JP5527195B2 - Video display device - Google Patents

Description

The present invention relates to a video processing technology or a video display technology that allows video to be input and viewed.

  Conventionally, an example of a multimedia computer system that converts an input RGB signal into a luminance signal and a color difference signal, extracts feature points of the luminance signal for each frame, corrects the luminance signal and the color difference signal, and displays it is proposed. (For example, refer to Patent Document 1, page 4, FIG. 1).

JP 2002-132225 A

  When applied to a portable terminal device that operates on a battery, if the luminance signal and the color difference signal are corrected for each frame, the power consumption increases. There is a case where the portable terminal device cannot be charged while going out, and when the power consumption increases, the use time is shortened and the usability is deteriorated. Therefore, there is a demand for an apparatus that can perform good image display with low power consumption. In addition, when external light is incident on the display device, it is difficult to see an image, and it is difficult to use the mobile terminal device outdoors.

Therefore, an object of the present invention is to provide a video processing technique or a video display technique that improves user convenience.

In order to solve the above-mentioned problem , for example, it may be configured as described in the claims .

According to the present invention, it is possible to provide video processing technology or video display technology with improved usability.

It is a block diagram which shows the structural example of a mobile telephone. It is a block diagram which shows the structural example of an image quality improvement circuit. It is a characteristic view explaining the relationship between color difference and saturation. It is a block diagram which shows the structural example of a feature point detection part. It is a flowchart which shows an example of the detection process of a brightness | luminance feature point detection part. It is an example of a brightness | luminance histogram. It is a flowchart which shows an example of the detection process of a hue feature point detection part. It is an example of a hue histogram. It is a flowchart which shows an example of the detection process of a saturation feature point detection part. It is an example of a saturation histogram. It is a block diagram which shows the structural example of an I / F part. It is a flowchart which shows an example of the detection process of a scene change detection part. It is an example of a processing flow of luminance correction in the modulation unit. It is an example of a brightness | luminance histogram and a correction characteristic. It is an example of a brightness | luminance histogram and a correction characteristic. It is an example of a brightness | luminance histogram and a correction characteristic. It is an example of the processing flow of the hue correction | amendment part in a modulation part. It is an example of a processing flow of the saturation correction unit in the modulation unit. It is a block diagram which shows the structural example of a mobile telephone. It is a figure which shows the input-output characteristic example of an illumination intensity sensor. It is an example of correction data. It is a block diagram which shows the structural example of an image quality improvement circuit. It is a figure which shows the example of a characteristic of the output gradation with respect to the input gradation of a luminance signal. It is a figure which shows the example of a characteristic of the output gradation with respect to the input gradation of a luminance signal. It is a block diagram which shows the structural example of a backlight and a backlight drive circuit. It is a figure which shows an example of LED electric current value.

  The present invention can be applied to mobile terminal devices in general, for example, mobile phones, PHS, PDAs, notebook PCs, portable TVs, portable video recording / reproducing devices, etc. Here, a mobile phone will be described as an example. .

  FIG. 1 is a block diagram illustrating a configuration example of a mobile phone. The communication antenna 1 receives a radio wave transmitted through the air, converts it into a high-frequency electrical signal, and inputs it to the radio circuit 2. The high-frequency electrical signal output from the radio circuit 2 is converted into a radio wave and transmitted. The radio circuit 2 demodulates the high-frequency electric signal received by the communication antenna 1 based on an instruction from a CPU (Central Processing Unit) 7 and inputs the demodulated signal to the code decoding processing circuit 3. Also, the output signal of the code decoding processing circuit 3 is subjected to modulation processing, converted into a high-frequency electric signal, and output to the communication antenna 1. The code decoding processing circuit 3 performs a decoding process on the output signal of the radio circuit 2 under the control of the CPU 7, outputs a voice signal for call to the receiver 5, and outputs characters and image data to the CPU 7. Also, the encoding process is performed on the voice input from the microphone 4 or the character or image data edited by the user operating the key 7. In this embodiment, a key is used as an operation unit used for inputting information and instructions. However, the present invention is not limited to this, and a voice input unit or a touch panel type input unit may be used.

  The CPU 7 performs general cellular phone processing. For example, the program is acquired from the memory 9 via the CPU bus 8, and the code decoding processing circuit 3, the radio circuit 2, and the communication antenna 1 are controlled to wait for an incoming call. In addition to the above programs, the memory 9 stores ringtones such as fixed patterns and melody that are recorded in advance on the mobile phone, personal information such as a telephone directory and address book, downloaded melody and image data, and the like. When there is an incoming call, the CPU 7 reads the name of the caller, the incoming melody, and the incoming call image from the phone book in the memory 9 and outputs the audio data from the speaker 11 via the DAC (Digital Analog Converter) 10 and the image. The data is displayed on the display device 16 via the video I / F (Interface) 14 and the image quality improving circuit 15 to notify the user that there is an incoming call. Then, when the user operates the key 6, it is possible to send and receive calls and mails.

