JP2008111910A - Video processing circuit and video display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video processing circuit capable of maintaining the same brightness as that of original video signal, when preventing image quality deterioration due to blurring of a dynamic image, in a holding type display device. <P>SOLUTION: This video processing circuit comprises a frame rate conversion means 11 which converts a frame string of original input video signals (a) into a rate converted output (b) comprising a sub-frame string having a frame rate of two or more integral multiple of that of the original video signal (a), by dividing each frame of the frame string into two or more pieces of sub-frames; an amplitude control means 21 which produces two or more amplitude-changed sub-frames for each sub-frame, by changing the video amplitude of each sub-frame; and a signal change-over means 41, which outputs either of the two or more amplitude-changed sub-frames, by changing them over for each frame cycle of the sub-frames, wherein on the screen when displaying an image on the holding type display device, a changed-over signal output d has substantially the same brightness as that of the original video signal (a). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a video processing circuit and a video display device, and more particularly to a video processing circuit and a video display device that supply a video signal to a hold type display device typified by a liquid crystal display device.

  When a video signal is input, a hold-type display device typified by a liquid crystal television holds each pixel value at a frame period and displays a video. When the video is displayed on the hold-type display device in this way, the display brightness of each pixel becomes substantially constant during the period for displaying one frame of the video. That is, the screen remains in a so-called “lighted” state for one frame period.

  On the other hand, in the CRT that has been used for image display so far, the phosphor irradiated with the electron beam during scanning emits light instantaneously, but thereafter its luminance decreases due to the afterglow characteristics. The afterglow characteristic at this time is sufficiently short for one frame period of the video. That is, the CRT shows an impulse response, and it can be said that the time during which light is emitted within one frame is sufficiently shorter than that of the hold type display device.

  As described above, since the hold type display device is less responsive than the CRT, it is known that when a moving image is displayed on the hold type display device, a moving image blur that does not occur in the CRT occurs and the image quality deteriorates. . As an improvement measure, in the invention described in Patent Document 1, a voltage higher than the voltage of the video signal of the current frame is set in advance according to the combination of the video signal of the previous frame and the video signal of the current frame (overload). A drive voltage that has been shot or a drive voltage that has been previously set low (undershoot) is supplied to the liquid crystal display device (overdrive method). In the invention described in Patent Document 2, the video signal is converted into a frame rate to create a subframe having a frame rate that is N (N is an integer of 3 or more) times, and a black level video is generated in the last subframe. A signal is being inserted.

Japanese Patent Laid-Open No. 4-365094 JP 2002-215111 A

  The invention described in Patent Document 1 has been tackled in the direction of increasing the response speed of the hold type display device itself, but the effect of improving the response speed is limited. Further, since the invention described in Patent Document 2 inserts a black level video signal, the video displayed by the converted video signal is darker than the video by the video signal before conversion.

  The present invention has been made to solve such a problem, and an object of the present invention is to maintain the same brightness as that of an original video signal in a hold-type display device when image quality deterioration due to moving image blur is prevented. And

  In the video processing circuit according to the present invention, the frame sequence of the input original video signal is made into a plurality of subframes for each frame of the frame sequence, so that N (N is the frame rate of the original video signal) A frame rate conversion means for converting into a frame-multiplied video signal composed of a subframe sequence having a frame rate of an integer of 2 or more, and changing the video amplitude of each of the subframes, Amplitude control means for generating an amplitude change subframe, and signal switching means for switching and outputting any of the plurality of amplitude change subframes for each frame period of the subframe, and the output of the signal switch means is a hold type The brightness of the screen when displayed on the display device is the screen brightness when the original video signal is displayed on the hold-type display device. That is substantially equal.

  According to the video processing circuit of the present invention, the hold-type display device can maintain the same brightness as that of the original video signal when image quality deterioration due to moving image blur is prevented.

<Embodiment 1>
In this embodiment, a video display device including a video processing circuit according to the present invention and a hold-type display device will be described. FIG. 1 is a block diagram showing a schematic configuration of a video processing circuit of the video ideographic apparatus. As shown in FIG. 1, the video processing circuit includes a frame rate conversion unit 11, an amplitude control unit 21, an amplitude control memory 31, and a signal switching unit 41. The hold type display device corresponds to, for example, a liquid crystal display device. FIG. 2 is a timing chart schematically showing how the video processing circuit having this configuration converts the video signal.

  The frame rate conversion unit 11 includes, for example, a frame memory, and stores an image in the frame memory frame by frame from the frame sequence of the input original video signal a. Then, one frame is read N (N is an integer of 2 or more) times during the frame period of the original video signal a. That is, the frame rate conversion means 11 performs time compression by reading the frame sequence of the original video signal a at a frame frequency N times the frame frequency of the original video signal a.

