JP2001016592A - Image encoder and image decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect overlapped fields more correctly by stopping encoding of a television signal for one frame period when overlapped fields are detected for at least once in a first field and a second field respectively and stopping encoding process for a data period insufficient in timewise by thinning the overlapped fields. SOLUTION: In a signal converter, overlapped fields are detected in a telecine signal (Vin) inputted from an input terminal 100 by an overlapped field detecting means 400 and overlapped identification information is outputted. Also, the inputted telecine signal is delayed for one frame by an overlapped field detecting means 400. On the encoding side, when overlapped fields are thinned once in first and second fields respectively, data output is stopped just for a period when they are short of two fields. On the decoding side, input of data is stopped when the overlapped fields are inserted once in the first and second fields respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal conversion apparatus for encoding or transmitting a video signal formed by removing a redundant field from a video signal formed by a 2-3 pull-down system or the like from a cinema film. The present invention relates to an image decoding device that decodes encoded data.

[0002]

2. Description of the Related Art With the development of digital storage media, techniques for compressing and encoding long-time video signals and recording the video signals on the storage media are being studied. International Organization for Standardization (IS
O), the International Electrotechnical Commission (IEC) MPE
G (Moving PictureImage Cod
ing Expert Group), a standardization activity of a moving image compression coding system is being carried out.

[0003] As is well known, the following two are used as video signals.
Kind can be considered. One is a television signal such as the NTSC system, which has 30 frames per second, and the other is a movie film, which has 24 frames per second. As a method of converting the number of frames of a movie film into the number of images of a television signal (NTSC system), a 2-3 pull-down system is known.

[0004] The 2-3 pull-down method which is often used at present is converted as shown in FIG. From the first frame of the cinema film shown in the upper part of FIG. 4, a first field and a second field shown in the middle part are formed. The third field, the fourth field, and the fifth field from the second frame of the motion picture film
Are formed. Sixth and seventh fields are formed from the third frame of the movie film, and eighth, ninth, and tenth fields are formed from the fourth frame of the movie film. Hereinafter, by repeating this, the movie film in the upper part of FIG. 4 is converted to the television signal (NTSC system) shown in the lower part, and the video signal converted from the movie film to the television signal is called a telecine signal.

[0005] It can be seen from FIG. 4 that the telecine signal converted by the 2-3 pull-down method includes an overlap field periodically. In FIG. 4, the third field and the fifth field are exactly the same field (duplicate field), and the eighth field and the tenth field are exactly the same field (duplicate field).

Therefore, if the telecine signal converted by the 2-3 pull-down method is compression-coded as it is, the redundant overlapping field is also compression-coded. Therefore, when a video signal to be compression-encoded is a telecine signal, a means for deleting a duplicated field before compression-encoding and thereafter encoding or transmitting is performed.

A conventional method for detecting and deleting an overlapping field of a telecine signal obtained by converting a motion picture film into a television signal as described above will be described with reference to FIG.

FIG. 5 is a block diagram of a conventional television signal converter. In FIG. 5, the telecine signal input from the input terminal 10 is directly input to the subtractor 50, and is also input to the subtracter 50 via the field memories (one frame delay) of the delay circuits 40 and 41, and the subtracter 50
Thus, an inter-frame difference signal is output. The one-frame difference signal output from the subtracter 50 has its absolute value taken by the absolute value circuit 60 and then the cumulative addition circuit 70 performs cumulative addition for one field. The accumulation result, which is an output from the accumulation circuit 70, is input to the comparator 80,
At 0, the predetermined threshold value input from the threshold value input terminal 30 is compared with the cumulative addition result output from the cumulative addition circuit 70, and the cumulative addition result of the cumulative addition circuit 70 is compared with the predetermined threshold value. If the value is smaller, a duplicated field is generated. If the result of the cumulative addition by the cumulative addition circuit 70 is larger than a predetermined threshold value, duplicated field identification information indicating that the field is not a duplicated field is output to the output terminal 20.

[0009]

However, the above-described conventional method for detecting a duplicated field in a television signal converter has the following problems.

(1) Noise included in a telecine signal has a great effect. This is because the result of the accumulation circuit 70 is larger than a predetermined threshold value because the noise included in the telecine signal is large, and it is an overlapping field.
It may be regarded as not a duplicated field, and the duplicated field may not be detected correctly.

The above-mentioned problem will be specifically described below with reference to FIG.

FIG. 6 is a diagram in which the output of the accumulator 70 in FIG. 5 when a certain telecine signal is input is shown on the vertical axis, and the number of fields is shown on the horizontal axis. Since the telecine signal converted by the 2-3 pull-down method includes an overlapped field periodically as described above, the accumulation circuit 7
The output result of 0 periodically decreases.

As shown in FIG. 6, when a telecine signal (scene 1) containing much noise and a telecine signal (scene 2) containing little noise are successively input as a series of telecine signals, a conventional method is used. Detecting duplicate fields causes the following problems. When the result of the accumulator circuit 70 is compared with the threshold value 1, a duplicate field can be accurately detected in the scene 1, but the result of the accumulator circuit 70 is always less than or equal to the threshold value in the scene 2. Are considered duplicate fields. When the result of the accumulation circuit 70 is compared with the threshold value 2, no duplicate field can be detected in the scene 1, and all the fields in the scene 2 are regarded as duplicate fields. Comparing the result of the accumulating circuit 70 with the threshold value 3, no duplicate field can be detected in the scene 1, and the duplicate field can be detected accurately in the scene 2. However, the thresholds 1, 2, and 3 are input from the input terminal 30 in FIG. Therefore, in such a telecine signal, the overlap method may not be able to be accurately detected by the conventional method.