  The TV antenna 12 converts the received TV broadcast radio wave into a high frequency electric signal and outputs it to the TV tuner 13. The TV tuner 13 demodulates the input signal to convert it into a CMOS level electric signal and outputs it to the CPU 7. The CPU 7 initializes the TV tuner 13 and instructs the channel selection. The tuner 13 periodically transmits information indicating a reception state such as a bit rate error to the CPU 7 in response to a request from the CPU 7.

  The CPU 7 performs video and audio separation processing and respective decoding processing on the signal input from the TV tuner 13, and the video is displayed on the display device 16 via the image quality improving circuit 15, and the audio passes through the DAC 10. And reproduced by the speaker 11. Thereby, the user can view the TV broadcast. The TV broadcast to be received may be either analog broadcast or digital broadcast. In this embodiment, the CPU 7 has an interface that can directly connect the output of the TV tuner 13, but the present invention is not limited to this, and an interface conversion circuit may be used. The interface conversion circuit may be mounted on the CPU or mounted in a stack form. Also, if the mobile phone is equipped with an image processing device such as an application processor or coprocessor, the interface conversion circuit may be mounted on the same silicon chip as this processor, or mounted in a separate silicon chip stack. good. Further, an interface conversion circuit may be mounted inside the controller, driver IC, or TV tuner 13 of the display device 16. Also, the interface conversion circuit and CPU 7 may be connected to a dedicated terminal on the CPU 7 or connected to the CPU bus 8.

  The battery 20 is composed of a rechargeable secondary battery such as lithium ion or nickel metal hydride, and supplies power for operating each component constituting the mobile phone. The power supply circuit 19 supplies a voltage to each component of the mobile phone based on the power supplied from the battery 20. Further, when the remaining amount of the battery 20 is low, the battery 20 is charged with electric power supplied from a household outlet, a car battery, or the like. In FIG. 1, the connection relationship between each component of the mobile phone and the power supply circuit 19 is not shown.

  Further, the image quality improving circuit 15 performs an image quality improving process on the video signal output from the CPU 7 and outputs the processed video signal to the display device 16. The backlight 17 generates illumination light of the display device 16 by power supply from the backlight drive circuit 18 and irradiates the display device 16 with the illumination light. As the light source of the backlight 17, for example, a cold cathode light, a white LED, a red, green, or blue three-color LED is used. The backlight drive circuit 18 increases or decreases the voltage supplied from the power supply circuit 19 or the battery 20 in order to drive the backlight 17. The backlight drive circuit 18 can adjust brightness and color under the control of the CPU 7. The backlight drive circuit 18 may be independent as shown in FIG. 1 or may be a part of the power supply circuit 19. For example, when the power supply circuit 19 is implemented as an LSI, it may be mounted on the same silicon chip or in the form of a stack of different silicon chips.

  A block diagram showing a configuration example of the image quality enhancement circuit 15 is shown in FIG. The RGB-YUV converter 151 converts the RGB video signal input from the CPU 7 via the video I / F 14 into a luminance signal and a color difference signal, and outputs the luminance signal as Y, and the color difference signal as RY and BY. To do.

  The RGB video signal can be converted into a YUV signal by the following equation.

Y = 0.290 × R + 0.5870 × G + 0.1140 × B (1)
Cb = (-0.1687) x R + (-0.3313) x G + 0.5000 x B (2)
Cr = 0.5000 x R + (-0.4187) x G + (-0.0813) x B (3)
The color difference-HS conversion unit 153 performs hue and saturation conversion on the color difference signals RY and BY input from the RGB-YUV conversion unit 151, and outputs the hue H and the saturation S. The feature point detection unit 154 includes a minimum level, an average level of the video signal input from the luminance signal Y input from the RGB-YUV conversion unit 151 and the hue S and saturation H input from the color difference-HS conversion unit 153. Feature point data such as the maximum level and histogram is calculated and written to the I / F unit 155. The I / F unit 155 issues an interrupt signal 141 to the CPU 7 at a predetermined timing. When the CPU 7 detects the interrupt signal 141, the CPU 7 reads the feature point data stored in the I / F unit 155 via the internal bus 1551, determines correction data by a predetermined algorithm, and determines the I / F via the internal bus 1551. Write to F section 155. The modulation unit 152 modulates the input luminance signal Y, hue S, and saturation H according to the correction data written from the CPU 7 to the I / F unit 155 to obtain luminance Y ′, hue S ′, and saturation H ′. Output. The HS-color difference conversion unit 156 converts the input hue S ′ signal and saturation H signal into color difference signals (RY) ′ and (BY) ′ and outputs them. The YUV-RGB conversion unit 157 converts the input luminance Y ′ and color difference signals (RY) ′ and (BY) ′ into an RGB format and outputs it. The YUV-RGB conversion can be performed by the following formula.

