JPS61269584A - Half-tone control signal processing circuit - Google Patents

Abstract

PURPOSE:To vary automatically an output luminance level by a simple circuit constitution, and to make a character easily visible by shifting a parallel luminance signal of (n) bits by 1 bit, based on a Y<+> signal. CONSTITUTION:A composite signal which has been received and detected is supplied to a chrominance signal processing circuit 5 and a luminance signal processing circuit 6, through an A/D conversion circuit 4. A luminance signal of (n) bits which has been processed by the circuit 6 is sent to a Y<+> signal processing circuit 7, D/A-converted 9 and applied to a matrix circuit 10. The processing circuit 7 is provided with an input memory, a digital switch, and an output memory, and in a period in which a Y<+> signal is generated, a parallel luminance signal of (n) bits is shifted by 1 bit, based on the Y<+> signal. In this way, a 1/2 luminance level can be obtained automatically, and a character of a super time can be made easily visible.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a halftone control signal processing circuit in a digital television compatible with teletext broadcasting.

(Prior art) In recent years, there has been a remarkable progress in broadcasting and new media television from personal computers.In addition to the increasing number of personal computer televisions and personal computers equipped with RGB terminals and superimpose functions, new media equipped with text multiplex adapters are increasing. Compatible digital televisions are being developed.

Conventionally, when receiving a text multiplex broadcast, on a text multiplex compatible device, the RG
A halftone control signal (hereinafter referred to as Y+ times signal) is used to halftone the B video signal.

This Y+ signal is used, for example, to reduce the brightness of the background or outline of a white character to some extent in order to make it easier to see the character.

However, since the conventional Y+ signal processing method lowers the level of the RGB video signal and converts it into a halftone, the RGB video signal is There were drawbacks such as the need to use halftones, which made the circuit more complex.

OBJECTS OF THE INVENTION The present invention aims to eliminate the above-mentioned conventional drawbacks.

(Structure of the invention) The present invention has been made for the above purpose,
In particular, when receiving a teletext broadcast, the n-bit parallel digital luminance signal obtained by separating the A/D conversion output of a composite video signal is shifted by 1 bit based on the Y + times signal, so that the background or outline of the character can be processed. The brightness level is automatically lowered.

(Embodiment) FIG. 1 is a block diagram of an embodiment of a video signal processing system for a digital television according to the present invention. In Figure 1, tuner 2 selects a target station from among the television waves received by antenna 1, and the next block 3 performs intermediate frequency amplification and video detection to obtain a composite video signal as the video detection output. It will be done. This composite video signal is applied to an A, L/D conversion circuit 4, taken out as a parallel output into a digital composite video signal, and applied to a color signal processing circuit 5 and a luminance signal processing circuit 6. Then, it is separated into a color difference signal and a luminance signal. The luminance signal is composed of n-bisoto parallel digital signals and is applied to the Y+ signal processing circuit 7. The n-bit parallel digital luminance signal and the color difference signal processed by the Y+ signal processing circuit 7 are each converted into an analog signal by a D/A conversion circuit 8.9, and the RGB matrix circuit 10
added to. Reference numeral 11 denotes a text multiplex processing circuit section, which outputs a text signal Sl and a Y+ signal S2 for /'%-tone control when receiving a text multiplex broadcast. The character signal Sl is applied to the RGB matrix circuit 10, and the R
CR by RGB video signal via GB output circuit 12
The static characters suit-cooked are played back and displayed on the screen of Tl3.

On the other hand, the audio signal is outputted from the left and right channel speakers 15 and 16 via the audio signal processing circuit 14.

In the above configuration, the present invention is characterized by the Y+ signal processing circuit 7 that controls the n-bit parallel digital luminance signal based on the halftone control (Y+) signal.

FIG. 2 is a specific circuit configuration diagram of this Y+ signal processing circuit. In FIG. 2, reference numeral 71 is a manual memory, for example, a field memory, which temporarily stores and holds the n-bit parallel digital luminance signal input from the luminance signal processing circuit 6;
It can be configured with AM.

MSB is the most significant bit, LSB is the least significant bit, and 73 is a switching circuit corresponding to n bits. For example, it is a digital switch, and when the Y+multiple signal S2) is at a high level, the n-bit switch switches from the a position to the b position. When the switch is toggled, the n-bit contents of the input memory 71 are transferred to the output memory 72, from which the l-bit shifted parallel digital luminance signal is obtained. The output memory 72 can also be configured similarly to the input memory 71.

The following (1) is the storage state of the input memory 71, and (2)
shows the shifted storage state of the n-pit luminance signal in the output memory 72 when it is shifted from the input memory 71 to the output memory 72.

M S B LS B 101100'IO...(1) MSB LSB 01011001...(2) This (1)(
As is clear from 2), "0" is inserted into the most significant bit of the output memory 72, and the output luminance level becomes 1/2 of the input luminance level.

In this way, the output brightness level of I/2 can be automatically obtained by shifting the n-bit parallel digital brightness signal by 1 bit based on the Y+ times signal during the Y+ times signal generation period. It is possible to make it easier to see.

FIG. 3 shows the character signal S1, Y+multiple signal S2) and R
FIG. 3 is an example waveform diagram showing a relationship with a GB video signal. In FIG. 4, Sl and S2 are a character signal and a Y+ multiplied signal output from the text multiplex signal processing circuit section 11 when receiving teletext broadcasting, respectively, and S3 is halftoned by the Y+ signal S2, that is, the brightness is changed. This becomes the dropped signal S4.

The character signal Sl is added to this signal S4, and the character signal S
An RGB video signal S5 superposed with 1 is obtained.

(Effects of the Invention) As explained above, according to the present invention, the output luminance can be adjusted by shifting the n-bit parallel digital luminance signal by 1 bit based on the Y+ signal during the generation period of the Y+ (halftone) signal. The level can be automatically changed with a simple circuit configuration, and characters can be reproduced and displayed in an easy-to-read manner when receiving teletext broadcasting.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of a video signal processing system in a digital television according to the present invention, FIG. 2 is a specific circuit configuration diagram of a Y+ signal processing circuit, and FIG. 3 is a character signal Sl
, Y+ signal S2 and an RGB video signal. Explanation of symbols 6 is a luminance signal processing circuit, 7 is a Y+ signal processing circuit, 71 is an input memory, 72 is an output memory, 73 is a switching circuit, 11 is a character multiplex signal processing circuit section, St
is a character signal, S2 is a Y+ signal, and S3 is an RGB video signal.

Claims (1)

[Claims] (1) Means for temporarily storing and holding an n-bit parallel digital luminance signal obtained by separating the A/D conversion output of a composite video signal, and means for outputting a character signal and a halftone control signal when receiving teletext broadcasting. and means for shifting the n-bit parallel digital luminance signal by 1 bit based on the halftone control signal during the output period of the halftone control signal, thereby lowering the luminance level of the background or outline of the character. A halftone control signal processing circuit characterized by: