JP3102494B2 - Signal detection circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal detection circuit, and more particularly to a circuit for detecting a television signal converted from a movie film or the like.

[Prior Art] In the current television system (NTSC system), an image is transmitted by dividing one frame into two fields by interlaced scanning, and the number of images is 30 frames per second (60 fields). In contrast, standard films such as 16mm and 35mm have 24 frames per second. When a standard screen projector is used in combination with a TV camera for film transmission, the relationship between the shutter of the projector and the scanning of the TV,
Since clear horizontal stripes that move up and down appear in the video and violent flickering is not practical, a film image is generally converted into a television signal by a projector called a telecine.

Telecine is 24 frames per second on film and 60 per second on TV
In order to make the fields correspond, 1/12 seconds is one cycle,
Convert two frames of film into five fields. In a 2-3 pull-down type telecine which is often used at present, an odd-numbered film is scraped every two fields (2/60 seconds), and an even-numbered film is scraped every three fields. Frames and 5 fields correspond.

(References: For example, 1) Yuichi Iwase, “Video Glossary,” Photo Industry Publishing Co., 198
August 9th. 2) Edited by The Institute of Television Engineers of Japan, "Television Engineering Handbook," Ohmsha, December 1969. As a method for detecting a [telecine image signal] converted from a film into a television signal as described above, for example,
There is a method described in Japanese Patent Application No. 2-45408. As described above, two frames of film correspond to five fields of a television signal. At this time, for example, as shown in FIG. 4, first and second field images are created from the first film, and third, fourth, and fifth field images are created from the second film. I do. At this time, since the low-frequency components (2 MHz or less) of the third field image and the fifth field image become completely the same signal, they become "still fields" in which no frame difference signal is generated during one field period. Repetition in a cycle is detected and determined as [telecine image].

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

If the above conventional method is used for a television receiver such as an IDTV or EDTV, [telecine image] and [general image] can be determined by signal processing only on the receiver side. Since suitable luminance-color signal separation and sequential scanning can be performed, a remarkable image quality improvement effect can be obtained.

[Problem to be Solved by the Invention] In the above conventional example, the low frequency component of the frame difference signal is compared with a certain set value TH for each pixel. If at least one pixel becomes larger than TH during one field period, the low frequency component of the frame difference is determined as a motion field, and the rest is determined as a still field. In the case of [Telecine image], the determination of [Telecine image] and [General image] is performed by using the property that the still field always appears at least once in five fields.

However, when the image itself is stationary for a long time, the [general image] has a continuous still field similarly to the [telecine image], and the two cannot be essentially distinguished. For example, in the luminance-color signal separation method and the progressive scanning method described in Japanese Patent Application No. 2-45408, for a stationary still image, the [Telecine image] and the [General image] have the same signal processing result. It does not matter which mode is used. However, when the [general image] is sequentially scanned in the telecine mode in a transient state such as the beginning of movement, a remarkable image quality deterioration such as a double image of a reproduced image occurs.

The transitional state of the movement, that is, the change of the mode sandwiching the still image includes the following four types.

(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 example, since a still image is determined to be a [telecine image], even if the [general image] starts to move as in (change 1) or (change 3), five fields necessary for performing telecine detection are used. Is incorrectly detected as a [telecine image], and significant image quality degradation occurs.

Also, even when the [Telecine image] starts to move as in (Change 2) or (Change 4), if the number of still fields is more than one out of five, the field phase cannot be detected (undefined). For this reason, the first five fields cannot be processed by the [telecine mode].

Therefore, an object of the present invention is to output a detection result such that deterioration of a reproduced image is reduced even when an image signal that cannot be detected by telecine is input in principle, such as when a still image continues for a long time [Telecine Image detection circuit].

Means for Solving the Problems The object is to provide a means for detecting a motion of an image between frames, a means for detecting a 5-field cycle of the motion detection result, a means for holding the cycle detection result, This is achieved by using means for generating a signal having the same cycle according to the cycle detection result.

[Operation] First, as in the prior art, after performing inter-frame motion detection, a 5-field period of the motion detection result is detected, and a [telecine image] and a [general image] are determined. At this time, if there is only one “still field” with no difference between frames in a 5-field cycle, [Telecine image]
If there is no "still field", the mode is set to "general image", and the mode is stored in the holding circuit. When there are a plurality of "still fields", that is, when the still images are continuous, the mode before the still image state is read out from the holding circuit and the output is [Telecine image] or [General image]. Furthermore, there is only one “still field” in the five fields, and [Telecine image]
Is established, a signal is generated in a 5-field cycle by triggering the free-running circuit, and the output of the free-running circuit is used as a reference phase in the case of a still image having an undefined field phase.

