Patent Application
20090153442
The present application claims priority from Japanese application JP2007-324180 filed on Dec. 17, 2007, the content of which is hereby incorporated by reference into this application.
The invention relates to a plasma display apparatus for performing a gradation display by forming a plurality of subfields having different weights from one frame of a video signal and, more particularly, to a plasma display apparatus in which a technique to form subfields suitable to display movie contents has been made.
In a plasma display apparatus, the gradation display is performed by what is called a subfield display system. According to the subfield display system, a plurality of subfields added with weights corresponding to the nth power of 2 (n=0, 1, 2, . . . ) are formed from one frame of a video signal and discharge maintaining pulses (hereinbelow, also referred to as sustaining pulses) specified by the weight are applied every subfield to discharge cells constructing a plasma display panel (hereinbelow, abbreviated to a PDP), thereby expressing a gradation according to a visual integrating effect.
Since the plasma display apparatus has such a construction as mentioned above, when a vertical frequency (frame/field frequency) of the video signal is low, a flicker becomes conspicuous. As a related art to reduce such a flicker, for example, the technique disclosed in JP-A-2000-66630 has been known. It discloses such a technique that with respect to a video signal of 50 Hz, a subfield corresponding to one video frame is divided into two subfield groups, upper subfields in the respective subfield groups are made to coincide with each other, and further, lower subfield groups are made to differ from each other.
In JP-A-2000-66630, a consideration is made only to the video signal whose vertical frequency (frame/field frequency) is equal to 50 Hz based on the PAL system, SECAM system, or the like and no consideration is made with respect to, for example, a video signal of a movie contents whose frame frequency is equal to 24 Hz.
In order to display the video signal whose frame rate (frame frequency) is equal to 24 Hz to the PDP without making a flicker conspicuous, there is a method whereby by forming, for example, every three or four frames of the same video contents as those of each frame in the video signal, the frame rate is converted into 72 Hz or 96 Hz. However, if the frame rate of the video signal is raised, a period of one frame is shortened and the number of subframes which can be used per frame decreases, so that sufficient gradations cannot be obtained. In the case of forming every two frames of the same video contents and converting the frame rate into 48 Hz, since the frame rate is smaller than 50 Hz, the flicker increases.
What is called a telecine signal in which 24 movie films per second have been 2-3 pull-down processed and the frame rate has been converted into 60 Hz is known as a video signal of the movie contents. According to the telecine signal, since each frame is repeated by the 2-3 pull-down process in such a manner that two frames, three frames, two frames, . . . are repetitively displayed, a period of time during which a video image comes to rest is also repeated like 2/60 second, 3/60 second, and 2/60 second. Therefore, according to the telecine signal, a motion judder (jaggy feeling of a motion) caused by a change in still period of time of the video image occurs. In JP-A-2000-66630, no consideration is also made with respect to the motion judder.
Even in the case where the movie contents is viewed by a home-use display apparatus such as a television display apparatus or the like, it is desirable that the movie contents can be viewed so that a visual effect similar to that in the case of viewing it in a movie theater, that is, it can be viewed at a high presence. In JP-A-2000-66630, no consideration is also made with respect to such a problem.
The invention is made in consideration of the above problems and provides such a technique that even in the case where a video signal of a low frame rate such as a movie contents is displayed on the PDP, good gradations can be obtained and a large flicker can be suppressed. The invention also provides such a technique that the movie contents can be viewed at a high presence.
The invention is characterized by having constructions disclosed in claims. That is, according to the invention, by forming at least every two frames having video contents corresponding to each frame of a video signal, for example, a frame rate of a movie contents whose frame rate is equal to 24 Hz is converted into 48 Hz. A plurality of subfields corresponding to each frame of the conversion signal is divided into first and second division subfield groups, and each division subfield group is further classified into an upper subfield group on the side where a weight of a luminance is large and a lower subfield group on the side where a weight of a luminance is small. A weight of the upper subfield group in the first division subfield group and a weight of the upper subfield group in the second division subfield group are equalized or made symmetrical. A weight of each subfield belonging to the lower subfield group in the first division subfield group is set to be larger than a weight of each subfield belonging to the lower subfield group in the second division subfield group.
