present invention. It is a figure which illustrates the data structure of the determination table 220 which the determination part 22 has. It is a timing chart for demonstrating operation | movement of each video decoder in the case of switching from a high quality video to a low quality video. It is a timing chart for demonstrating operation | movement of each video decoder in the case of switching from a low quality video to a high quality video. It is a timing chart for demonstrating operation | movement of each audio | voice decoder at the time of switching from high quality audio | voice to low quality audio | voice. It is a timing chart for demonstrating operation | movement of each audio | voice decoder in the case of switching from a low quality audio | voice to a high quality audio | voice. 4 is a flowchart illustrating a video switching process executed by the in-vehicle receiving device 20. 5 is a flowchart illustrating an audio switching process executed by the in-vehicle receiving device 20. It is a conceptual diagram which illustrates the screen 40 on which data broadcasting is displayed. It is a conceptual diagram which shows the other example of the screen 40 on which data broadcasting is displayed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... In-vehicle receiving system, 11 ... Antenna, 12 ... Display apparatus, 13 ... Reproduction | regeneration apparatus, 20 ... In-vehicle receiving apparatus, 21 ... Demodulation part, 22 ... Determination part, 220 ... determination table, 221 ... reception quality data, 222 ... first prediction quality, 223 ... second prediction quality, 224 ... reference data, 23 ... DEMUX, 24 ..High quality video decoder, 25... Low quality video decoder, 26... High quality audio decoder, 27... Low quality audio decoder, 28. ... Time, 31 ... Time, 32 ... Time, 33 ... Time, 34 ... Time, 35 ... Time, 36 ... Time, 37 ... Time, 40 ...・ Screen display, 41 ... Video display area, 42 ... Data broadcast display area , 45 ... screen display, 46 ... data broadcast display area

Claims (12)