  FIG. 3 shows the frame sequence of the original video signal a on the upper side and the frame sequence of the new signal b read out with N = 2 on the lower side. In the new signal b, as shown in FIG. 3, the same frame (mesh shaded) as the previous frame is read between the frames (solid plain) of the original video signal a. Both the solid plain and medium shaded frames are collectively called a subframe. Here, two subframes are read from one frame of the original video signal a. That is, the read new signal b has a frame rate that is twice the frame rate of the original video signal a.

  In this way, the frame rate conversion means 11 makes the frame sequence of the input original video signal a a plurality of subframes for each frame of the frame sequence, so that N (N = 2) It is converted into a frame multiplied video signal b composed of a subframe sequence having a double frame rate.

  Here, although the case where N = 2 is described, the number of subframes covered with a medium halftone is further increased, and a frame-multiplied video signal composed of a subframe sequence having a frame rate N (N is an integer of 2 or more) times. You may convert into b. In the present embodiment, the case of N = 2 will be described in the following, but the present invention is not limited to N = 2. Further, the frame-multiplied video signal b after the frame rate conversion means 11 is referred to as an output b after rate conversion for simplicity. Further, in the present embodiment, the original video signal a is assumed to be a 60 Hz progressive scan signal. FIG. 2 shows a vertical synchronization signal b 'of the output b after rate conversion, in addition to the original video signal a and its vertical synchronization signal a'. The frequency of the output b after rate conversion is 120 Hz which is twice the original video signal a, and one vertical period of the vertical synchronizing signal b ′ indicating the frame display period (vertical display period) for the hold type display device is shown in FIG. Thus, 1/120 sec (8.3 msec) is obtained.

  The amplitude control means 21 changes the video amplitude of each subframe, and generates a plurality of amplitude change subframes for each subframe. In the present embodiment, the amplitude control unit 21 includes a first amplitude control unit 211 and a second amplitude control unit 212, and the first amplitude control unit 211 and the second amplitude control unit 212 respectively. An amplitude change subframe is generated. Hereafter, the video signal composed of the amplitude-changed subframe sequence generated by the first amplitude control unit 211 is referred to as an amplitude-changed output c1 hereinafter, and the amplitude-changed subframe sequence generated by the second amplitude control unit 212. The video signal consisting of is called an output c2 after amplitude change.

  FIG. 2 shows the outputs c1 and c2 after the amplitude change. In this figure, the amplitude change subframe of the output c1 after amplitude change is indicated as sub n, and the amplitude change subframe of the output c2 after amplitude change is indicated as sub n '. Since the first amplitude control unit 211 and the second amplitude control unit 212 do not convert the frame rate, the frame rates of the amplitude-changed outputs c1 and c2 are the same as the rate-converted output b as shown in FIG. Thus, it becomes twice the frame rate of the original video signal a. This figure shows a state in which the amplitude-changed outputs c1 and c2 are deviated from the original video signal a by one frame period of the original video signal a by the storage and reading operations in the frame rate conversion means 11. .

  The signal switching means 41 switches and outputs one of the plurality of amplitude changing subframes for each frame period of the subframe. The output after the signal switching means 41 is referred to as post-signal switching output d1. In FIG. 2, an after-switching output d <b> 1 is shown in which the signal switching unit 41 switches and outputs the amplitude-changing subframe of the amplitude-changing output c <b> 1 and the amplitude-changing subframe of the amplitude-changing output c <b> 2 for each frame period. Yes.

  The amplitude control memory 31 including the first amplitude control memory 311 and the second amplitude control memory 312 includes a first video amplitude of the original video signal a and brightness obtained by performing gamma correction on the original video signal a. A conversion table and a second conversion table composed of the video amplitude of the output d1 after signal switching and the brightness of the output d1 after signal switching subjected to gamma correction are stored. The first amplitude control memory 311 and the second amplitude control memory 312 are composed of, for example, a ROM (Read Only Memory) that generates an OS table memory.

  The first amplitude control unit 211 changes the video amplitude of each subframe based on the first conversion table and the second conversion table in the first amplitude control memory 311. Similarly, the second amplitude control unit 212 changes the video amplitude of each subframe based on the first conversion table and the second conversion table in the second amplitude control memory 312.

  In the video processing circuit of the video display device according to the present embodiment, the brightness of the screen when the output d1 after signal switching is displayed on the hold type display device is the same as when the original video signal a is displayed on the hold type display device. It becomes substantially equal to the brightness of the screen. In order to realize this, the amplitude control means 21 needs to change the video amplitude of the output c1, c2 after the amplitude change well. Since the video amplitude is changed based on the first conversion table and the second conversion table stored in the first and second amplitude control memories 311 and 312, in other words, the first conversion table. And the second conversion table must be successfully created. Therefore, creation of the first conversion table and the second conversion table will be described below.

  FIG. 4 is a graph showing the brightness and gradation of the original video signal a and a graph in which the brightness of the outputs c1 and c2 after the amplitude change is combined. The gradation represented on the horizontal axis in the figure is a name when the video amplitude is digitally displayed and has the same meaning as the video amplitude. Here, it is assumed that the original video signal a takes gradations from 0 to 255. Further, both the amplitude-changed output c1 and the amplitude-changed output c2 are assumed to have gradations from 0 to 255 as in the original video signal a. The brightness of each of the output c1 after amplitude change and the output c2 after amplitude change has a maximum gradation of 255 and the frequency is the same as that of the original video signal a. It shall match the maximum brightness of.

  When the brightness of the original video signal a is dark on the screen of the hold type display device, the brightness of the output c1 after the amplitude change is set to be twice the brightness of the original video signal a, and the output after the amplitude change is performed. The brightness of c2 is set to 0. If the output d1 after the signal switching at this time is displayed on the screen of the hold-type display device, it is displayed at the same period (8.3 msec) as the period of the sub-frame and at twice the brightness of the original video signal a, and then the same period. Is displayed with 0 brightness in the same period (8.3 msec). If this is repeated, the time average of the brightness of the output d1 after signal switching in the period 16, 7 msec is ideally equal to the time average of the brightness of the original video signal a in the same period.

  On the other hand, when the brightness of the original video signal a is bright, even if the gradation of the output c1 after changing the amplitude is set to the maximum gradation 255, the gradation of the output c2 after changing the amplitude is 0. Cannot be made equal to the time average of the brightness of the original video signal a. In that case, as shown in FIG. 4, the brightness of the output d1 after the signal switching is increased by increasing the gradation of the output c2 after changing the amplitude while keeping the maximum gradation 255 of the output c1 after changing the amplitude. Ideally, the time average of the brightness of the original video signal a can be made equal.

  When the gradation of the output d1 after signal switching generated based on the above is viewed in detail, the lowest gradation of the output d1 after signal switching is 0 (output c1 after changing amplitude) → 0 (output c2 after changing amplitude). → 0 (output c1 after amplitude change) → 0 (output c2 after amplitude change) →. As for the next gradation of the output d1 after the signal switching, only the gradation of the output c1 after the amplitude change is increased, and 1 (output c1 after the amplitude change) → 0 (output c2 after the amplitude change) → 1 (output c1 after the amplitude change). → 0 (output c2 after amplitude change) →. Similarly, when the gradation of the output d1 after the signal switching is increased, the gradation of the output c1 after the amplitude change is increased to the maximum gradation 255. The gradation of the output d1 after the signal switching at this time is 255 (output c1 after changing the amplitude) → 0 (output c2 after changing the amplitude) → 255 (output c1 after changing the amplitude) → 0 (output c2 after changing the amplitude) →・ ・

  The next gradation of the output d1 after the signal switching has the maximum gradation 255 of the output c1 after the amplitude change, and the gradation of the output c1 after the amplitude change no longer increases, so the output c2 after the amplitude change The gradation will increase. Therefore, the output d1 after signal switching is 255 (output c1 after amplitude change) → 1 (output c2 after amplitude change) → 255 (output c1 after amplitude change) → 1 (output c2 after amplitude change) →. . Similarly, when the gradation of the output d1 after the signal switching is increased, the gradation of the output c2 after the amplitude change is increased to the maximum gradation 255. The gradation of the output d1 after signal switching at this time is 255 (output c1 after amplitude change) → 255 (output c2 after amplitude change) → 255 (output c1 after amplitude change) → 255 (output c2 after amplitude change) →・ ・

  In this way, the gradation of the output d1 after the signal switching is m1 → 0 → m1 → 0 →... (M1 is the range of the output c1 after changing the amplitude: 0 ≦ m1 ≦ 255) and is high at the low gradation. In gradation, 255 → m2 → 255 → m2 →... (M2 is the range of the output c2 after amplitude change: 0 ≦ m2 ≦ 255). FIG. 5 and FIG. 6 show the relationship between gradation and luminance when the output d1 after such signal switching is output to the screen of the hold type display device.