Thus, for example, when the frame rate of the inputted video signal is equal to 24 Hz, since the subfields can be formed, for example, at a period of time of 1/48 second per frame, the subfields of the number per frame necessary to obtain good gradations can be assured. Since the weights of the upper subfield groups on the large weight side are equalized or made symmetrical between the two division subfields, the subfields of the high gradation can be formed at a frequency of 96 Hz and the flicker can be suppressed. Further, in each of the first and second division subfield groups, since the weights of the respective subfields belonging to the lower subfield group on the small weight side are made differ, in the case of displaying the movie contents in which the number of dark video images is relatively large, the gradations of the dark video images can be improved.
According to the invention, even in the case where, for example, the video signal whose frame rate is low like a movie contents is displayed on the PDP, the good gradations can be obtained and the video images can be displayed while suppressing the large flicker.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.
An embodiment of the invention will be described hereinbelow with reference to the drawings. In each diagram, elements having common functions or operations are designated by the same reference numerals and an overlapped explanation is omitted with respect to the component elements which have been described once.
According to the embodiment, as for a video signal of a movie contents or the like whose frame rate is equal to 24 Hz, first, every two frames of such a video signal are repeated (every two frames of the same video contents as those of each frame are formed), thereby converting (doubling) the frame rate into 48 Hz. The embodiment is characterized as follows. A plurality of subfields which are formed in correspondence to each frame of the doubled signal is divided into first and second division subfield groups. Further, each division subframe group is classified into an upper subframe group on the side where a weight of a luminance is large and a lower subframe group on the side where a weight of a luminance is small. The weight of each subfield belonging to the upper subframe group in the first division subfield group and the weight of each subfield belonging to the upper subframe group in the second division subfield group are made symmetrical. The weight of each subfield belonging to the lower subfield group in the first division subfield group and the weight of each subfield belonging to the lower subfield group in the second division subfield group are made asymmetrical. Such forming control of the subframes is called “asymmetrical SF control” hereinbelow. There is also a case where the subframe is called “SF” hereinbelow. There is also a case where the weight of the luminance to the SF is simply called “weight”.
First, an example of a plasma display apparatus according to an embodiment of the invention will be described with reference to
Several formats exist for the video signals which are inputted to the plasma display apparatus 100. For example, there are: a video signal of a normal format (instead of the pull-down format) whose vertical frequency, that is, frame frequency (hereinbelow, this frequency is called “frame rate”) is equal to 60 Hz; a telecine signal of the 2-3 pull-down format whose frame rate is equal to 60 Hz; a signal such as animation, movie contents, or the like whose frame rate is equal to 24 Hz; and the like. As a video signal having a frame rate of 24 Hz, for example, there is a video signal based on the video contents such as movie or animation reproduced from a Blu-ray disc. In the case where the video signal is transmitted by an interface according to a special standard (HDMI: High Definition Multimedia Interface), the video signal having the frame rate of 24 Hz can be inputted to the plasma display apparatus 100. Explanation will be made hereinbelow on the assumption that the video signal having the frame rate of 24 Hz or the telecine signal is inputted to the plasma display apparatus 100. Since the video signal whose frame rate is equal to 24 Hz and which is inputted to the plasma display apparatus 100 as mentioned above has a progressive (sequential operation) format, there is also a case where this signal is referred to “24p signal”.
The external video reproducing apparatus 200 is connected to a digital input terminal 1 of the plasma display apparatus 100 by the interface (HDMI interface) according to the foregoing HDMI standard. The external video reproducing apparatus 200 is, for example, a Blu-ray player. In the case where a Blu-ray disc on which a movie contents has been recorded is reproduced by the Blu-ray player and the Blu-ray player has been connected to the plasma display apparatus 100 by the HDMI interface, a 24p signal is formed. The 24p signal is transmitted by an HDMI transmitter 210 of the external video reproducing apparatus 200. The 24p signal from the HDMI transmitter 210 is inputted to the digital input terminal 1 through the HDMI interface and received by an HDMI receiver 2. The signal received by the HDMI receiver 2 is supplied to one contact of an input change-over switch 3. In the embodiment, the input change-over switch 3 has three contacts. As mentioned above, one of them corresponds to the signal from the HDMI receiver 2, another one corresponds to the signal inputted to the analog input terminal 21, and further another one corresponds to a TV signal received by a tuner 17. The analog video signal outputted from an external video apparatus such as DVD player, VTR, or the like is inputted to the analog input terminal 21. The analog video signal is separated into a video signal and a sync signal by a sync separating circuit 22 and, at the same time, converted into a digital signal by an A/D converter 23 on the basis of sampling clocks formed by the sync separating circuit 22 by using the sync signal as a reference. The video signal converted by the A/D converter 23 is supplied to another contact of the input change-over switch 3.
