JP2006238149A - Digital data receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital data receiver capable of switching an image and a still image, with noticing a specific image area on a screen. <P>SOLUTION: A digital data receiver (10) includes a digital data generator (16) to receive a broadcast wave in order to generate digital data, an image data generator (20, 21) to generate image data from the digital data, a detection part (20, 21) to detect an error signal from data corresponding to specific image areas (52, 54, 55, 56) in the digital data, and a switching control part (34) to control switching from the image data to freeze image data, base on the error signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a digital data receiver such as a digital broadcast receiver capable of switching and outputting video data and freeze image data.

  In an analog TV broadcast receiver, an image state is detected by detecting a temporal fluctuation (jitter) state of a synchronization pulse separated from a received video signal, and a moving image and a still image according to program contents. Is known (for example, Patent Document 1).

  By the way, in digital broadcasting, hierarchical transmission in which a plurality of layers having different transmission characteristics are simultaneously transmitted is possible. Therefore, for example, different types of encoded digital data (MPEG2, MPEG4, H.264, etc.) are received in the same channel by digital broadcasting, and one type of encoded digital data is received according to the reception status. There is known a technique for switching to (for example, Patent Document 2).

  However, when switching to different types of encoded digital data depending on the reception situation, the video data decoded from each encoded digital data is not always completely synchronized, so switching Therefore, there is a disadvantage that the video cannot be switched seamlessly. Also, if the reception status of one encoded digital data deteriorates, the reception status of the other encoded digital data is not necessarily good, and it may not be possible to provide a good video even after switching. there were. Further, if switching is performed frequently, there is a disadvantage that the user feels uncomfortable.

JP-A-11-88726 (page 6, FIG. 1) JP 2002-158726 A (page 2, FIG. 1)

  It is also conceivable that an error signal is detected from the received digital data, and a video and a freeze (still) image are switched and displayed in accordance with the detected error signal. That is, when the reception state is poor and the video contains a lot of noise and cannot be viewed, the video is switched to the frozen image for display. However, in TV images, important information often appears in a specific image area (for example, the center of the screen) on the screen that the user is interested in, and other areas (for example, the periphery of the screen). Even if some noise is generated, it is not a big problem.

  Therefore, an object of the present invention is to provide a digital data receiver that can switch between a video and a freeze image while paying attention to a specific image area on a screen.

  It is another object of the present invention to provide a digital data receiver capable of optimizing the conditions for switching between video and freeze images according to the situation.

  In order to solve the above problems, a digital data receiver according to the present invention includes a digital data generation unit that receives broadcast waves and generates digital data, a video data generation unit that generates video data from digital data, and a digital data receiver. Among the data, a detection unit that detects an error signal from data corresponding to a specific image region, and a switching control unit that performs switching control from video data to freeze image data according to the error signal are characterized.

  In the digital data receiver according to the present invention, the specific image area is preferably an area at the center of the screen. This is because normally, in a TV image, important information is often displayed in the central area of the screen.

  In the digital data receiver according to the present invention, the specific image area includes a first area and a second area different from the first area, and the detection unit generates an error signal for each of the first and second areas. Preferably, the switching control unit performs switching from the video data to the freeze image data for each of the first and second regions in accordance with an error signal for each of the first and second regions. A plurality of areas are set on the screen, and switching from a video to a frozen image can be performed for each area.

  Furthermore, in the digital data receiver according to the present invention, it is preferable that the first area is an area in the center of the screen and the second area is an area around the first area.

  Further, in the digital data receiver according to the present invention, the first area is a central area of the first video displayed on the screen, and the second area is a central area of the second video displayed on the screen. A region is preferred. For example, when two images are simultaneously displayed on one display, important information is often displayed in the area at the center of the screen of each image.

  Furthermore, the digital data receiver according to the present invention preferably includes a setting unit for setting the specific image area and a storage unit for storing the setting contents by the setting unit. The specific image area is configured so that the user can freely set it.

