JPS6163185A - Luminance signal offset processing device - Google Patents

Abstract

PURPOSE:To make a pedestal level constant even when a level of a compound video signal changes and to detect a pedestal level precisely during a horizontal scanning period by removing a offset part from a separated digital luminance signal. CONSTITUTION:An analog-processed compound video signal S1 of a processing device is added to an A/D converter 2, and a scope from a bottom of a pedestal included in part of a horizontal synchronizing signal lower than a pedestal level to a white level is digitized. The digitized compound video signal S2 is separated to a chrominance component S3 and a digital luminance signal S4 by a luminance signal chrominance component separating part 3, and the signal S3 is outputted to a chrominance component output terminal 7. The signal S2 is processed at a burst signal processing part 4 and a digital burst signal S6 is added to a subtractor part 6. At the subtractor part 6, an offset part is removed from the luminance signal S4 from the separating part 3, even when a level of the compound video signal changes, the pedestal is made constant and the pedestal is precisely detected during the horizontal scanning period.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a brightness signal offset processing device for reducing the bed scale level of a digital brightness signal to digital zero in a television signal digital processing device.

(Prior Art) Conventionally, television signals have been subjected to analog processing. No luminance signal offset occurs in this analog processing process. However, due to the recent advances in television technology associated with IC and LSI technology.

Digital signal processing, in which television signals are digitally converted and processed, is becoming increasingly popular.

In such a digital processing process of a television signal, there is a problem in that a luminance signal offset occurs, which does not occur in a conventional analog processing process.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and in the process of digitally processing television signals, the pedestal level is always set to digital zero even in response to level changes that may occur in the video signal transmission system. It is an object of the present invention to provide a luminance signal offset processing device.

(Structure of the Invention) The luminance signal offset processing device of the present invention includes a conversion means for converting a composite video signal ranging from a level including a color burst signal below a pedestal level to a white level into a digital signal, and a offset extracting means for extracting an offset by averaging the maximum and minimum values of the digital color burst signals included in the horizontal retrace period out of the digitized composite video signal; and the composite video signal digitized by the converting means. and a subtraction means for subtracting the offset extracted by the offset extraction means from the digital luminance signal separated by the luminance signal separation means. be.

(Embodiment) FIG. 1 shows a schematic block diagram of a luminance signal offset processing device according to the present invention.

1 is an input terminal, which receives an analog-processed composite video signal S1.
is input from this input terminal 1 to an analog-to-digital converter 2.

The analog-digital converter 2 converts the analog-processed composite video signal Sl to a level including a part of the horizontal synchronization signal below the pedestal level, or from the bottom to the white level of the color burst signal that controls the phase of the color subcarrier. Digitize the range up to. This digitized composite video signal S2 is output to the luminance signal/chrominance signal separation section 3 and the burst signal processing section 4.

The luminance signal/chrominance signal separation section 3 separates a digital luminance signal and a digital chrominance signal from the composite video signal S2. The separated digital color signal S3 is outputted to the color signal output terminal 5, and the digital luminance signal S4 is outputted to the subtraction section 6.

In the burst signal processing section 4, as shown in FIG.
Based on the digital color burst signal S5 inserted into the back porch of the horizontal synchronization signal of the composite video signal S2, the digital signal a at time t0 of the color burst signal S5 and the time t.

The offset C is calculated by averaging the digital signals at
Extract. The extracted offset C is outputted to the subtraction section 6 as an offset signal S6. In Figure 2, A is the level of digital zero.

B. Habedestal level.

The subtraction unit 6 removes the offset signal S6 output from the burst signal processing unit 4 from the digital luminance signal S4 output from the luminance signal/chrominance signal separation unit 3, and converts the pedestal level B to digital zero A. The brightness signal S7 is output to the brightness signal output terminal 7.

(Effect of the invention) According to the luminance signal offset processing device of the present invention.

Accurate pedestal levels can be extracted in any horizontal scanning period of a composite video signal. Furthermore, by removing the offset from the nine-separated digital luminance signal, it is possible to extract a digital luminance signal with the pedestal level always at digital zero even if the composite video signal changes in level.

Accurate RGB signals can be demodulated.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a luminance signal according to the present invention, and FIG.
The figure is a diagram showing the relationship between a digital luminance signal and a digital color burst signal. 2...Analog-digital converter 3...Luminance signal/chrominance signal separation unit 4...Burst signal processing unit 6...Subtraction unit, 1 person

Claims (1)

[Claims] 1) Conversion means for converting a composite video signal ranging from a level including a color burst signal below a pedestal level to a white level into a digital signal, and a composite video signal digitized by the conversion means. Among them, an offset extraction means for extracting an offset by averaging the maximum value and minimum value of the digital color burst signal included in the horizontal retrace period; A luminance signal offset processing comprising: a luminance signal separating means for separating a digital luminance signal; and a subtracting means for subtracting the offset extracted by the offset extracting means from the digital luminance signal separated by the luminance signal separating means. Device.