JPH0216636B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an apparatus for converting an interlaced video signal, including teletext broadcasting and a captain system, into a progressive scanning video signal.

BACKGROUND TECHNOLOGY When displaying a video signal from a teletext broadcast or a captain system on a display device such as a CRT, the interlaced scanning of the NTSC system is generally adopted as is in order to synchronize with the signal of the television broadcast. There are many.

FIG. 1 is an example of a schematic configuration of a receiving video circuit system for television broadcasting, teletext broadcasting, and a captain system.

The TV radio waves that propagated through the air were Chuyuna 1,
The IF detector 2 converts it into a baseband signal.
The audio signal passes through the A system, is converted to an audible level by the amplifier 3, and is radiated into the air as sound by the speaker 10. On the other hand, the ○ and B lines are video signals and are supplied to the character signal extractor 4, the video demodulator 6, and the sync separator 7.

Here, if the display mode is selected as television broadcasting, as is well known, the video demodulator 6
The three primary color analog video signals are R2, G2,
It is output as B2. This output is the character/
By switching the video switching circuit 11 to the side
The signal is supplied to the CRT8 and displays the television broadcast image on the screen. In FIG. 1, a signal line is connected directly from the switching circuit 11 to the CRT 8. but,
Although various circuits for driving the CRT 8 are required here, they are omitted for convenience of explanation.

When the display mode is selected as teletext, the signal extracted from the television signal by the character signal extractor 4 is converted into three primary color digital character signals R1, G1,
Converted to B1. At the same time, brightness information K1 representing bright spots on the screen is output here.

On the other hand, when the display mode is selected as the captain system, the well-known modem interface unit 9 converts the information transmitted through the telephone line into digital data that is easy to process by the decoder unit 5, as shown by the broken line. The signal is supplied to the decoder section 5 as follows.

The decoder section 5 receives and stores such text information data of the teletext broadcasting and the captain system in buffer memories 51 and 52, respectively. The data in buffer memories 51 and 52 is
Depending on the selection of the display mode set by the selection control section 57, either one is read out. The selection control section 57 is constructed of well-known components including a manual key switch or remote control receiving section, a decoder for decoding the superimposed display mode, etc. transmitted by teletext broadcasting, etc., as appropriate. Therefore, this control unit 57 issues commands for selecting reception of television broadcasting, teletext broadcasting, captain system, etc., and commands for display modes such as full screen display or superimposed display. . Here, as an example, a high-level signal is sent to the line 571 in the case of full-screen display, and a low-level signal is sent to this line in the case of superimposed display. A high-level signal is sent to the line 572 when teletext broadcasting or a captain system is selected, and a low-level signal is sent when television broadcasting is selected. A bus line 573 is connected to the data bus 54 and sends data corresponding to various commands from the selection control section 57 to the central processing unit (hereinafter referred to as CPU) 53.
Here, numbers 55 and 56 are well-known programs that store programs necessary for predetermined arithmetic processing of the CPU 53.
RAM and ROM. Also, numbers 58-6
0 is a color memory corresponding to each of the three primary colors, and the color data that determines the emitted color of the bright spot on the screen is stored.
Written from CPU53. And number 61
is a display memory in which brightness information representing bright spots on the screen is written. Therefore, the luminance information signal k1 read from the display memory is output to the OR gate 6.
5. It is drawn out through the AND gate 66. At the same time, this signal is supplied for gate control to each AND gate 62-64 through which the color data read from each color memory 58-60 passes. Therefore, each of these AND gates 62~
64, digital character signals R1, G1, and B1 are individually drawn out.

As already mentioned, there is a superimpose display mode, which is a composite mode in which television broadcast images are displayed as they are, and text and graphics are displayed on the background. When displaying this mode, the image is divided into each scanning line, and the brightness information signal k1 shown in FIG. This is done by the character/video switching circuit 11 according to the following. In this case, in the example shown in FIG. 3, the signal corresponds to k1.

The signal shown in FIG. 3 corresponds to k1 when a high level signal is sent from the line 571 of the selection control section 57 of the decoder section 5 described above. Therefore, this case corresponds to a display mode in which digital character signals R1, G1, and B1 are displayed on the entire screen. The low level period of the signal is a display blanking period, and if blanking is applied by another circuit (not shown), there is no need to set the signal to low level. Also, when displaying information received by the captain system, this signal corresponds to k1. As a result, when the signal is at high level, the text/video switching circuit 11 side is turned on and character information is displayed, and when the signal is at low level, the switching circuit 11 side is turned on and the video of the television broadcast is displayed. The three primary color video signals switched by the character/video switching circuit 11 are processed horizontally and vertically by the horizontal and vertical synchronizing signals HD and VD separated by the synchronizing separator 7 as is well known
It is displayed on the CRT8 with timing in the vertical scanning direction.

As mentioned above, this is the conventional display system, but in order to synchronize with the video signal of television broadcasting, the digital character signal also had to be interlaced scanned, resulting in large differences in shading. Flickering occurred on the text screen, significantly degrading the image quality.

Also, without interlacing, the same scan line can be
A method of scanning using a field and a second field may also be considered, but in this case, although flicker is eliminated, the structure of the scanning line becomes more noticeable, so there is a problem that the degree of improvement is not so great.

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above points, and its purpose is to eliminate flickering in character images and to realize finely sharp images in normal television images, as well as to eliminate the problem of interlacing. The purpose of this invention is to solve the difference in sampling rate when a television video signal and a character signal such as a captain system or a teletext broadcast are digitized.