  Furthermore, in the digital data receiver according to the present invention, the switching condition from the video data to the freeze image data is set, the vehicle speed of the vehicle on which the digital data receiver is mounted, the reception frequency of the broadcast wave, and the digital data receiver Vehicle speed and broadcast wave reception frequency, genre of program corresponding to video data (news, sports, etc.), type of video data, video size of video data (high definition size, standard size, mobile size, etc.) It is preferable to change according to the type of digital data (MPEG2, MPEG4, H.264, etc.) or past switching history information. The switching condition from video data to freeze image data can be set optimally according to the situation.

  Furthermore, the digital data receiver according to the present invention preferably includes a setting unit for setting a switching condition from video data to freeze image data, and a storage unit for storing setting contents by the setting unit. In this configuration, the user can freely set the switching condition from the video data to the freeze image data.

  Furthermore, the digital data receiver according to the present invention preferably includes an arithmetic processing unit that performs processing so that video data generated from data corresponding to a specific image region is enlarged and output.

  Furthermore, the digital data receiver according to the present invention has a tuner unit that receives broadcast waves and outputs an electric field strength signal of the received broadcast waves, and the switching control unit displays video according to the error signal and the electric field strength signal. It is preferable to perform switching control from data to freeze image data. In addition to the error signal, an electric field strength signal (AGC signal) is used together so that switching control from video data to freeze image data can be performed.

  Furthermore, in the digital data receiver according to the present invention, the freeze image data is preferably still image data, and still image data generated by a still image generation unit from still image data or video data stored in advance. It is preferable that

  The digital data receiver according to the present invention can appropriately switch between video data (moving image) and freeze image data (still image) depending on the situation while paying attention to a specific image area. Therefore, even if a lot of noise occurs in an area other than the specific image area, it is possible to continue to view the video, and it is not necessary to frequently switch between digital data.

  In the digital data receiver according to the present invention, in particular, the switching condition from the video data to the freeze image data is changed according to the vehicle speed and / or the reception frequency of the broadcast wave of the vehicle in which the digital data receiver is mounted. When controlled, the conditions for switching between video data and freeze image data can be optimized regardless of the external environment.

  A digital data (broadcast) receiver according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing an outline of a digital data receiver 10 according to the present invention.

  The digital data receiver 10 includes a tuner unit 12, an OFDM demodulation processing unit 14, a TS decoding processing unit 16, a first audio decoder 18, a second audio decoder 19, a first video decoder 20, a second video decoder 21, and an audio switching process. The unit 22 includes a video switching processing unit 24, a presentation processing unit 26, a delay circuit 30, a D / A converter 31, a RAM 32, a ROM 33, a control unit 34, an I / O 36, a system bus 38, and the like. The digital data receiver 10 includes an antenna 40, a vehicle-mounted display unit 50, a speaker 60, a remote controller 70, and a running state detection unit 80 for outputting vehicle speed data of a vehicle on which the digital data receiver 10 is mounted. It is connected.

  The digital data receiver 10 is controlled by operation inputs from various input devices (buttons, touch panel, etc.) provided in the remote controller 70 and / or the display unit 50. Note that the digital data receiver 10 may be configured to include any one or more of the antenna 40, the on-vehicle display unit 50, the speaker 60, the remote controller 70, and the traveling state detection unit 80 described above.

  The tuner unit 12 receives a broadcast wave from the antenna 40, extracts an OFDM (Orthogonal Frequency Division Multiplexing) signal existing in a desired band, adjusts the level by a built-in AGC (Auto Gain Control) circuit, and then performs an OFDM demodulation process. Send to part 14. The OFDM signal is controlled to a desired level by the AGC signal. In addition, the tuner unit 12 transmits an AGC signal to the control unit 34 via the system bus 38.

  The OFDM demodulation processing unit 14 demodulates the digitally modulated OFDM signal, performs error correction processing, and the like, and sends a TS (transport stream) packet signal to the TS decoding processing unit 16. At the same time, the OFDM demodulation processing unit 14 transmits transport errors (TS-ERR): A, B, and C to the control unit 34 via the system bus 38. TS-ERR: A indicates an error for mobile broadcasting, and TS-ERR: B or C indicates an error for fixed broadcasting.

