JPH09200644A - Aspect ratio determination device for video software - Google Patents

Abstract

(57) Abstract: An object of the present invention is to improve the S / N ratio of a video signal, prevent the loss of a black portion of a video, and improve the accuracy of discriminating the aspect ratio of video software. A clamp circuit for clamping a black level of a video signal, an A / D converter, an S / N ratio of a video signal converted into a digital signal, and an accuracy of discriminating an aspect ratio of video software are improved. Frame recursive filter 3, one horizontal scanning period processing circuit 4, comparison circuit 5 for comparing the detected or held average value or peak value with a predetermined comparison value (Vth), and latch circuit 6
And a microcomputer 7 which outputs the signal for controlling the aspect converter by discriminating the aspect ratio of the video software from the held value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention determines the aspect ratio of a television (hereinafter abbreviated as TV) screen to determine a CPT (Col (Col) having a horizontally long TV (tube surface aspect ratio 16: 9).
The present invention relates to a device for determining an aspect ratio of a screen for displaying video software on a TV) screen using an or picture tube).

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing an example of a conventional aspect ratio discriminating apparatus. As shown in the figure, a clamp circuit 1 for clamping a video signal (composite video signal or luminance signal), an A / D converter 2 for converting the clamped video signal from an analog signal to a digital signal, and an average value for one horizontal scanning period. Alternatively, an average value for detecting and holding a peak value, a peak hold circuit, or a horizontal scanning period processing circuit 4 composed of a combination of these two circuits and a value detected and held by the horizontal scanning period processing circuit 4 in advance. A comparison circuit 5 for comparing a specified comparison value (Vth) with 1
It comprises a latch 6 for latching the result of comparison by the comparison circuit 5 at the end of the horizontal scanning period, and a microcomputer 7 for discriminating the aspect ratio of video software from the latched value.

When the video signal enters the clamp circuit 1, the black level of the video signal is clamped. After the analog-to-digital signal is converted by the A / D converter 2, the average value or peak value of the video signal in one horizontal scanning period is detected by the one horizontal scanning period processing circuit 4. Then, the next comparison circuit 5 compares it with a predetermined comparison value (Vth) and latches the result in the latch 6 at the end of one horizontal scanning period. Based on the latched value, the microcomputer 7 is
If it is determined that the video software is not 16: 9 video software, the control signal for zooming the video is output to the NTSC-high definition converter (not shown).

[0004]

In the above-mentioned conventional image software aspect ratio discriminating apparatus, there is a possibility that the aspect ratio of the image software is erroneously discriminated if there is a black level in one screen or if there are many black levels. high. If there is a black level in the image, the level of the signal detected by the one horizontal scanning period processing circuit 4 becomes low. Therefore, the comparison value (V
There was a problem that comparison with th) could not be performed well.

In order to reduce the possibility of such misjudgment, the present invention adds a frame recursive filter 3 between the A / D converter 2 and the one horizontal scanning period processing circuit 4,
An object of the present invention is to improve the S / N ratio of a video signal, prevent the black portion of a video from being lost, and improve the accuracy of discriminating the aspect ratio.

[0006]

FIG. 1 is a diagram showing the basic structure of an aspect ratio discriminating apparatus for video signals according to the present invention. The same reference numerals or symbols are given to the same configurations as the conventional ones already described in FIG. As shown in the figure, the aspect ratio discriminating apparatus for video software of the present invention includes a clamp circuit 1 for clamping a video signal, an A / D converter 2 for converting the clamped video signal from an analog signal to a digital signal, and a digital signal. Frame recursive filter 3 that improves the S / N ratio of converted data and improves the accuracy of determining the aspect ratio of video software, and detects and holds the average value or peak value of the video signal during one horizontal scanning period 1
A horizontal scanning period processing circuit 4; a comparison circuit 5 for comparing the held value with a predetermined comparison value (Vth);
A latch circuit 6 for latching the comparison result at the end of the horizontal scanning period and an aspect ratio of video software are discriminated from the latched value and a control signal for zooming the video is output to an aspect converter (not shown). And a microcomputer 7.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention shown in FIG. 1 will be described. The gist of the present invention lies in the following points. According to the first embodiment of the present invention, a clamp circuit 1 for clamping a black level of a video signal, an A / D converter 2 for converting the clamped video signal from an analog signal to a digital signal, and a video signal converted to a digital signal. Frame recursive filter 3 for improving the S / N ratio and improving the accuracy of determining the aspect ratio of video software, and one horizontal scanning period process for detecting and holding the average value or peak value of the video signal in one horizontal scanning period A circuit 4; a comparison circuit 5 for comparing the detected or held average value or peak value with a predetermined comparison value (Vth); and a latch circuit 6 for latching the comparison result at the end of one horizontal scanning period. A micro controller that determines the aspect ratio of video software from the latched value and outputs a signal that controls an aspect converter (not shown).
And a computer 7.

The embodiment of the present invention shown in FIG. 1 will be described in more detail. Reference numeral 1 is a clamp circuit for clamping the black level of the video signal. The video signal clamp fixes the black level of the composite video signal when the vertical and horizontal synchronizing signals are separated, that is, when sync separation and A / D conversion are performed.
Reference numeral 2 is a known A / D converter that converts the clamped video signal from an analog signal to a digital signal. The video signal is sampled at a frequency N times that of the horizontal synchronizing signal. N
In the case of TSC, N = 910 is often set.

Reference numeral 3 is a frame recursive or feedback digital filter which improves the S / N ratio of the digital signal converted by the A / D converter 2 and improves the accuracy of discriminating the aspect ratio. This filter is a first-order IIR (Infin
ite Impulse Response) digital filter whose output feeds back to the input,
An infinite impulse train is obtained. Similar to the IIR filter, FIR (Finite Impulse)
Although there is a response filter, this has the advantage that the phase straight line and the group delay characteristic are good, but has the disadvantage that the number of components increases.

FIG. 2 is an internal block diagram of the frame recursive filter 3. As shown, the frame recursive filter 3 includes a multiplier 8, an adder 9, and a frame memory 10.
And a multiplier 11. Normally, a digital filter is composed of a delay element and an adder, but here, the frame memory 10 is used as the delay element. The frame memory 10 uses a DRAM of about 3.64 Mbits.

However, N = 910 and the number of quantization bits = 8 bits, and the following calculation is performed. 910 dots x 525
(Scan line) × 8 bits≈3.64 Mbits. The multiplier 8 multiplies the video signal converted into a digital signal by the A / D converter 2 by the coefficient 1-α, the multiplier 11 multiplies the value read from the frame memory 10 by the coefficient α, and the adder 9 The values multiplied by the multipliers 8 and 11 are added, and the frame memory 1
Store to 0. This output delayed by the frame memory is fed back to the multiplier 11, and the above process is repeated.

When the transfer function H (z) of the frame recursive filter 3 is calculated from the impulse response, H (Z) = (1−α) / (1−α · Z ⁻ τ), where Z ⁻ τ is 1 frame delay, NT
In the SC standard, τ = 1/30 seconds. Next, the frequency characteristic is obtained from the transfer function.

Y = 1 / (1-a) / [1-a · exp (−jωT)] = 1 / (1-a) / [1-a · cos (ωT) + a · j
Sin (ωT)] where ω = 2πf, T = 1/30 sec, and α is the feedback amount. However, 0 ≦ α ≦ 1.

FIG. 3 shows frequency characteristics of the frame recursive filter 3. In this figure, if the coefficient α is small, the gain near 15 Hz is large, and if the coefficient α is large, the gain is small and the S / N ratio is improved. However, when α is increased, when the video signal moves, the frequency characteristic in the time axis direction deteriorates due to the movement of the screen, resulting in blurring and afterimage. S
The improvement of / N ratio is obtained from the following formula.