The TV signal which has been received by the antenna (not shown) and transmitted by the cable 27 is received by the tuner 17. It is assumed here that the TV signal has been compression-encoded by, for example, MPEG2. Under control of the CPU 151 constructing the control unit 15, a station selecting unit 81 of the tuner 17 selects a desired broadcasting channel included in the broadcasting signal (RF signal) received by the antenna, demodulates, and outputs a TS (Transport Stream) to which various kinds of data have been multiplexed. An MPEG decoder 82 executes a decoding process to the TS, forms a non-compression digital video signal, and supplies to further another contact of the input change-over switch 3.
The input change-over switch 3 selects one of the video signals supplied to the three contacts according to a control signal from the control unit 15 and outputs. The signal selected by the input change-over switch 3 is supplied to one contact of a switch 5 and is also supplied to a telecine IP converting circuit 4.
In the case where an output signal from the input change-over switch 3 is a telecine signal of an interlace format, the telecine IP converting circuit 4 is a circuit element for converting the output signal into a signal of a progressive format. The telecine IP converting circuit 4 includes: a telecine detecting unit 42 for detecting whether or not the output signal from the input change-over switch 3 is the telecine signal; and an IP converting unit 41 for converting the telecine signal of the interlace format into the telecine signal of the progressive format.
The telecine detecting unit 42 detects whether or not the inputted video signal is the telecine video signal of the 2-3 pull-down format.
To explain the telecine detecting operation which is executed by the telecine detecting unit 42, first, the telecine signal of the 2-3 pull-down format will be described with reference to
On the broadcasting station side, as shown in
In this manner, the telecine signal is successively and repetitively formed every five fields, as a set, constructed by the two fields converted from the video image of the same frame (odd-number designated frame) and the three fields converted from the video image of the next same frame (even-number designated frame). Therefore, for example, since the third field Bo and the fifth field Bo in
Further, the telecine detecting unit 42 also detects a telecine phase of the telecine signal. An example of the detection of the telecine phase will be described with reference to
For example, when the difference is shifted from “absence” to “presence” in the difference 2 simultaneously with that the difference is shifted from “absence” to “presence” in the difference 1, “1” is allocated as a telecine phase. After that, for a period of time during which “presence” continues in the difference 2, if the difference is shifted from “absence” to “presence” in the difference 1, “2” is allocated as a telecine phase. When the difference is again shifted from “absence” to “presence” in the difference 1, “3” is allocated as a telecine phase. When the difference is again shifted from “absence” to “presence” in the difference 1, “4” is allocated as a telecine phase. If both of the difference 1 and the difference 2 are “absence”, “0” is allocated as a telecine phase.
In this manner, a telecine phase signal in which “0, 1, 2, 3, 4” is repeated as shown in the bottom portion of
When it is detected that the inputted video signal is the telecine signal of the interlace format of the 2-3 pull-down format, the telecine detecting unit 42 transmits a telecine detection F (telecine detection flag) showing the detection result and the telecine phase signal to the IP converting unit 41. When the inputted video signal is the telecine signal of the progressive format of the 2-3 pull-down format, the telecine detecting unit 42 does not execute the telecine detection.