  The TS decode processing unit 16 filters (selects) the TS packet signal and delivers only necessary data to the corresponding decoder. More specifically, the digital data for fixed broadcasting (general household use) is encoded, and the encoded digital data encoded by the MPEG2 system is separated into audio and video and sent to the first audio decoder 18 and the first. It is delivered to the video decoder 20 and is compatible with digital broadcasting for portable broadcasting. H.264 system (one of the video compression systems also known as MPEG-4 Part 10) (or MPEG4 system) encoded digital data separated into audio and video, and a second audio decoder 19 and a second video decoder Delivered to 21. In addition, the TS decode processing unit 16 simultaneously sends a decode error signal for fixed wave broadcast data and a decode error signal for portable broadcast data to the control unit 34 via the system bus 38. Further, the TS decode processing unit 16 acquires EPG (program guide information) data from the TS packet signal and transmits it to the control unit 34 via the system bus 38.

  Encoded digital data for fixed wave broadcasting is encoded by the MPEG2 system and is high quality, but the bit rate is high, so noise resistance is weak, and good when the distance from the broadcasting station is long Reception may be difficult. On the other hand, encoded digital data for portable broadcasting is H.264. H.264 format (or MPEG4 format) encoded with a lower bit rate than the MPEG2 format, so it has high noise resistance and can be received well even when the distance from the broadcasting station is longer. It becomes possible.

  In the OFDM scheme, three types of signal carriers can be carried simultaneously, so that a maximum of three types of video data can be separated from the TS decode processing unit 16. Two types of encoded digital data encoded by the H.264 system (or MPEG4 system) are handled. However, the present invention is not limited to this, and a third audio decoder and a third video decoder can be provided.

  The first audio decoder 18 and the first video decoder 20 decode the bit stream of the encoded digital data received from the TS decoding processing unit 16, and output the first audio output for fixed broadcasting (MPEG2 system). One audio data and first video data for display are generated. Further, the second audio decoder 19 and the second video decoder 21 decode the bit stream of the encoded data received from the TS decoding processing unit 16 and use it for portable broadcasting (H.264 system or MPEG4 system). Second audio data for audio output and second video data for display are generated.

  Further, the first video decoder 20 and the second video decoder 21 detect motion vector data added to each macroblock which is a unit of motion compensation from the encoded digital data, and the motion vector is abnormal for each macroblock. A motion vector error signal indicating what percentage of macroblocks constituting one screen has an abnormal value is transmitted to the control unit 34 for each screen. .

  Since the motion vector is two-dimensional data indicating the amount of deviation on the reference screen (the playback screen encoded at the previous time and decoded for use at the next timing), the screen becomes large due to a reception error or the like. When disturbed, it indicates a large movement state. That is, when the motion vector shows an abnormal value (larger than a preset value), it can be understood that the corresponding macroblock data is abnormal data. Furthermore, when there are a large number of such macroblocks in one screen, it can be determined that a lot of noise is generated or the video is greatly distorted and cannot be viewed.

  One of the first audio data and the second audio data from the first and second audio decoders 18 and 19 is selected by the audio switching processing unit under the control of the control unit 34, and predetermined delay processing is performed by the delay circuit 30. After being synchronized with the video data, it is converted into an analog signal by the D / A converter 31 and output from the speaker 60.

  Either one of the first video data and the second video data from the first and second video decoders 20 and 21 is selected by the video switching processing unit 24 under the control of the control unit 34, and the presentation processing unit 26 performs an operation described later. After the processing, it is displayed on the display unit 50.

  The presentation processing unit 28 is a processing unit for displaying the selected video data for fixed wave broadcasting or portable broadcasting in conformity with the display unit 50, such as a VRAM for temporarily storing the video data. As will be described later, the storage unit 27, an arithmetic processing unit 28 for performing arithmetic processing including interpolation processing, replacement processing, and the like for generating still image data (freeze image data) from the first video data or the second video data have.

