JP3225145B2 - Noise reduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a noise reduction (NR) device.

[0002]

2. Description of the Related Art Conventionally, in order to reduce the circuit scale, a plurality of signals to be subjected to NR are time-division multiplexed and subjected to NR processing by one circuit. Such a conventional NR device is shown in FIG. FIG.
, The multiplexer 101 includes a luminance signal (Y _F ) 115 to be subjected to the frame NR, a color difference signal (C _F ) to be subjected to the frame NR, and a color difference signal (C _L ) 11 to be subjected to the line NR.
9 is time-division multiplexed and supplied to the next stage NR processing unit as a time-division multiplexed original signal 121.

Next, the NR processing section will be described. The signal 123 from which noise is removed from the first subtraction circuit 103 is
The signals are supplied to the frame memory 105 and the line memory 107, and are respectively delayed by one frame and one line.
Then, the selection circuit 109 selects and outputs one of the frame memory 105 or the line memory 107. This selection operation is controlled in accordance with the time axis multiplexing order of the signals 115, 117, and 119 in the multiplexer 101. For example, when the timing corresponds to the frame luminance signal 115 and the frame color difference signal 117, the H level signal 124 is supplied and the timing is set to the line color difference signal 1
In the case corresponding to 19, an L level signal 124 is supplied. Then, the selection circuit 109 outputs the H-level signal 12.
4 is supplied, the output of the frame memory 105 is selected. When the L level signal 124 is supplied, the output of the line memory 107 is selected.

The second subtraction circuit 111 subtracts the output 125 of the selection circuit 109 from the time-division-multiplexed original signal 121 from the multiplexer 101, and outputs a non-interphase signal 127. The multiplier (k) 113 multiplies the non-interphase signal 127 by a coefficient less than 1 to obtain a noise signal 129. First
Subtraction circuit 103 subtracts the noise signal 129 from the time-division multiplexed original signal 121 from the multiplexer 101, and outputs a signal 123 from which the above-described noise has been removed. The signal 123 from which noise has been removed is supplied to the frame memory 105 and the line memory 107. As described above, NR processing is performed.

As post-processing, the demultiplexer 113 converts the noise-removed signal 123 into a frame luminance signal (Y _F ) 131 and a frame color difference signal (C _F ) 13.
3 and the line color difference signal (C _L ) 135 are separated and output.

As described above, the conventional NR apparatus of FIG. 3 multiplexes a signal to be subjected to a frame NR and a signal to be a line NR on a time axis and shares one NR circuit. This is a configuration of a cyclic NR. The recursive NR improves the S / N ratio of the luminance signal, but has a disadvantage that "afterimages" are conspicuous in an image having a lot of motion.

[0007] Although there is a non-cyclic NR as an NR having little adverse effect on the motion, the conventional NR device cannot make the NR of the frame luminance signal a non-cyclic NR as necessary.

[0008]

However, the conventional NR apparatus has a disadvantage that "afterimages" are conspicuous in an image having a sharp movement. Then, the NR of the frame luminance signal could not be changed to the non-cyclic NR as necessary.

An object of the present invention is to provide an NR apparatus that selects between a cyclic NR and a non-cyclic NR according to the properties of each signal to be NR.

[0010]

According to the present invention, a luminance signal, a color difference signal,
Including at least, N (N ≧ 2) pieces of the first time-axis multiplexing means for time-axis multiplexing original signal to be noise reduction, the time base multiplexed from the first time-axis multiplexing means a carrier chrominance signal A first subtraction unit to which an original signal is supplied, the time base multiplexed original signal from the first time base multiplexing unit, and an output of the first subtraction unit are input, and one of them is output. Selection means, delay means for delaying the output of the selection means, second subtraction means for subtracting the output from the delay means from the time-axis multiplex original signal from the first time-axis multiplex means, The output from the second subtraction means is multiplied by a coefficient to supply the output to the first subtraction means, and the output from the first subtraction means is separated into N
Separation means for outputting the signal of
In the case of an image with fast movement corresponding to each of the N original signals
Binary control corresponding to the case when the image is not fast moving
The signal is time-division multiplexed, and this time-division multiplex control signal
A second time axis multiplexing means for controlling the selecting operation of the selecting means
And a selecting means, wherein the selecting means is a means for noise reduction.
When each of the N original signals is a rapidly moving image,
Is the time axis multiplex source from the first time axis multiplexing means.
Select and output a signal.
The output of the first subtraction means is selectively output .

[0011]

When the selection means selects and outputs the time-division multiplexed original signal, the NR device performs a non-recursive NR process on the time-division multiplexed original signal. Conversely, when the selection means selects and outputs the output of the first subtraction means, NR
The apparatus performs a cyclic NR process on the time-division multiplexed original signal. Further, the operation of the selection means is controlled in a time-series manner in accordance with the multiplex timing of each of the N original signals to be subjected to the NR by the second time base multiplex control signal.

