JP2974354B2 - Video signal processing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a recording / reproducing apparatus, and has a Y / C separating unit using a memory and a noise reducing unit.

(Prior Art) Generally, in a home video tape recorder (VTR), after a composite video signal is separated into a luminance signal and a chrominance signal portion, the luminance signal is FM-modulated, and the chrominance signal is converted into a low frequency band and the FM
It is recorded so as to be superimposed on the low band of the luminance signal. A one-dimensional filter was used for a separation circuit (hereinafter referred to as a Y / C separation circuit) for separating a luminance signal and a chrominance signal, but a two-dimensional filter using a charge-coupled device (CCD) or a glass delay element was used. Is used.

The two-dimensional filter uses the fact that the phase of the chrominance carrier of the NTSC signal is inverted for each line.
The luminance signal Y is obtained by taking the sum of the lines before 1H (H: horizontal period), and the color signal C is obtained by taking the difference.

FIG. 7 shows a configuration example of a two-dimensional filter. Input terminal 70
The composite video signal input from 0 is input to the line memory 701 and the subtractor 704. The input and output of the line memory 701 are subjected to a subtraction process in a subtractor 702. As a result, the color signal C is obtained from the subtractor 702, and is output to the output terminal 705 via the bandpass filter 703. The output of the bandpass filter 703 is supplied to a subtractor 704. As a result, the luminance signal Y is obtained from the subtractor 704 and is output to the output terminal 706.

The two-dimensional filter makes it possible to extract the horizontal high-frequency component of the luminance signal from the composite video signal. However, it is difficult to separate the luminance signal and the chrominance signal in the horizontal and vertical high frequency components, and the image quality is degraded due to mutual interference.

In a home VTR, a luminance signal and a chrominance signal are recorded in a frequency-divided form. Therefore, a one-dimensional filter is sufficient to separate the luminance signal and the chrominance signal during reproduction. At the time of reproduction, the luminance signal is FM-demodulated and then input to a noise reduction circuit (hereinafter, NR circuit) via a de-emphasis circuit and a drop-out compensation circuit.

 FIG. 8 shows a conventional NR circuit.

A luminance signal is introduced into an input terminal 800 and input to a high-pass filter (HPF) 801 and a low-pass filter (LPF) 802. The horizontal high-frequency component extracted by the high-pass filter 801 is input to the coring circuit 803, where a signal having a certain level or less is reduced to zero and output, and supplied to the adder 804. The output of the low-pass filter 804 is also guided to the adder 804, and a luminance signal with reduced noise is obtained at the output terminal 805. The characteristics of this coring circuit are shown in FIG.

The above-described NR circuit is effective for suppressing noise from being noticeable on a flat screen, but a small amplitude component of the signal is lost.

As another method of noise reduction and other methods, there is a method of performing an addition process with a previous line using a line memory, utilizing the fact that an image has relatively high correlation in the vertical direction. In this method, a highly correlated video signal is passed as it is, and random noise without correlation is reduced. In this case, when the level of the vertical high frequency component is larger than a predetermined value, the addition is stopped to prevent the level of the high frequency component from being reduced. However, when the level of the vertical high frequency component is low, the addition operation is performed. To obtain noise reduction. However, for this reason, the minute amplitude component of the vertical high frequency component is lost.

(Problems to be Solved by the Invention) As described above, in the conventional recording / reproducing apparatus, the separation of the luminance signal and the chrominance signal is not sufficient in the Y / C separation at the time of recording. The image quality is degraded by the interference component. Further, at the time of reproduction, there is a problem that the minute amplitude of the horizontal high-frequency component of the reproduced signal is lost, or when added in the vertical direction, the minute amplitude of the horizontal or vertical component is lost, thereby deteriorating the image quality.

Therefore, the present invention is applied to a circuit for processing the Y / C separation of a composite video signal and a separated luminance signal and a chrominance signal.
An object of the present invention is to provide a video signal processing circuit capable of obtaining C separation and good noise reduction.