  The control unit 34 operates in accordance with a preinstalled program using the RAM 32 and the ROM 33, and controls each element connected to the system bus 38. The control unit 34 also includes an AGC signal from the tuner unit 12, TS-ERR: A and B (or C) from the OFDM demodulation processing unit 14, a decoding error signal from the decoding processing unit 16, or the first video decoder 20. And a motion vector error signal from the second video decoder 21, and based on all or a part of each signal, it is determined whether or not the data for fixed wave broadcasting and the data for portable broadcasting can be received. Controls switching of display to still image data. Furthermore, as will be described later, the control unit 34 performs display switching control from video data to still image data based on a motion vector error signal corresponding to a specific image area set in advance or set by a user. . Further, as will be described later, the control unit 34 changes the display switching condition from the video data to the still image data in accordance with the situation of the digital data output device, and performs control so that optimum switching is performed.

  FIG. 2 shows an example of a flow of switching processing (freeze processing) from video data to still image data.

  The flow of FIG. 2 is mainly executed by the control unit 34 of the digital data receiver 10 in cooperation with each element of the digital data receiver 10 according to a program installed in advance.

  First, from a broadcasting station, fixed wave broadcasting using encoded digital data encoded by the MPEG2 system, It is assumed that a broadcast program having the same content by portable broadcasting using encoded digital data encoded by the H.264 system (or MPEG4 system) is hierarchically transmitted on the same broadcast channel. The digital data receiver 10 is assumed to be in a state where the power is turned on and various functions can be operated (S201).

  Next, the control unit 34 acquires information indicating the specific image area (S202). The information indicating the specific image region is information indicating a region that takes into account an error signal of a motion vector for performing display switching control from video data to still image data. Information indicating the specific image area is set in advance and stored in the ROM 33.

  FIG. 3 shows a setting example of the specific image area.

As shown in FIG. 3, the display unit 50 has an image display area 51 of 800 (X ₁ ) × 480 (Y ₁ ) pixels. In the present embodiment, a specific image area 52 of 600 (X ₂ ) × 300 (Y ₂ ) pixels is set in advance in the center of the image display area 51. Further, the peripheral area 53 of the specific image area 52 is indicated by hatching. The specific image area shown in FIG. 3 is an example, and the present invention is not limited to this.

  Next, the control unit 34 obtains information on the genre of the program currently displayed on the display unit 50, that is, whether the program has a low error tolerance such as a news or a talk program or a high error tolerance program such as a sports program. (S203). In a sports program or the like in which the video content changes drastically, it is preferable to continue to display the video rather than overlooking an important scene even if the video is somewhat disturbed. In that sense, it can be said that the error tolerance of video is high in sports programs. As described above, since the error tolerance of the video differs depending on the genre of the program, the switching condition for switching from the video to the still image described later can be changed according to the genre. Further, the genre of the program currently displayed on the display unit 50 is obtained from the EPG data output from the TS decode processing unit 16.

  Next, the control unit 34 acquires size information of the video data currently displayed on the display unit 50 (S204). Since the error tolerance of the video differs depending on the video size (high definition size, standard size, mobile size, etc.), the switching condition can be changed according to the video size. The size information of the video data is obtained from the first video decoder 20 and / or the second video decoder 21.

  Next, the control unit 34 selects the type of encoded digital data currently displayed on the display unit 50, that is, fixed wave broadcasting using encoded digital data encoded by the MPEG2 system, or H.264. Information on whether the broadcast is for portable use with encoded digital data encoded by the H.264 system (or MPEG4 system) is acquired (S205). Since the error tolerance of video varies depending on the type of encoded digital data (video stream), the switching condition can be changed according to the type of encoded digital data.

