JP3413118B2 - Liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an LCD (Liquor).
The present invention relates to a liquid crystal display device capable of reducing the power consumption required for driving an id Crystal Display).

[0002]

2. Description of the Related Art First, a technique for making a refresh rate of an LCD variable will be described, and then an outline of a moving image coding technique used in the present invention will be described by taking MPEG4 as an example.

<LCD Variable Refresh Rate Control>
FIG. 4 shows a block diagram of an image display device conventionally used. The compressed image data 1 is stored in the reception buffer 29 and then input to the image reproduction circuit 2. Image reproduction circuit 2
Then, the image is reproduced from the compressed image data 1, and the image signal 3 thereof is sent to and held in the image display buffer 4. On the other hand, a periodic clock signal 5 is input to the display device 6 at intervals of, for example, 1/60 second, and an image held in the buffer 4 when the clock signal 5 is input is used as an image signal 7 for display. The image is read and displayed on the display device and the displayed image is refreshed. That is, it is rewritten with a new image.

Generally, when displaying an image on a liquid crystal panel,
When the capacitance C of the liquid crystal cell, the polarity reversal frequency of the display image is F, the signal voltage of the display image is V, and the power consumption for displaying the image is P, P = CFV2 (1) is consumed. To do. That is, in the liquid crystal display device, the more the image is rewritten, the more the power consumption increases. Currently, the rewriting frequency of the screen is 60 in a personal computer in which liquid crystal display devices are widely used.
Since it is performed at [Hz] and at a constant rewriting frequency regardless of the content of the displayed image, a large amount of power is constantly consumed for displaying the image on the liquid crystal display device.

In order to reduce power consumption, the cycle of the clock signal 5 is lengthened to reduce the frequency of image rewriting, that is, the rewriting frequency and the polarity reversal frequency F can be reduced. There is a problem that movement becomes awkward. In particular, when scrolling a text or a telop in which a character image moves, a character that cannot be displayed may occur due to a reduction in the rewriting frequency of the display image, and information may be lost.

These problems are caused by constantly rewriting the screen at a constant frequency and simply reducing the rewriting frequency regardless of the contents of the displayed image. <Outline of MPEG4 (Reference: "MPEG-4 standardization trend toward multimedia", Journal of Image Information Media, Vol. 51 No. 12 pp. 1957-2]
003, 1997)> FIG. 5 is a block diagram of an MPEG4 encoder and decoder. The basic composition (5
0,600) is the same as MPEG1 or MPEG2, motion compensation prediction + discrete cosine transform (MC + DCT)
It depends on.

Further, in MPEG4, by utilizing the shape information, it becomes possible to encode each object (person in the example of the figure) having an arbitrary shape as shown in FIG. For an object of arbitrary shape to be encoded in the screen (frame), the encoding area that includes it is set,
The area is divided into macro blocks of 16 × 16 pixels, and the shape information and the texture information are encoded for each macro block. Here, the size of Bounding-Box (vop_width, vop_height
t) and position vector (Spatial_reference)
Since the value of (ce) is also encoded, the display position of the object is specified.

The moving picture information is normally 29.9 in NTSC.
It is updated at 7 fps and 25 fps in PAL. However, in compression-coded video, information may exist only at intervals shorter than the update interval. H.264 of the moving picture coding system. 261, H.264. In H.263, MPEG-4, etc., high-efficiency compression is realized by thinning out frame update intervals (FIG. 7). Instead of the frame update interval according to the standard of NTSC or PAL, time information (time reference or time stamp) indicating the timing of displaying the frame is usually added to the video with the frame thinned out. It FIG. 8 shows the structure of general image coding information. A sync signal indicating the start of a frame is present at the beginning, and following that, there is time information indicating the timing of displaying the frame, encoding mode information, and the like.

[0009]

In the conventional liquid crystal display device, the screen is updated at a fixed interval, generally 60 [Hz]. Therefore, when the update is performed earlier than the update interval of the compression-encoded image. However, even when displaying the exact same image, useless screen updating is performed to increase power consumption.

