JP2003046961A - Picture signal converting method and picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize picture display by making the deterioration of picture quality inconspicuous without increasing the scale of a horizontal deflecting circuit even at the time of using a picture signal of a format whose horizontal synchronizing frequency is different. SOLUTION: The synchronizing signal of a picture signal Dga is detected by a synchronization detecting part 21, and the signal format of the picture signal Dga is judged by a control unit 30 based on the detected synchronizing signal. When it is judged that the judged signal format is a progressive scanning system, and the horizontal synchronizing frequency is higher than a horizontally deflectable frequency, the vertical synchronizing frequency of the picture signal Dga is changed by a signal converting part 22, and the picture signal Dga is converted into a picture signal Dgb whose horizontal synchronizing frequency is the horizontally deflectable frequency as an interlace scanning system signal, and picture display is executed by using the picture signal Dgb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal conversion method and an image display device. Specifically, when the signal format of the input image signal is determined and it is determined that the input image signal is of the progressive scanning type and has a horizontal synchronizing frequency higher than the horizontal synchronizing frequency that can be followed by the image display device, The image display is performed after changing the vertical synchronization frequency of the signal and using the signal of the horizontal synchronization frequency that can be followed by the image display device as the signal of the interlaced scanning system.

[0002]

2. Description of the Related Art In an image display device, an image can be displayed by using a plurality of image signals of different formats. For example, in a television device using a cathode ray tube, the number of effective scanning lines is 1080, the field frequency is about 60 Hz, and an image is displayed by using an interlaced scanning signal, that is, a signal of a high-definition format called a so-called 1080i / 60 system. Has been done.
When an image is displayed using this 1080i / 60 system signal, the horizontal synchronizing frequency is 33.75 kHz.
The number of effective scanning lines is 720 and the frame frequency is about 6
720p / which is progressive scan at 0Hz
When an image is displayed using a 60-system signal, the horizontal synchronizing frequency is 45 kHz. As described above, since the horizontal synchronizing frequency differs depending on the format, a horizontal deflection circuit capable of operating not only at 33.75 kHz but also at 45 kHz is used. Also, 720p / 60
Interpolation processing is performed on the signal of the system and 1080i / 60
The horizontal sync frequency is converted to 33.7 by converting it to a standard signal.
Image display at 5 kHz is also performed.

[0003]

By the way, if the horizontal deflection circuit can be operated not only at 33.75 kHz but also at 45 kHz, the horizontal synchronizing frequency becomes high, so that the circuit scale becomes large and the loss in the horizontal deflection circuit becomes large. Since the heat sink and the like become large due to the increase, the horizontal deflection circuit cannot be made inexpensive and small.

Further, in the method of performing interpolation processing on a signal of 720p / 60 system and converting it to a signal of 1080i / 60 system, the signal waveform becomes dull due to the interpolation processing and the image quality deteriorates. For example, when the 720p / 60 system signal is a signal as shown in FIG. 5A, the pixel position P
From the signals of p1 and the pixel position Pp2, 1080i shown in FIG. 5B.
A signal at the pixel position Ps1 in the second field in the / 60 system signal is generated. The signal level of the generated signal is higher than that of the pixel position Pp2 where the signal level is low. Further, the signal of the pixel position Pf2 of the first field is generated from the signals of the pixel position Pp2 and the pixel position Pp3, and the signal level of the generated signal becomes higher than that of the pixel position Pp2 having a low signal level. .

Therefore, if image display is performed using the converted 1080i / 60 system signal, in the first field, display is performed at pixel positions Pf1, Pf2, Pf3 ... In accordance with each signal level. At the same time, in the second field, since the display according to each signal level is performed at the pixel positions Ps1, Ps2, Ps3 ..., The display according to the signal level at the pixel position Pp2 is not performed, and this portion is not displayed. Is displayed according to the signal levels at the pixel positions Ps1 and Pf2, the signal waveform becomes dull and the image quality deteriorates.