  Next, the control part 34 acquires the information regarding the reception frequency of the program currently displayed on the display part 50 (S206). As the reception frequency increases, the noise component of the received data increases. Therefore, if the switching conditions are the same when the reception frequency is low and high, switching occurs frequently when the reception frequency is high. Become. Therefore, the switching condition can be changed according to the reception frequency. In Japanese terrestrial digital broadcasting, reception center frequencies of 13ch to 62ch are assigned in order between 473.142867 MHz and 767.142857 MHz. Therefore, in this embodiment, the channel and the reception frequency are considered to correspond to each other, and the channel number is used instead of the reception frequency to obtain information regarding the reception frequency. However, information on the reception frequency itself may be acquired based on the reception frequency signal from the tuner unit 12.

  Next, the control unit 34 acquires speed information of the vehicle on which the digital data output device 10 is mounted from the traveling state detection unit 80 (S207). As the vehicle moves at a higher speed, the noise component of the received radio wave increases. Therefore, if the switching conditions are the same when the vehicle speed is low and high, frequent switching occurs when the vehicle speed is high. It becomes. Therefore, the switching condition can be changed according to the vehicle speed.

  Next, the control unit 34 receives a reference screen (encoded at the previous time and the next timing) from the first video decoder 20 or the second video decoder 21 that is outputting the video data currently displayed on the display unit 50. A motion vector error signal corresponding to the specific image region (region 52 in FIG. 3) set in S202 in the playback screen decoded for use in (S209) is acquired (S209).

  Next, the control unit 34 determines whether or not the current state is a frozen state (a state in which still image data is being output) (S209). If the current state is not the frozen state, the motion vector error acquired in S208 is determined. The signal is compared with switching conditions (see FIGS. 4 and 5, which will be described later) based on the information acquired in S202 to S207, and whether the freeze state is turned on (switching from video data to still image data) or not A determination is made (S210).

  FIG. 4 shows an example of switching conditions between video data and still image data.

  FIG. 3 shows a threshold 404 for turning on the freeze state according to the program genre 401, the video stream type 402, and the video size 403. For example, when a sports program is viewed in the standard size of the MPEG2 system, when 35% or more of macroblocks in a specific image area (area 52 in FIG. 3) show an abnormal value, the digital data output device The ten control units 34 switch output from video data (moving image) to still image data (still image). Needless to say, the threshold value 404 for freeze-on is an example, and other values can be adopted.

  FIG. 5 shows an example of correction values for switching conditions between video data and still image data.

  In the table of FIG. 5, the vertical axis indicates the channel number acquired in S206 (13 ch to 62 ch is divided into 5 levels), and the horizontal axis indicates the vehicle speed acquired in S206 (km / h: 0 to 100 km / h in 10 levels). Division). Each numerical value in FIG. 5 indicates a correction coefficient for correcting the freeze-on threshold 404 and the freeze-off threshold 405 shown in FIG. That is, the control unit 34 controls to change the switching condition based on the reception frequency and the vehicle speed. Note that the correction values shown in FIG. 5 are merely examples, and it goes without saying that other values can be adopted.

  For example, if a user is watching a high-definition size and MPEG2 news talk program on 14 channels while driving at 60 km / h at a certain point in time, the threshold value for freeze-on is 12.5% (= 25 × 0). .5). Therefore, at that time, when 12.5% or more of the motion vectors corresponding to the specific image region show an abnormal value, the control unit 34 performs switching control from the video data to the still image data.

  Next, the control unit 34 performs control so that the presentation processing unit 26 creates freeze screen (still image) data (S211).

  The presentation processing unit 26 does not use the data of the macroblock having the abnormal value, creates the data by interpolating using the data of the macroblock around the macroblock having the abnormal value, and generates the still image data. create.

  FIG. 6 shows an outline of the data structure of the video stream output from the TS decode processing unit 16.