The gray scale represented on the horizontal axis in FIG. 5 represents the gray scale of the output c1 after amplitude change. In this figure, the gray scale of the output c2 after amplitude change is fixed to zero. The luminance represented on the vertical axis in FIG. 5 is the luminance measured when the output d1 after amplitude change is repeatedly output by the hold type display device for several cycles. From the graph of FIG. 5, it can be seen that if the luminance is 200 (cd / m ² ) or less, it is possible to display only with the luminance of the output c1 after amplitude change. The gradation represented on the horizontal axis in FIG. 6 represents the gradation of the output c2 after the amplitude change. In this figure, the gradation of the output c1 after the amplitude change is fixed at the maximum gradation 255. The luminance represented on the vertical axis in FIG. 6 is the luminance measured when the output d1 after amplitude change is repeatedly output by the hold type display device for several cycles. Note that the luminances in FIGS. 5 and 6 are subjected to gamma correction.

  The second conversion table corresponds to the gradation and luminance graph (FIG. 5) of the output c1 after amplitude change and the gradation and luminance graph (FIG. 6) of the output c2 after amplitude change thus obtained. On the other hand, FIG. 7 shows gradation and luminance when the original video signal a of 60 Hz is output to the screen of the hold type display device. The first conversion table corresponds to the gradation and luminance graph (FIG. 7) of the 60 Hz original video signal a obtained in this way. Thus, although the first conversion table and the second conversion table are created, the brightness of the screen varies depending on the characteristics and performance of the hold-type display device even if the input signal value is the same. Therefore, it is desirable to create the first conversion table and the second conversion table for each hold type display device.

  The operation of the video processing circuit of the video display device configured as described above will be described. The frame rate conversion means 11 converts the original video signal a of 60 Hz having a frame period of 16.7 msec into an output b after rate conversion having a frame rate of 120 Hz (period of 8.3 msec). Then, the first amplitude control unit 211 changes the video amplitude of the subframe of the rate-converted output b based on the first amplitude control memory 311 to generate the amplitude-changed output c1. Similarly, the second amplitude control means 212 changes the video amplitude of the subframe of the rate-converted output b based on the second amplitude control memory 312 to generate the amplitude-changed output c2.

Here, the change of the video amplitude will be described, for example, when the gradation of the original video signal a of 60 Hz is 100. The first amplitude control unit 211 refers to the first table stored in the first amplitude control memory 311. Similarly, the second amplitude control unit 212 refers to the first table stored in the second amplitude control memory 312. Then, the first amplitude control means 211 and the second amplitude control means 212 are based on the first conversion table corresponding to the graph of FIG. It is read that the brightness of the screen is 40 (cd / m ² ).

Next, the first amplitude control unit 211 refers to the second table stored in the first amplitude control memory 311, and the gradation of the output c1 after amplitude change corresponding to the luminance 40 (cd / m ² ). Read. Referring to FIG. 5 corresponding to the second table, the gradation of the output c1 after amplitude change corresponding to the luminance 40 (cd / m ² ) is 160. Similarly, the second amplitude control unit 212 refers to the second table stored in the second amplitude control memory 312, and determines the gradation of the output c2 after amplitude change corresponding to the luminance 40 (cd / m ² ). read. Referring to FIG. 6 corresponding to the second table, the luminance 40 (cd / m ² ) of the original video signal a is equal to or lower than the luminance 200 (cd / m ² ), and there is no corresponding value. The gradation of c2 is 0.

  The signal switching means 41 switches the output c1 after amplitude change and the output c2 after amplitude change every subframe period (8.3 msec), and after switching signals of gradations of 160 → 0 → 160 → 0 →. Output d1.

Furthermore, as another example, a description will be given of a change in video amplitude when the gradation of the original video signal a of 60 Hz is 230. In the same manner as described above, the first amplitude control unit 211 and the second amplitude control unit 212 are configured such that when the gradation of the original video signal a is 230 from the first conversion table corresponding to the graph of FIG. It is read that the brightness of the screen of the hold type display device is 310 (cd / m ² ).

Next, the first amplitude control unit 211 refers to the second table stored in the first amplitude control memory 311 and refers to the gradation of the output c1 after amplitude change corresponding to the luminance 310 (cd / m ² ). Read. Referring to FIG. 5 corresponding to the second table, since the luminance 310 (cd / m ² ) of the original video signal a exceeds the luminance 200 (cd / m ² ), the gradation of the output c1 after the amplitude change. Is the maximum gradation 255. Similarly, the second amplitude control unit 212 refers to the second table stored in the second amplitude control memory 312, and determines the gradation of the output c2 after amplitude change corresponding to the luminance 310 (cd / m ² ). read. Referring to FIG. 6 corresponding to the second table, the gradation of the output c2 after amplitude change corresponding to the luminance 310 (cd / m ² ) is 150.