R = Y + 1.402 × V (4)
G = Y + (-0.34414) x U + (-0.71414) x V (5)
B = Y + 1.772 × U (6)
The selector 158 selects the output of the YUV-RGB conversion unit 157 or the through signal 142 of the video I / F 14 and outputs it to the display device 16. The control of the selector 158 may be performed from the CPU, or may be switched in conjunction with opening and closing when the remaining battery level is below a certain value, or in the case of an open / close type mobile phone. Also, when interlocking with opening and closing, it is better to select the YUV-RGB converter 157 side when opened in the case of a folded shape, and in addition to the rotation axis in the folding direction, even if it is a folded shape, slide and rotate If the display device can be viewed in a closed state, such as a two-axis hinge-type mobile phone having a second axis that rotates the display device by 180 °, the selector 158 will close the YUV-RGB when the display device is closed. The conversion unit 157 side may be selected. Further, when viewing TV, still image, or moving image viewing, the selector 158 may select the YUV-RGB conversion unit 157 side to switch according to the content to be displayed. Further, the through signal 142 may be selected in the standby state regardless of the shape of the mobile phone and the open / closed state.

  Note that when text data such as a mail text or subtitles is input, processing such as RGB-YUV conversion in the image quality enhancement circuit 15 is unnecessary, and the CPU 7 controls to select the through signal 142. In this case, the operation of the portion surrounded by the dotted line 159 is stopped. Thereby, low power consumption can be achieved. Specifically, the operation clock supply to the image quality improving circuit 15 is stopped, or the power supply to the block inside the dotted line 159 is stopped. When the power supply is stopped, the output of the power supply circuit 19 may be stopped, or the power supply may be stopped by providing a switch for cutting the power supply suction path on the image quality improving circuit 15 side.

  Next, an outline of the operation of the color difference-HS conversion unit 153 will be described with reference to the drawings. FIG. 3 is a characteristic diagram for explaining the relationship between hue (H) and saturation (S). The horizontal axis represents the level of the BY signal, and the vertical axis represents the level of the R-Y signal. The vector sum of the B-Y signal and the R-Y signal is a vector representing hue / saturation, the angle is hue H, and the magnitude is saturation S. Therefore, the hue H can be obtained from the equation (7), and the saturation S can be obtained from the equation (8).

H = tan ^-1 ((R = Y) / (BY)) (7)
S = SQR ((RY) ² + (BY) ² ) (8)
As shown in FIG. 4, for example, the feature point detection unit 154 includes a luminance feature point detection unit 1541, a hue feature point detection unit 1542, and a saturation feature point detection unit 1543. FIG. 5 is a flowchart showing an example of detection processing of the luminance feature point detection unit 1541. As shown in the flow, the luminance feature point detector 1541 determines the level of the luminance signal Y that is input every moment in units of frames, and determines the maximum level, minimum level, and level for each area. Feature point data such as frequency and average level is acquired. FIG. 5 illustrates an example of detection processing in the case where the input gradation of the luminance level is 0 to 255 and the input gradation is divided into 16 gradation areas. However, the detection processing is not limited to this. . For example, it can be set freely within a range in which resources such as memory and gate capacity are provided, such as 8 stages and 32 stages. Note that the detection processing program executed by the luminance feature point detection unit 1541 may be stored in the memory 9, or may be stored in the memory provided in the luminance feature detection unit 1541.

  First, it is compared whether or not the luminance level Y (n) of the nth pixel is smaller than the minimum level Ymin stored in the memory 9 (S501). Note that 255 and 0 are stored in the memory 9 as initial values of the minimum level Ymin and the maximum level Ymax, respectively. If the brightness level is smaller than the current minimum level, the brightness level of the nth pixel is stored in the memory 9 as the minimum level (S502). If the luminance level is equal to or higher than the minimum level, a comparison is made to determine whether the luminance level of the nth pixel is greater than the maximum level (S503). If the luminance level is greater than the maximum value, the luminance level of the nth pixel is set to the maximum value (S504). If the luminance level is less than or equal to the maximum value, it is determined whether the luminance level of the nth pixel is 0 to 15 (S505). When the luminance level is 0 to 15, 1 is added to the value of Yhst0 (S606). Yhst0 indicates the number of luminance levels included in the 0 to 15 gradation area.

  If the luminance level is not 0-15, it is determined whether the luminance level is 16-31 (S507). If Yes, 1 is added to the value of Yhst1 (S508). In the case of No, it is determined whether or not it is included in other gradation areas one after another.

  When the luminance level area division is completed, the luminance level of the nth pixel is added to the current total luminance level (S511). In S512, it is determined whether or not the processing for one frame has been completed. If yes, the average luminance level is calculated by dividing the total luminance level by the number of pixels n, and the processing ends (S514). In the case of No, 1 is added to n, and the process returns to S501 to process the luminance level of the next pixel.

  FIG. 6 shows an example of a luminance histogram. The horizontal axis is the luminance histogram area, and the vertical axis is the frequency. By acquiring this histogram, it is possible to easily grasp the characteristics of luminance. For example, it can be determined whether the screen is simply a dark screen or a screen in which a bright place such as a moon or a star exists in the dark screen.

  FIG. 7 is a flowchart illustrating an example of detection processing of the hue feature point detection unit 1542. As shown in the flow, the hue feature point detection unit 1542 determines the level of the hue signal H input every moment in units of frames, and obtains the maximum level, the minimum level, the frequency of the level for each area, and the average level. To do. In FIG. 7, the hue level range is 0 to 359, and a processing example in the case where this level is divided into 12 hue areas will be described, but the detection process is not limited to this. As in the case of the luminance feature point detection, the detection processing program to be executed may be stored in the memory 9 or may be stored in the memory provided in the hue feature point detection unit 1542.