In the figure, one screen (picture) 600 includes a plurality of slices 601 in which one screen is sectioned in a strip shape, and each slice includes a plurality of macroblocks composed of a plurality of blocks. . Each macroblock includes, for example, luminance data and color difference data for 16 pixels × 16 lines. In the figure, reference numeral 602 indicates nine adjacent macroblocks n _{1 to} n ₉ . For example, when the motion vector of the macro block n ₅ indicates an abnormal value, the arithmetic processing unit 28 uses the reference screen data stored in the storage unit 27 to use the eight macro blocks n adjacent to the macro block n _5. An interpolation process is performed in which the average value of the data of _{1 to} n ₄ and n _{6 to} n ₉ is newly set as the data of the macro block n ₅ . The presentation processing unit 26 performs such interpolation processing on all macroblocks having abnormal values, and creates still image data.

Next, the still image data created in S211 is output to the display unit 50 (S212), and a series of processing ends (S215).

If it is determined in S210 that the freeze-on condition is not met, control is performed to maintain the output of the video data as it is, and the series of processing ends (S215).

  If it is determined in S209 that the current state is in the freeze ON state, the control unit 34 next switches the switching condition (FIG. 4 and FIG. 4) based on the motion vector error signal acquired in S208 and the information acquired in S202 to S207. Compared with FIG. 5 (described later), it is determined whether or not the freeze state is to be turned off (switching from still image data to video data) (S213).

  If it is determined in S213 that the freeze-off condition is satisfied, the output is switched from still image data (still image) to video data (moving image) (S214), and the series of processing ends (S215). FIG. 3 shows a threshold value 405 for turning off the freeze state. For example, if the user is in a frozen state at a certain point but is trying to watch a high-definition size and MPEG2 news talk program on 14 channels while running at 60 km / h, the threshold for freeze-off is 10% ( = 20 × 0.5). Therefore, at that time, if less than 10% of the motion vectors corresponding to the specific image region show an abnormal value, the control unit 34 performs switching control from still image data to video data.

If it is determined in S213 that the freeze-off condition is not satisfied, control is performed so as to maintain the output of still image data as it is, and the series of processing ends (S215).

  As described above, the control unit 34 compares the motion vector error signal corresponding to the specific image area with the switching condition, and performs switching control between the video data and the still image data. The processing flow shown in FIG. 2 is repeated at every predetermined timing. Therefore, if there is little noise in the specific image area, switching from video data to still image data is not performed even if there is a lot of noise outside the specific image area. In other words, since the switching control from the video data to the still image data is performed only when a lot of noise is generated in the area that the user is paying attention to, the problem that the video data becomes difficult to view due to unnecessary switching. It became possible to solve.

  In the above embodiment, only one specific image area (area 52 in FIG. 3) is set in advance. However, the user may arbitrarily set the specific image area using setting means such as the remote controller 70. In addition, user registration may be performed, and a specific image area may be set for each user.

  FIG. 7 shows another setting example of the specific image area.

  In the example of FIG. 7, the specific image area 54 is set at the upper left of the image display area 51 in the display unit 50. The specific image area 54 corresponds to a part for displaying the score of the baseball game. In baseball broadcasting, players and balls move quickly, so even if there is a little noise in the video, it will not be a big problem for viewing, but if you can make it a freeze (still image) you want to avoid it. However, since the area for displaying the team name and score is small and close to a still image, it is difficult to view if a large amount of noise is included in this portion of the video. Therefore, the part for displaying the score of the baseball broadcast is set as the specific image area 54. As described above, it is desirable that the specific image area is set in advance according to the program content or the like, or configured so that the user can set the specific image area for each program using the remote controller 70.

  FIG. 8 shows another setting example of the specific image area.

  The example of FIG. 8 is an example in which two separate first video 81 and second video 82 are displayed in the image display area 51 of the display unit 50, and specific image areas 55 and 56 are respectively displayed in the central part of the video. Set. For example, when a 20-channel program is output as the first video and a 30-channel program is output as the second video, the motion vector error signals corresponding to the specific image areas 55 and 56 of each video are compared with the switching conditions. Thus, switching control between video data and still image data is performed separately. Since the video is different and the situation is different, for example, only the portion corresponding to the first video 81 may be switched to a still image, and the portion corresponding to the second video 82 may continue to output video. Thus, in the present invention, a plurality of specific image areas can be set.