  The signal switching unit 41 switches between the amplitude change subframe of the output c1 after amplitude change and the amplitude change subframe of the output c2 after amplitude change every subframe period (8.3 msec), and 255 → 150 → 255 → 150 → The output d1 is output after the signal switching of the gradation.

  By the operation of the video processing circuit as described above, the video display device according to the present embodiment instantaneously outputs and darkens the output c2 after changing the amplitude below the gradation of the original video signal a, so Therefore, it is possible to reduce image quality deterioration due to occurrence of image blur. On the other hand, by outputting the output c1 after the amplitude change equal to or higher than the gradation of the original video signal a, the output d1 after the signal switching obtained by blending the output c2 after the amplitude change is substantially equal to the brightness of the original video signal a. Can be equal. It should be noted that by changing the gradation of the output d1 after the signal switching, it is possible to deal with the brightness of gradation 0 to 255 of the original video signal a.

  Further, since the first table and the second table store the brightness subjected to the gamma correction, it is possible to display with the optimum brightness.

  In this embodiment, the creation of the conversion table based on 0 and 255 is taken as an example. However, 0, 128, 256 is used as a reference, and 0, 64, 128, 196, 256 is used as a reference. However, although there is a difference in degree, the same effects as those described above can be obtained if they are created in the same manner.

<Embodiment 2>
FIG. 8 is a block diagram showing a schematic configuration of a video processing circuit of the video display device according to the present embodiment. As shown in FIG. 8, the video processing circuit further includes a motion detection means 51, a switching signal generation means 61, and a signal selection means 71 in addition to the configuration of the first embodiment. FIG. 9 is a diagram schematically showing, in a timing chart, how the video processing circuit having this configuration converts a video signal. Hereinafter, in the present embodiment, configurations not newly described below are the same as those in the first embodiment.

  The motion detection means 51 detects the amount of motion of the image of the original video signal a, and further detects whether the image is moving or stopped from the amount of motion. Here, the video of the original video signal a is a video when it is displayed on the screen of the hold type display device. This motion detection means 51 detects the motion of the video of the original video signal a in correlation with the previous frame in pixel units. Alternatively, the motion detection means 51 may detect the motion of the video of the original video signal a on a frame basis by correlating with the previous frame. The detection in units of frames here is, for example, when the number of pixels determined to be moving is equal to or greater than a certain threshold, the frame is detected to be moving, and the number of pixels determined to be moving is If it is less than the threshold, it is detected by detecting that the frame is stopped.

  For example, the switching signal generating unit 61 sets the level of the amount of motion of “0” when the motion detecting unit 51 detects “stop”, and sets it to “1” when detecting “moving”. Set the amount of movement. Alternatively, a plurality of levels, for example, “0” to “7” are set as the amount of movement, “0” is set when “stopped” is detected, and “moving” is detected when “moving” is detected. As the amount of movement increases, the level of the amount of movement is increased. Then, the switching signal generating means 61 outputs a switching signal e corresponding to the set amount of motion.

  For example, when the level of the motion amount is “0”, the switching signal generator 61 outputs the switching signal e having a low level for the entire frame period of the original video signal a. When the motion level is “7”, the high level switching signal e is output during the frame period of the original video signal a. When the level of the motion amount is any one of “1” to “6”, the high level output time is extended with respect to the low level output time in the switching signal e as the level of the motion amount increases. However, the switching signal generating means 61 has a restriction that the switching signal e is changed in accordance with one of the motion amount levels “0” to “7” every frame period (16.7 msec) of the original video signal a. Provided. FIG. 9 shows the switching signal e in the case where the amount of motion is any one of “1” to “6”.

  The signal selection means 71 is provided, for example, in the form as shown in FIG. 10, and receives the output b after rate conversion, the output d1 after signal switching, and the switching signal e. The signal selection means 71 selects and outputs the output b after rate conversion when the switching signal e is at the low (0) level, and switches the signal when the switching signal e is at the high (1) level. The rear output d1 is selected and output. As a result, the signal selection means 71 outputs an output signal f as shown in FIG.

  This switching signal e is a signal corresponding to the amount of motion detected by the motion detecting means 51. Therefore, in other words, the signal selection unit 71 selects and outputs either the output b after rate conversion or the output d1 after signal switching according to the amount of motion detected by the motion detection unit 51. To do. In particular, the signal selection means 71 selects the output b after rate conversion when the motion detection means 51 does not detect the amount of motion. Further, as the amount of motion detected by the motion detection unit 51 increases, the signal selection unit 71 increases the ratio of the time for selecting the output d1 after signal switching to the time for selecting the output b after rate conversion.

  The operation of the video display circuit configured as described above increases the proportion of time for outputting the output d1 after the signal switching as the video motion amount of the original video signal a increases. On the other hand, as the video motion amount of the original video signal a becomes smaller, the ratio of the time for outputting the output b after rate conversion is increased.