[0010]

A liquid crystal display device of the present invention is a time information indicating a frame display timing.
Image reproducing means for reproducing an image from compressed data including, a storage means for holding the reproduced image, an image held in the storing means in response to the refresh request signal, and until the next refresh request signal. A liquid crystal display device having a display means for holding the image is characterized by having a refresh control means for determining the timing of generating the refresh request signal based on the time information contained in the compressed data. that's all

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Specific Examples of Embodiments of the Present Invention) Specific examples of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an image display device according to the present invention. The compressed image data 1 is input to the image reproduction circuit 8 after being accumulated in the reception buffer 29. The image reproduction circuit 8 reproduces the image from the compressed image data 1, and the image signal 3 thereof is sent to and held in the buffer 4 for image display. Here, the refresh rate determining circuit 27 generates a refresh request signal according to the information 26 supplied from the image reproducing circuit 8 and is held in the buffer 4 when the refresh request signal 28 is input to the display device 6. The image is read and displayed on the display device 6 as an image signal 7 for display. The display device 6 is a liquid crystal panel. (First Embodiment) FIG. 3 shows an example of the image reproducing circuit 8. The compressed image data 1 is input to the signal separation circuit 9, where the header information 10, the motion information 11, and the pixel value information 1
2. Shape information 13 is separated. The compressed image data 1 is
For example, it is an international standard MPEG-4 standard for moving image coding, and in the rectangular mode of MPEG-4, an image is coded as one data as a rectangle,
In the object mode, the image is data divided into several objects such as the car 14, the telop 15, and the background 16 in FIG.

The header information 10 includes a compression mode (rectangle mode / object mode), an image size, a time reference (TR) of the frame, position information of each subject in the object mode, and the like. It is input to the image synthesis circuit 17. Motion information 1
1 includes a code obtained by coding the motion vector of each block when the subject is divided into blocks, which is reproduced by the motion vector reproducing circuit 18. The pixel value information 12 includes a conversion coefficient when the pixel value of each block is subjected to the discrete cosine transform, and the pixel value is reproduced by the pixel value reproducing circuit 19. The shape information 13 includes a code obtained by encoding the contour line of the subject, which is reproduced by the shape reproducing circuit 20. In the MPEG-4 rectangle mode,
The shape information 13 is not included in the compressed image data. In that case, of course, it is not necessary to reproduce the contour line, and the shape of the image is reproduced in a rectangular shape.

The reproduced motion vector 21 is sent to the motion compensation circuit 22, where the reference frame is motion-corrected by the motion vector 21, and the motion-compensated image 23 is obtained.
Is sent to the image synthesis circuit 17. Further, the reproduced pixel value 24 and the contour line 25 are also sent to the image synthesizing circuit 17. In the image synthesizing circuit 17, the pixel value 24 is added to the motion-compensated image 23 with respect to the pixels inside the contour 25, and a reproduced image for each subject is obtained. Then, the position of each subject is indicated by the header information 10 (Spatial_reference in FIG. 6).
(position indicated by ce) to generate a composite image, which is output as the image signal 3. Further, the contour line 25 is also output.

Returning to FIG. 1, the image signal 3 is sent to and held in the image display buffer 4. On the other hand, the contour line 25 is
It is sent to the refresh rate determining circuit 27.

The refresh rate determining circuit 27 first determines whether or not the subject is a character image by using the contour line 25. Specifically, for example, the average width of the subject is detected, and when the width is smaller than a predetermined value, it is determined to be a character image. Alternatively, if the width is a constant value, it is determined to be a character image. Alternatively, when the ratio of the length of the contour line and the length of the circumference of the rectangle surrounding the subject is larger than a predetermined value, the character image is determined. A refresh request signal 27 is sent from the refresh rate determination circuit 27 to the display device 6. However, when there is no character image on the subject, the refresh request signal 28 is sent with a gap longer than the original frame interval. On the contrary, when the subject includes a character image, the refresh request signal 28 is sent at the frame interval.