[0012] This means that for each original signal to be NR, it is possible to select between a cyclic NR and a non-cyclic NR according to the nature of the signal and in consideration of the effects and adverse effects of the NR. means. Also, since the original signals to be NR are time-division multiplexed and processed by one piece of hardware, an NR device can be provided with a small circuit scale.

[0013]

FIG. 1 shows a first embodiment of the NR apparatus according to the present invention. In FIG. 1, a first multiplexer 1 includes a luminance signal (Y _F ) 21 to be subjected to a frame NR and a frame NR.
The color difference signal (C _F ) 23 to be subjected to the line NR and the color difference signal (C _L ) 25 to be subjected to the line NR are multiplexed on the time axis, and supplied to the NR processing section at the next stage as an original signal 27 multiplexed on the time axis.

Next, the NR processing section will be described. The first selection circuit 5 includes the time-division multiplexed original signal 27 and the first subtraction means 3
From which the noise 29 is removed. First
The selection circuit 5 performs a selection operation in a time series according to a time axis multiplexing control signal 45 to be described later.
Or the signal 29 from which noise has been removed.
The output of the first selection circuit 5 is supplied to a frame memory 7 and a line memory 9 and each is delayed by one frame and one line. Then, the second selection circuit 11 selects and outputs one of the outputs of the frame memory 7 or the line memory 9. This selection operation is performed by the signals 21 and
The control is performed according to the time multiplexing order in the first and third multiplexers 1 and 3. For example, when the timing corresponds to the frame luminance signal 21 and the frame color difference signal 23, H
When the level signal 32 is supplied and the timing corresponds to the line color difference signal 25, the L level signal 32 is supplied. The second selection circuit 11 selects the output of the frame memory 7 when the H-level signal 32 is supplied, and selects the output of the line memory 9 when the L-level signal 32 is supplied. I do.

The second subtraction circuit 13 subtracts the output 33 of the second selection circuit 11 from the time-division multiplexed original signal 27 from the first multiplexer 1 and outputs a non-correlation signal 35. The multiplier (k) 15 multiplies the decorrelation signal 35 by a coefficient less than 1 to obtain a noise signal 37. The first subtraction circuit 3 subtracts the noise signal 37 from the time-division-multiplexed original signal 27 from the first multiplexer 1 and outputs a signal 29 from which the above-mentioned noise has been removed.

The second multiplexer 17 applies a cyclic NR or a non-cyclic NR to each of the frame luminance signal 21, the frame chrominance signal 23, and the line chrominance signal 25.
Multiplexing is performed on the control signals 39, 41, and 43 in order to perform the time axis. The time axis multiplex control signal 45 from the second multiplexer 17 is supplied to the control terminal of the first selection circuit 5.

The first selection circuit 5 includes a time axis multiplexed signal 27
In the period corresponding to the inner frame luminance signal 21, the control signal 39 of the time multiplex control signal 45 selects the time multiplex original signal 27 or the signal 29 from which noise has been removed. Thereby, the non-recursive NR process or the cyclic NR process is performed on the frame luminance signal 21. Also, the first
Is selected by the control signal 41 of the time axis multiplexing control signal 45 during the period corresponding to the inner frame color difference signal 23 of the time axis multiplexing original signal 27 or the signal whose noise has been removed. Select 29. This allows
A non-cyclic NR process or a cyclic NR process is performed on the frame color difference signal 23. Furthermore, the first selection circuit 5
Is a period corresponding to the inner line color difference signal 25 of the time axis multiplex original signal 27, and the control signal 4 of the time axis multiplex control signal 45
3, the time-division multiplexed original signal 27 or the noise-removed signal 29 is selected. As a result, a non-recursive NR process or a cyclic NR process is performed on the line color difference signal 25. Here, for example, for the frame luminance signal 21, S
In order to improve the / N ratio, cyclic NR processing can be performed, and in the case of a rapidly moving image, non-cyclic NR processing can be performed.

The demultiplexer 19 converts the noise-removed signal 29 from the first subtracting means 3 into a frame luminance signal (Y _F ) 47, a frame color difference signal (C _F ) 49, and a line color difference signal (C _L ) 51. And supplied to the next stage.

As described above, for each of the frame luminance signal 21, frame color difference signal 23, and line color difference signal 25 constituting the time axis multiplexed original signal 27, the effect and harmful effects of NR are considered in accordance with the properties of the signals. Thus, it is possible to select between a cyclic NR and a non-cyclic NR. Also, NR
Since the original signal to be processed is time-multiplexed and processed by one piece of hardware, an NR device can be provided with a small circuit scale.