When the telecine detection F and the telecine phase signal are received, the IP converting unit 41 executes an IP conversion to the telecine signal. The operation of the IP converting operation will be described with reference to
When the input video signal is the 24p signal, the switch 5 selects the foregoing one contact, that is, the output signal from the HDMI receiver 2. When the input video signal is the telecine signal of the 2-3 pull-down format and the interlace format, the switch 5 selects the other contact, that is, the output signal from the telecine IP converting circuit 4 and outputs it to a scaler 6. Thus, the signal of the progressive format is always inputted to the scaler 6. The switch 5 is controlled by the CPU 151 of the control unit 15. When the video signal is transmitted by the HDMI interface, information regarding the format of the video signal is also transmitted from the external video reproducing apparatus 200. The HDMI receiver 2 receives the format information and outputs it to the CPU 151. When the format information from the HDMI receiver 2 indicates the progressive format, the CPU 151 selects one contact (output from the HDMI receiver 2) of the switch 5. When the format information indicates the interlace format, the CPU 151 selects the other contact (output from the telecine IP converting circuit 4).
The scaler 6 executes what is called a scaling process for magnifying or reducing a video image by interpolating pixels in the horizontal and vertical directions to the output signal from the switch 5 so as to obtain a resolution which can be displayed by a video display unit 14. The scaling-processed signal is supplied to a twice-reading circuit 7, a frame rate converting unit (FRC) 9, and a telecine detecting unit 8, respectively.
In the embodiment, it is assumed that the following two processes are executed as a process for converting the frame rate. One of them is a process in which the 24p signal or telecine signal is inversely telecine converted and the frame rate of the signal of the progressive format whose frame rate is equal to 24 Hz (hereinbelow, such a signal is referred to as “inverse telecine signal”) is doubled (48 Hz) by the twice-reading circuit 7. The other is a process in which the 24p signal or the inverse telecine signal is motion-compensated by the frame rate converting unit (FRC) 9 and its frame rate is converted into 60 Hz, thereby allowing the motion image to be seen as a smooth image. The former converting process is called a frame repeating process and the latter converting process is called a smooth cinema process.
Prior to explaining each converting process, first, the inverse telecine converting process will be described. The inverse telecine converting process is executed by the telecine detecting unit 8 and contents of fundamental processes are substantially the same as those of the telecine detecting unit 42 in the telecine IP converting circuit 4. However, besides the functions of the telecine detecting unit 42, a function for executing the inverse telecine conversion by using the telecine phase signal shown in
Subsequently, the frame repeating process will be described. The twice-reading circuit 7 constructs a frame doubling unit. The twice-reading circuit 7 selects either the 24p signal or the inverse telecine signal in response to an instruction from the CPU 151 and doubles the frame rate. For example, the twice-reading circuit 7 is equipped with one frame memory. That is, the twice-reading circuit 7 holds data of one frame of the 24p signal or the inverse telecine signal, updates the data at a period of 1/24 second corresponding to the frame rate of the 24p signal, and reads out it at a period of 1/48 second that is twice as high as its updating period. Thus, as shown in
Subsequently, the smooth cinema process will be described. According to the smooth cinema process, as shown in
First, the detecting process of the motion vector MV will be described with reference to
First, search windows W2 and W4 showing a search range of the motion vector are set with respect to the frames A and B which time-dependently continue in the 24p input. The search window W2 of the frame A has a size of, for example, 7 pixels in the vertical direction and 7 pixels in the horizontal direction in which a pixel P02 of the frame A existing at the spatially same position as that of an interpolation pixel P03 is set to a center. Likewise, the search window W4 of the frame B also has a size of, for example, 7 pixels in the vertical direction and 7 pixels in the horizontal direction in which a pixel P04 of the frame B existing at the spatially same position as that of the interpolation pixel P03 is set to a center. Coordinates of the pixels P02 and P04 are also conveniently assumed to be (0, 0) for convenience of explanation.
Subsequently, a straight line which passes through the search window W2 of the frame A and the search window W4 of the frame B around the interpolation pixel P03 as a center is set. For example, assuming that the coordinates of the pixel existing at the left lower edge of the search window W2 are equal to (−3, −3), the pixel in the search window W4 existing on the straight line connecting the above pixel and the interpolation pixel P03 becomes the pixel at the right upper edge and its coordinates are equal to (3, 3). Such a straight line is set with respect to all pixels in the search windows W2 and W4. In this example, since the number of pixels in the search windows W2 and W4 is equal to 7×7=49, 49 straight lines are set as straight lines which pass through the interpolation pixel P03.