  According to the video display apparatus according to the present embodiment as described above, the same effect as in the first embodiment can be obtained when the amount of motion of the video of the original video signal a is large. On the other hand, when the motion amount of the video of the original video signal a is small, the ratio of the time for outputting the output b after rate conversion having the same video amplitude as that of the original video signal a is increased. As a result, the luminance does not change excessively, and the occurrence of flickering is suppressed, so that, for example, an effect that is gentle to the eyes can be provided. Thus, it is possible to perform appropriate video processing corresponding to the motion of the video.

  As shown here, when the switching signal e is a binary value or more, a signal in which the output d1 after the signal switching is corrected as correction 1, correction 2,... Is generated, and signal selection as shown in FIG. You may input into the means 71. FIG. The correction here is performed by applying a coefficient or selecting from a table.

<Embodiment 3>
FIG. 12 is a block diagram showing a schematic configuration of a video processing circuit of the video display device according to the present embodiment. As shown in FIG. 12, the video processing circuit includes a plurality of amplitude control memories 31 to 35, a plurality of amplitude control units 21 to 25, and a plurality of signal switching units 41 to 45. In the present embodiment, the configuration is provided with five each, but is not limited thereto.

  FIG. 13 is a diagram schematically illustrating how the video processing circuit having this configuration converts a video signal in a timing chart. The original video signal a in the present embodiment is a 50 Hz progressive scan signal as shown in FIG. Therefore, the frequency of the output b after rate conversion is 100 Hz, and the vertical synchronization signal b ′ indicating the frame display period (vertical display period) for the screen of the hold-type display device of the output b after rate conversion is 1/100 (10. 0 msec). Hereinafter, in the present embodiment, configurations not newly described below are the same as those in the first embodiment.

  The following operations are performed for each, but are described collectively in this paragraph. As in the first embodiment, the amplitude control means 21 to 25 change the video amplitude of the subframe of the output b after rate conversion based on the amplitude control memories 31 to 35 to create a plurality of amplitude change subframes. To do. As a result, the amplitude control means 21 to 25 output the amplitude change outputs c11 to c15 corresponding to the amplitude change output c1 and the amplitude change outputs c21 to c25 corresponding to the amplitude change output c2. Then, the signal switching means 41 to 45 change the amplitude changing subframe of any of the changed amplitude outputs c11 to c15 and the amplitude changing subframe of any of the changed outputs c21 to c25 for each frame period of the subframe. Are switched to output signals d1 to d5 after signal switching.

  In the present embodiment, the first conversion table of the amplitude control memories 31 to 35 and the first conversion table are set so that the difference in video amplitude between the amplitude-changed outputs c11 to c15 and the amplitude-changed outputs c21 to c25 increases in this order. Two conversion tables are set.

  As a result, the change in video amplitude increases in the order of the output after signal switching d1 to d5. As in the first embodiment, the amplitude control is performed so that the brightness when the outputs d1 to d5 after signal switching are displayed on the screen of the hold-type display device is substantially equal to the brightness of the original video signal a. The first and second conversion tables of each of the memories 31 to 35 are well set.

  The motion detection means 51 detects the amount of motion of the image of the original video signal a, and further detects whether the image is moving or stopped from the amount of motion. Here, the video of the original video signal a is a video when it is displayed on the screen of the hold type display device. This motion detection means 51 detects the motion of the video of the original video signal a in correlation with the previous frame in pixel units. Alternatively, the motion detection means 51 may detect the motion of the video of the original video signal a on a frame basis by correlating with the previous frame. The detection in units of frames here is, for example, when the number of pixels determined to be moving is equal to or greater than a certain threshold, the frame is detected to be moving, and the number of pixels determined to be moving is If it is less than the threshold, it is detected by detecting that the frame is stopped.

  For example, the switching signal generating unit 61 sets the level of the amount of motion of “0” when the motion detecting unit 51 detects “stop”, and sets it to “1” when detecting “moving”. Set the amount of movement.

  For example, as shown in FIG. 13, the switching signal generator 61 outputs a low level switching signal e during the frame period of the original video signal a when the level of motion is “0”. When the level of the motion amount is “1”, the high level switching signal e is output during the frame period of the original video signal a.

  The signal selection means 71 is provided, for example, in the form as shown in FIG. 14, and receives the output b after rate conversion, the outputs d1 to d5 after signal switching, and the switching signal e. When the switching signal e continues to maintain the low (0) level, the signal selection means 71 selects and outputs the output b after rate conversion, and the switching signal e continues to maintain the high (1) level. When maintaining, one of the outputs d1 to d5 after signal switching is selected and output. As a result, the signal selection means 71 outputs an output signal f as shown in FIG.

