JPH04137892A - Signal detection circuit - Google Patents

Abstract

PURPOSE:To suppress the deterioration in a reproduced picture when a still picture is consecutive for a long time by providing a means detecting a 5-field period of the result of movement detection, a means storing a period detection result, and a means generating a signal of the same period according to the result of period detection to the title detection circuit. CONSTITUTION:After the detection of inter-frame movement, a 5 field period detection circuit 7 detects a 5 field period being the result of movement detection and when only one 'still field' without difference between frames is in existence in 5 field periods, the picture is used as a tele-cine picture, when no 'still field' is in existence, the picture is used as a general picture and the mode is stored in a storage circuit 8. When plural 'still fields' are in existence, the mode before reaching the still picture state is read from the storage circuit 8. Furthermore, when the tele-cine picture is confirmed, a self-running circuit 9 is triggered to generate a signal of 5 field periods and it is used for a reference phase in the case of a still picture causing unstable field phase. Thus, the deterioration in the reproduced picture is less when the still picture is consecutive for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal detection circuit, and particularly to a circuit for detecting a television signal converted from a movie film or the like.

[Conventional technology] In the current television system (NTSC system).

Images are transmitted by dividing one frame into two fields using interlaced scanning, at a rate of 30 frames per second (
60 fields).

In contrast, standard films such as 16 mm and 35 mm have a rate of 24 frames per second. If you combine a standard screen projector with a TV camera and send film,
Because of the relationship between the shutter of the projector and the scanning of the television, clear horizontal stripes moving up and down and severe flickering occur in the image, making it impractical, so a projector called a telecine is generally used to convert the film image into a television signal.

Telecine has 24 frames per second for film and 6 frames per second for television.
In order to correspond to the 0 field, 2 frames of film are converted into 5 fields, with 1/12 second being one cycle. In the 2-3 pulldown telecine system that is commonly used today, odd-numbered films are processed using 2 fields (2/3).
By scraping off every 60 seconds) and scraping off every 3 fields for even-numbered films, 2 frames of film correspond to 5 fields.

(References: For example, 1) Yu Iwase - 2'Video Terminology Dictionary,'Shashin Kogyo Publishing,
August 1989.

2) Edited by the Television Society of Japan, ``Television Engineering Handbook,'' Ohmsha, December 1969) As a method for detecting [telecine image signals] converted from film to television signals as described above, for example, a patent application has been proposed. Hei 2-4
There is a method described in No. 5408.

As mentioned above, two frames of film correspond to five fields of television signals. At this time, for example, as shown in FIG. 4, first and second field images are created from the first film, and third and fourth field images are created from the second film.
．． It is assumed that a fifth field image is created. At this time, since the low frequency components (2 MHz or less) of the third field image and the fifth field image become exactly the same signal, they become a "static field" in which no frame difference signal occurs during one field period. It is detected that this is repeated every 5 fields, and it is determined that this is a telecine image.

Furthermore, the phase of the field currently being processed is detected from the position of the "still field" and used as a reference when performing different processing for each field.

If the above-mentioned conventional method is applied to a television receiver such as IDTV or EDTV, it is possible to determine whether a ``telecine image'' or ``general image'' is determined by signal processing only on the receiver side, and in the case of a ``telecine image'', the characteristics Since suitable luminance-chrominance signal separation and sequential scanning can be performed, a significant image quality improvement effect can be obtained.

[Problems to be Solved by the Invention] In the above conventional example, the low frequency component of the frame difference signal,
A comparison is made for each pixel with a certain set value TH.

If the low frequency component of the frame difference becomes larger than TH for even one pixel during one field period, it is considered a motion field,
The rest is a static field.

[In the case of telecine images, taking advantage of the property that this static field always appears at least once in five fields, [
[Telecine image] and [General image] are determined.

However, when the image itself remains stationary for a long time, the still field in the general image is continuous, just like in the telecine image, and it is essentially impossible to distinguish between the two. For example, in the luminance-color signal separation method and progressive scanning method described in Japanese Patent Application No. 2-45408, for regular still images, the same signal processing results are obtained for both telecine images and general images. , there is no problem in determining which mode it is. However, in a transient state such as the start of movement, if normal images are sequentially scanned in telecine mode, significant image quality deterioration occurs, such as double images in the reproduced image.

There are four types of transitional states of motion, ie, mode changes between still images, as follows.

(Change 1) General image → Still image → General image (Change 2) General image → Still image → Telecine image (Change 3) Telecine image →
Still image → General image (Change 4) Telecine image → Still image → Telecine image In the above conventional example, since the still image is determined to be a [telecine image], it is changed as in (Change 1) and (Change 3). [Even if the general image starts to move, it will be erroneously detected as a [telecine image] during the five fields required for telecine detection, resulting in significant image quality deterioration.

In addition, as in (Change 2) and (Change 4), even when the telecine image starts moving, it is impossible to detect the field phase (undefined) if there are more than 1 stationary field in 5 fields. Therefore, the first 5 fields cannot be processed by Telecine Motoko.