Therefore, according to the present invention, even if the image signals of the formats having different horizontal synchronizing frequencies are used, the image display can be performed without increasing the scale of the horizontal deflection circuit and making the deterioration of the image quality inconspicuous. An image signal conversion method and an image display device capable of performing the same are provided.

[0007]

An image signal conversion method according to the present invention changes a vertical synchronizing frequency of an input image signal of a progressive scanning system and converts it into an interlaced scanning system signal, and the horizontal direction of the input image signal. An image signal having a horizontal synchronizing frequency different from the synchronizing frequency is generated.

Further, the image display device is an image display device which displays an image using an image signal of a predetermined horizontal synchronizing frequency, and is discriminated by the format discriminating means for discriminating the signal format of the input image signal and the format discriminating means. When the signal format is a progressive scanning method and is determined to be a horizontal synchronizing frequency higher than the predetermined horizontal synchronizing frequency, the vertical synchronizing frequency of the input image signal is changed and an interlaced scanning method signal is used, It has an image signal converting means for converting the image signal of the predetermined horizontal synchronizing frequency.

According to the present invention, the input image signal is of the progressive scanning system, and when the horizontal synchronizing frequency is higher than the horizontal scannable frequency in the image display device, the input image signal is line-wise to the input image signal. And the interlace scanning system signal is thinned out to change the vertical synchronization frequency of the interlace system signal so that the horizontal synchronization frequency becomes a frequency capable of being horizontally scanned by the image display device. For example, a 720p / 60 format signal is converted into a 720i / 90 format signal having a frequency lower than the horizontal synchronizing frequency of the 720p / 60 format signal.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an image display device, for example, a television device. The terrestrial broadcast reception signal received by the antenna 11 and the antenna 12
The received signal of the satellite broadcast received at is supplied to the tuner unit 15. The tuner unit 15 selects a desired broadcast wave signal and performs demodulation processing. Here, the signal obtained by performing the demodulation processing is, for example, MPEG (Moving
When the signal is coded based on the standard of Picture Experts Group), the obtained signal is coded signal D
It is supplied to the decoder unit 16 as te. When not encoded, the obtained signal is supplied to the signal switching unit 20 as the image signal Dtu.

When the image signal input from the signal input section 17 is an encoded signal, this signal is supplied to the decoder section 16 as an encoded signal Die, and
If it is not an encoded signal, this signal is supplied to the signal switching unit 20 as an image signal Din.

In the decoder section 16, the supplied encoded signal Dte is decoded, and the obtained signal is converted into the image signal Dte.
The signal is supplied to the signal switching unit 20 as td. In addition, the supplied encoded signal Die is decoded, and the obtained signal is supplied to the signal switching unit 20 as an image signal Did.

In the signal switching section 20, based on the selection control signal CS supplied from the control section 30, the image signal Dtu supplied from the tuner section 15, the image signals Dtd and Did supplied from the decoder section 16, or the signal. Select one of the image signals Din supplied from the input unit 17,
The image signal Dga is supplied to the synchronization detector 21 and the signal format converter 22.

The sync detector 21 detects the sync signal SY of the image signal Dga and supplies it to the controller 30. The signal format conversion unit 22 has a memory, and controls the writing of the image signal Dga to the memory and the reading of the image signal written to the memory based on the conversion control signal CC from the control unit 30. The conversion processing of the signal format is performed by. The image signal Dgb obtained by performing the signal format conversion processing in the signal format conversion unit 22.
Is supplied to the signal processing unit 23 and the deflection processing unit 24.