  Similar to the luminance level, in S701 to S710, it is detected which of the hue areas Hhst0 to Hhst11 the hue level H (n) of the nth pixel is included. When the hue level area is determined, the hue level of the nth pixel is added to the current total hue level (S711), and it is determined whether the processing for one frame is completed (S712). When the process is completed (yes), the average hue level is calculated and the process ends (S714). If No, 1 is added to n (S713), and the process returns to S701 to process the hue level of the next pixel.

  FIG. 8 shows an example of a hue histogram created using the area frequency detected as described above. The horizontal axis is the hue histogram area, and the vertical axis is the frequency. By generating the histogram, it is possible to easily grasp the characteristics of the hue change. FIG. 9 is a flowchart showing an example of detection processing of the saturation feature point detection unit 1543. The saturation feature point detection unit 1543 determines the level of the saturation signal S input every moment in units of frames, and acquires the maximum level, the minimum level, the frequency of the level for each area, and the average level. FIG. 9 illustrates a processing example when the saturation level range is 0 to 99 and the level is divided into 10 areas. However, the detection processing is not limited to this. Similar to the luminance feature point detection, the detection processing program to be executed may be stored in the memory 9, or may be stored in the memory provided in the saturation feature point detection unit 1543.

  Similar to the luminance level, in S901 to S910, it is detected which of the hue areas Shst0 to Shst9 includes the saturation level S (n) of the nth pixel. When the saturation level area is determined, the saturation level of the nth pixel is added to the current total saturation level (S911), and it is determined whether the processing for one frame is completed (S912). When the process is completed (yes), the average saturation level is calculated and the process is terminated (S914). If No, 1 is added to n (S913), and the process returns to S901 to process the saturation level of the next pixel.

  FIG. 10 shows an example of a saturation histogram. The horizontal axis is the saturation histogram area, and the vertical axis is the frequency. By obtaining this hue histogram, it is possible to detect a change in the saturation of the input video signal.

  FIG. 11 is a block diagram illustrating an example of an internal configuration of the I / F unit 155. Signals are written and read between the CPU 7 and the image quality improving circuit 15 via the I / F register unit 1551. When the scene change detection unit 1552 receives feature point data of luminance level, hue, and saturation from the feature point detection unit 154, the scene change detection unit 1552 stores the data. When new data is input, the data is rewritten and whether or not there is a difference between the old and new data is determined. If there is a difference, it is determined that a scene change has occurred, and INT 141 is issued to the CPU 7. The CPU 7 reads new feature point data from the I / F register 1551, generates new correction data, and updates the correction data in the I / F register 1551. In this example, the CPU 7 reads the feature point data from the I / F register 1551, but the I / F register 1551 may transmit data to the CPU 7. A scene change is, for example, when a program changes to a commercial message (CM), when a program changes from a day scene to a night scene, or when a shooting location changes, or from a studio image to a local image. And switching of TV cameras in studios and stadiums.

  FIG. 12 is a flowchart showing an example of the detection process of the scene change detection unit 1552. In S1201, a difference between the old and new minimum luminance levels is obtained and new data is written to the I / F register 1551. Differences are similarly obtained for the maximum luminance level, the average luminance level, and the frequency for each area. When the difference in the frequency of the area 15 is obtained (S1202), the process proceeds to the process of the hue feature point. Regarding the hue, the difference between the minimum hue level, the maximum hue level, the average hue level, and the frequency is obtained by S1203 to S1204 in the same manner as the luminance, and the difference between the saturation feature points is obtained (S1205 to S1206). It is determined whether the difference between the feature points of brightness, hue, and saturation is “0”, that is, the same as the previous frame (S1207). If there is no difference, it is determined that the correction data need not be updated, and the process ends. . On the other hand, if no, it is determined that a scene change has occurred, an interrupt request 141 is output to the CPU 7 (S1208), and the process ends.

  As described above, when the scene change detection unit 1552 operates, in the case of the same pattern as the previous frame, the CPU 7 omits the feature point data reading, correction data generation, and writing to the I / F register 1551. Therefore, the processing load on the CPU 7 can be reduced, and the current consumption for data transfer can be reduced.

  Although FIG. 12 shows an example in which all differences in luminance, hue, and saturation are detected, the present invention is not limited to this. Further, it is not necessary to detect the difference for all feature points such as the minimum value and the maximum value. In order to reduce the processing load on the CPU 7, it is most effective to detect a scene change based on the presence or absence of a difference in the average level of the luminance signal that has a great influence on the user's vision. Further, for example, when both the minimum value and the maximum value of luminance change, the determination may be made by a combination of each feature point data such as the minimum value of luminance and the average value of hue. A scene change may be determined when the histogram distribution area (horizontal axis) changes.

  In the example of FIG. 12, it is determined that there is no scene change when the difference between the feature point data is 0. However, a scene change may be determined when a certain threshold value is set and exceeded. This threshold is preferably set individually for each feature point data. Also, in order to prevent the correction data from being updated due to the presence or absence of captions, a specific gradation area or frequency area may be ignored, for example, it is not determined as a scene change even if the frequency of the histogram on the white side changes. . In addition, when a scene change is detected using a luminance level or the like, the scene change detection unit 1552 may determine that a scene change occurs at a certain time or the number of frames and output an INT 141.