[Means for Solving the Problems] The present invention separates a composite video signal into a luminance signal and a chrominance signal, performs predetermined processing on each signal, and records the signals on a recording medium. In a video signal processing circuit that performs processing opposite to the above-described predetermined processing on the reproduced signal to obtain the original luminance signal and color signal, when the composite video signal is separated into a luminance signal and a color signal, A motion-adaptive three-dimensional Y / C separation circuit whose separation characteristic is varied according to the motion and operates with a clock phase-synchronized with the chrominance subcarrier; noise of a reproduced luminance signal or noise of a reproduced chrominance signal from the recording medium; Alternatively, when reducing the noise of both signals, the image motion of the signals is detected, and the motion detection signal is used to calculate between adjacent frames or fields in a still image region, and the noise is calculated between lines in a moving image region. Means for operating with a clock phase-synchronized with the horizontal synchronization signal.

By the above means, a good Y / C separation process and a noise reduction process can be realized with an appropriate clock.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a recording circuit and a reproducing circuit according to an embodiment of the present invention. A video signal for recording is input to an input terminal 10, and a luminance signal and a chrominance signal separation circuit (Y / C separation circuit) 1
Introduced in 1. The Y / C separation circuit 11 is a motion-adaptive separation circuit as described later, and has excellent separation characteristics between a luminance signal and a chrominance signal. The separated luminance signal is subjected to gain control in the automatic gain control circuit 12 and input to the pre-emphasis circuit 13. Here, the luminance signal subjected to the frequency characteristic control is frequency-modulated by the FM modulation circuit 14 and input to the synthesizer 25 via the high-pass filter 15. Hereinafter, this signal is called an FM luminance signal.

The color signal separated by the Y / C separation circuit 11 is passed through a band-pass filter (BPF) 21 to an automatic color control circuit (ACC circuit).
Entered in 22. Then, the color signal subjected to the constant amplitude control by the ACC circuit 22 is converted to a low frequency in the frequency converter 23. Hereinafter, this signal is referred to as a low-frequency conversion color signal. The low-frequency conversion color signal is input to a synthesizer 25 via a low-pass filter (LPF) 24, synthesized with the FM luminance signal, and output from the synthesizer 25. The recording signal output from the synthesizer 25 is input to the magnetic head 18 via the recording amplifier 16 and the rotary transformer 17.

The signal reproduced from the magnetic head 18 is transmitted to the rotary transformer 3
1. High pass filter (HPF) 33 through regenerative amplifier 32
And a low-pass filter (LPE) 41. The high-pass filter 33 separates and derives the FM luminance signal and inputs it to the FM demodulator. The luminance signal subjected to the FM demodulation is subjected to an emphasis process in a de-emphasis circuit 35, and is input to a dropout compensation circuit 36. The luminance signal output from the drop-out compensation circuit 36 is reduced in noise by a luminance signal noise reduction circuit 37 and is led to an output terminal 38.

The low-pass conversion color signal derived from the low-pass filter 41 is noise-reduced by the color signal noise reduction circuit 42,
Input to the C circuit 43. The signal whose amplitude is controlled by the ACC circuit 43 is converted into a color signal of the original frequency by the frequency converter 44 and is led to the output terminal 45.

In this system, the Y / C separation circuit 11 has a motion adaptive configuration as shown in FIG.

That is, the composite video signal supplied to the input terminal 100 is digitized by the analog-to-digital converter 101 and input to the motion detection circuit 102, the frame memory 103, the line memory 110, and the subtractor 114.

The input and output of the frame memory 103 are subjected to a subtraction process in a subtractor 104, so that the output becomes a color signal component, is multiplied by a factor of 105 by a coefficient unit 105, and is input to a mixer 107 via a band-pass filter 106. Is done. On the other hand, the input and output of the line memory 110 are also subjected to subtraction processing by the subtractor 111, and the output becomes a color signal component, which is multiplied by で in the coefficient unit 112 and input to the mixer 107 via the band pass filter 113. You. Mixer 10
7 controls the mixture ratio of the two inputs according to the motion detection signal from the motion detection circuit 102, and when the image motion is large (moving image), increases the ratio of the signal from the line memory 111 side, When the motion is small (still image), the ratio of the signal from the frame memory 103 is increased to mix. The color signal obtained from the mixer 107 is output to the digital / analog converter 1
At 15, the signal is converted into an analog signal, led to the output terminal 116, and input to the subtractor 114. In the subtractor 114,
Since the process of subtracting the color signal from the composite video signal is performed,
The output is a luminance signal. The luminance signal is converted into an analog signal by the digital-to-analog converter 115 and is output to the output terminal 117.

