JPH03214878A - Scanning line interpolation circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a scanning line interpolation circuit for television signals.
In particular, it relates to a circuit that interpolates and reproduces scanning lines that are not transmitted in interlaced scanning using a progressive scanning auxiliary signal (VT signal). [Prior Art] In the current television system (NTSC system), images are transmitted by dividing one frame into two fields using interlaced scanning. Conventional television receivers display images using interlaced scanning, so 1
The coarseness of the reproduced image due to the alternate scanning line structure and interference with the printer (flickering) were causes of image quality deterioration. In order to reduce this picture quality deterioration, we introduced the high-definition television system (EDTV), which is completely compatible with the current television system.
), or in the current system (IDTV) in which television signals are made high-definition through signal processing on the receiving side, the receiving side performs interlaced-progressive scan conversion and displays the signal. At this time, the receiving side detects the movement and performs scanning line interpolation processing using processing parameters according to the movement (for example, Japanese Patent Laid-Open No. 130685/1983). However, since the information sent is an interlaced signal, there are restrictions, and there are movements that cannot be detected in principle.

For example, an image that moves at exactly the frame period (1/30 second) cannot be distinguished from a still image, so interpolation processing is performed in still image mode even though it is a moving image, causing a large deterioration in image quality. Additionally, in areas that are determined to be moving images, scanning lines that are not transmitted are created by correcting the upper and lower scanning lines in the same field, so images with high vertical frequencies (such as fine horizontal stripes) cannot be reproduced. ．． In order to compensate for the above drawbacks, a sequential scanning camera is used on the transmitting side.
A normal transmission signal (
Below, the main scanning line signal and abbreviation f[! ) as well as
It has been considered to transmit a signal (hereinafter abbreviated as a progressive scanning auxiliary signal) to assist scanning line interpolation processing on the receiving side. For example, the United States D S R C (David
Sarnoff Research Center)
A C T V (Advanced C
Compatible TV), a difference signal (field difference signal) between a scanning line that is not transmitted because it is skipped during interlace scanning and a scanning line at the same position one field before and after that scanning line is transmitted as a sequential scanning auxiliary signal. As a conventional example, FIG. 3 shows a simplified configuration example of a scanning line interpolation circuit used in the above-mentioned AC TV receiver [IEEE Trans.
actions on ConsumerElectr
onics). Vol 34, Ncilw 1
9 February 1988)]. In the same figure, separation circuit 1
is used to separate the multiplexed main scanning line signal (interlay input signal) and progressive scanning auxiliary signal (V-T helper), and the interpolation scanning line recovery circuit 100 is used to separate the scanning lines that are not transmitted. Interpolate and play. FIG. 4 shows a method for reproducing untransmitted scanning lines from transmitted scanning lines. Figure (a) shows the positional relationship of the main scanning line signals to be transmitted, and figure (b) shows the positional relationship of the progressive scanning auxiliary signals.
In the same figure (a), for the scanning line X that is not transmitted,
Let the scanning lines of the fields before and after the same position be scanning lines A and B, respectively. In the ACTV example above, the same figure (
As shown in b), as the progressive scanning auxiliary signal Y, (X-
(A+B)/2). On the other hand, on the receiving side, as shown in FIG.
10B) / 2) To achieve this, the third
In the interpolation scanning line reproducing circuit 100 shown in the figure, a frame average ((A+B)/2) is created from the main scanning line signal using an l-frame delay circuit 2, an adder 3, and a multiplier 4. is used to calculate the sum with the progressive scanning auxiliary signal Y to obtain an interpolated scanning line signal X (=Y+ (A+B)/2). In addition to the above, for the scanning line X that is not transmitted,
Scan the scanning lines above and below within the same field.
c and D, and the progressive scanning auxiliary signal Y is (x−(
It is also possible to transmit c+D)/2). In this case, on the receiving side, the transmitted scanning line C. Scanning line X that is not transmitted from D and auxiliary signal Y (=Y+(C+D)/2
) to play.

Therefore, regarding the band in which the progressive scanning auxiliary signal was transmitted, the original progressive scanning signal can be reproduced without deterioration on the receiving side. [Problem to be Solved by the Invention] There is no problem if the progressive scanning auxiliary signal can be transmitted over the same frequency bandwidth as the main scanning line signal by using a plurality of channels. However, in Japan, where there are few vacant channels, it is necessary to transmit both the main scanning line signal and the progressive scanning auxiliary signal in one channel.

In the above ACTV example, as shown in FIG. 5(a), for the video RF carrier wave for modulating the main scanning line signal,
The sequential scanning auxiliary signal is modulated using orthogonal (90 degrees out of phase) RF carrier waves and transmitted in one channel. However, in this method, the progressive scanning auxiliary signal is
Only about z can be transmitted.