  Based on the correction data generated by the CPU 7, the modulation unit 152 modulates luminance, hue, and saturation. Hereinafter, the modulation method will be described.

  FIG. 13 shows an example of a processing flow when the modulation unit 152 modulates the luminance signal. First, it is determined whether or not the first gradation area (Yhst0) of the luminance histogram is 0 (S1301). If No, Blacklevel is set to 0 (S1302). Here, Blacklevel indicates an input gradation range in which the output gradation is fixed to 0. If Blacklevel is 0, there is no range in which the output gradation is 0. If Yes, it is determined whether or not the second gradation area (Yhst1) of the luminance histogram is 0 (S1303). In the case of No, Blacklevel is set to 0 to 15 (S1304). If Yes, it is determined whether the third gradation area (Yhst2) of the luminance histogram is 0 (S1305). In the case of No, Blacklevel is set to 0 to 31 (S1306). In the case of Yes, the determination of the fourth gradation area (Yhst3) shift is not performed, and Blacklevel is set to 0 to 47. By providing the limit value in this way, it is possible to prevent the luminance from being excessively corrected.

  Next, it is determined whether the 16th gradation area (Yhst15) of the luminance histogram is 0 (S1308). In the case of No, Whitelevel is set to 255 (S1309). Here, Whitelevel indicates an input gradation range in which the output gradation is fixed to 255, and Whitelevel is 255 when there is no range in which the output gradation is 255. If Yes, it is determined whether the 15th gradation area (Yhst14) of the luminance histogram is 0 (S1310). In the case of No, Whitelevel is set to 239 to 255 (S1311). If Yes, it is determined whether the 14th gradation area (Yhst13) of the luminance histogram is 0 (S1312). In the case of No, Whitelevel is set to 223 to 255 (S1313). If Yes, the 13th gradation area (Yhst12) of the luminance histogram is not determined, and Whitelevel is set to 207 to 255 (S1314). By providing the white side limit value in this way, overcorrection can be prevented.

  When the range in which the output gradation is fixed to 0 or 255 is determined, 0 can be output to the input gradation excluding the gradation in which the gradation on the black side and the white side is fixed to 0 or 255 (crushed portion). The expansion processing is performed so as to use the gradations up to ˜255 (S1501). As a result, it is possible to perform correction so as to increase the gradient (Ygain) of the output gradation with respect to the input gradation.

  An example of a luminance signal modulation method in the modulation unit 152 will be described with reference to FIGS.

  FIG. 14A is a luminance histogram. In this example, there are no gradations from 0 to 47 (Yhst 0 to 2) on the black side. That is, this is an example of a case where a video signal with little black and whitish (black level is floating) is input. When applied to the processing flow of FIG. 13, Blacklevel = 0 to 47 and Whitelevel = 255, and the slope Ygain = 1.22 is corrected by the extension processing. What correct | amends the relationship of the output gradation with respect to an input gradation is called a correction characteristic.

  FIG. 14B shows a correction image based on this correction characteristic. A dotted line 1401 indicates the characteristics of the output gradation with respect to the input gradation when correction is not performed. A solid line 1402 is a correction characteristic. The inclination of the output gradation with respect to the input gradations 47 to 255 is increased by fixing 0 to 47 where the gradation of the input video signal does not exist to 0. Thereby, the contrast of the output hierarchy with respect to the input hierarchy can be increased, and an image easy to view can be displayed.

  FIG. 15 is a diagram illustrating an example of correction when a video signal having no gradation on the white side is input. FIG. 15A is a luminance histogram of the input video signal. This is an example of the case where there are no gray levels from 207 to 255 (Yhst 13 to 15) on the white side, that is, a black video signal is input. When applied to the processing flow of FIG. 13, Blacklevel = 0, Whitelevel = 207 to 255, and Ygain = 1.22.

  An image of correction by this correction characteristic is shown in FIG. A dotted line 1501 indicates the characteristics of the output gradation with respect to the input gradation when correction is not performed. A solid line 1502 is a correction characteristic. Since the output hierarchy of 207 to 255 where the gradation of the input video signal does not exist is fixed to 255, the inclination of the output gradation with respect to the input gradation 0 to 207 is increased, and the output dynamic range limit is extended to zero. With such correction characteristics, the contrast of the output layer with respect to the input layer can be increased, and an image in which the black-side gradation is easy to see can be displayed.

  FIG. 16 shows an example of correction when a video signal having no gradation on the black side and the white side is input. FIG. 16A is a luminance histogram of the input video signal. In this example, there are no gradations from 0 to 31 (Yhst 0 to 1) on the black side and 223 to 255 (Yhst 14 to 15) on the white side. When applied to the processing flow of FIG. 13, Blacklevel = 0 to 31, Whitelevel = 223 to 255, and Ygain = 1.33.