Therefore, an object of the present invention is to output pressure detection results that reduce deterioration of reproduced images even when image signals that cannot be detected by telecine in principle are input, such as when still images continue for a long time. The purpose of the present invention is to provide a telecine image detection circuit].

[Means for Solving the Problems] The above object includes a means for detecting movement of an image between frames, a means for detecting a 5-field cycle of the motion detection result, and a means for holding the cycle detection result. This is achieved by using means for generating signals of the same period according to the period detection result.

[Operation] First, as in the conventional case, after performing inter-frame motion detection, the 5-field cycle of the motion detection results is detected, and a determination is made between a telecine image and a general image. At this time, if there is only one "still field" with no difference between frames in a 5-field period, it is considered a [telecine image], and if there is no "still field" at all, it is considered a [general image]. and stores the mode in the holding circuit. Also,
When a plurality of "still fields" exist, that is, when still images are continuous, the mode before the still image state is read from the holding circuit and outputs whether it is a telecine image or a general image. Furthermore, when there is only one "still field" among the 5 fields and the [telecine image] is determined, the free-running circuit is triggered to generate a signal with a period of 5 fields, and the field The output of the free-running circuit is used as a reference phase when a still image has an unstable phase.

By performing the above processing, cases in which there is no mode change before and after the still image (change 1) and (change 4) can be completely repaired. Furthermore, during the transition period when the still image changes to the telecine image (change 2), the image is processed as a general image, so although the image quality may deteriorate slightly, the damage will be less. Therefore, it is only in the case of (change 3) that a result similar to that of the conventional telecine detection method is obtained.

Therefore, by using the above means, it is possible to minimize the deterioration of reproduced images when still images continue for a long time, and the above object can be achieved.

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

In addition, the logical values “0” and “
1'' represents the "L level" and "'H level" of the signal, respectively.

FIG. 1 shows a specific configuration example of an embodiment of the present invention.

In the figure, the interframe motion detection circuit 100 performs
The presence or absence of movement between frames for each pixel of the input NTSC signal is detected. Here, interframe motion detection circuit 1
00 is 525H (IH is 1 horizontal scanning period: approximately 63.5μ
S) Delay circuit 1, subtraction circuit 2, low frequency of luminance signal (2M
3. A filter 3 that passes only the frequency (below Hz), and a TH setting circuit 4 that outputs a threshold value. and a comparison circuit 5 that compares the output of the filter 3 with a fixed value. The output of the interframe motion detection circuit 100 is held for one field period by the hold circuit 6, and if even one pixel moves during one field, a "motion field" is generated.
If all pixels are stationary, it is called a "static field." The periodicity of the output of the hold circuit 6 is detected using a 5-field period detection circuit 7, which will be described later. Furthermore, using this period detection result, a holding circuit 8 and a free-running circuit 9, which will be described later, determine whether the telecine mode or the general mode is selected, and detect the field phase. , these circuits are controlled by field cycle pulses generated by the control circuit 10.

Also, an integrating circuit is used instead of this hold circuit 6,
The amount of motion for each pixel may be integrated over one field period and output.

Using FIG. 2, the above-mentioned 5-field period detection circuit 7
, holding circuit 8. A more detailed configuration of the free-running circuit 9 will now be described. First, in the 5-field period detection circuit 7 shown in the figure, the output signal of the hold circuit 6 is connected in series to delay circuits 11 to 20 operated by field pulses.
Delayed by At this time, the NOR circuit 21 is used to calculate the inverted AND of the signals every 5 clocks (5 fields) delayed. Here, every 5 fields it O”(
Two consecutive periods of periodicity resulting in a stationary field are detected. Here, the number of delay circuits 11 to 20 may be increased to perform detection for two or more cycles to improve detection accuracy. Further, using the delay circuits 22 to 26, the NOR circuit 21
The output of the signal is delayed and inputted to the ROM 27. here,
``Telecine/general mode signal'', ``clock gate signal'', 1' power counter clear signal'' are generated according to the table described later.

In the holding circuit 8 shown in the figure, a field pulse signal serving as a clock is gated with a clock gate signal generated by the 5-field period detection circuit 7 using an AND circuit 28. In other words, the "clock gate signal" is
'', the clock is input to the D flip-flop 29, and the ``telecine/-general mode signal'' generated by the 5-field period detection circuit 7 is held.

In the free-running circuit 9 in the figure, the counter 30 calculates tL.
A "field phase signal" with a period of 5 fields expressed as OPI~i+4++ is generated. At this time, the "
Use the "counter clear signal" to reset the counter.

Using the above-mentioned "telecine/general mode signal" and "field phase signal", luminance-chrominance signal separation processing, sequential scanning processing, etc. suitable for [telecine image] are performed.

