JPH06303459A - Video signal processor - Google Patents

Abstract

PURPOSE:To set the dynamic range of a video signal added with a synchronizing signal at the same level as the dynamic range of a D/A converter without increasing the number of D/A converters. CONSTITUTION:A digital synchroizing signal generating part 3 is prepared to add the DC offset to a synchronizing signal so that the dynamic range of the part 3 is included in the dynamic range of a video signal, together with a DC voltage source 7 which deletes the offset of the signal of a blanking period of the synthetic video signal that undergone the D/A conversion through a D/A converter 6, a differential amplifier 8, and a selector B 5B which selectively outputs the output signal of the converter 6 in a video valid period and the output signal of the amplifier 8 as an analog video signal in a blanking period respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing device for synthesizing a digitally converted video signal with a synchronizing signal and a blanking signal for analog conversion.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing the configuration of a conventional video signal processing device. In the figure, reference numeral 1 denotes a timing signal generator that generates a timing signal that determines the operation timing of each unit, and the digital video signal generator 2 synchronizes the digital video signal with the timing signal generated by the timing signal generator 1. The digital sync signal generator 3 generates digital data of the sync signal in synchronization with the timing signal generated by the timing signal generator 1, and the blanking signal generator 4 generates the timing signal generated by the timing signal generator 1. A blanking signal indicating a blanking period of the digital video signal output from the digital video signal generator 2 is generated in synchronization with the blanking signal.

Based on the blanking signal generated by the blanking signal generator 4, the selector 5 outputs the output signal of the digital synchronizing signal generator 3 during the blanking period and outputs the digital video signal during the video valid period other than the blanking period. The output signals of the generator 2 are selected and output, and the D / A converter 6 converts the output signal of the selector 5 into an analog signal.

Next, the operation of the conventional video signal processing apparatus shown in FIG. 6 in the case of generating a Y or GBR video signal of the high definition format shown in the high definition studio standard BTAS-001 will be described with reference to FIG. A waveform diagram will be introduced for description. In this figure, attention is paid to one horizontal period, and the output portion of the digital data shows a D / A converted waveform. The video signal in the figure has a so-called ramp waveform such that the left end of the screen has a white peak level and the right end has a black level. Further, the D / A converter 6 has a linear characteristic of 8 bits, the smallest output level of the 256 gray levels that can be output is 0 level, and the largest output level is 2 levels.
55 levels.

The digital video signal generator 2, the digital synchronization signal generator 3, and the blanking signal generator 4 generate respective signals in synchronization with the timing signal output from the timing signal generator 1. Digital video signal generator 2
As shown in FIG. 7 (a), the white peak level is 255 and the black level is 76, which is a black level of the sync signal described later. As shown in FIG. 7B, the digital sync signal generator 3 generates a positive / negative bipolar ternary sync signal having a black level of 76 levels, a positive polarity pulse level of 152 levels, and a negative polarity pulse level of 0 levels. ing.

The selector 5 operates on the basis of the blanking signal shown in FIG. 7 (d) during the video effective period to generate the digital video signal generator 2.
During the horizontal blanking period, the digital video signal from is output as digital data of a positive / negative bipolar ternary sync signal.
The output signal from the selector 5 is D / A converted by the D / A converter 6 to obtain an analog composite video signal in the high-definition format as shown in FIG. 7 (c).

The level of the dynamic range of each signal is
The D / A converter 6 is set to maximize the dynamic range of the D / A converter 6, and the video signal is set to 180 gradations. The vertical sync signal is added to the video signal in the same manner as the horizontal sync signal, but the description thereof is omitted here.

[0008]

Since the conventional video signal processing device is constructed as described above, the D / A converter 6 is used.
Dynamic range, which is 256 gradations in the conventional example, the dynamic range of the most important video signal becomes as small as 180 gradations.
Since the entire dynamic range of the A converter 6 cannot be allocated for the video signal and the dynamic range is narrowed, D /
The quantization error increases more than the error due to the performance of the A converter 6,
There is a problem that the deterioration of the S / N ratio of the video signal becomes larger than the deterioration due to the performance of the D / A converter 6.

As a video signal processing apparatus which avoids the deterioration of the video signal due to such digital conversion and analog conversion, in order to successfully perform the black level adjustment of the video signal including the black level higher than the blanking level. A video signal processing device for offsetting a blanking period of a digital video signal (Japanese Patent Laid-Open No. 4-111578), and a dynamic of the analog video signal by clamping the blanking period of the analog video signal before digital conversion at a predetermined level. A video signal processing device for making a range included in the dynamic range of an A / D converter (Japanese Patent Laid-Open No. 61-
However, there is no proposal for a device that sets the dynamic range of a digital video signal obtained by combining a video signal, a synchronizing signal and a blanking signal to the same range as the dynamic range of a D / A converter.