Furthermore, as shown in FIG. 5(b), there is a method in which a part of the screen is masked with a black tint, and an auxiliary signal is inconspicuously multiplexed onto this masked part. Even if this method is used, it is essentially impossible to enlarge the mask portion, so the frequency band of the auxiliary signal is reduced to 1/. It is necessary to transmit by limiting the angle to 3 to 1/58 degrees.

In the ACTV example shown in FIG. 3 as the conventional example above, 7
Using the progressive scanning auxiliary signal transmitted with the band limited to 50 kHz and the full-band main scanning line signal, scanning line correction 1 is performed by the method shown in FIG. 4. Therefore, 7
For signals of 50 kHz or higher, the interframe average (Y=(A+B)/2) is output as an interpolation scanning line, resulting in a decrease in temporal resolution and blurring of the moving image. Furthermore, as shown in Figure 6, components with high temporal frequencies (near 30 Hz) are folded back into components with high vertical frequencies due to interlaced scanning, so they are observed as fine horizontal striped distortions. In this case, any high temporal frequency component becomes a blocking region when averaged between frames, and as a result, only aliasing distortion is observed. In addition, when scanning line interpolation is performed from upper and lower scanning lines C and D, the horizontal high range of the interpolated scanning line is the inter-scanning average (y =
(C+D)/2) will be output, and the vertical resolution will drop. In addition, the vertical frequency is high (525
/2 cph) components are folded back into higher temporal frequency components by interlaced scanning, so they are observed as flicker-like distortion. In this case, the original high vertical frequency component becomes a blocking region when the line-to-line average is taken, and as a result, only aliasing distortion is observed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a scanning line interpolation circuit in which the resolution is less degraded even in a frequency band in which progressive scanning auxiliary signals are not transmitted, and image quality deterioration due to aliasing distortion is less noticeable.

[Means to solve the problem]

The above object is achieved by using means for limiting the frequency band of the interpolated scan line signal to approximately the same frequency band as the transmitted progressive scanning auxiliary signal.

[Effect]

First, an interpolated scanning line signal is created from the transmitted main scanning line signal and progressive scanning auxiliary signal using the method shown in FIGS. 3 and 4 using an interpolating scanning line reproducing circuit. Among these interpolated scanning line signals, regarding the frequency band in which the progressive scanning auxiliary signal was transmitted, even the signals of the scanning lines that are not transmitted due to interlaced scanning can be correctly reproduced as they were. However, as mentioned above, in the frequency band where the progressive scanning auxiliary signal is not transmitted, the signal has degraded temporal resolution or vertical resolution. Extract only the interpolated scanning line signal of component). On the other hand, for frequency bands that cannot be reproduced correctly (for example, horizontal high frequency components), conventional interpolation processing is not performed.
Leave interlaced scanning as is. In this case, the aliasing distortion of the vertical temporal frequency due to interlaced scanning cannot be removed as in the conventional case, but since incorrect interpolation is not performed, the original component is not removed either, resulting in improved image quality and achieving the above purpose. can do. [Example] The present invention will be explained in detail below using the drawings. The following explanation assumes that the horizontal frequency of the progressive scanning auxiliary signal is band-limited and transmitted. FIG. 1 shows a specific configuration diagram of an embodiment of the present invention.

In the figure, a separation circuit 1 separates the main scanning line signal and the sequential scanning auxiliary signal, which are transmitted using multiple channels or multiplexed into one channel as shown in FIG. do. An interpolated scanning line signal is created from these separated signals using an interpolated scanning line reproducing circuit 100. Up to this point, the configuration is the same as the conventional example shown in Figure 3 above. Here, in order to maintain interlaced scanning in the frequency band where the progressive scanning auxiliary signal is not transmitted, the filter 6 is used to limit the band of the interpolated scanning line signal to be equal to the band of the progressive scanning auxiliary signal. At this time, if the sequential scanning auxiliary signal has already been band-limited by the separation circuit 1 on the transmitting side or the receiving side, the filter 6 acts only on the main scanning line signal before being input to the adder 5. All you have to do is let it happen. Figure 2 shows the scanning line structure of the reproduced image. FIG. 5(a) shows the scanning line structure of the horizontal reduction component to which the progressive scanning auxiliary signal is transmitted, and the scanning lines are accurately reproduced in a progressive scanning manner. Figure (b) shows the scanning line structure of the horizontal high-frequency component to which the progressive scanning auxiliary signal is not transmitted, and since the component exists only in the main scanning line signal, it is in an interlaced format. In addition, in the case of interlaced scanning, the signal power is halved, so the components that are not subjected to interpolation processing (horizontal high frequency components) of the main scanning line signal are amplified approximately twice and the frequency characteristics are corrected. You may do so. Furthermore, since complete interpolation can be performed using the conventional method for still images, it is also possible to use the present invention only for moving images and switch in a motion-adaptive manner.