Subsequently, with respect to each of the 49 straight lines, a difference between the pixel in the search window W2 and the pixel in the search window W4 through which each straight line passes is calculated. It is assumed here that a difference between the luminance signals of each pixel is obtained. A straight line having a pair of pixels in which the difference is smallest is set as a motion vector of the interpolation pixel P03. In the example of
Subsequently, an interpolation frame forming process will be described. An interpolation frame is formed by using the motion vector MV detected as mentioned above and the frames A and B. For example, each video data of the pair of pixels (pixels P12 and P13) indicated by the detected motion vector MV is extracted from the video data of the frames A and B, each video data is multiplied by a predetermined coefficient, and the resultant data is added, thereby calculating a pixel value of an interpolation pixel or an interpolation block. Assuming that the predetermined coefficient is set to k here, the data of the interpolation pixel P03 is obtained by the following equation 1.
P03=(1−k)·P12+k·P22 (where, k<1) (1)
A value of k is decided by a ratio between a time-dependent distance between the interpolation frame AB and the frame A and a time-dependent distance between the interpolation frame AB and the frame B. For example, in the case of the interpolation frame A1B1, a ratio between the time-dependent distances for the frames A and B is equal to 1:2, k=⅓. In the case of the interpolation frame A2B2, a ratio between the time-dependent distances for the frames A and B is equal to 1:1, k=½. In the case of the interpolation frame A3B3, k=⅔.
The value of the interpolation pixel in the interpolation frame is obtained in this manner. By executing the above process with respect to all interpolation pixels, one interpolation frame is formed. By executing the above process with respect to all of the interpolation frames A1B1 to A3B3, three interpolation frames are formed. By inserting those interpolation frames between the frames A and B of the 24 p input, the 24 p input is frame-rate converted into the signal of 60 Hz as shown in
The signal subjected to the frame repeating process in the twice-reading circuit 7 and the signal subjected to the smooth cinema process in the FRC 9 are inputted to a cinema mode change-over switch 10, respectively. Further, a signal of the frame rate of 60 Hz obtained by executing, for example, the 2-3 pull-down process as shown in
An output signal from the cinema mode change-over switch 10 is subjected to various kinds of picture quality correcting processes such as contrast correction, color correction, gamma correction, and the like by a picture quality correcting unit 11. After that, an OSD (On Screen Display) image such as a menu display screen or the like is synthesized by an OSD inserting circuit 12. An example of the OSD image is shown in
On the menu display screen of
That is, in the case where the input signal is the 24p signal or the inverse telecine signal, the cinema mode change-over switch 10 is controlled in such a manner that when “OFF” or “FILM THEATER” is selected by the user on the menu display screen of
The signal in which the OSD image has been inserted by the OSD inserting circuit is inputted to a subfield control circuit 13. The subfield control circuit 13 includes: an SF control unit 132 for executing a normal SF process such as a process to form and output fourteen SFs having different weights to one frame; and an asymmetrical SF control unit 131 for making the foregoing asymmetrical SF control.
A group of SF formed by the SF control unit 132 and a group of SF formed by the asymmetrical SF control unit 131 are supplied to an SF change-over switch 133, respectively. The SF change-over switch 133 selects one of those SF groups by a control signal from the CPU 151. The control signal from the CPU 151 is outputted in response to the cinema mode selected by the user. For example, the control signal for allowing the SF change-over switch 133 to select the SF group from the asymmetrical SF control unit 131 when “REAL CINEMA” is selected on the menu display screen of FIG. 8 and to select the SF group from the SF control unit 132 when the mode other than “REAL CINEMA” is selected is outputted.
The SF group outputted from the SF change-over switch 133 is supplied to the display unit 14 constructed by the PDP. The sustaining pulses (discharge maintaining pulses) of the number based on the SF group are applied to the discharge cells of the PDP 14, thereby allowing the gradation display to be performed on the display screen of the PDP 14.
