JPH0348714B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a changed part extraction circuit, and more specifically to a circuit configuration of a changed part extractor that extracts changed parts of a color television signal.

For monochrome television signals, information on the movement of the subject is extracted as a changing part from the difference between the previous frame signal and the current frame signal stored in the frame memory, and only the changing part is encoded and transmitted. A method is known that achieves significant data compression and uses low-speed lines to transmit moving images.

Consider the case where this is applied to a color television signal. When the color television signal format is a signal separated into each component (hereinafter referred to as a separated color signal), such as a three primary color signal or a luminance signal and two types of color difference signals, each component signal is treated in the same way as a monochrome signal. It is possible to perform various processing.

On the other hand, the color television signal format is a signal in which two types of color difference signals are modulated at a subcarrier frequency and superimposed on a luminance signal (hereinafter referred to as a composite color signal), as used in normal color television broadcasting. ), the phase of the subcarrier signal differs between successive frames. For example, in the composite color signal of the NTSC system, the phase is shifted by 180°, and 2
The frame is back to normal. Therefore, if you store an NTSC signal and try to extract the changing part from the difference signal between frames, the polarity of the carrier color signal is reversed, so the color signal component will appear in the difference signal, making it difficult to extract the changing part. Become. For this reason, a circuit (hereinafter referred to as a chroma inversion circuit) that inverts the polarity of the carrier color signal of the composite color signal stored in the frame memory is provided, and after inverting the polarity of the carrier color signal, the difference between frames is It was necessary to take it. In this case, in the chroma inversion circuit, it is difficult to accurately phase-invert only the carrier color signal component due to the circuit configuration, and some of the luminance signal components may be mixed in and inverted, or some of the carrier color signal components may be phase-inverted. It will be left uninverted. As a result, changes may not be extracted with high accuracy, and some changes may not be detected.
Problems such as unchanging parts being extracted incorrectly occurred.

When first separating and converting a composite color signal into separate color signals and then extracting the changing part,
Although the chroma inversion circuit becomes unnecessary, when converting a composite color signal into a separate color signal, the separation operation of the luminance signal and the carrier color signal cannot be expected to be complete, and the above-mentioned problem still occurs.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a highly accurate and simple-configured change part extraction circuit for a color television signal.

In order to achieve the above object, the present invention is characterized in that a changing portion is extracted from a difference signal between frames whose phases of carrier color signals match each other in color frame period units of a composite color signal. That is, since it is a difference between signals of frames whose carrier color signals have the same phase, the difference signal contains only information regarding the movement of the subject, and it is possible to extract a changing portion with high precision.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows an example of a configuration in which the changed portion extraction circuit of the present invention is applied to an interframe encoding device.
In the figure, a composite color signal input to an input terminal 1 is digitized by an A/D converter 2, and the signal of the previous color frame stored in an image memory 5 having a delay amount of a color frame period and a change portion are Only the image signals of the portions compared by the extraction circuit 3 and determined to have changed are encoded by the encoding circuit 6 via the switching circuit 4 and at the same time as the image memory 5 is rewritten. On the other hand, the address information of the image determined to be changed by the change detection circuit 3 is encoded by the encoding circuit 7 and sent to the transmission line 9 via the buffer memory 8 together with the output code of the encoding circuit 6.

In this configuration diagram, the capacity of the image memory 5 is the capacity of the color frame period of the composite color signal, so the output signal of the image memory 5 is in phase with the output signal of the A/D converter 2 and the carrier color signal. There is. Therefore, as shown in FIG. 2, in the change detection circuit 3, if the difference between the A/D converter 2 and the image memory 5 is calculated by the subtraction circuit 10, it is possible to determine whether or not there is a change in the input image signal in the color frame period. can. This difference signal D is converted into an absolute value |D| by an absolute value circuit 11, and its low frequency component is extracted by a low pass filter (LPF) 12. By comparing the output of the LPF 12 with a threshold value in the comparison circuit 13, information on the presence or absence of a change in the image can be obtained.

In Fig. 2, the output of the LPF 12 is converted into a binary signal by the comparison circuit 13, but by providing a coefficient circuit in place of the comparison circuit 13, a signal corresponding to the amount of change in the amplitude direction of the image signal can be obtained. . If this is used, it can also be used in motion adaptive processing, such as a noise removal circuit or an interpolation circuit, in which the mixing ratio of a signal before a field period or frame period and a current signal is controlled by the amount of change.

FIG. 3 shows a configuration diagram when the changed portion extraction circuit of the present invention is applied to a color still image transmission device that transmits still images via a narrowband transmission path. In the figure, a composite color signal obtained by capturing a still image or a slowly moving subject inputted to an input terminal 1 is digitized by an A/D converter 2. This input image signal is compared with an image signal stored in an image memory 14 having a storage capacity of 1 field in a change detection circuit 17, and the image signal determined to have a change is passed through the switching circuit 4 and then the image signal is memory 14
is input. The image signal determined to have a change is encoded by the encoding circuit 15, and the change detection circuit 1
It is sent to the low-speed transmission line 19 via the transmission control circuit 16 together with the changed address information outputted from 7. When a telephone line is used as the low-speed transmission line 19, it takes several times to transmit one field image.
It takes 10 seconds. When all image signals with changes in one field of images are sent out, the control circuit 16 outputs a sending completion signal. Upon generation of this signal, the change detection circuit 17 starts the above-described operation for determining the presence or absence of a change. However, in the change extraction circuit of the present invention, the change detection operation does not start only when the transmission completion signal is generated. That is, the synchronization information of the input signal is separated by the synchronization separation circuit 18, and a signal indicating a predetermined field within the color frame of the input image signal is output. After the transmission is completed, when this predetermined field signal is output, a change detection operation is started. Thereby, the image signal of the predetermined field is always stored in the image memory 14.

FIG. 4 shows the configuration of the change detection circuit 17, in which a difference signal between the output of the image memory 14 and the A/D converter 2 is calculated by a subtraction circuit 20, and converted into an absolute value by an absolute value circuit 21. The absolute value of the obtained difference is accumulated in an adder circuit 22 and a register 23 during a block period consisting of fixed pixels, and the accumulated results are compared in a comparator circuit 24 every block period. The AND gate 25 outputs a change presence/absence signal only when the above-mentioned transmission completion signal and the predetermined field signal are both 1.

In the embodiments shown in FIGS. 1 and 3 above, a case has been described in which a changing part is extracted by directly comparing composite color signals, but the input composite color signals are first converted into separated color signals and then post-processed. Even in this case, if the present invention is applied to extract the changed portion in synchronization with the color frame period, erroneous extraction due to leakage of the carrier color signal will be eliminated, and accurate change extraction will be possible.

According to the present invention, since the change detection operation is performed in synchronization with the color frame period of the composite color signal, there is no erroneous detection due to the mixing of the carrier color signal, and highly accurate change portion detection is possible. Additionally, changes can be detected by directly comparing composite color signals.
There is no need for circuits such as chroma inverters, and the changing part extraction circuit can be configured with a simple circuit configuration.
When applied to various processing circuits that utilize motion information of color image signals, it is highly effective in improving signal processing performance and reducing costs.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an interframe encoding device to which the present invention is applied, FIG. 2 is a block diagram of its changing part extraction unit, and FIG. 3 is a block diagram of a color still image transmission device to which the present invention is applied. FIG. 4 shows a configuration diagram of the changed portion extracting section, which is the main part. 2... A/D converter, 3, 17... Change detection circuit, 5, 14... Image memory, 6, 7, 15...
Encoding circuit, 8... Buffer memory, 10, 2
0, 22... Addition (subtraction) circuit, 11, 21... Absolute value circuit, 12... Low pass filter, 13, 2
4... Comparison circuit, 16... Transmission control circuit, 18...
...Synchronization separation circuit, 25...AND gate.

Claims (1)

[Claims] 1: an image memory that delays an input color television signal by a color frame period; a subtraction circuit that obtains the difference between the input color television signal and the output signal of the image memory; and a signal related to the absolute value of the output of the subtraction circuit. an absolute value circuit; a low-pass filter that passes low frequency components of the output of the absolute value circuit;
A changing portion extraction circuit comprising a discrimination circuit that compares the output signal of the low-pass filter with a reference value and discriminates a moving portion of an image based on a magnitude relationship with the reference value.