In other words, in order to achieve the above-mentioned purpose, an analog video signal demodulated by receiving interlaced television broadcasting is converted into a digital video signal using an A/D converter, and a captain system, teletext, etc. The sampling rate of the received and decoded digital character signal is converted to the sampling rate of the digital video signal, which is scanned at twice the speed of the conventional horizontal scanning frequency, and by signal interpolation, one frame is displayed in one field display period. In addition, the signal interpolation method is switched in accordance with the switching of reception between television broadcasting, teletext broadcasting, and a captain system.

As a result, the superimposed display mode is particularly effective in removing flicker and making it possible to display fine, sharp images.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 4 is a block diagram showing an embodiment of the present invention, and parts having the same functions as those in the block diagram of FIG. 1 are given the same numbers and symbols. .

The analog video signal converted into the three primary color signals by the video demodulator 6 is converted into a 11.5MHz (8/5
×2f _SC , where f _SC is the frequency of the subcarrier). On the other hand, the digital character signals of the teletext broadcasting and captain system converted into three primary color signals with a sampling rate of 5.73MHz (8/5f _SC ) by the decoder section 5 are converted into digital character signals by the A/D converter 18. In order to match the number of bits, the level is shifted by a level converter 19. For example, if the teletext and captain system signals are 4-bit gradation data and the video is converted by an 8-bit A/D converter, the top four of the teletext and captain system signals are
The number of bits is matched by using the information in the bits as they are and by setting all the lower 4 bits to 0 level.

Here, the subscripts R, G, and B correspond to the three primary color signals of red, green, and blue, and the subscripts will be omitted from the names of the various parts in the following description.

The A/D-converted digital video signal and the level-converted digital character signal of the teletext broadcasting and captain system are multiplexed into text and video by the text/video switching circuit 11, as in the conventional method. is output. At this time, the sampling rate of the digital character signal is 8/5f _SC , but the clock rate converter 20
By latching with the 20f _SC sampling clock, 8/5 x 2f _SC , which is similar to a digital video signal, is
sampling rate. In other words, the same data will be latched twice.

The output data of the clock rate converter 20 is data for interlaced scanning, but a method of converting it to sequential scanning will be described below. Regarding interpolation when converting to progressive scanning, for digital video signals, the arithmetic average of scanning lines, or line interpolation, is used to obtain a more natural-looking, fine-grained image with no visible scanning lines, and for digital character signals, interpolation is used within the lines. Since vertical resolution decreases when interpolation is performed, interpolation is performed by scanning the same scanning line twice.

Regarding line interpolation, since the three systems of R, G, and B are the same, only one system will be explained below. Regarding this line interpolation, the line memory 21
Adder 2 adds the scanning line delayed signal to the current signal.
2, and this is 1/2 by attenuator 23.
line interpolation calculator 27 that extracts the signal as a
is used. The output of the line interpolation calculator 27 is supplied to an interpolation signal switch 24, and is selectively extracted from the output of the clock rate converter 20 described above by the switch 24. At this time, this interpolation signal switch 24 is connected to the character/video switching circuit 1 described above.
It is activated by the same signal k1 that activates K1.
Therefore, this switch 24 switches the interpolation of the information of the current scanning line between the digital character signal and the digital video signal.

The two systems of interlaced signals thus obtained are converted into one system of progressive scanning signals with a sampling rate doubled by the time axis compressor 25 at the next stage and output. This time axis compressor 25
For example, those already filed by the present applicant as Japanese Patent Application No. 16432/1982, and those published in Japanese Patent Application Laid-open No. 207482/1982 and Japanese Patent Application No. 159177/1988 are used. Therefore, the details are omitted here.

The output of the time base compressor 25 is converted into an analog signal by the A/D converter 26 in the next stage using a sampling clock of 8/5×4f _SC . Therefore, this signal is extracted as the final video signal to drive the CRT8. As a result, detailed flicker-free text and video information can be displayed.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram showing the schematic configuration of a conventional similar device, Fig. 2 is a block circuit diagram showing the contents of a part of the block circuit of the device shown in Fig. 1, and Fig. 3 shows the timing and waveform of the luminance information signal. Waveform diagram shown,
FIG. 4 is a block circuit diagram showing the configuration of one embodiment of the present invention. 18... A/D converter, 5... Digital character signal decoder section, 11... Character/video switching circuit, 27...
Line interpolation calculator, 25... Time axis compressor, 24...
Interpolation signal switch, k1...Signal for operating the character/video switching circuit.

Claims (1)

[Claims] 1. An analog video signal demodulated by receiving interlaced television broadcasting is converted to a sampling rate of 8/5×2fsc (fsc:
A digital video signal obtained by digitizing at a subcarrier frequency) and a digital character signal with a sampling rate of 8/5 fsc decoded by receiving a captain system or teletext broadcast, etc., or by combining both. This is a device that processes television video signals for superimposed display, and also synthesizes new video information by signal interpolation from the existing video information of the television broadcast, and doubles the number of scanning lines as in the above method. A television video signal processing device using an interlace/progressive scan conversion method that is capable of displaying one frame of video information in one field period by displaying either the digital video signal or the digital character signal. a character/video switching circuit capable of selectively drawing out the digital character signal according to the mode and, in the case of superimposed display, performing a switching operation according to the brightness information of the captain system and teletext; a clock rate converter that converts a sampling rate to a sampling rate of the digital video signal; a line interpolation calculator that outputs the digital video signal as the new video information by line interpolation; a time axis compressor that compresses screen scanning time for video information to be displayed in one field period; and when the display mode is the television broadcast, the output of the line interpolation calculator is sent to the time axis compressor for the one frame; and an interpolation signal switcher that supplies the digital character signal as video information for one frame when the display mode is the captain system, text multiplex broadcasting, etc., the text/video switching circuit A television video signal processing device characterized in that the interpolation signal switch is activated by a signal that activates the interpolation signal switch.