FIG. 7 shows a specific configuration diagram of another embodiment of the present invention that takes these into consideration. First, the separation circuit 1 separates the main scanning line signal and the progressive scanning auxiliary signal from the transmission signal.
Interpolation scanning line reproducing circuit 1 having the same configuration as that shown in FIG.
00, an interpolated scanning line is created from the main scanning line signal and the progressive scanning auxiliary signal, and only the components (horizontal low frequency components) that can be accurately reproduced by the filter 6 are cut out. In addition, using a motion detection circuit 13 (described later), an image motion amount k (0≦k≦1) is detected from the transmitted signal and inputted to the interfield scanning line interpolation circuit 200 and the frequency characteristic correction circuit 14. do. At this time, for example, if the image is stationary, k=o
When there is a large movement, k = 1, and in the middle, O < k < 1 is output. The interfield scanning line interpolation circuit 200, which includes a 1-frame delay circuit #17, an adder 8, a multiplier 9, and a multiplier 10, creates an interpolated scanning line from only the main scanning line signal. At this time, the frame average (i.e. ((A+B)/2)' in Fig. 4)
) is multiplied by a coefficient (1-k) according to the movement and outputs a signal. In other words, only for still images ((A+B)/2)
is output, and if the image is moving significantly, "'0" is output.
is output. From this output, a filter 11 having frequency characteristics complementary to that of the filter 6 extracts only horizontal high frequency components, and an adder 12 extracts the filter 6 from the filter 6.
In addition to the output of , it is used as an interpolated scanning line signal. On the other hand, the main scanning line signal is outputted through a frequency characteristic correction circuit 14, which will be described later. In addition, the interpolation scanning line reproducing circuit 100 and the interfield scanning line interpolation circuit 200 share the same circuit and are equipped with
You can reduce the size. For example, 1 frame delay time wI
r2 and 7, adders 3 and 8, multipliers 4 and 9, etc. can be shared. FIG. 8 shows the frequency characteristic correction circuit 1.
A detailed configuration example of No. 4 is shown below. From the input main scanning line signal, a frequency band (for example, a horizontal high frequency component) in which the progressive scanning auxiliary signal is not transmitted is extracted using a filter 15.
Using the multiplication $16, this signal is given the amount of motion (0≦k≦1)
After multiplying by The operation of the frequency characteristic correction circuit 14 will be explained with reference to FIG. At frequencies higher than afc, the gain is constant at 1.0 regardless of the amount of motion k (0≦k≦1).
It varies from 0 to 2.0. In other words, in motion mode, the horizontal high frequency range is interlaced scanning, so by increasing the signal power of the horizontal high frequency component of the main scanning line signal and keeping the total power constant, the image quality is improved by attenuating the Takagi component. Reduce deterioration. In addition, taking into account the gamma characteristics of the picture tube,
The gain k may be controlled according to the level of the main scanning line or the interpolation scanning line in addition to the amount of movement. In Figure 10. Shows the positional relationship of scanning lines. The black circle ● represents the main scanning line signal to be transmitted, and the white circle 0 represents the interpolation scanning line. Further, FIG. 11 shows a specific example of the configuration of the motion detection circuit 13. In the current television system (NTSC system), a color signal modulated by frame inversion is multiplexed in the high frequency range of the luminance signal, so after taking the frame difference of the main scanning line signal by the one frame difference detection circuit 18, , filter 19 extracts only low frequency components. Further, a two-frame difference detection circuit 20 detects a two-frame difference between the main scanning line signals. In addition, the 1-field difference detection circuit 21 calculates the difference between the main scanning line signal and the reproduced auxiliary scanning line signal, and then the filter 22 limits the frequency band to be equal to the transmitted progressive scanning auxiliary signal. shall be. The mixing circuit 23 mixes the 1 frame difference, 2 frame difference, and 1 field difference to obtain a motion amount k (0≦k≦1). Figures 12, 13, and 14 show the above 1 frame difference,
Passage area with 2 frame difference and 1 field difference (i.e.
motion detection area). Furthermore, it is not necessary to use all of these detection areas, and although the performance will drop slightly, the scale of the device may be reduced in consideration of economic efficiency. The amount of motion k detected in this way is used not only for scanning line interpolation, but also for scanning line interpolation.
It can also be used to separate multiplexed signals (for example, separation of luminance signals and color signals, separation of high-definition signals, etc.). In addition, in the figure, for the sake of simplicity, average interpolation from neighboring scanning lines is explained as inter-field scanning line interpolation and inter-line scanning line interpolation, but the present invention is not limited to this. You can improve the interpolation characteristics by increasing the number of taps, or you can reduce the circuit scale by performing previous value interpolation (using the value of the immediately preceding field or scanning line directly as the interpolated value), although the performance will be slightly lower. Good too. Furthermore, if the motion vector can be accurately determined, previous value interpolation from a vector-corrected position may be performed instead of previous value interpolation at the same position.

In addition, when the present invention is applied to a television receiver, luminance signal Y, color signal and Q (or R-Y and B-Y)
．． Alternatively, it is not necessary to apply all of the red, green, and blue (R, G, B) signals, and only the luminance signal Y, which has the highest image quality improvement effect, may be applied. Furthermore, considering visual characteristics,
The invention may also be used in visually linear areas. In other words, the input signal is once reversely gamma corrected (y = x”・2
) and logarithm (y=1n(x)), the present invention is applied to the output signal, and the inverse processing ((
x=yO・4B) or (y=exp(x))). The present invention has many variations and applications, such as the examples below. (1) The present invention is applicable not only to the case of transmitting signals, but also to the case of recording main scanning line signals and progressive scanning auxiliary signals on VTRs, video discs, etc.

(2) The original signal is a sequential scanning signal (525 lines, 1:1)
In addition to double-speed interlaced signals (1 0 5 0
It can be similarly applied to cases such as 1125 books, 2:1 and 1125 books, 2:1. (3) If it is determined that the auxiliary scanning line signal is not being sent due to the presence or absence of a command, etc., motion adaptive processing is applied to the low horizontal frequency range. Alternatively, it may be controlled using a manual switch depending on the viewer's preference. [Effects of the Invention] By applying the present invention, the original progressive scanning signal can be obtained completely for the frequency band in which the progressive scanning auxiliary signal was transmitted, and for the other frequency bands, the still image can be obtained. Complete scanning line interpolation is possible, and the image quality for moving images is almost the same as that of current interlaced receivers.The scanning line interpolation method with the least image quality deterioration is selected depending on the movement, so it can be used to improve image quality. The improvement effect is extremely large.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a scanning line interpolation circuit according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the present invention, and FIG. 3 is a block diagram showing the configuration of a conventional scanning line interpolation circuit. , 4th
The figure is an explanatory diagram of a method of creating a scanning line signal that is not transmitted from a transmitted signal, Figure 5 is an explanatory diagram of a method of transmitting an auxiliary signal, Figure 6 is an explanatory diagram of problems in the conventional technology, and Figure 7 is an explanatory diagram of a method of creating a scanning line signal that is not transmitted from a transmitted signal. is a block diagram showing the configuration of a scanning line interpolation circuit according to another embodiment of the present invention, FIGS. 8 and 11 are block diagrams showing the configuration of a part of the circuit according to another embodiment of the present invention, and FIG. , 1st
0 and 12 to 14 are explanatory diagrams of the operation of the circuit according to the embodiment of the present invention. 1... Separation circuit, 2,
7...1 frame delay circuit, 3, 6, 8, 12.17
... Adder, 4, 9, 10, 16 ... Multiplier, 6,
11, 15, 19.22... Filter, 13... Motion detection circuit, 14... Frequency characteristic correction circuit, l8...
・1 frame difference detection circuit, 20...2 frame difference detection circuit, 21...1 frame difference detection circuit, 23...Mixing same path, 100...Interpolated scanning line reproduction 3rd Figure 11 k Taku 9 mouth HrF/Sl'j Kazuto talent i [奢tJ-product 1 exhibition number taku j2 country V 13th solid V 2 frame A: 1 F2 ” Field difference * X e - X-2y.r

Claims (1)

[Claims] 1. In a scanning line interpolation circuit that interpolates and reproduces scanning lines that are not transmitted from transmitted main scanning line signals and auxiliary signals, with respect to the frequency band in which the auxiliary signals are transmitted, the main scanning line signal and an auxiliary signal to create an interpolated scanning signal, and do not perform scanning line interpolation for a frequency band in which the auxiliary signal is not transmitted. 2. In a scanning line interpolation circuit that interpolates and reproduces scanning lines that are not transmitted from the transmitted main scanning line signal and auxiliary signal, regarding the frequency band in which the auxiliary signal was transmitted, interpolation scanning is performed from the main scanning line signal and auxiliary signal. For frequency bands where auxiliary signals are not transmitted, if the image is stationary, an interpolated scanning line signal is created using information from the previous and following fields, and as the image movement increases, the signal is A scanning line interpolation circuit that reduces output and does not perform scanning line interpolation when the movement of an image is very large. 3. In a scanning line interpolation circuit that interpolates and reproduces scanning lines that are not transmitted from the transmitted main scanning line signal and auxiliary signal, regarding the frequency band in which the auxiliary signal was transmitted, interpolation scanning is performed from the main scanning line signal and auxiliary signal. A scanning line interpolation circuit that creates a line signal, corrects the amplitude of the main scanning line signal, and outputs the main scanning line signal for a frequency band in which no auxiliary signal is transmitted.