FIG. 10 shows a block diagram of the display unit 6. In the example shown in FIG. 10, the liquid crystal panel 100 is used as a display device for displaying a video signal, and the display signal 7 from the image display buffer 4 and the refresh determination circuit 2 are used.
The display image displayed on the liquid crystal panel 100 is updated, that is, refreshed, based on the refresh request signal 28 from 7.

In the display unit 6, the display signal 7 from the image display buffer 4 and the refresh request signal 28 from the refresh determination circuit 27 are first input to the display timing controller 150, and the signal line is supplied in the display timing controller 150. An X driver drive signal 130 for operating the (X) driver 110 and a Y driver drive signal 140 for operating the scanning line (Y) driver 120 are created.

FIG. 11 is a detailed block diagram of the liquid crystal panel 100, the X driver 110 and the Y driver 120. The X driver drive signal 130 output from the display timing controller 150 is the display data 131,
Data transmission start signal 132, clock pulse 133, X
It is composed of a driver output control signal 134. When the display of the liquid crystal panel 100 is refreshed, the display data 7 from the image display buffer 4 is rearranged by the display timing controller 150 according to the pixel arrangement of the liquid crystal panel 100, and rearranged. The data transmission start signal 132 is output at the timing of the first data of the display data 131 after the above. The display data 131 and the transmission start signal 132 are the clock pulse 13
The signal is transmitted to the X driver 110 in synchronism with 3. When the signal transmission for one scanning line is completed, the X driver output control signal 134 for supplying the display signal from the X driver 110 to the liquid crystal panel 100 is turned on and X1 to X1.
A display signal is supplied to the signal lines up to Xn.

The Y driver drive signal 140 output from the display timing controller 150 is composed of a display data scan start signal 141, a scan pulse 142, and a Y driver output control signal 143. From the display timing controller 150, the scanning start signal 14 is sent at the first time of the writing frame corresponding to the clock 5 described above.
1 is output for one scanning line equivalent time, and the scanning start signal 14
1 is sequentially shifted in the Y driver 120 according to the scanning pulse 142, so that the scanning signal, that is, the gate-on signal of the TFT 101 is sequentially applied to the scanning lines Y1 to Ym. Note that Y is the same as the X driver 110.
Since the output control of the Y driver 120 is possible by controlling the driver output control signal 143 on / off, the Y driver output is performed only when the display signal 7 is transmitted from the image display buffer 4 to the display unit 6. Control signal 1
By turning on 43, the TFT of only the desired scanning line
It becomes possible to turn on the gate of 101.

FIG. 12 shows a timing chart showing an example of the operation timing of the Y driver. In the figure,
The STV signal is the scanning start signal 141, and is applied to the Y driver 120 for one pulse and one scanning time at the beginning of the frame to be rewritten. The scan start signal STV
141 is taken in by the Y driver 120 in synchronization with the scanning pulse CPV 142, and a signal for turning on the gate of the TFT 101 is output to the scanning line Y1. A signal for turning on the gate of the TFT 101 is sequentially applied to Ym in synchronization with the scanning pulse CPV 142, and its output is controlled by turning on / off the Y driver output control signal YEN143 as shown in FIG. In the example shown in FIG. 12, only the TFTs 101 from Ym-3 to Ym in which the Y driver output control signal YEN143 is turned on have their gates turned on and writing is performed.

Therefore, by controlling the ON / OFF of the Y driver output control signal YEN143 by the refresh request signal 28, the refresh rate determining circuit 2
It is possible to refresh only the portion determined to be a character image by 7. For example, in FIG. 2, only the portion surrounding the telop 15 is the refresh rate determining circuit 27.
Since it is determined to be a character image by the Y driver output control signal YEN143 is turned on only for the scanning line portion,
It is possible to refresh only the telop 15 portion without writing or refreshing other display portions. That is, it is possible to refresh only the character image displayed on the liquid crystal panel 100 a number of times and reduce the number of refreshes for the natural image. Refresh, that is, Y driver output control signal YEN
The polarity inversion frequency F in Expression 1 becomes zero by setting the output of the X driver 110 to a constant value except when the 143 is turned on, so that the power consumed in the liquid crystal panel 100 becomes zero and the liquid crystal panel is driven. The electric power for the operation can be extremely saved. In the case of a character image, if the frequency of rewriting is reduced, it is not preferable because the characters will appear double or characters that cannot be displayed will occur. Does not deteriorate. Even if deterioration occurs, the influence on information transmission is less in the case of natural image information than in the case of loss of character information. Therefore, according to the present invention, it is possible to suppress the loss of information and reduce the power consumption without substantially degrading the image quality.