An in-vehicle receiver that is mounted on a vehicle and receives a digital broadcast,
A high-quality video decoder that decodes signals contained in radio waves for digital broadcasting and outputs high-quality video data;
A low-quality video decoder that decodes signals contained in radio waves for digital broadcasting and outputs low-quality video data;
According to the reception quality of the radio wave for digital broadcasting, it is determined whether the high-quality video decoder or the low-quality video decoder is to execute the video decoding process for decoding the signal included in the digital broadcast radio wave. A determination means for outputting a result;
Output means for outputting the video data output from the high quality video decoder or the low quality video decoder to a display device for displaying video;
Depending on the determination result from the determination means, the high quality video decoder or the low quality video decoder is caused to execute the video decoding process, and the video data from either the high quality video decoder or the low quality video decoder is Decoder switching means for instructing the output means whether to output to the display device,
The decoder switching means
In the high-quality video decoder and the low-quality video decoder, a determination result indicating that the determination unit causes the other decoder to execute the video decoding process while the video decoding process is performed by one decoder. When output, the other decoder is activated to start the video decoding process, and after the first predetermined period has elapsed, the output source of the video data to be output to the display device is sent from the one decoder to the An in-vehicle receiving apparatus characterized by instructing the output means to switch to the other decoder and stopping the one decoder. The in-vehicle receiving device according to claim 1,
The high quality video decoder and the low quality video decoder are:
PTS (Presentation Time Stamp) decoded in the video decoding process is output to the decoder switching means and the output means,
The decoder switching means
In the high-quality video decoder and the low-quality video decoder, a determination result indicating that the determination unit causes the other decoder to execute the video decoding process while the video decoding process is performed by one decoder. When outputting, the PTS value after the first period is calculated from the PTS value output from the one decoder, and the video corresponding to the calculated PTS value after the first period has elapsed. From the data, instruct the output means to output the video data from the other decoder to the display device,
The output means includes
A vehicle-mounted receiving device that switches the output source of video data to be output to the display device from video data corresponding to a PTS value instructed by the decoder switching means. The vehicle-mounted receiving device according to claim 1 or 2,
The determination means includes
When the reception quality of the radio wave for digital broadcasting is equal to or higher than a predetermined first threshold value, a determination result that causes the high-quality video decoder to execute the video decoding process is output,
An in-vehicle receiving apparatus that outputs a determination result indicating that the video decoding process is to be executed by the low-quality video decoder when reception quality of radio waves for digital broadcasting is less than the first threshold. The vehicle-mounted receiving device according to claim 1 or 2,
The determination means includes
The reception quality of the digital broadcast radio wave after the first period is predicted according to the quality of the radio broadcast radio wave being received, and the predicted reception quality is equal to or higher than a predetermined first threshold. A determination result indicating that the video decoding process is to be performed by the high-quality video decoder,
An in-vehicle receiving apparatus that outputs a determination result indicating that the low-quality video decoder performs the video decoding process when the predicted reception quality is less than the first threshold. The vehicle-mounted receiving device according to claim 4,
The determination means includes
The first data, which is data indicating temporal fluctuations in the reception quality of radio waves for digital broadcasting, and the first data are associated with the first data, and the first data is included in the first data. A video determination table for storing a plurality of video reference data composed of second data that is data indicating reception quality expected after the period of
The video having the first data having the highest correlation with the temporal variation of the measured reception quality by measuring the temporal variation of the quality of the radio wave for digital broadcasting being received and referring to the video determination table An in-vehicle receiving apparatus characterized by specifying reference data for video and predicting second data included in the specified video reference data as reception quality of a digital broadcasting radio wave after the first period has elapsed. The vehicle-mounted receiving device according to any one of claims 1 to 5,
A high-quality audio decoder that decodes signals contained in radio waves for digital broadcasting and outputs high-quality audio data;
A low-quality audio decoder that decodes signals included in radio waves for digital broadcasting and outputs low-quality audio data;
The determination means further includes:
According to the reception quality of the radio wave for digital broadcasting, it is determined whether the high-quality audio decoder or the low-quality audio decoder is to execute an audio decoding process for decoding a signal included in the radio wave for digital broadcasting. Output the result,
The output means further includes:
Outputting the audio data output from the high-quality audio decoder or the low-quality audio decoder to a playback device that reproduces audio;
The decoder switching means further includes:
In the high-quality audio decoder and the low-quality audio decoder, while the one decoder is executing the audio decoding process, the determination unit displays a determination result indicating that the other decoder executes the audio decoding process. When output, the other decoder is activated to start the audio decoding process, and after the second predetermined period has elapsed, an output source of audio data to be output to the playback device is output from the one decoder An in-vehicle receiving apparatus characterized by instructing the switching means to switch to the other decoder and stopping the one decoder. The vehicle-mounted receiving device according to claim 6,
The high quality audio decoder and the low quality audio decoder are:
Outputting the PTS decoded in the audio decoding process to the decoder switching means and the output means;
The decoder switching means
In the high-quality audio decoder and the low-quality audio decoder, while the one decoder is executing the audio decoding process, the determination unit displays a determination result indicating that the other decoder executes the audio decoding process. When outputting, the PTS value after the second period has been calculated from the PTS value output from the one decoder, and the audio corresponding to the calculated PTS value after the second period has elapsed. From the data, instruct the output means to output the audio data from the other decoder to the playback device,
The output means includes
An in-vehicle receiving apparatus characterized by switching an output source of audio data to be output to the playback apparatus from audio data corresponding to a PTS value instructed by the decoder switching means. The in-vehicle receiving device according to claim 6 or 7,
The determination means includes
When the reception quality of the radio wave for digital broadcasting is equal to or higher than a predetermined second threshold, a determination result indicating that the high-quality audio decoder performs the audio decoding process is output,
An in-vehicle receiving apparatus that outputs a determination result indicating that the low-quality audio decoder performs the audio decoding process when reception quality of a digital broadcasting radio wave is less than the second threshold. The in-vehicle receiving device according to claim 6 or 7,
The determination means includes
When the reception quality of the digital broadcasting radio wave after the elapse of the second period is predicted according to the quality of the digital broadcasting radio wave being received, and the predicted reception quality is equal to or higher than a predetermined second threshold value To output a determination result to the effect that the high-quality audio decoder performs the audio decoding process,
A vehicle-mounted receiving device that outputs a determination result to the effect that the low-quality audio decoder performs the audio decoding process when the predicted reception quality is less than the predetermined second threshold. The vehicle-mounted receiving device according to claim 9,
The determination means includes
The second data is associated with the third data, which is the data indicating the temporal variation of the reception quality of the digital broadcasting radio wave, and the second data from the last data included in the third data. A voice determination table for storing a plurality of voice reference data composed of fourth data that is data indicating reception quality expected after the period of
The voice having the third data having the highest correlation with the temporal fluctuation of the measured reception quality by measuring the temporal fluctuation of the quality of the radio wave for digital broadcasting being received and referring to the voice determination table An in-vehicle receiving apparatus characterized by specifying reference data for data and predicting fourth data included in the specified reference data for audio as the reception quality of radio waves for digital broadcasting after the second period has elapsed. It is an in-vehicle receiving device according to any one of claims 8 to 10,
The in-vehicle reception device characterized in that the reception quality corresponding to the first threshold is lower than the reception quality corresponding to the second threshold. It is an in-vehicle receiving device according to any one of claims 6 to 11,
The decoder switching means
When the decoder that decodes audio data is switched from the high-quality audio decoder to the low-quality audio decoder, the decoder that decodes the audio data is not switched to the high-quality audio decoder until the vehicle engine stops. In-vehicle receiver.

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