  This switching signal e is a signal corresponding to the amount of motion detected by the motion detecting means 51. Therefore, in other words, the signal selection means 71 selects either the output b after rate conversion or the outputs d1 to d5 after signal switching according to the amount of motion detected by the motion detection means 51. Output. Further, the signal selection unit 71 selects the output b after rate conversion when the motion detection unit 51 does not continuously detect the amount of motion.

  Further, the signal selection means 71 changes the video amplitude of the output signal f that is its own output as the time during which the motion detection means 51 continuously detects that the video of the original video signal a is moving becomes longer. Increase Here, the signal selection means 71 outputs the output b after the rate conversion b → the output d1 after the signal switching as the time during which the motion detection means 51 continuously detects that the video of the original video signal a is moving becomes longer. Output after switching signal d2 →... → output after switching signal d5 in this order. Thereafter, when the motion detecting means 51 detects that the video of the original video signal a is moving, the output d5 after signal switching is output.

  FIG. 15 shows the output signal f output from the signal selection means 71 and the original video signal a. This figure shows an output signal f when attention is paid to a certain pixel. And when the gradation of the original video signal a is changing, it represents that the image | video of the original video signal a is moving. First, when the video of the original video signal a is stopped and the switching signal e is at the low (0) level, the signal selection means 71 outputs the output b after rate conversion with the smallest change in video amplitude ( Before the dotted line). When the motion detector 51 detects that the video of the original video signal a is moving, the switching signal e becomes high (1) level (dotted line) as shown in the figure. Then, as the time for continuously detecting that the video of the original video signal a is moving, that is, the time for which the switching signal e continues to be in the high level becomes longer, the signal selection means 71 outputs the output d1 after the signal switching. → Output after signal switching d2 →... → Output after signal switching d5 (after the dotted line). In this way, the signal selection means 71 increases the change in the video amplitude of its output.

  Further, the signal selection means 71 changes the video amplitude of the output signal f that is its own output as the time during which the motion detection means 51 continuously detects that the video of the original video signal a is stopped becomes longer. Make it smaller. Here, the signal selection means 71 outputs after switching the signal d5 → output after switching the signal d4 → as the time during which the motion detection means 51 continuously detects that the video of the original video signal a has stopped becomes longer. ... → Selection of output after switching signal d1 → output b after rate conversion and output. After that, when the motion detection means 51 detects that the video of the original video signal a has stopped, the output b after rate conversion is output.

  FIG. 16 shows a diagram showing the output signal f output from the signal selection means 71 and the original video signal a. As in FIG. 15, the output signal f when attention is paid to a certain pixel is shown. And when the gradation of the original video signal a is changing, it represents that the image | video of the original video signal a is moving. First, when the video of the original video signal a is moving and the switching signal e is at a high (1) level, the signal selection means 71 outputs the post-switching output d5 having the largest video amplitude change ( Before the dotted line). When the motion detection means 51 detects that the video of the original video signal a has stopped, the switching signal e becomes low (0) level (dotted line) as shown in the figure. Then, as the time for continuously detecting that the video of the original video signal a is stopped, that is, the time for which the switching signal e continues in the low level state becomes longer, the signal selection means 71 outputs the output d5 after the signal switching. → Output after signal switching d4 →... → Output after signal switching d1 → Output after rate conversion b (after the dotted line). In this way, the signal selection means 71 reduces the change in the video amplitude of its output.

  As described above, by gradually increasing or decreasing the change in the video amplitude of the output of the signal selection means 71, the switching portion between the moving image and the still image is prevented from being unnaturally switched.

  The operation of the video display circuit configured as described above increases the change in the video amplitude of the output signal f as the time during which the video of the original video signal a is moving becomes longer. On the other hand, the change in the video amplitude of the output signal f is reduced as the time during which the video of the original video signal a stops is longer.

  According to the video display apparatus according to the present embodiment as described above, the same effect as in the first embodiment can be obtained when the video of the original video signal a is moving for a long time. On the other hand, when the video of the original video signal “a” has been stopped for a long time, a change in luminance can be prevented. As a result, the luminance does not change excessively, and the occurrence of flickering is suppressed, so that, for example, an effect that is gentle to the eyes can be provided. Thus, it is possible to perform appropriate video processing corresponding to the motion of the video.

  In this embodiment, a plurality of amplitude control units 21 to 25 and a plurality of amplitude control memories 31 to 35 are used to change the video amplitude. However, other methods such as applying a correction coefficient are used. It may be.