The refresh rate determining circuit 27 can also determine whether or not it is a character image by using other information instead of the contour line.

For example, the reproduced pixel value 24 and the image signal 3
However, if it is constant within the outline of the subject, it can be determined as a character image. Alternatively, when the power of the high frequency component of the conversion coefficient 12 is equal to or higher than a predetermined value, it can be determined as a character image. This method is effective even when the data compressed in the rectangular mode is input, and when the power of the high frequency component of the conversion coefficient 12 is equal to or more than a predetermined value, it is determined that the rectangular image includes characters. You can judge. In these cases, the information used for the determination is sent from the image reproduction circuit 8 to the refresh determination circuit 27.

If the refresh rate can be changed for each screen portion, only the character portion, for example, in FIG. 2, the lower 1/4 further character area can be rewritten. The area is smaller and the power consumption can be further saved. In the case of object mode data, the part with an image that is determined to be a character image is determined to be the character part, and in the case of rectangle mode data, the screen is divided into several blocks and each block is divided into blocks. Then, the high frequency component of the transform coefficient 12 is examined and it is determined that the block in which it is larger than the threshold value is the character portion.
Therefore, in the signal input to the buffer 4 that supplies the display signal 7 to the display unit 6, the image determined to be a character image in the case of object mode data and the address of its pixel are input, and the signal of the rectangular mode is input. In the case of data, an address for each block and a display signal are input.

An example of the display unit 6 is shown in FIG. Also, FIG.
3 shows a second detailed example of the peripheral portion of the liquid crystal panel. The display signal 7 and the address signal input from the buffer 4 are supplied to the signal line (X) driver 110 by the display timing controller 150, the display data 131, and the liquid crystal panel 1.
It is separated into a scan line (row) address and a column address indicating the position of the pixel in 00. The display data 131 is supplied to the X driver 130 in synchronization with the clock pulse 133, and X
The liquid crystal panel 100 is controlled by the driver output control signal 134.
A display signal is applied inside. Further, in the display timing controller 150, the address of the image is displayed on the liquid crystal panel 1.
The row driver 1 is decoded into a signal line direction (column) address and a scanning line direction (row) address corresponding to the pixel array of 00.
The row address 144 is applied to 20 and the column address 161 is applied to the column address line driver 160.

The row driver 120 and the column address line driver 160 decode the applied row address 144 and column address 161, and turn on the row address line and column address line corresponding to the address. The column address TFT 107 and the row address TFT 101 connected to the turned-on column address line and row address line are turned on, and the display signal from the X driver 110 is written in the pixel electrode 106. That is, row address 14
4. It is possible to write the display signal output from the X driver 110 only to the pixel designated by the column address 161. Therefore, in the case of data in the object mode, writing can be performed only in the liquid crystal panel pixel corresponding to the image determined as a character image and the address of the pixel.

That is, it becomes possible to refresh a large number of times only for the pixels of the necessary portion in the liquid crystal panel 100, and the refresh frequency can be reduced for other natural image portions, and the power consumption can be reduced. Furthermore, X
In the circuit inside the driver 110, the signal line address 16
It is possible to further reduce the power consumption by turning off the power supply of the output buffer circuit other than the circuit corresponding to 1 or by greatly reducing the circuit bias current.