  An image of correction by this correction characteristic is shown in FIG. A dotted line 1601 indicates the characteristics of the output gradation with respect to the input gradation when correction is not performed. A solid line 1602 is a correction characteristic. Since the output hierarchy of 0 to 31 and 223 to 255 where the gradation of the input video signal does not exist is fixed to 0 and 255, the gradient of the output gradation with respect to the input gradations 31 to 223 is increased, and the output dynamic range limit From 0 to 255. By correcting in this way, it is possible to display an image that has a large contrast in the middle layer and is easy to view.

  FIG. 17 shows a flow example of hue correction. In this embodiment, the user selects in advance a color to be particularly vivid or emphasized from among colors such as yellow, red, magenta, blue, cyan, and green. Then, color correction is performed based on the color selected by the user and the peak area Hhst max of the hue histogram. FIG. 17 shows a correction process when, for example, blue is selected. First, it is determined whether the peak Hhst max of the hue histogram corresponds to H hst8 that is the area before the area H hst9 corresponding to blue (S1701). If the determination result is yes, the hue adjustment value Hadj is set to 10 (S1702). In the case of No, it is determined whether the peak area Hhst max of the hue histogram corresponds to H hst10 that is an area after the area H hst9 corresponding to blue (S1703). If the determination result is yes, the hue adjustment value Hadj is set to −10 (S1704). If No, Hadj is set to 0 and the process is terminated. Thereby, the color set by the user can be emphasized.

  In the example of FIG. 17, the correction is performed based on the color set in advance by the user, but the present invention is not limited to this. For example, the peak area of the hue histogram may be detected, and the color of the area before and after the peak area may be corrected to the color of the peak area. Thereby, when there are many components near blue, such as in the case of a beach image, the hue can be adjusted to the blue side to display an image in which blue is emphasized.

  FIG. 18 shows a flow example of saturation correction. It is determined whether the maximum level of saturation is 80 or less (S1801). If no, the saturation gain Sgain is set to 1.2 (S1802). If Yes, Sgain is set to 1.0 (S1803), and the process ends. Thereby, when the maximum saturation is equal to or smaller than a certain value, the saturation gain can be emphasized and more vivid display can be performed. In the example of FIG. 18, the correction is performed when the maximum saturation is equal to or less than a certain value, but the present invention is not limited to this. When the maximum saturation is equal to or greater than a certain value, the gain may be reduced in order to avoid color collapse.

  As described above, by detecting a scene change and performing signal modulation, it is possible to view a good image with clear contrast while suppressing power consumption.

  The timing at which the modulation unit 152 modulates the input video signal may be immediately after an instruction from the CPU 7, or may be after a certain time or frame has elapsed. Further, it may be performed transiently so as to gradually converge to the target correction characteristic. Also, if the CPU 7 determines that the compression rate is high based on the header information of the image file before decoding, or if it is determined that the reception state is not good due to the bit error rate obtained from the TV tuner 13, block noise occurs. Therefore, the degree of correction may be weakened to prevent the block noise from being emphasized. Conversely, if it is determined that the compression rate is low, the possibility of block noise is low, so that the degree of correction may be increased to display higher quality images. For example, when the compression rate is high, the limit value of Blacklevel is changed to 23, the hue adjustment value Hadj is changed to 5, or the saturation gain Sgain is changed to 1.1 to weaken the degree of correction.

  In this embodiment, an example in which the above-described image quality improvement processing is realized by the image quality improvement circuit 15 has been described. However, if the CPU 7 has sufficient processing capability, the image quality improvement circuit 15 is not used and the image quality improvement processing is not performed. A part or all of the processing may be performed by the CPU 7 in software.

  In this embodiment, the scene change detection unit 1552 is provided in the I / F unit 155, and the CPU 7 performs generation and update processing of correction data using the INT 141 from the block. This may be performed when a specific picture such as an I picture or IDR (Instantaneous Decoding Refresh) picture is generated when the image is decoded.

  FIG. 19 is a block diagram illustrating another configuration example of the mobile phone. The same parts as those in FIG. Since mobile phones are used indoors and outdoors, the ambient illuminance varies depending on the usage situation. In a bright environment such as outdoors on a sunny day, ambient light is incident on the display device 16, and there is a problem that it is difficult to identify the low luminance side, that is, the black side gradation of the display image. The mobile phone shown in FIG. 19 has an illuminance sensor 21 and superimposes correction data based on illuminance in addition to correction based on feature points of the input signal.

  The illuminance sensor 21 is configured by a phototransistor, a photodiode, or the like. An example of output characteristics of the illuminance sensor 21 is shown in FIG. The horizontal axis represents the environmental illuminance, and the vertical axis represents the output level of the illuminance sensor. The output level of the illuminance sensor 21 increases as the environmental illuminance increases. In this example, the illuminance sensor 7 is provided as a means for detecting the illuminance. However, the illuminance may be detected by using an output signal of a CMOS or CCD camera.

  The memory 9 stores correction data for correcting the output gradation when the illuminance detected by the illuminance sensor 21 exceeds a predetermined value. FIG. 21 shows an example of the correction data. A correction value is set for each gradation area Yhst. In this example, the black output hierarchy is corrected so that the black gradation can be easily identified. In this example, one type of correction data is provided when the illuminance is greater than or equal to a predetermined level. May be. These plural types of correction data may be stored in the memory 9, or may be calculated, for example, by using the correction data shown in FIG. 21 as reference data and multiplying this by a coefficient corresponding to illuminance. .