The original signal to be NR may be a field luminance signal or a field color difference signal instead of the frame luminance signal 21 and the frame color difference signal 23.
At this time, a field memory is provided instead of the frame memory 7. Further, the frame color difference signal 23,
Instead of the line color difference signal 25, a frame carrier color signal or a line carrier color signal may be used.

Next, a second embodiment of the NR apparatus of the present invention is shown in FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and the description of the operation thereof will be omitted. The decorrelation signal 35 from the second subtraction circuit 13 is supplied to the filter circuit 53. The filter circuit 53 prevents the noise component included in the decorrelation signal 35 due to the poor S / N ratio of the frame luminance signal 21 from being supplied to the comparison circuit 55 in the next stage.

Then, the filter circuit 53 extracts the low-frequency component of the decorrelation signal 35 and supplies it to the comparison circuit 55.
The comparison circuit 55 compares the output level of the filter circuit 53 with the reference value of the reference value signal 59, and outputs the output when the output level of the filter circuit 53 is higher than the reference value.
7 The determination circuit 57 determines that the output from the comparison circuit 55 has continued for a certain period of time, and outputs a control signal 63 that causes the NR for the frame luminance signal 21 to be acyclic, to one input terminal of the logic circuit 65. To supply. The other input terminal of the logic circuit 65 has a frame luminance signal 2
For 1, the control signal 39 for performing the cyclic NR or the non-cyclic NR is input. Then, the output of the logic circuit 65 is supplied to the second multiplexer 17 and time-multiplexed. As described above, in the case of an image in which the S / N ratio of the frame luminance signal 21 is good and the motion is sharp, the logic circuit 65 outputs the control signal 63 in preference to the control signal 39. Further, regarding the NR of the color difference signal, the adverse effect of the cyclic NR is not conspicuous due to the nature of the human eye, so there is no need to forcibly switch to the non-cyclic NR processing.

As in the first embodiment, the original signal to be NR may be changed.

[0024]

According to the present invention, for each original signal to be NR, the cyclic NR is selected from the non-cyclic NR in accordance with the nature of the signal and in consideration of the effects and harmful effects of the NR. It can be performed. Furthermore, in the second embodiment, in the case of an image having a good S / N ratio of the luminance signal and a sharp movement, the luminance signal can be automatically shifted to the non-recursive NR processing.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an NR device according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the NR device according to the present invention.

FIG. 3 is a circuit diagram showing a conventional NR device.

[Explanation of symbols]

1 ... first multiplexer, 3 ... first subtraction circuit, 5 ...
1st selection circuit, 7 ... frame memory, 9 ... line
Memory, 11 second selection circuit, 13 second subtraction circuit, 15 multiplier, 17 second multiplexer, 19
... demultiplexer, 53 ... filter circuit, 55 ... comparison circuit, 57 ... judgment circuit, 65 ... logic circuit.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 9/44-9/78 H04N 5/14-5/217

Claims (2)

(57) [Claims] 1. A method for converting a luminance signal and a color difference signal or a carrier color signal into
A first time axis multiplexing means for time axis multiplexing N (N ≧ 2) original signals to be subjected to noise reduction , including the time axis multiplexed original signal from the first time axis multiplexing means; A first subtraction unit, a selection unit that receives the time-division multiplexed original signal from the first time-axis multiplexing unit and the output of the first subtraction unit, and outputs one of the input signals; Delay means for delaying the output of the selection means; second subtraction means for subtracting the output from the delay means from the original time-division multiplex signal from the first time-division multiplex means; And the output from the first subtracting means is separated from the multiplying means for multiplying the output from the coefficient by a coefficient and supplying the output to the first subtracting means.
Separating means for outputting a signal, corresponding to each of the N original signals to be noise-reduced
And images with fast-moving and non-fast-moving images
The binary control signal corresponding to the case is time-division multiplexed.
The selection operation of the selection means is controlled by an inter-axis multiplex control signal.
And a second time axis multiplexing means for controlling the noise , wherein the selecting means comprises:
If each of the original signals is a rapidly moving image, the first
Selective output of the time axis multiplex original signal from time axis multiplexing means
If the image is not a fast-moving image, the first subtraction operation is performed.
A noise reduction device for selectively outputting an output of a stage . 2. Reference value signal generation means for generating a reference value signal; comparison means for comparing the output from the second subtraction means with the level of the reference value signal from the reference value signal generation means; the output from the comparator means, said status output is greater than the reference value signal of the subtraction means is operable to determine that the subsequent predetermined time, thereby a determination means for generating a control signal, among the N control signals And a logic circuit to which a control signal from the determination means is input, and a logic circuit to supply the control signal from the determination means to the second time axis multiplexing means with priority. Claim 1
The noise reduction device as described.