In the case of rectangular mode data, writing can be performed only in the liquid crystal panel pixel corresponding to the address of each block. FIG. 14 shows a third detailed example of the peripheral portion of the liquid crystal panel. The display signal 7 and the address signal input from the buffer 4 indicate the display data 131 supplied to the signal line (X) driver 110 by the display timing controller 150 and the position of the pixel in the liquid crystal panel 100 divided into blocks. The scan line (row) address and the block address 166 are separated. The display data 131 is transmitted to the X driver 130 by the clock pulse 133.
And is supplied in synchronization with the X driver output control signal 134.
Thus, a display signal is applied to the liquid crystal panel 100.

Further, the display timing controller 15
At 0, the block address 166 of the image is the liquid crystal panel 1
00 is decoded into a block address and a scanning line direction (row) address corresponding to a pixel array divided for each pixel of 00, the row address 144 is applied to the row driver 120, and the block address 166 is applied to the block address line driver 165. Is applied. The row driver 120 and the block address line driver 165 decode the applied row address 144 and block address 166, and turn on the row address line and block address line corresponding to the address.

As shown in FIG. 14, the block address line has a structure in which one output of the block address line driver 165 is connected to a plurality of column address lines. The column address TFT 107 and the row address TFT 1 connected to the turned-on block address line and row address line
01 becomes conductive, and the display signal from the X driver 110 is written in the pixel electrode 106. That is, it is possible to refresh a large number of blocks only in a necessary portion of the liquid crystal panel 100, and the number of refreshes can be reduced for other natural image portions, and power consumption can be reduced. Further, among the circuits in the X driver 110, other than the circuit corresponding to the block address 166, especially the power of the output buffer circuit is turned off or the circuit bias current is greatly reduced, whereby the power consumption can be further reduced. is there.

As described above, the power consumption consumed in the liquid crystal panel 100 can be reduced by writing the display signal only to the pixels to be refreshed or only to the blocks to be refreshed, and the pixels not to be refreshed. Alternatively, by turning off the power source of the driver connected to the block or reducing the bias current of the driver circuit, it is possible to further reduce the power consumption. (Second Embodiment) In this specific example, the refresh rate determining circuit 27 shown in FIG.
More time information 26 is supplied. In the refresh rate determining circuit 27, as shown in FIG. 9, the refresh request signal 2 is timed to the time information 26.
8 is supplied to the display unit 6.

When the refresh request signal 28 is generated in synchronization with the time information 26, it can be realized by making the operations of the Y driver 120 and the X driver 110 shown in FIG. 11 different from those of the first embodiment. When the refresh rate is varied depending on whether the display signal is a character image, the X driver output control signal 134,
Also, the refresh rate of the character image was changed by the Y driver output control signal 143. However, when the refresh rate of the entire screen is changed by adjusting the timing to the time information 26, the display timing controller 150
The display data 131 and the data transmission start signal 132 output from the Y driver 120 are transmitted to the signal line driver 110 only when the refresh request signal 28 is generated.
This can be realized by transmitting the display data scan start signal 141 and the scan pulse 142 supplied to the Y driver 120 only when the refresh request signal 27 is generated.

FIG. 15 shows a timing chart of an example of the operation timing of the Y driver 120. In the example shown in FIG. 15, the scan start signal STV141 and the scan pulse 142
Is output from the Y driver 120 in synchronization with the scan pulse 142 in sequence from Y1 to Ym, that is, a signal for turning on the gate of the TFT 101 in the panel 100 is a scan start signal STV141.
Only one frame to which is applied is output. In this way, by operating each driver only for the frame in which the refresh request signal 28 is generated, the refresh rate can be changed in frame cycle units according to the time information 25.

Further, when the refresh request signal 28 is not generated, the output control signal of each driver, that is, the X driver output control signal 134 of the X driver 110 is turned off to turn off the output circuit to the panel, or the output buffer circuit. The Y driver output control signal Y of the Y driver 120 is turned off while the power is turned off or the bias is low.
By fixing the output of EN143 to the gate-off potential of the TFT, the power consumption consumed in the output stage of each driver can be reduced, so that the refresh request signal 28 is simply generated.
As a result, the power consumption can be reduced as compared with the case where each driver is operated intermittently. <Modifications of First and Second Embodiments> In the case of liquid crystal display, it is necessary to update the screen at least within a certain period. Therefore, the refresh rate determination circuit 26 sets the maximum value of the screen update interval and forcibly refreshes the refresh request signal at the time when the maximum value of the update interval is reached, even if the screen update is not necessary for a period exceeding this. 27 will be output.