  FIG. 22 shows an internal block diagram of the image quality improving circuit 15. An RGB gain adjustment unit 1510 is added to the image quality improvement circuit shown in FIG. The same parts as those in FIG.

  The illuminance detected by the illuminance sensor 7 is input to the CPU 7. When the illuminance is greater than or equal to the predetermined value, the CPU 7 outputs a control signal that instructs the RGB gain adjustment unit 1510 to correct the output gradation. The RGB gain adjustment unit 1510 reads the correction data from the memory 9 through the I / F unit 155 and adjusts the gain of the video signal in accordance with control from the CPU 7. Hereinafter, the operation of superimposing correction data based on illuminance by the RGB gain adjustment unit 1510 will be described with reference to FIG.

  FIG. 23A shows the characteristics of the output gradation with respect to the input gradation of the luminance signal when Blacklevel = 0 and Whitelevel = 255 and are not corrected by the modulation unit 152. When the illuminance is greater than or equal to a predetermined value, the output gradation relative to the input gradation is corrected as shown in FIG. Specifically, the RGB gain adjustment unit 1510 performs correction so as to emphasize the output gradation on the black side, and an image that is easy to view can be displayed even in a bright environment. On the other hand, when the illuminance is less than the predetermined value, the RGB gain adjustment unit 1510 does not perform correction, and the output gradation relative to the input gradation remains as shown in FIG.

  FIG. 23C shows a state in which Blacklevel = 0 to 47 and Whitelevel = 255, and the output gradation for the input gradations 47 to 255 is corrected by the modulation unit 152. When the illuminance is greater than or equal to the predetermined value, the RGB gain adjustment unit 1510 corrects the output gradation with respect to the input gradation using the correction data read from the memory 9 as shown in FIG. In this example, control is performed so that correction is not performed by the RGB gain adjustment unit 1510 in the range of Blacklevel = 0 to 47. However, when the correction amount in the RGB gain adjustment unit 1510 is less than a certain value, There is no problem even if modulation is applied.

  In the above example, the gradation on the black side is emphasized according to the illuminance. However, the present invention is not limited to this, and the correction may be performed according to the color of ambient light. For example, when the color of the external light is reddish light such as sunset, there is a problem that the color of the display image is reddish due to the influence of the external light.

  In order to solve this problem, the illuminance sensor 21 has three detection elements independent of RGB (Red-Green-Blue), and the ratio of these detection elements is calculated by the CPU 7. Thus, modulation is performed by color in addition to the intensity of outside light.

  The CPU 7 calculates the ratio of each RGB output color of the illuminance sensor 21, and when any component of RGB is large, the CPU 7 controls the RGB gain adjustment unit 1510 to lower the correction value for the color having many components. . For example, when it is detected that the ambient light has a large R component, such as when the ambient light is a sunset or an incandescent lamp, the RGB gain adjustment unit 1510 has less R correction data for G and B. Instruct.

  FIG. 24A shows a state in which the RGB gain adjustment unit 1510 corrects the output tone for the input tone of the luminance signal that has not been corrected by the modulation unit 152. FIG. 24B shows a state in which the RGB gain adjustment unit 1510 corrects the output gradation corresponding to the input gradations 47 to 255 by the modulation unit 152. Accordingly, correction is made so that the gain of R is lowered with respect to G and B. Thereby, the ratio of RGB on the display device 16 can be maintained at a desired ratio, and good display can be performed. Here, an example in which there is a large amount of R component in the external light has been described, but the same correction can be made when the external light has a large amount of G or B.

  Also according to the color of the ambient light in addition to the modulation of the input signal. The color of the backlight 17 may be modulated. A configuration example of the backlight 17 and the backlight driving circuit 18 is shown in FIG. The light source elements (LEDs) 171 to 173 are R-LED, G-LED, and B-LED, respectively. The current control means 183 to 185 individually control the currents of the LEDs 171 to 173 based on instructions from the control circuit 181. The DC-DC converter 182 boosts or steps down the voltage supplied from the battery 20 so as to drive the LEDs 171 to 173. The control circuit 181 sets the current value of the current control means 183 to 185 according to an instruction from the CPU 7. In general, the luminous intensity of the LEDs 171 to 173 is proportional to the current flowing between the anode and the cathode. Therefore, the luminous intensity for controlling the currents of the LEDs 171 to 173 can be individually controlled from the CPU 7 via the control circuit 181 and the adjusting means 183 to 185.

  FIG. 26 shows a control example of the LEDs 171 to 173 when the ambient light has many R components. The vertical axis indicates the current that flows through the LEDs 171 to 173. When the R component is large, control is performed so that the current of the R-LED 171 is decreased with respect to the LED 172 and the LED 173. By controlling in this way, it is possible to prevent the color of the display image from changing due to the color of ambient light. The case where there is a lot of R component in the outside light has been explained. However, if there is a lot of G in the outside light, the current of the green LED 172 can be reduced compared to that of R and B, and B- The current of LED 173 may be reduced compared to that of R and G.