Subsequently, details of the SF control unit 132 as a characteristic portion of the embodiment will be described. Prior to explaining it, a concept or principle of the invention will be described with reference to
The human being feels flickering to a periodic fluctuation of the luminance. When a single pulse is first generated and, subsequently, a flickering frequency is gradually raised, although the human being feels the flickering first, the human being feels the flickering at a certain frequency and higher as a stationary average luminance. A frequency at which the flicker is fused to a predetermined luminance (that is, frequency at which the human being does not feel the flickering) is referred to as a flicker fusion frequency CFF (Critical Fusion Frequency or Critical Flicker Frequency) here. The CFF depends on the luminance of the light and, generally, there is such a tendency that the higher the luminance is, the higher the CFF is.
For example, a movie film whose frame rate is equal to 24 Hz is projected onto a screen at a rate of once per 48 seconds and at a duty ratio of 50% in a movie theater. Now assuming that the luminance changes in a range of 0 to 1, when the light emission in the case of a white display is Fourier transformed, the GW is equal to about 0.64.
In the case of displaying the 24p signal in the embodiment, since the signal of 24 Hz has been once converted into 48 Hz by the frame repeating process and inputted to the PDP, a fundamental frequency is equal to 48 Hz.
Further, the PDP is driven on a subfield (SF) unit basis, the numbers of light emitting times of the subfields SFs are made different, and the gradation expression is performed by a combination of them. At this time, in the case where the video signal of 48 Hz is inputted to the PDP and displayed as it is, for example, a frequency component whose intensity is strongest is lower than the CFF and its intensity is equal to about 50% and is a large value as shown in
However, when the viewer actually views in the movie theater, he slightly feels the flicker. This point will be explained with reference to
In the case of displaying the movie contents by the PDP, it is considered that if the viewer is made to visually sense a flicker similar to that in the case where the movie is actually viewed in the movie theater, the viewer can obtain a feeling as if he viewed in the movie theater although he is actually monitoring the movie by the PDP.
In the PDP, a flicker level can be changed by controlling the weight of the luminance of each SF (that is, light emitting times ratio), a time-dependent layout of each SF, a time-dependent interval between predetermined SFs, or the like. In the embodiment, therefore, by dividing the SFs per frame into the two groups and falsely driving the PDP at 96 Hz as mentioned above, the large flicker (of 48 Hz) is suppressed. On the other hand, the weight of the subfield group on the low gradation side (side where the weight is small) in the first division subfield group and the weight of the subfield group on the low gradation side (side where the weight is small) in the second division subfield group are made asymmetrical, thereby expressing the slight flicker which is sensed when the movie is viewed in the movie theater as mentioned above. By this method, a presence as if the viewer actually viewed the movie in the movie theater can be given to the viewer.
At this time, assuming that the weights of the first division subfield group and the second division subfield group are perfectly symmetrical, this is substantially equivalent to a state where the PDP is driven at 96 Hz, so that the PDP has to be driven by the SFs of the number which is half of the number of SFs upon driving at 48 Hz. If the number of SFs is small, since the number of combinations of them also decreases, such a method is disadvantageous in the case of performing the gradation expression. To solve such a problem, in the embodiment, in each of the first and second division subfield groups, the weights of the subfield groups on the high gradation side (side where the weight is large) in the division subfield groups are made symmetrical, thereby reducing the flicker, and the weights of the subfield groups on the low gradation side (side where the weight is small) in the division subfield groups are made asymmetrical, thereby expressing the slight flicker as mentioned above and enabling gradation expressing ability to be located in the middle between the 48 Hz driving and the 96 Hz driving. That is, according to the subfield control in the embodiment, in the case of the bright signal whose luminance level is high, since the flicker is conspicuous, symmetry is raised, and in the case of the dark signal whose luminance level is low, since the flicker is inconspicuous, symmetry is reduced. By making the SFs on the low gradation side asymmetrical, the sufficient gradations can be obtained in the movie contents including a large number of dark scenes.
An example of the asymmetrical SF control according to the embodiment is shown in
As will be obvious from
On the other hand, the lower SF groups on the side of the small weight are asymmetrical between the first and second division SF groups, that is, the numbers of SFs belonging to the lower SF groups are different and the weights of the SFs are also different. The weight of each of the SFs 9 to 11 belonging to the lower SF group of the second division SF group is set to be larger than the weight of each of the SFs 1 to 5 belonging to the lower SF group of the first division SF group. A time interval between the SFs belonging to the lower SF group of the first division SF group and a time interval between the SFs belonging to the lower SF group of the second division SF group may be also set to be different.