For example, as shown in FIG. 11, the pixel electrode 106 in the liquid crystal panel 100 contains a liquid crystal 102 and a storage capacitor (Cs) 103 for holding a display signal. When a display signal is written in the pixel electrode and refreshed, display signal charges are written in the electrostatic capacitance of the liquid crystal 102 itself and the electrostatic capacitance of Cs 103.
The written charges are reduced due to a leak current through the TFT 101 and a leak current resulting from the pixel electrode structure and the liquid crystal material, and an accurate display signal voltage cannot be maintained when the refresh interval becomes long. In addition, there are cases where the pixel electrode has a memory, or the liquid crystal itself has a memory property. In this case, if the same electric field is continuously applied to the liquid crystal material, that is, if the liquid crystal material is continuously driven by a DC electric field, the liquid crystal material deteriorates. Therefore, it is necessary to drive the liquid crystal material with an alternating current. This will be described with reference to the block diagram shown in FIG.
A driving state in which a voltage is applied to the 4 side to drive the TFT 10
It is necessary to alternately take the driving state in which the − voltage is applied to 1 and the + voltage is applied to the Vcom 104 side.

Considering the leak of charges of the pixel electrode and the problem of reliability of the liquid crystal material as described above, the refresh cycle of the display image displayed on the liquid crystal panel is 1 to at the longest.
It is desirable to refresh every few seconds. That is, in the refresh rate determination circuit 27, it is desirable to set the maximum value of the screen update interval to 1 to several seconds. (Third Embodiment) As described above, the charge written in the pixel electrode 106 in the liquid crystal panel 100 is reduced (fluctuated) in the amount of charge in the pixel electrode 106, that is, the pixel potential, due to the leak current through the TFT 101. The amount of change in the pixel potential is such that when a positive voltage is applied to the TFT 101 and a negative voltage is applied to the Vcom 104 side for driving (hereinafter referred to as positive polarity driving), the negative voltage is applied to the TFT 101 to Vco.
This is different from the case of a driving state in which a + voltage is applied to the m104 side to drive (hereinafter referred to as negative driving). That is, TF
The difference is the difference in pixel potential with respect to the gate voltage of T101, the gate-source voltage, the difference between the potential applied to the signal line side and the pixel potential, and the gate-drain voltage. Therefore, the way of changing the pixel potential is different between the positive polarity driving and the negative polarity driving. There are various driving methods for AC driving the liquid crystal panel, that is, driving in which positive driving and negative driving are alternately performed for each pixel, and AC driving.

16 to 19 show a typical AC driving method. FIG. 16 shows a frame inversion driving method in which the pixels of the entire screen are inverted with the same polarity. FIG. 17 shows a signal line inversion driving method in which pixels in the column direction are alternately inverted with the same polarity. FIG. 18 shows a line inversion driving method in which pixels in the scanning line direction are alternately inverted with the same polarity. FIG. 19 shows a dot inversion driving method in which the polarity is changed for each adjacent pixel.

As described above, since the leak amount of the electric charge accumulated in the pixel electrode differs depending on the polarity, the variation amount of the pixel potential that occurs when the refresh is not performed for a long time varies depending on the polarity. Therefore, when the polarity inversion is performed at the time of refresh, the frame inversion drive method of FIG.
That is, it is detected as a surface flicker and the image quality is deteriorated. Similarly, the signal line inversion method of FIG. 17 produces vertical line flicker, the line inversion drive method of FIG. 18 produces horizontal line flicker, and the dot inversion drive method of FIG. 19 produces dot flicker.

Considering human visual characteristics, the dot inversion driving method, which has a high spatial frequency, is the most difficult to detect flicker for the same amount of luminance fluctuation. That is, the dot inversion driving method is most suitable when the refresh cycle becomes long and the potential fluctuation of the pixel becomes large. However, as shown in the above formula 1, in the line inversion driving method and the dot inversion driving method, the polarity is inverted for each scanning line, so that the polarity inversion frequency F is substantially increased and the power consumption is increased.

Therefore, when the refresh rate is variable depending on the character information and the time information of the image signal, when the refresh rate is equal to the frame frequency before encoding, the polarity inversion is performed by the frame inversion drive method and the refresh is performed. When the rate becomes small (the cycle becomes long), the polarity inversion is performed by the dot inversion drive method to reduce the power consumption,
In addition, it is possible to suppress image quality deterioration due to flicker. That is, when the refresh cycle is equal to a normal NTSC frame frequency, the polarity inversion driving method with a small polarity inversion frequency in one screen is used, and when the refresh cycle is long, the dot inversion driving method is used. The polarity inversion driving method that has a high polarity inversion frequency in the screen and can realize low flicker is used.

It can also be realized by using a multi-field (MF) driving method (reference: Japanese Patent Application No. 2-69706) as a low flicker driving method similar to the dot inversion driving method. The switching between the dot inversion driving method, the MF driving method, and the frame inversion driving method is performed by monitoring the refresh interval of each pixel or block in the refresh rate determining circuit 26.

Further, when the encoding device is applied to a videophone or the like, it is desirable that the reproduction of compressed image data and the display thereof are performed in a short time. For this purpose, the refresh rate determining circuit 27 monitors the refresh interval of each pixel or block to make the refresh rate variable, and monitors the increase / decrease amount of the signal receiving buffer memory 29 in which the compressed image data 1 is accumulated. It is also possible to substitute it. That is, when the free space of the signal receiving buffer memory 29 is low, the image thinning amount is large and the refresh interval is long, so that the signal is driven by dot inversion, and the free space of the signal receiving buffer memory 29 is reduced. When the number of images is changing in a large amount, the amount of thinning-out of the image is small, so the refresh interval may be controlled to be short.

[0044]

As described above, the information contained in the compressed data of the moving image is used to adaptively switch the refresh rate in the screen, so that the driving power of the LCD can be reduced without impairing the subjective display image quality. It will be possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment according to the present invention.

FIG. 2 is a diagram showing components of an image.

FIG. 3 is a block diagram of an image reproduction circuit.

FIG. 4 is a block diagram showing a conventional example.

FIG. 5 is a block diagram illustrating MPEG4 encoding / decoding.

FIG. 6 is a diagram illustrating encoding of an object having an arbitrary shape.

FIG. 7 is a diagram illustrating a frame interval of a compression-coded moving image signal.

FIG. 8 is an example of moving image encoded information.

FIG. 9 shows an example of the timing of the refresh request signal according to the frame interval.

FIG. 10 is a block diagram showing an example of a display unit.

FIG. 11 is a block diagram showing a first configuration example around a liquid crystal panel.

FIG. 12 is a timing chart showing a first operation timing of the Y driver.

FIG. 13 is a block diagram showing a second configuration example around a liquid crystal panel.

FIG. 14 is a block diagram showing a third configuration example around a liquid crystal panel.

FIG. 15 is a timing chart showing a second operation timing of the Y driver.

FIG. 16 is a diagram for explaining a frame inversion driving method.

FIG. 17 is a diagram for explaining a signal line inversion driving method.

FIG. 18 is a diagram for explaining a line inversion driving method.

FIG. 19 is a diagram for explaining a dot inversion driving method.