S / N = 10 · log [(1 + α) / (1-α)] The digital filter utilizes the fact that signal components have frame correlation but noise components have no frame correlation. When the signals are added many times, the signal components have frame correlation, so they strengthen each other, but the noise components have no frame correlation, so they cancel each other out, so only noise is removed, blackout is prevented, and the aspect ratio of the screen is determined. Great effect for improvement. This effect cannot be obtained with a normal noise reducer or the like.

FIG. 4 shows the output voltage during the vertical scanning period.
In this figure, it can be seen that the bright part has a high output voltage and the dark part has a low output voltage. As can be seen from FIG. 3, the frame recursive filter of the present invention has a low-pass characteristic. Reference numeral 4 denotes a 1 horizontal scanning period processing circuit which improves the S / N ratio of the signal by the frame recursive filter 3 and detects and holds the average value or peak value of the digitized video signal during 1 horizontal scanning period. The one horizontal scanning period processing circuit 4 may use an average value circuit (not shown) for detecting an average value, a peak hold circuit (not shown) for detecting and holding a peak value, or a combination thereof.

Reference numeral 5 is a comparison circuit for comparing the average value or peak value detected and held by the one horizontal scanning period processing circuit 4 with a predetermined comparison value (Vth). A latch circuit 6 latches the result of comparison by the comparison circuit 5 at the end of one horizontal scanning period. Latch is HD (horizontal drive pulse)
It goes in sync with. Reference numeral 7 is a microcomputer which determines the aspect ratio of the video software from the value held by the latch 6 and outputs a signal for controlling an aspect converter (not shown).

[0018]

As described above, the present invention has the following effects. Since the frame recursive filter 3 is used, the S / N ratio of the video signal is improved, the comparison value Vth can be reduced, and the ability to determine the presence / absence of a signal is improved even on a black screen. Further, since a plurality of fields are added, even if black is present in a part of the screen, black can be filled in the other screens and averaged, and the discriminating ability is further improved. As a result, it is possible to prevent the black portion of the video signal from being lost and improve the aspect ratio discrimination accuracy of the video software.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of an aspect ratio discriminating apparatus for video software according to the present invention.

FIG. 2 is a diagram showing a detailed block diagram of a frame recursive filter.

FIG. 3 is a diagram showing frequency characteristics of a frame recursive filter.

FIG. 4 is a diagram showing an output voltage during a vertical scanning period.

FIG. 5 is a block diagram showing a main part configuration of a conventional aspect ratio discriminating circuit of video software.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Clamp circuit 2 ... A / D converter 3 ... Frame recursive type filter 4 ... 1 Horizontal scanning period processing circuit 5 ... Comparison circuit 6 ... Latch 7 ... Micro computer 8,11 ... Multiplier 9 ... Adder 10 ... Frame memory

Claims (2)

[Claims] 1. A clamp circuit (1) for clamping a video signal, an A / D converter (2) for converting the clamped video signal from an analog signal to a digital signal, and an average value of the video signal in one horizontal scanning period or One horizontal scanning period processing circuit (4) that detects and holds the peak value, a comparison circuit (5) that compares the held value with a predetermined comparison value, and a latch circuit (6) that latches the comparison result.
And an aspect ratio discriminator for video software, which comprises a microcomputer (7) for discriminating the aspect ratio of the video software from the latched value and transmitting a signal for controlling the TV, the A / D converter (2 ) And the 1 horizontal scanning period processing circuit (4), a frame recursive filter (3) is added to improve the S / N ratio of the video signal and improve the accuracy of discriminating the aspect ratio of the video software. Characteristic video software aspect ratio discrimination device. 2. The frame recursive filter (3) comprises:
A first multiplier (8), an adder (9), a frame memory (10), and a second multiplier (11) are provided, and the first multiplier (8) includes the A / D converter (2 ) Is multiplied by the coefficient (1-α), the second multiplier (11) multiplies the output of the frame memory (10) by the coefficient α, and the adder (9) is the first The output of the multiplier (8) and the output of the second multiplier (11) are added, the frame memory (10) stores the output of the adder (9), and the output is the one horizontal The aspect ratio discriminating device for video software according to claim 1, wherein the aspect ratio discriminating device outputs the scanning period processing circuit (4).