Envelopes of the weights of the SF groups formed as mentioned above are shown at 301 and 302 in
As will be obvious from profiles of those weight envelopes, with respect to one frame, two weight peaks are formed as shown by the first envelope 301 and the second envelope 302 regarding the upper SFs of the large weight, and one weight peak is formed as shown by the third envelope 303 regarding the lower SFs of the small weight.
That is, according to the asymmetrical SF control in the embodiment, the frequency of the high luminance is equal to 96 Hz due to the two peaks and the frequency of the low luminance is equal to 48 Hz due to the one peak. Frequency components of the video image displayed by those SF groups are shown in
The flicker characteristics in the embodiment to which the asymmetrical SF control has been made as mentioned above will be described with reference to
As will be obvious from
As mentioned above, in the embodiment, both of the suppression of the flicker and the good gradation expression having a trade-off relation can be realized. Further, in the movie contents of 24p, a slightly low flicker similar to that of the movie which is displayed in the movie theater can be given. Therefore, according to the embodiment, in the “REAL CINEMA” mode, the gradation expression is improved while suppressing the large flicker and, further, the movie contents can be reproduced by an expression similar to that in the movie theater. In the “REAL CINEMA” mode, since a method whereby the telecine signal of the 2-3 pull-down format is displayed as in the “FILM THEATER” mode or the like is not used, the motion judder caused by the still period of time of the video image mentioned above is also reduced and the video image which can be easily seen can be provided. However, in the “REAL CINEMA” mode, since the frame rate is doubled by the frame repeating process and the motion compensation is not performed, a visual sense of discomfort may occur in the motion. However, in such a case, by selecting the foregoing “SMOOTH CINEMA” mode, the video contents can be viewed by the smooth motion. In the “SMOOTH CINEMA” mode, since the interpolation frame is formed by the motion vector of the video image, a correlation between the interpolation frame and the original video frame is absent or small depending on the motion of the video image, so that there is a case where a deterioration in picture quality occurs. In such a case, if the foregoing motion judder can be permitted, it is sufficient to select “OFF” or “FILM THEATER” mode as a cinema mode.
In the embodiment, 14 SFs are allocated to one frame and divided into the first division SF group having 8 SFs and the second division SF group having 6 SFs. However, the invention is not limited to such a dividing ratio. For instance, 11 SFs may be allocated to one frame and divided into the first division SF group having 6 SFs and the second division SF group having 5 SFs. Further, in the embodiment, in the division SF groups, the numbers of SFs of the upper SF groups are set to 3 and the numbers of SFs of the lower SF groups are set to 5 and 3. However, the invention is not limited to such numerical values. For instance, the numbers of SFs of the upper SF groups may be set to 2 and the numbers of SFs of the lower SF groups are set to 6 and 4. Further, the number of SFs of the first division SF group and the number of SFs of the second division SF group may be equalized and the numbers of SFs of the lower SF groups may be equalized between the first division SF group and the second division SF group. Naturally, those numbers of SFs can be also set to other numerical values. Moreover, in the embodiment, although the SFs are arranged in order from the larger weight with the elapse of time, they may be reversed.
Furthermore, in the embodiment, although the weights of the SFs belonging to the lower SF groups and/or the numbers of SFs are set to be asymmetrical between the first division SF group and the second division SF group, the time intervals between the SFs belonging to the lower SF groups may be set to be asymmetrical.
Subsequently, the second embodiment of the invention will be described with reference to
An SF time base converting circuit 403 rearranges the SF group outputted from the SF converting circuit 402 as shown in, for example,
The SF group rearranged by the SF time base converting circuit 403 is inputted to an SF interval adjusting circuit 404, by which a time-dependent interval between the first division SF group 501 and the second division SF group 502 is controlled as shown in, for example,
As mentioned above, in the embodiment, by controlling the time-dependent interval between the first division SF group 501 and the second division SF group 502 by the SF interval adjusting circuit 404, the intensity of flicker according to, for example, the brightness of the video image can be controlled and the expression which further conforms with the contents of the video image can be performed.
It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-324180 | Dec 2007 | JP | national |