By performing the above-described processing, (change 1) and (change 4) without mode change before and after the still image can be completely relieved. [Telecine image] from the still image of (Change 2)
Since the processing is performed as a [general image] during the transition period, the image quality is slightly degraded, but the damage is reduced. Therefore, a result similar to that of the conventional telecine detection method is obtained only in the case of (change 3).

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

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. Also,
The logical values “0” and “1” used in the following description represent “L level” and “H level” of the signal, respectively.

FIG. 1 shows a specific configuration example of one embodiment of the present invention. In the figure, an inter-frame motion detection circuit 100 detects the presence or absence of inter-frame motion for each pixel of an input NTSC signal. Here, the inter-frame motion detection circuit 10
0 is 525H (1H is one horizontal scanning period: about 63.5 μs), a delay circuit 1, a subtraction circuit 2, a filter 3 for passing only a low band (2 MHz or less) of a luminance signal, a TH setting circuit 4 for outputting a threshold value, and A comparison circuit 5 compares the output of the filter 3 with a fixed value. The output of the inter-frame motion detection circuit 100 is held by the hold circuit 6 for one field period. If one pixel is moving during one field, the "motion field" is displayed. If all pixels are stationary, the "motion field" is displayed. Still field ". The periodicity of the output of the hold circuit 6 is detected using a 5-field cycle detection circuit 7 described later. Further, using this cycle detection result, the [Telecine mode] and the [General mode] are determined by the holding circuit 8 and the free-running circuit 9 described later, and the field phase is detected. These circuits are controlled by a pulse having a field period generated by the control circuit 10.

Further, an integration circuit may be used in place of the hold circuit 6, and the output obtained by integrating the motion amount for each pixel for one field period may be used.

A more detailed configuration of the above-described five-field period detection circuit 7, holding circuit 8, and free-running circuit 9 will be described with reference to FIG. First, in the five-field period detection circuit 7 in FIG. 6, the output signal of the hold circuit 6 is delayed by delay circuits 11 to 20 which are connected in series and operated by a field pulse. At this time, the NOR circuit 21 is used to take the inverted logical product of the signals every five clocks (five fields). Here, it is detected that the periodicity of "0" (still field) every five fields is continuous for two periods. Here, the number of the delay circuits 11 to 20 may be increased to perform detection for two or more cycles to improve the detection accuracy. The output of the NOR circuit 21 is further delayed by using delay circuits 22 to 26, and the ROM 27
To enter. Here, "telecine / general mode signal", "clock gate signal",
Generates a “counter clear signal”.

In the holding circuit 8 in the figure, a field pulse signal serving as a clock is gated with a clock gate signal generated by a 5-field period detection circuit 7 using an AND circuit 28. That is, only when the “clock gate signal” is “1”, the clock is input to the D flip-flop 29 and
The “telecine / general mode signal” generated by the field cycle detection circuit 7 is held.

In the self-running circuit 9 in FIG.
A "field phase signal" having a 5-field period represented by .about. "4" is generated. At this time, the "counter clear signal" generated by the 5-field period detection circuit 7 is used as a phase reference, and the counter is reset by this signal.

Using the above “telecine / general mode signal” and “field phase signal”, a luminance-color signal separation process, a sequential scanning process, and the like suitable for the [telecine image] are performed.

FIG. 3 shows the ROM 2 used in the five-field period detection circuit 7.
7 shows an example of the table of FIG. If the input signals I0 to I4 are all "0", that is, if no "still field" can be detected in five fields, it is determined to be a "general image" and "1" is output as a "clock gate signal". Then, a clock is applied to the holding circuit 8, and the self-running counter 30 is not cleared. If only one of the input signals I0 to I4 is "1", that is, if only one "still field" is detected in five fields, it is determined that it is a "telecine image" and "clock". "1" is output as a gate signal to clock the holding circuit 8, and the input signal
The self-running counter 30 is cleared only when I0 is “1”. When there are a plurality of “1” in the input signals I0 to I4, that is, when there are a plurality of “still fields” and the field phase is undefined, the “clock gate signal” is set to “0”.
And do not clear the counter. By using such a table, continuity between the previous mode and the field phase is maintained even when the still images are continuous.