  In the above embodiment, when the error signal of the motion vector corresponding to the specific image area (area 52 in FIG. 3) satisfies the switching condition, the switching control is performed between the entire video and the entire still image. However, the switching control may be performed so that only the portion corresponding to the specific image area is switched. For example, in FIG. 3, the area 52 is set as the first area and the area 53 is set as the second area, and the motion vector error signal corresponding to the first area does not meet the switching condition (noise is low), and the second area corresponds. When the motion vector error signal to be applied satisfies the switching condition (high noise), it is possible to control so that only the region 53 is switched to a part of the still image. Furthermore, in that case, the image of the area 52 may be enlarged and displayed to the full size of the image display area 51.

In the above embodiment, the switching condition (threshold) is set according to the three conditions of program genre, video stream type and video size (see FIG. 4), and the switching condition (threshold) is further set to the reception frequency and vehicle speed. It was set to correct with the corresponding correction coefficient (see FIG. 5). However, it is also possible to employ a table that directly determines the switching condition (threshold value) from the five conditions of program genre, video stream type, video size, reception frequency, and vehicle speed. Further, the switching condition (threshold value) may be determined using an arbitrary condition (1 to 5) among the above five conditions.

  Further, the switching condition may be changed according to the video source (moving image / still image). For example, the switching condition is to be changed between a case where a video to be displayed is a moving image such as a sports program and a case where the video is a still image including only a graph or a table. Whether the video source is a moving image or a still image is determined by the difference between frames calculated by the difference calculation between one decoded frame and another frame one screen before that frame in the presentation processing unit 26. can do. When the inter-frame difference amount is large, it can be determined that the video source is a moving image and has high noise resistance, and when the inter-frame difference amount is small, the video source is a still image and has low noise resistance.

  Furthermore, the switching condition may be changed according to past switching history information. For example, when still image data is output continuously for 10 s (seconds), the threshold of the abnormality rate of the error signal of the motion vector to be switched to the freeze screen is lowered (it is easier to display video data). It is preferable to change. This is because it is not preferable that the freeze screen is displayed for a long time.

  In the above embodiment, the switching condition (threshold value) is set so as to have hysteresis when the freeze is on and when the freeze is off. However, it is also possible to set the switching condition (threshold value) when the freeze is on and when the freeze is off to the same value.

  In the above-described embodiment, the arithmetic processing unit 28 of the presentation processing unit 26 creates still image data by interpolation processing using data of macro blocks having abnormal values and data of surrounding macro blocks. However, the arithmetic processing unit 28 of the presentation processing unit 26 stores the screen data to be displayed at the previous timing in the storage unit 27, and the macro block data having an abnormal value on the reference screen is one previous level. It is also possible to create still image data by a replacement process that replaces the data of the same macroblock on the screen displayed at this timing. Further, the arithmetic processing unit 28 of the presentation processing unit 26 has both the interpolation processing and replacement processing functions described above, and performs either or both of the processing according to the motion vector error signal, and still image data It can also be configured to create

  In the above-described embodiment, the arithmetic processing unit 28 of the presentation processing unit 26 creates still image data by interpolation processing using data of macro blocks having abnormal values and data of surrounding macro blocks. However, predetermined still image data (screen saver or the like) may be stored in the storage unit 27 in advance, and control may be performed so as to switch the still image data stored in advance to video data. In addition, the user selects either interpolation processing or replacement processing as a method for creating still image data using operation means such as the remote controller 70, and / or the created still image data is stored in advance. It is also possible to configure to select which of the still image data is selected.

  In the above embodiment, switching control between video data and still image data is performed using a motion vector error signal. However, using an AGC signal, a TS-ERR signal, an error signal set in a sequence header of a bit stream of encoded digital data, etc., the video data and still image data It is also possible to perform switching control. For example, if the reception level is not high enough to display video as determined from the AGC signal, control is performed to switch from video data to still image data without making a determination based on the motion vector error signal. May be. That is, the determination based on the AGC signal is performed as the first step, and when a sufficient reception level is ensured, the error signal of the motion vector may be compared with the threshold value as the second step.