FIG. 3 shows the ROM used in the 5-field cycle check circuit 7.
An example of 27 tables is shown. If input signals ■0 to 4 are all 110 P+, that is, "static field"
If no one is detected in the 5 fields, it is assumed that it is a [general image] and it is used as a "clock gate signal".
1'' is output to apply a clock to the holding circuit 8, and the free-running counter 30 is not cleared.If only one of the input signals 0 to 4 is ``1'', that is, ``stand still''. If only one "field" is detected among the five fields, it is determined that it is a telecine image, and "1" is output as the "clock gate signal" to clock the holding circuit 8, and the input The self-running counter 30 is cleared only when the signal 0 is "1".If there are multiple "1"s in the input signals 0 to 4, that is, there are multiple 'stationary fields' and the field When the phase becomes unstable, the "clock gate signal" is set to "0" and the counter is not cleared. By using such a table, the continuity of the previous mode and field phase is maintained even when still images are consecutive.

FIG. 5 shows a specific configuration example of another embodiment of the present invention. Here, if [General image] is mistakenly detected as [Telecine image], image quality deterioration will be serious, and [Telecine image]
Focusing on the fact that the deterioration in image quality is slight when erroneously detecting a [general image], we decided to process a series of still images as a [general image]. Therefore, the above-mentioned mode changes, namely: (Change 1) General image → Still image → General image (Change 2) General image → Still image → Telecine image (Change 3) Telecine image →
Still image → General image (Change 4) Telecine image → Still image → Telecine image, there is no deterioration for (Change 1) and (Change 3), and for (Change 2) and (Change 4) there is no deterioration at the beginning of movement. Only 5 fields [processed as a general image]. This figure shows a modification of the circuit configuration shown in FIG. 2, and does not use the holding circuit 8 and the self-propelled port u9.

In the figure, the basic configuration of the 5-field period detection circuit N7 is the same as that in FIG. 2, but the table in the ROM 31 is different. Further, a "field phase signal" is also output from the ROM 31 along with a "telecine/general mode signal".

FIG. 6 shows an example of the table of the ROM 31 mentioned above. If all of the input signal signals 0 to I4 are 110 P+, that is, if no "still field" can be detected among the five fields, the image is set to [General image]. If only one of the input signal fields 0 to ■4 is "1", that is, only one static field is detected among the five fields, it is assumed that this is a telecine image, and the input Outputs a "field phase signal" in response to signals IO to ■4. If there are multiple "1"s among the input signals ■0 to ■4, that is, there are multiple "stationary fields" and the mode is undefined. In this case, select [General image].

By using such a table, when still images are consecutive, the signal processing of the general image is performed in a transient state such as the start of movement, and image quality deterioration due to false detection can be reduced.

In addition, [To perform telecine detection more accurately,
It is conceivable to wait for mode determination when the motion is in a transient state, and perform the determination when the motion becomes steady. That is, it is also possible to delay the image signal by several fields using a field memory or the like, and to perform a preliminary determination of the mode (mode determination of a future field) during that time.

The above explanation was based on the current NTSC signal, but it is not limited to this, and for example, MUSE
The present invention can be similarly applied to television signals such as high-definition signals and EDTV signals. Also,
The present invention is not limited to movie films, and can be similarly applied to cases where the number of transmitted frames is greater than the number of frames of the signal source (including signals in which frames of the signal source are intentionally dropped).

Furthermore, the present invention can be used not only for transmitted television signals but also for signals recorded on VTRs, video discs, and the like.

[Effects of the Invention] By applying the present invention, it is possible to accurately determine between a [telecine image] and a [-general image] by signal processing only on the television receiver side, and it is possible to accurately determine a [telecine image] and a [-general image]. Since it becomes possible to perform signal processing suitable for this purpose, the effects of implementation are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 and FIG.
Figure 4 is a diagram explaining one embodiment of the present invention in more detail.
This figure is a diagram for explaining the principle of conventional telecine detection, and FIGS. 5 and 6 are diagrams for explaining other embodiments of the present invention. Explanation of symbols 1.11, 12, 13, 14, 15, 16, 17, 18
, 19, 20, 22, 23, 24゜25.26... Delay circuit; 2... Subtraction circuit; 3... Filter; 4...
・TH setting circuit; 5... Comparison circuit; 6... Hold circuit; 7... 5-field period detection circuit; 8... Holding circuit; 9... Free-running circuit; 10... Control circuit ;21...
・NOR circuit; 27, 31...ROM; 28...A
ND circuit; 29...Flip-flop; 3o...Counter. 〆

Claims (1)

[Claims] 1. A signal detection circuit that detects that the number of frames per second of a signal source is smaller than the number of frames per second transmitted of a television signal, comprising a motion detection circuit and a periodicity of the motion detection result. a period detection circuit that detects the presence or absence of periodicity and detects the phase during the period; a holding circuit that holds the period detection result;
A signal detection circuit comprising a free-running circuit that generates signals having the same period and the same phase according to the period detection result. 2. In a signal detection circuit that detects that the number of frames per second of a signal source is smaller than the number of transmitted frames per second of a television signal, there is a motion detection circuit, and the presence or absence of periodicity of the motion detection result and periodicity. If the periodicity is detected, even if the periodicity is detected, and the phase detection result is indefinite, the detection is the same as when there is no periodicity. A signal detection circuit characterized by outputting a result.