The signal processor 23 generates the three primary color signals SR, SG, SB based on the supplied image signal Dgb,
The cathode ray tube 40 is driven based on these three primary color signals SR, SG, SB. The deflection processing unit 24 separates the sync signal from the image signal Dgb and generates a horizontal sync signal and a vertical sync signal based on the sync signal. Further, the horizontal deflection circuit of the deflection processing unit 24 drives the horizontal output transistor based on the horizontal synchronization signal to supply the deflection current IdH to the horizontal coil of the deflection yoke 45 attached to the cathode ray tube 40. In the vertical deflection circuit of the deflection processing unit 24, the vertical output transistor is driven based on the vertical synchronizing signal to supply the deflection current IdV to the vertical coil of the deflection yoke 45. The high voltage generator 25 generates the anode voltage HV by utilizing the switching operation of the horizontal output transistor and supplies it to the cathode ray tube 40.

An operation unit 31 is connected to the control unit 30, and a selection control signal CS is generated according to a signal selection operation on the operation unit 31 and is supplied to the signal switching unit 20. Further, the signal format of the image signal Dga supplied to the signal format conversion unit 22 is determined from the horizontal synchronization frequency, the vertical synchronization frequency, etc. based on the detection signal SD from the synchronization detection unit 21, and conversion control is performed based on this determination result. The signal CC is generated and supplied to the signal format conversion unit 22. That is, when the image signal Dga is progressive scanning and the horizontal synchronizing frequency is not a frequency at which the deflection processing unit 24 can operate, the conversion control signal CC is generated so that the signal format conversion unit 22 executes the conversion process.

The signal format of the converted image signal Dgb generated by the signal format conversion unit 22 is preset by the signal format conversion unit 22. Alternatively, the signal format of the converted image signal Dgb is set by the conversion control signal CC.

Further, the determination of the signal format of the image signal Dga is not limited to the case where it is performed based on the detection signal SD from the synchronization detection section 21, and the encoded signals Dte and Die supplied to the decoder section 16 are determined. When the information about the signal format included in the sequence layer is read and determined, or when the control signal for determining the signal format is input to the signal input unit 17 together with the image signal, the signal format is used by using this control signal. May be determined.

Next, the conversion processing operation of the signal format conversion unit 22 will be described. In the signal format conversion unit 22, when a progressive scanning signal having a horizontal synchronizing frequency higher than the horizontal scanning frequency that can be supported by the deflection processing unit 24 is supplied as the image signal Dga, the interlace with the vertical synchronizing frequency increased. The deflection processing unit 2 converts the horizontal synchronizing frequency of the image signal Dgb by converting it into a scanning signal.
4 is output as a horizontal scanning frequency range that can be handled.

For example, as shown in FIG. 2A, the image signal D
When a 720p / 60 format signal is supplied as ga, the image signal Dga written in the memory is set to 1
An interlace signal is generated by thinning out and reading out each line. Further increase the vertical sync frequency to 2
Signals of three fields are sequentially generated from the frame. That is, as shown in FIG. 2B, a 720i / 90 system signal is generated and output as an image signal Dgb. This 720i / 9
In the 0-system signal, the number of scanning lines is 750 and the field frequency is 90 Hz, which is an interlaced scanning signal.
The horizontal sync frequency is 33.75 kHz, and even if a signal with a horizontal sync frequency of 45 kHz is used, the horizontal sync frequency is 3
Image display can be performed using a 3.75 kHz horizontal deflection circuit. Therefore, the scale of the horizontal deflection circuit is not increased.

The vertical synchronizing frequency increases from the frame frequency of 60 Hz to the field frequency of 90 Hz, but since the vertical synchronizing frequency is low, the scale of the vertical deflection circuit is large even if the frequency is high. It does not increase greatly like a circuit.

Further, as shown in FIG. 2, since the image signal Dgb is generated by thinning out the image signal Dga for each line, deterioration of the image which would occur when interpolation processing in the vertical direction is performed is prevented. it can. Particularly in the still image portion, the number of effective lines per frame is 7 for the image signal Dga and the image signal Dgb.
It will be 20 lines. Therefore, even if the image signal Dgb is used, it is possible to display an image with the same image quality as that of the image signal Dga. Further, even in the moving image portion, interlaced scanning is performed, but since the image is moving, deterioration of the image is at a level that is not noticeable.