  Further, it is also possible to configure so that the user can arbitrarily set the threshold value when the freeze is on and when the freeze is off, using the operation means such as the remote controller 70.

It is a block diagram which shows the outline | summary of the digital data receiver which concerns on this invention. It is a figure which shows an example of a switching process flow. It is a figure which shows the example of a setting of a specific image area | region. It is a figure which shows an example of switching conditions. It is a figure which shows an example of the correction value of switching conditions. It is a figure which shows the outline of a data structure. It is a figure which shows the other example of a setting of a specific image area | region. It is a figure which shows the other example of a setting of a specific image area | region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Digital data receiver 14 OFDM demodulation process part 16 TS decoding process part 18 1st audio | voice decoder 19 2nd audio | voice decoder 20 1st video decoder 21 2nd video decoder 22 Audio | voice switching process part 24 Video | video switching process part 26 Presentation process part 27 Storage unit 28 Arithmetic processing unit 34 Control unit 50 Display unit 60 Speaker 70 Remote control unit 80 Running state detection unit

Claims (16)

A digital data receiver,
A digital data generator that receives broadcast waves and generates digital data;
A video data generator for generating video data from the digital data;
Among the digital data, a detection unit that detects an error signal from data corresponding to a specific image region;
A switching control unit that performs switching control from video data to freeze image data in accordance with the error signal;
A digital data receiver comprising:   The digital data receiver according to claim 1, wherein the specific image area is an area in a central portion of the screen. The specific image area includes a first area and a second area different from the first area;
The detection unit detects an error signal for each of the first and second regions,
2. The digital data according to claim 1, wherein the switching control unit performs switching from video data to freeze image data for each of the first and second regions in accordance with an error signal for each of the first and second regions. Receiver device.   4. The digital data receiving apparatus according to claim 3, wherein the first area is an area in a central portion of the screen, and the second area is an area around the first area.   The said 1st area | region is an area | region of the center part of the 1st image | video displayed on a screen, The said 2nd area | region is an area | region of the center part of the 2nd image | video displayed on a screen. Digital data receiver.   Furthermore, the digital data receiver as described in any one of Claims 1-5 which has a memory | storage part which memorize | stores the setting content for setting the said specific image area | region, and the setting content by a setting part.   The said switching control part changes the switching conditions from the said video data to the said freeze image data according to the vehicle speed of the vehicle by which the said digital data receiver is mounted. Digital data receiver.   The digital data receiver according to any one of claims 1 to 7, wherein the switching control unit changes a switching condition from the video data to the freeze image data in accordance with a reception frequency of the broadcast wave.   The digital data according to any one of claims 1 to 6, wherein the switching control unit changes a switching condition from the video data to the freeze image data according to a genre of a program corresponding to the video data. Receiving machine.   The digital data receiver according to claim 1, wherein the switching control unit changes a switching condition from the video data to the freeze image data according to a type of the video data.   The digital data receiver according to claim 1, wherein the switching control unit changes a switching condition from the video data to the freeze image data according to a video size of the video data.   The digital data receiver according to claim 1, wherein the switching control unit changes a switching condition from the video data to the freeze image data according to a type of the digital data.   The digital data receiver according to claim 1, wherein the switching control unit changes a switching condition from the video data to the freeze image data according to past switching history information.   Furthermore, the digital part as described in any one of Claims 1-13 which has a setting part for setting the switching conditions from the said video data to the said freeze image data, and a memory | storage part which memorize | stores the setting content by a setting part. Data receiver.   The digital data receiving apparatus according to any one of claims 1 to 14, further comprising an arithmetic processing unit that performs processing to enlarge and output video data generated from data corresponding to the specific image region. . In addition, a tuner unit that receives the broadcast wave and outputs an electric field strength signal of the received broadcast wave,
The digital data receiver according to claim 1, wherein the switching control unit performs switching control from video data to freeze image data in accordance with the error signal and the electric field strength signal.

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