Further, although the problem of the dynamic range can be solved by independently D / A converting the video signal and the synchronizing signal and then synthesizing them, two D / A converters are required, resulting in an increase in cost.

The present invention has been made in order to solve such a problem, and the dynamic range of a digital video signal to which a sync signal is added can be adjusted to D / A without increasing the number of D / A converters. An object of the present invention is to provide a video signal processing device that can be set to the same range as the dynamic range of the converter.

[0012]

A video signal processing apparatus according to the present invention includes a means for adding a DC offset to a sync signal added to a video signal so that the dynamic range of the sync signal falls within the dynamic range of the video signal. It is characterized in that it is provided with means for removing the DC offset from the signal during the blanking period of the composite video signal which has been subjected to analog conversion after the signals have been combined.

[0013]

The video signal processing device according to the present invention adds a DC offset to the digital sync signal so that the dynamic range of the digital sync signal falls within the dynamic range of the digital video signal, and the offset digital sync signal is digitalized. Generates digital data of the composite video signal by adding it to the video signal, converts the digital data of the composite video signal to analog, and then outputs the analog-converted composite video signal during the video valid period other than the blanking period, while blanking During the period, by outputting the composite video signal from the offset removing means from which the DC offset is removed, the dynamic range of the video signal can be set to the same range as the dynamic range of the D / A converter which is the analog converting means. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments. Example 1. FIG. 1 is a block diagram showing the configuration of a video signal processing device according to the present invention (hereinafter referred to as the device of the present invention). Incidentally, the same or corresponding parts as those of the conventional example shown in FIG. In the figure, 5B indicates the output signal of the differential amplifier 8 during the blanking period according to the blanking signal generated by the blanking signal generating unit 4, and the output of the D / A converter 6 during the video valid period other than the blanking period. Selectors B and 7 for selecting and outputting signals respectively are D corresponding to the DC offset added to the synchronizing signal.
A DC voltage source that generates a C voltage, and 8 is a differential amplifier that subtracts the DC voltage output from the DC voltage source 7 from the output signal of the D / A converter 6.

Next, the operation of the apparatus of the present invention shown in FIG. 1 when generating a Y or GBR video signal of the high definition format shown in the high definition studio standard BTA S-001 is shown in the waveform chart of each part in FIG. Introduce and explain. In this figure, attention is paid to one horizontal period, and the output portion of the digital data shows a D / A converted waveform. The video signal in the figure shows the white peak level at the left edge of the screen,
This is a so-called ramp waveform that produces a black level at the right end. Further, the D / A converter 6 has an 8-bit linear characteristic, and the smallest output level of 256 gray levels that can be output is 0 level, and the largest output level is 255 level. Further, the differential amplifier 8 has a gain of 1.

The digital video signal generator 2, the digital sync signal generator 3, and the blanking signal generator 4 generate their respective signals in synchronization with the timing signal output from the timing signal generator 1. Digital video signal generator 2
Generates a video signal having a white peak level of 255 and a black level of 0 as shown in FIG. 2 (a). As shown in FIG. 2B, the digital sync signal generator 3 generates a positive / negative bipolar tri-level sync signal having a black level of 109 level, a positive polarity pulse level of 218 level, and a negative polarity pulse level of 0 level. ing.

According to the blanking signal of FIG. 2 (e), the selector A5A receives the digital video signal from the digital video signal generator 2 during the video valid period and the digital data of the positive / negative bipolar tri-level sync signal during the horizontal blanking period. Output.
The output signal of the selector A5A is D / A converted by the D / A converter 6, and a composite video signal obtained by adding a DC offset to the signal during the blanking period is obtained, as shown in FIG. 2 (c).

The DC voltage source 7 is set to a DC voltage corresponding to the 109 level at the output of the D / A converter 6, and the output signal of the D / A converter 6 from the differential amplifier 8 is minus by the amount corresponding to the 109 level. 2C, the 0 level is -109 level, 109 level is 0 level, 218 level is 109 level, 255
A signal whose level is 146 is output.
The selector B5B outputs the output signal of the D / A converter 6 during the video valid period and the output signal of the differential amplifier 8 during the horizontal blanking period according to the blanking signal of FIG. 2 (d). As a result, a high-definition format analog composite video signal as shown in FIG. 2 (e) is obtained.

The level of the dynamic range of each signal is
It is set to maximize the dynamic range of the D / A converter 6, and the video signal is set to 256 gradations. The vertical sync signal is added to the video signal in the same manner as the horizontal sync signal, but the description thereof is omitted here.