[Explanation of symbols]

50 ... Texture information encoding unit 200 ... Shape information coding unit 300 ... Data multiplexing unit 400 ... Data separation unit 500 ... Shape information decoding unit 600 ... Texture information decoding unit

Front page continuation (72) Inventor Takashi Ida 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center Co., Ltd. (72) Inventor Ken Nakajo 1 Komukai-shi Toshiba-cho, Kawasaki-shi, Kanagawa Company Toshiba R & D Center (72) Inventor Yoko Sanbonsugi 1 Komukai Toshiba Town, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Toshiba Research and Development Center (72) Inventor Go Nagai Komukai Toshiba Town, Kawasaki City, Kanagawa Prefecture No. 1 in Toshiba Research & Development Center (72) Inventor Rieko Furukawa Komukai Toshiba-cho, Sachi-ku, Kawasaki City, Kanagawa No. 1 In Toshiba Research & Development Center (72) Inventor Haruhiko Okumura Shinisogo, Isogo-ku, Yokohama-shi, Kanagawa 33 Machi-cho, Toshiba Production Engineering Laboratory (72) Inventor Hisao Fujiwara 33, Shinisogo-cho, Isogo-ku, Yokohama, Kanagawa Prefecture In-house Toshiba Production Engineering Laboratory (72) Inventor Go Ito Komukai, Sachi-ku, Kawasaki, Kanagawa Prefecture Toshiba Town No. 1 Toshiba Corporation Research and Development Center (72) Inventor Kobayashi et al. 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki City, Kanagawa Prefecture Research and Development Center, Toshiba Corporation (56) Reference JP-A-7-239463 (JP, A) (58) Survey Areas (Int.Cl. ⁷ , DB name) G09G 3/36 G09G 3/20 611 G09G 3/20 633 G09G 3/20 660 H04N 5/66 102

Claims (6)

(57) [Claims] 1. A timing for displaying a frame is displayed.
Image that is played back from compressed data that includes time information.
Image reproducing means, storage means for holding the reproduced image,
The image stored in the storage means in response to the refresh request signal
The image is displayed and the next refresh request signal is displayed.
In a liquid crystal display device having a display unit for holding the image of
The timing to generate the refresh request signal.
Riff determined by the time information included in the compressed data
Liquid crystal display device characterized by having a flash control means
Place 2. The liquid crystal display device according to claim 1,
The refresh control device determines whether or not the image or a part thereof is a character image based on the information contained in the compressed data, and when the image is not a character image, the refresh request signal is generated more than when the image is a character image. A liquid crystal display device characterized in that an interval for generating the light is extended. 3. The liquid crystal display device according to claim 1,
The refresh control device has an update interval determining means for determining an update interval of the screen from the time information included in the compressed data, and in the refresh control device, the refresh request signal is sent according to the update interval determined by the update interval determining means. A liquid crystal display device characterized by controlling the intervals at which it is generated. 4. The liquid crystal display device according to claim 1, 2 or 3, wherein the compressed data reproduced by the image reproducing means is reproduced at the same frame frequency as that of the image signal input to the encoding device which created the compressed data. In this case, the polarity inversion cycle of the display signal applied to the liquid crystal cell is the frame cycle,
When the compressed data reproduced by the image reproducing means is reproduced at a frame frequency lower than the image signal input to the encoding device that created the compressed data, the polarity inversion cycle of the display signal applied to the liquid crystal cell is scanned. A liquid crystal display device characterized by displaying as a line period. 5. The liquid crystal display device according to claim 1, 2 or 3, wherein the compressed data reproduced by the image reproducing means is reproduced at the same frame frequency as that of the image signal input to the encoding device which created the compressed data. In this case, the display signal applied to the liquid crystal cell is sequentially scanned, and the compressed data reproduced by the image reproducing means is reproduced at a lower frame frequency than the image signal input to the encoding device that created the compressed data. In this case, the display signal applied to the liquid crystal cell is displayed as interlaced scanning. 6. The liquid crystal display device according to claim 1, 2, 3 or 5, wherein the refresh rate of the screen is the frame frequency of the image signal input to the encoding device that created the compressed data according to the information included in the compressed data. If it is lower, or if the refresh interval is longer than that of the character image, or if the display signal displayed on the display device is interlaced scanning, either the pixel to be scanned or the refresh is performed. A liquid crystal display device characterized by cutting off the power supply of a display signal drive circuit connected to a pixel other than the pixel or reducing the bias current of the display signal drive circuit.