Further, when the vertical synchronizing frequency becomes high, flicker becomes inconspicuous. For example, when a pattern in which the brightness changes in a sine wave is displayed, it is known that the change in brightness cannot be felt at a frequency higher than about 70 Hz. Has been. Here, the signal format conversion unit 22 converts the progressive scanning signal into the interlaced scanning signal. However, since the field frequency of the 720i / 90 system signal is 90 Hz, the image signal Dgb is converted into the image signal Dgb. Line flicker is not noticeable in the base image even in interlaced scanning.

By the way, the sampling frequency of the 720p / 60 system signal is 74.25 MHz.
If the same sampling frequency is used for the / 90 format signal, the horizontal direction of the 720i / 90 format signal is 33.75 kHz.
Sample required. Therefore, the interpolation processing in the horizontal direction is performed, and one line has 1650 samples, that is, 720p / 60.
A signal having 2200 samples per line is generated from the signal of the system.

FIG. 3 shows a signal format. FIG. 3A shows a signal format of the 720p / 60 system, and FIG.
Is a signal format of 720i / 90 system. Further, FIG. 3C shows the signal format of the above 1080i / 60 system. In the signal format of the 720p / 60 system shown in FIG. 3A, the number of scanning lines is 750 lines and the number of horizontal samples is 1650 samples, and an area of 720 vertical pixels × 1280 horizontal pixels is an effective screen. In the signal format of this 720p / 60 system, the horizontal synchronizing frequency is 45 kHz as described above,
The vertical synchronizing frequency is 60 Hz and the sampling frequency is 74.
It is 25 MHz.

In the signal format of the signal of the 720i / 90 system obtained by the signal format conversion unit 22 described above, as shown in FIG. 3B, the number of scanning lines is 750 and the number of horizontal samples is 1650. An area of 720 vertical pixels × 1280 horizontal pixels is the effective screen. In this 720i / 90 system signal format,
As described above, the horizontal synchronizing frequency is 33.75 kHz, the field frequency is 90 Hz, and the sampling frequency is 74.25 MHz. That is, 108 shown in FIG. 3C.
Similar to the 0i / 60 system signal format, image display can be performed with a horizontal synchronizing frequency of 33.75 kHz and 1920 pixels in the horizontal direction as an effective screen.

By the way, in the above-mentioned embodiment, the field frequency is converted into the signal of 90 Hz, but the field frequency may be different from 90 Hz.
For example, assuming that the field frequency is 70 Hz as shown in FIG. 4, when the horizontal synchronizing frequency is 33.75 kHz, 1
The number of lines in the frame is 964 lines. If the field frequency is 80 Hz, the horizontal sync frequency is 3
When set to 3.75kHz, the number of lines in one frame is 8.
There are 43 lines.

Here, when the field frequency is 70 Hz due to the difference in vertical synchronizing frequency and the difference in scanning method, for example, once every seven fields, two field signals are generated from the same frame of the 720p / 60 method signal. Therefore, it is possible to obtain 7 from 6 frame signals of 720p / 60 system
Generates signals for interlaced scanning of fields. When the field frequency is 80 Hz, for example, once every four fields, a signal of two fields is generated from the same frame of a 720p / 60 system signal,
A 4-field interlaced scanning signal is generated from a 720p / 60 3 frame signal.

Further, the effective screen signal selected line by line from the 720p / 60 signal is used as the effective screen signal even after conversion. For example, when the field frequency is 70 Hz, the number of lines is 964i, but 720p
The signal of 720 lines selected from the signal of / 60 is set as the effective screen and the signal. Similarly, the field frequency is 80
The number of lines is 843i at Hz, but 720p /
A signal for 720 lines selected from the 60 signals is set as an effective screen and a signal.