Example 2. FIG. 3 is a block diagram of another embodiment of the device of the present invention, in which the same or corresponding portions as those in the above-mentioned embodiment are designated by the same reference numerals and the description thereof is omitted. In the first embodiment, the combination of the DC voltage source 7 and the differential amplifier 8 removes a predetermined offset from the output signal of the D / A converter 6, but in the second embodiment, the timing signal from the timing signal generator 1 is used. A D / A converter 6 according to a clamp pulse generator 10 that generates a clamp pulse in synchronization and a clamp pulse that the clamp pulse generator 10 outputs.
The offset is removed by the clamp circuit 11 that clamps the output signal of 1 to a predetermined level.

Example 3. FIG. 4 is a block diagram of still another embodiment of the device of the present invention, in which the same or corresponding parts as those in the above-mentioned embodiment are designated by the same reference numerals and the description thereof is omitted.
In the first embodiment, the combination of the timing signal generator 1, the digital video signal generator 2, the digital synchronization signal generator 3, the blanking signal generator 4, and the selector A5A digitally adds a DC offset to the signal during the blanking period. Although a composite video signal is generated, in the third embodiment, a similar digital composite video signal is generated using a programmable semiconductor element 12 such as a ROM, a RAM, a microcomputer, a digital signal processor or the like.

Example 4. FIG. 5 is a block diagram of still another embodiment of the device of the present invention, in which the same or corresponding parts as those in the above-mentioned embodiment are designated by the same reference numerals and the description thereof is omitted.
In the first embodiment, the combination of the timing signal generator 1, the digital video signal generator 2, the digital synchronization signal generator 3, the blanking signal generator 4, and the selector A5A digitally adds a DC offset to the signal during the blanking period. Although a composite video signal is generated, in the fourth embodiment, a similar digital composite video signal is generated using a digital data recording medium 13 such as an optical disk, a magneto-optical disk, a magnetic tape, a floppy disk.

[0023]

As described above, the device of the present invention adds the offset to the sync signal to be combined with the video signal to keep the dynamic range of the sync signal within the range of the dynamic range of the video signal, and after the analog conversion, the blanking period. Since the offset is removed from the composite video signal inside, the dynamic range of the video signal must be set to the same range as the dynamic range of the D / A converter without D / A converting the video signal and the sync signal independently. And an excellent effect that a high-quality video signal having the maximum gradation and maximum S / N ratio obtained by the D / A converter can be obtained without increasing the number of D / A converters. .

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the device of the present invention.

FIG. 2 is a waveform diagram illustrating the operation of each part of the device of the present invention.

FIG. 3 is a block diagram showing the configuration of another embodiment of the device of the present invention.

FIG. 4 is a block diagram showing the configuration of still another embodiment of the device of the present invention.

FIG. 5 is a block diagram showing the configuration of still another embodiment of the device of the present invention.

FIG. 6 is a block diagram of a conventional video signal generator with a sync signal.

FIG. 7 is a waveform diagram illustrating the operation of each unit of the conventional device.

[Explanation of symbols]

 1 Timing signal generator 2 Digital video signal generator 3 Digital synchronization signal generator 4 Blanking signal generator 5 Selector 6 D / A converter 7 DC voltage source 8 Differential amplifier 10 Clamp pulse generator 11 Clamp circuit 12 Programmable semiconductor Element 13 Digital data recording medium

Claims (5)

[Claims] 1. A video signal processing device for processing a digital video signal for analog conversion, wherein a DC power supply for applying a DC offset to the digital sync signal and a digital sync signal for applying the DC offset are blanked for the digital video signal. Digital data generating means for generating digital data of a composite video signal in addition to the signal during the period, means for converting the digital data to analog, and offset removal for removing the DC offset from the analog-converted composite video signal Means and an analog video signal output means for selectively outputting the analog-converted composite video signal except during the blanking period and the composite video signal from the offset removing means from which the DC offset has been removed during the blanking period. A video signal processing device characterized by. 2. A DC voltage source for generating a voltage corresponding to an offset added to a digital synchronizing signal by an offset removing means, and a difference signal between an analog-converted composite video signal and a voltage generated by the DC voltage source. 2. The video signal processing device according to claim 1, comprising a differential amplifier for outputting, and the analog video signal output means being a selector. 3. The video signal processing device according to claim 1, wherein the offset removing means comprises a clamp circuit for clamping the analog-converted composite video signal at a predetermined level, and the analog video signal output means comprises a selector. 4. A video signal processing apparatus according to claim 1, wherein the digital data generating means comprises a programmable semiconductor element. 5. The video signal processing device according to claim 1, wherein the digital data generating means comprises a digital data recording medium.