FIG. 5 shows a specific configuration example of another embodiment of the present invention. Here, attention is paid to the fact that the image quality degradation is significant when the [general image] is erroneously detected as [telecine image], and the image quality degradation is small when the [telecine image] is erroneously detected as [general image]. However, when a series of still images is processed, it is processed as a [general image]. Therefore, the mode change described above, that is, (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 In image → still image → telecine image, (change 1) and (change 3) have no deterioration, and (change 2) and (change 4) are processed as [general image] for only the first five fields of motion. . This figure is a modification of the circuit configuration shown in FIG. 2, and does not use the holding circuit 8 and the free-running circuit 9. In this figure, the basic configuration of the five-field period detection circuit 7 is the same as that of FIG.
1 table is different. The ROM 31 also outputs a "field phase signal" together with the "telecine / general mode signal".

FIG. 6 shows an example of the table of the ROM 31 described above.
If the input signals I0 to I4 are all "0", that is, if no "still field" can be detected in five fields, it is determined as "general image". When only one of the input signals I0 to I4 is "1", that is, when the "still field" is 5
If only one is detected in the field, it is determined to be a "telecine image", and a "field phase signal" is output according to the input signals I0 to I4. When there are a plurality of “1” in the input signals I0 to I4, that is, when there are a plurality of “still fields” and the mode is undetermined, it is determined as “general image”. By using such a table, when a still image is continuous, signal processing of a [general image] is performed in a transient state such as a start of motion, and image quality deterioration due to erroneous detection can be reduced.

Further, in order to perform [Telecine detection] with higher accuracy, it is conceivable to wait for mode determination when the movement is in a transient state, and to make a determination when the movement becomes a steady state. In other words, the image signal can be delayed by several fields using a field memory or the like, and in the meantime, the mode advance determination (mode determination of a future field) can be performed.

The above description has been made on the assumption that the current NTSC signal is used.However, the present invention is not limited to this. For example, the present invention is similarly applied to a high definition signal such as MUSE or a television signal such as an EDTV signal. Applicable. The present invention is not limited to movie film, and the present invention is similarly applied to a case where the number of frames per second of a transmission signal is larger than the number of frames of a signal source (including a signal in which a frame of a signal source is intentionally dropped). be able to.

Further, the present invention can be used not only for a transmitted television signal but also for a signal recorded on a VTR, a video disc, or the like.

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

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIGS.
FIG. 4 is a diagram for explaining an embodiment of the present invention in more detail.
FIG. 5 is a diagram for explaining the principle of conventional telecine detection, and FIGS. 5 and 6 are diagrams for explaining another embodiment of the present invention. Explanation of reference numerals 1,11,12,13,14,15,16,17,18,19,20,22,23,24,25,26 ……
Delay circuit; 2 Subtractor circuit; 3 Filter; 4 TH setting circuit; 5 Comparison circuit; 6 Hold circuit; 7 5 Field period detection circuit; 8 Holding circuit; … Self-running circuit; 10 ……
Control circuit; 21 NOR circuit; 27, 31 ROM; 28 AND circuit;
29 …… Flip-flop; 30 …… Counter.

Continuation of the front page (56) References JP-A-4-72966 (JP, A) JP-A-4-40788 (JP, A) JP-A-3-250881 (JP, A) JP-A-3-58677 (JP) , A) JP-A-2-199970 (JP, A) JP-A-4-502545 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 7/01 H04N 5/253 H04N 9/78

Claims (2)

(57) [Claims] A signal detecting circuit for detecting a television signal obtained by converting an image of n frames into an image of m frames (m> n), wherein a motion detecting motion based on a difference signal between the frames. A detection circuit, monitoring means for monitoring the detection result of the motion detection circuit over a period of 2 m frame or more, and detecting two or more predetermined repetitive patterns continuous in the detection result within the period; Determining means for monitoring a detection result over m frame periods, and determining the television signal when the two or more predetermined repetitive patterns are detected only once during the period. Characteristic signal detection circuit. 2. The television signal according to claim 1, wherein said television signal is an NTSC television signal obtained by converting an image of two frames out of 24 frames per second into an image of 2.5 frames out of 30 frames per second. Is repeated with a period of 2.5 frames (5 fields) (without motion-with motion-with motion-
(Motion-Motion), (Motion-Motion-Motion-Motion-Motion-Motion), (Motion-Motion-Motion-No-Motion-Motion-Motion), (Motion-Motion-Motion-Motion) 2. The signal detection circuit according to claim 1, wherein the pattern is a repetition pattern of -no motion-motion present or (motion-motion present-motion present-motion present-no motion).