As described above, in this embodiment, a motion-adaptive Y / C separation circuit is used. There is an additional requirement that the ratio of the two types of separated signals be changed according to the region and the still image region. For this reason, the ability to separate the luminance signal and the chrominance signal in the horizontal and vertical high frequency components is improved, and the signal quality in the still image area is improved.

FIG. 3 shows another embodiment of the motion adaptive Y / C separation circuit 11.

2 are given the same reference numerals as in FIG. In the above example, the signal obtained by the operation between lines and the signal obtained by the operation between frames for the color signal system were input to the mixer 107, and the mixing ratio was controlled according to the motion detection signal. . However, in the example of FIG. 3, as for the luminance signal, the mixing ratio between the signal obtained between lines and the signal obtained between frames is controlled in accordance with the motion detection signal. That is, since the color signal obtained by the operation between frames is derived from the coefficient unit 105, a luminance signal by the operation between frames can be obtained by subtracting this color signal from the composite video signal in the subtractor 120. . Further, since the color signal obtained by the operation between the lines is derived from the bandpass filter 113, when this color signal is subtracted from the composite video signal by the subtractor 121, the luminance signal by the operation between the lines can be obtained. it can. The two luminance signals thus obtained are mixed in the mixer 122 by the motion detection circuit 102.
If the mixture ratio is controlled according to the motion detection signal from the camera, a luminance signal with further improved quality can be obtained.

FIG. 4 shows the noise reduction circuit 37 shown in FIG.
Is shown in detail.

The luminance signal from the dropout compensation circuit 36 is digitized by the analog-to-digital converter 201 via the input terminal 200, and the motion detection circuit 202, the frame memory 203, and the adder
206, 207 and the line memory 204. Adder 206,
The output of 207 is input to a mixer 205, the mixing ratio of which is controlled according to a motion detection signal, and the obtained luminance signal is converted to an analog signal by a digital-to-analog converter 208 and led to an output terminal 209. You. The adder 206 is a frame memory
The input and output of the line memory 203 are added and output, and the adder 207 adds the input and output of the line memory 204 and outputs the result. In the mixer 205, control is performed to increase the weight of the frame addition signal in the still image area and increase the weight of the line addition signal in the moving image area.

In still images, the signal between adjacent frames has a strong correlation, so the result of adding the original signal is similar, but random noise is reduced when viewed from the result of addition since there is no correlation between frames. become. Therefore, the noise reduction effect in the still image area is improved. As for the components of the moving image area, the ratio of the addition result between lines increases, so that random noise having no correlation between lines is reduced.

In the case of performing motion detection, a reproduced signal can be easily separated by a one-dimensional filter because a luminance signal and a chrominance signal are not multiplexed due to a frequency interleaving relationship unlike a composite video signal. Therefore, it is sufficient for the motion detection in the noise reduction circuit to be formed from the difference signal between one frame.

 FIG. 5 shows another example of the noise reduction circuit 37.

In this embodiment, the noise is reduced by field addition as compared with the circuit of FIG. That is, the output of the field memory 203 is input to the line memory 211.
The input and output of the line memory 211 are added in an adder 212 and are multiplied by 1/2 by a coefficient unit 213.
Supplied to 4.

Accordingly, in a circuit composed of the field memory 203, the line memory 211, the adder 212, the coefficient unit 213, and the adder 214, an image adding process as shown in FIG. 6 is performed.
That is, the pixel is sent from the analog-to-digital converter 201 to the adder 214.
Assuming that 0H is input, the coefficient unit 213 outputs a signal obtained by adding the pixels -263H and -262H and halving the sum. Processing between lines is the same as in the previous example.

According to this noise reduction circuit, although the vertical resolution is reduced in a still image, there is an advantage that the memory capacity used for this is small.

The above description is based on a noise reduction circuit for a luminance signal.
Although the configuration example of 37 has been described, the noise reduction circuit 42 for color signals has a similar configuration.

In the above description, the circuit of FIG. 3 has been described as the motion adaptive Y / C separation circuit 11, but this circuit can also be used as a noise reduction circuit. At the time of recording, a Y / C separation operation can be performed, and at the time of reproduction, a noise reduction operation can be performed.

That is, regarding the luminance signal, from the subtractor 104,
A noise component is obtained. This noise component is
Further, since it is subtracted from the current signal in the subtractor 120,
From this subtractor 120, a luminance signal with reduced noise can be obtained. Also, a noise component can be obtained in the subtractor 111, and the noise component is subtracted from the current signal in the subtractor 121, so that the luminance signal from the subtractor 121 has a reduced noise component. At the time of signal reproduction, it may be used as a noise reduction circuit for only a luminance signal. As a clock for the entire circuit, a clock synchronized with the color width carrier is used at the time of recording, and a clock synchronized with the horizontal synchronization signal is used at the time of reproduction. In this circuit, since the frame memory 103 and the line memory 110 can be sufficiently shared during recording and reproduction, the memory can be reduced.

[Effects of the Invention] As described above, according to the present invention, it is possible to effectively utilize vertical correlation of a video signal and effectively utilize storage means, and to obtain good Y / C separation and noise reduction.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing an example of a Y / C separation circuit in FIG. 1, and FIGS. 4 and 5 are diagrams in FIG. FIG. 6 is a diagram showing an example of a noise reduction circuit, FIG. 6 is a signal explanatory diagram shown for explaining the rotation operation of FIG. 5, FIG. 7 is a diagram showing a conventional Y / C separation circuit,
FIG. 8 is a diagram showing a conventional noise reduction circuit, and FIG.
The figure shows the characteristics of the coring circuit of FIG. 11: Y / C separation circuit, 12: Automatic gain control circuit, 13:
Pre-emphasis circuit, 14 ... FM modulation circuit, 15, 33 ...
High-pass filter, 16: Recording amplifier, 17, 31, Rotary transformer, 18: Magnetic head, 21: Band-pass filter, 22: ACC circuit, 23: Frequency converter, 24: Low-pass Pass filter, 25 ... Synthesizer, 32 ... Regenerative amplifier, 34 ...
... FM demodulator, 35 ... De-emphasis circuit, 36 ... Dropout compensation circuit, 37, 42 ... Noise reduction circuit, 41 ... Low-pass filter, 43 ... ACC circuit, 44 ...
Frequency converter.

Continuation of the front page (72) Inventor Kazumasa Ikeda 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Pref. JP-A-63-290484 (JP, A) JP-A-60-163592 (JP, A) JP-A-62-299181 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04N 9 / 64-9/898

Claims (2)

(57) [Claims] 1. A composite video signal is separated into a luminance signal and a chrominance signal, each signal is subjected to predetermined processing and recorded on a recording medium, and the signal reproduced from the recording medium is subjected to the predetermined processing. In a video signal processing circuit for performing an inverse process to obtain an original luminance signal and color signal, when separating the composite video signal into a luminance signal and a color signal, a separation characteristic is varied according to image motion, and A motion-adaptive three-dimensional Y / C separation circuit that operates on a clock phase-synchronized with a carrier wave, and when reducing noise of a reproduced luminance signal or noise of a reproduced color signal or noise of both signals from the recording medium,
It detects the image motion of the signal and calculates between adjacent frames or fields in a still image area using a motion detection signal, and calculates between lines in a moving image area to reduce noise. A video signal processing circuit comprising: 2. A frame memory used in said Y / C separation circuit for separating a luminance signal and a chrominance signal during recording is shared as a memory used in said noise reduction means during reproduction. 2. The video signal processing circuit according to 1.