  In this example, the case where one R-LED 171, one G-LED 172, and one B-LED 173 is used as the light source element has been described. However, the present invention is not limited to this, and a plurality of micro LEDs are arranged in each color. This control method may be applied when a self-luminous display such as an LED array type backlight or an organic EL display is used as a light source.

  As described above, the example in the case of correcting the color of the external light by the backlight 17 has been described. However, when the external light illuminance is high, it is possible to view a good image by increasing the currents of the LEDs 171 to 173 at the same rate. is there. Conversely, when the illuminance of outside light is low, the power consumption can be reduced by reducing the currents of the LEDs 171 to 173 at the same rate.

  As described above, the mobile terminal device such as a mobile phone has been described as an example. However, the application of the present invention is not limited to the mobile terminal device. The present invention may be applied to any device as long as it is a video processing device capable of viewing video. For example, a terminal device that does not have a communication function may be used. In addition, since it is possible to reduce power consumption for high-quality display, it is particularly effective for a portable terminal that operates with a battery. However, a stationary terminal apparatus that operates with power supply from a household outlet may be used.

DESCRIPTION OF SYMBOLS 1 ... Communication antenna, 2 ... Wireless circuit, 3 ... Code decoding process circuit, 4 ... Microphone, 5 ... Receiver, 6 ... Key, 7 ... CPU, 8 ... CPU bus, 9 ... Memory, 10 ... DAC, 11 ... Speaker, DESCRIPTION OF SYMBOLS 12 ... TV antenna, 13 ... TV tuner, 14 ... Video I / F, 15 ... Image quality improvement circuit, 16 ... Display apparatus, 17 ... Backlight, 18 ... Backlight drive circuit, 19 ... Power supply circuit, 20 ... Battery, 151 ... RGB-YUV conversion circuit, 152 ... modulation unit, 153 ... color difference-HS conversion unit, 154 ... feature point detection unit, 155 ... I / F unit, 156 ... HS-color difference conversion, 157 ... YUV-RGB conversion unit, 158... Selector, 159... Power-off possible area, 1551... Internal bus, 1541. Luminance feature point detector, 1542. Hue feature point detector, 1543. Saturation feature point detector, 1510. RGB gain adjuster, 21. Illuminance sensor, 171 ... R-LED 172 ... G-LED, 173 ... B-LED, 181 ... control circuit, 182 ... DC-DC converter, 183-185 ... current control means, 141 ... INT, 21 ... illumination sensor

Claims (7)

  An illuminance sensor for detecting brightness;
  A video processing unit that performs correction processing on the input video signal;
  A display unit for displaying video processed by the video processing unit;
  A control unit that controls input / output characteristics of a luminance signal in the correction processing of the video processing unit,
  In the control state by the control unit,
  When there is a change in the input video signal, the luminance signal input / output characteristics in the correction process are updated according to the luminance or hue or saturation distribution of the video signal and the brightness detected by the illuminance sensor. A first control state to
  When there is no change in the input video signal and the brightness detected by the illuminance sensor is a predetermined value or more, there is a second control state in which the input / output characteristics of the luminance signal in the correction process are updated.
A video display device characterized by that.   A light amount variable unit that varies the light amount of the light source of the display unit;
  The light quantity variable unit varies the light quantity of the light source according to the brightness detected by the illuminance sensor, and the light quantity is larger when the brightness detected by the illuminance sensor is higher than when the brightness is low. The video display device according to claim 1, wherein the video display device is changed as follows.   The video display device according to claim 2, wherein the light quantity variable unit varies the light quantity without changing a color ratio of the light source.     An illuminance sensor for detecting brightness;
    A wireless receiver capable of receiving signals transmitted in the air;
    A video processing unit that performs a correction process on the input video signal using a video signal based on a reception signal of the wireless reception unit as an input video signal;
    A display unit for displaying video processed by the video processing unit;
  A control unit for controlling input / output characteristics of a luminance signal in the correction processing of the video processing unit;
  A light amount variable unit that varies a light amount of a light source of the display unit;
With
  In the control state by the control unit,
  When there is a change in the input video signal, the luminance signal input / output characteristics in the correction process are updated according to the luminance or hue or saturation distribution of the video signal and the brightness detected by the illuminance sensor. A first control state to
  There is a second control state in which the input / output characteristics of the luminance signal in the correction process are updated when the input video signal is not changed and the brightness detected by the illuminance sensor is equal to or greater than a predetermined value. ,
  The light quantity variable unit varies the light quantity without changing the color ratio of the light source according to the brightness detected by the illuminance sensor, and the brightness detected by the illuminance sensor is higher than when the brightness is low. Change the amount of light to be larger
A video display device characterized by that.   5. The control unit according to claim 1, wherein the control unit includes a state in which the second control state updates an input / output characteristic of a luminance signal in the correction processing according to a gradation range. The video display device according to item.   The said control part has a state which updates the input-output characteristic of the luminance signal in the said correction process so that the black side gradation of the said luminance signal may be enlarged in the said 2nd control state. The video display device according to any one of 1 to 5.   7. The video display device according to claim 1, wherein the change of the input video signal is a scene change portion.

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