In this way, 720 without performing vertical interpolation
Since the p / 60 signal is used as it is, it is possible to prevent the image quality deterioration of the display image, which is caused by the vertical interpolation. Furthermore, when the field frequency of the converted image signal Dgb is high, the flicker on the screen can be made inconspicuous, and when the field frequency is low, smooth image display can be performed.

Some conventional television apparatuses have a two-screen display function for displaying two screens and an index display function for displaying one screen and a plurality of index screens. A television device having such a function is provided with an image conversion unit that controls writing and reading of an image signal to and from a memory to enable multi-screen display. Therefore, if the image conversion unit is used instead of the signal format conversion unit 22 and the conversion process described above is performed by this image conversion unit, the horizontal synchronization can be performed without newly providing the signal format conversion unit. An image can be displayed by converting a signal having a high frequency format into a signal having a low horizontal synchronization frequency format. It should be noted that the signal formats shown in the above-mentioned embodiments are mere examples and are not restrictive.

[0032]

According to the present invention, the horizontal synchronizing frequency different from the horizontal synchronizing frequency of the input image signal is changed by changing the vertical synchronizing frequency of the progressive scanning type input image signal and converting into the interlaced scanning type signal. Image signals are generated. Therefore, even when an image signal whose horizontal synchronizing frequency is higher than the frequency capable of being horizontally scanned by the image display device is input, the input image signal is an image signal having a horizontal synchronizing frequency capable of being horizontally scanned by the image display device. Since the image display is performed in this way, it is possible to perform image display using image signals of formats having different horizontal synchronization frequencies without increasing the scale of the horizontal deflection circuit. Further, since the input image signal of the progressive scanning system is thinned out in units of lines to generate the signal of the interlace scanning system, it is possible to prevent the image quality deterioration of the displayed image.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an image display device.

FIG. 2 is a diagram showing an operation of a signal conversion unit.

FIG. 3 is a diagram showing a signal format.

FIG. 4 is a diagram showing the number of lines when the vertical synchronization frequency is changed.

FIG. 5 is a diagram for explaining an operation when a vertical interpolation process is performed.

[Explanation of symbols]

11, 12 ... Antenna, 15 ... Tuner part, 1
6 ... Decoder part, 17 ... Signal input part, 20 ...
-Signal switching unit, 21 ... synchronization detecting unit, 22 ... signal converting unit, 23 ... signal processing unit, 24 ... deflection processing unit, 25 ... high voltage generating unit, 30 ... Control unit, 31
... Operating part, 40 ... Cathode ray tube, 45 ... Deflection yoke

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Claims (5)

[Claims] 1. An image signal of a horizontal synchronizing frequency different from the horizontal synchronizing frequency of the input image signal is generated by changing a vertical synchronizing frequency of an input image signal of the progressive scanning method and converting the vertical synchronizing frequency of the input image signal of the progressive scanning method. An image signal conversion method characterized by the above. 2. The interlace scanning type signal is generated by thinning out the input image signal of the progressive scanning type on a line-by-line basis.
The described image signal conversion method. 3. An image display device for displaying an image using an image signal of a predetermined horizontal synchronizing frequency, wherein a format discriminating means for discriminating a signal format of an input image signal and a signal format discriminated by the format discriminating means are provided. When the horizontal scanning frequency is a progressive scanning method and the horizontal synchronizing frequency is higher than the predetermined horizontal synchronizing frequency, the vertical synchronizing frequency of the input image signal is changed and the predetermined horizontal synchronizing frequency is used as a signal of the interlaced scanning method. An image display device comprising an image signal converting means for converting an image signal of a synchronous frequency. 4. The image according to claim 3, wherein the image signal converting means thins the input image signal of the progressive scanning method in units of lines to generate the signal of the interlaced scanning method. Display device. 5. The input image signal has a signal format of a 720p / 60 system.
The image display device described.