2 is a block diagram illustrating a video processing circuit of the video display device according to Embodiment 1. FIG. 3 is a timing chart of a video signal converted by a video processing circuit of the video display device according to the first embodiment. 6 is a diagram for explaining a frame rate conversion method of the video processing circuit of the video display device according to Embodiment 1. FIG. 6 is a diagram for explaining an amplitude changing method of the video processing circuit of the video display device according to Embodiment 1. FIG. 6 is a diagram for explaining a conversion table of a video processing circuit of the video display device according to Embodiment 1. FIG. 6 is a diagram for explaining a conversion table of a video processing circuit of the video display device according to Embodiment 1. FIG. 6 is a diagram for explaining a conversion table of a video processing circuit of the video display device according to Embodiment 1. FIG. 6 is a block diagram illustrating a video processing circuit of a video display device according to Embodiment 2. FIG. 10 is a timing chart of a video signal converted by a video processing circuit of the video display device according to the second embodiment. It is a figure which shows the signal selection means of the video processing circuit of the video display apparatus which concerns on Embodiment 2. FIG. It is a figure which shows a signal selection means in the video processing circuit of the video display apparatus concerning Embodiment 2. 6 is a block diagram showing a video processing circuit of a video display device according to Embodiment 3. FIG. 10 is a timing chart of a video signal converted by a video processing circuit of the video display device according to the third embodiment. FIG. 10 is a diagram showing signal selection means of a video processing circuit of a video display device according to Embodiment 3. FIG. 10 is a diagram illustrating an output of a video processing circuit of a video display device according to a third embodiment. FIG. 10 is a diagram illustrating an output of a video processing circuit of a video display device according to a third embodiment.

Explanation of symbols

  11 Frame rate conversion means, 21, 22, 23, 24, 25 Amplitude control means, 31, 32, 33, 34, 35 Amplitude control memory, 41, 42, 43, 44, 45 Signal switching means, 51 Motion detection means, 61 switching signal generation means, 71 signal selection means, 211, 221, 251 first amplitude control means, 212, 222, 252 second amplitude control means, 311, 321, 351 first amplitude control memory, 312, 322 352, second amplitude control memory, a original video signal, b output after rate conversion, c1 first amplitude change output, c2 second amplitude change output, d1, d2, d5 signal switching output, e switching Signal, f output signal.

Claims (10)

A frame rate of N (N is an integer of 2 or more) times the frame rate of the original video signal by making the frame sequence of the input original video signal into a plurality of subframes for each frame of the frame sequence. Frame rate conversion means for converting into a frame multiplied video signal comprising a subframe sequence having
Amplitude control means for changing the video amplitude of each subframe and generating a plurality of amplitude change subframes for each of the subframes;
Signal switching means for switching and outputting any of the plurality of amplitude change subframes for each frame period of the subframe,
The brightness of the screen when the output of the signal switching means is displayed on the hold type display device is substantially equal to the brightness of the screen when the original video signal is displayed on the hold type display device.
Video processing circuit. A first conversion table comprising the video amplitude of the original video signal and the brightness of the original video signal subjected to gamma correction; the video amplitude of the output of the signal switching means; and gamma correction of the output of the signal switching means An amplitude control memory storing a second conversion table composed of the brightness to which
The amplitude control means includes
Changing the video amplitude of each subframe based on the first conversion table and the second conversion table of the amplitude control memory;
The video processing circuit according to claim 1. Motion detection means for detecting the amount of motion of the video of the original video signal;
A signal selection unit that selects and outputs either the frame-multiplied video signal or the output of the signal switching unit according to the amount of motion detected by the motion detection unit;
The video processing circuit according to claim 1. The signal selection means includes
As the amount of motion detected by the motion detection means increases, the ratio of the time for selecting the output of the signal switching means to the time for selecting the frame-multiplied video signal is increased.
The video processing circuit according to claim 3. The signal selection means includes
When the video of the original video signal is moving, the change in the video amplitude of its own output is increased as the time that the motion detecting means continuously detects increases.
The video processing circuit according to claim 3 or 4. The signal selection means includes
When the video of the original video signal is stopped, the change in the video amplitude of its own output is reduced as the time for which the motion detection means continuously detects becomes longer.
The video processing circuit according to claim 3. The signal selection means includes
When the motion detection unit does not detect the amount of motion, the frame multiplied video signal is selected.
The video processing circuit according to claim 3. The motion detection means includes
Detecting the movement of the video of the original video signal in units of pixels;
The video processing circuit according to claim 3. The motion detection means includes
Detecting the motion of the video of the original video signal in units of frames;
The video processing circuit according to claim 3. The video processing circuit according to any one of claims 1 to 9,
The hold type display device,
Video display device.

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