(2) In the case of performing variable-length coding, there is a method in which provisional coding is performed first, parameters for main coding are determined, and then main coding is performed. At this time, detection and removal are performed during provisional coding. The duplicated field that has been added needs to match the duplicated field to be removed during the main encoding. If they do not match, the parameters at the time of the main encoding obtained at the time of the temporary encoding will be different from the parameters at the time of the main encoding.

On the other hand, if a telecine signal is reproduced and input from a recording medium such as a VTR, noise may be generated during reproduction from the recording medium. At this time, even if the same telecine signal is reproduced from the same recording medium at the time of the provisional encoding and the main encoding, different telecine signals may be reproduced due to the inclusion of noise. In such a case, the detection result of the duplicated field at the time of the provisional encoding may be different from the detection result of the duplicated field at the time of the main encoding, and the parameters in the subsequent encoding means are different from those obtained at the time of the preliminary encoding Thus, there is a problem that image quality is significantly deteriorated at the time of decoding.

(3) While the telecine signal is input at a frame rate of 30 Hz, the converted signal has a frame rate of 24 Hz, and the reference clock of the input telecine signal and the output signal, or Since the reference clocks for operating the stages are separately required, there is a problem that the circuit operation becomes unstable.

[0017]

In order to solve the above-mentioned problem (1), the present invention estimates a cumulative addition result in a field where a duplicated field exists as a noise amount, and determines whether the field is a duplicated field according to the noise amount. A predetermined threshold value serving as a criterion for detecting the presence or absence is determined, and the predetermined threshold value is updated each time a duplicate field exists.

Further, in order to solve the above-mentioned problem (2), according to the present invention, when a new series of television signals is inputted, the identification information of the duplicated field is stored in a storage device such as a memory, and is again stored. When the same series of telecine signals are input, the overlapping field is deleted using the overlapping field identification information stored in the storage device.

Further, in order to solve the above-mentioned problem (3), the present invention operates both the input telecine signal and the converted output signal at a frame rate of 30 Hz, and
The output to the next stage is stopped when it is detected once in each of the second field and the second field, and the period of the data which is short in time due to the thinning out of the duplicated field is subjected to the encoding process in the next and subsequent stages. Will be suspended. On the decoding side, the first field and the second field also
When the duplicated field is inserted each time, the input from the preceding stage is stopped, and the decoding process of the preceding stage is suspended for the period of the data which becomes redundant when the duplicated field is inserted.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, in order to solve the above-mentioned problem (1), a cumulative addition result in a field where a duplicated field exists is estimated as a noise amount included in a telecine signal, and the noise amount is used. By determining a threshold value as a criterion for determining whether or not a field is a duplicate field, and updating the threshold value each time a duplicate field exists, the duplicate field is reliably detected.

In order to solve the above-mentioned problem (2), the identification information of the duplicated field at the time of provisional encoding is stored in a storage device such as a memory, and when this encoding is performed, the duplicated information stored in the storage device is stored. By adopting a configuration in which the duplicate field is deleted using the field identification information, the duplicate field is surely deleted at the same position.

Further, with respect to the problem (3), when the encoding field decimates the duplicated fields once each in the first field and the second field, the data output is performed for a period in which two fields are insufficient. , The consistency of the difference between the number of fields of the input telecine signal and the number of fields of the converted output signal is ensured, and one reference clock can be used. On the decoding side, the first field and the second field
When the duplicated fields are inserted once in each of the fields, the data input is stopped only for the period of the surplus of two fields, thereby ensuring the consistency regarding the difference in the number of fields between the input coded signal and the converted television signal. To make it possible to use only one reference clock.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a television signal converter according to an embodiment of the present invention will be described with reference to the drawings. In the following embodiment, an NTSC television signal converted by 2-3 pull-down will be described as an example of a telecine signal. However, the present invention is not limited to such a signal, and an overlapping field is used. It goes without saying that the present invention can be applied to all signals inserted into the input television signal. Therefore, the present invention can be easily applied even when the number of scanning lines and the frame rate, such as a PAL signal and a Hi-Vision signal, are different from those in this embodiment. In this embodiment, each process is described as a circuit block for ease of explanation. However, the method of the present invention is described in a program as software, and a microcomputer, a digital signal processor (DSP), or the like is used. The present invention can be easily analogized, and is within the scope of the present invention.

First, a first embodiment of the television signal converter according to the present invention will be described. FIG. 1 is a block diagram showing the configuration of the television signal conversion device of the present invention relating to the above-mentioned problem (1). In FIG. 1, 100
Is an input terminal, and 200 is an output terminal. In the figure, reference numeral 300 denotes a VF generating means for generating a field alternation signal (VF) indicating whether a telecine signal input from the input terminal 100 is an odd-numbered field or an even-numbered field, and 400 detects a duplicated field. Duplicate field detecting means, 500 is a noise amount estimating means, and 600 is a duplicate field removing means.

The operation of the first embodiment of the present invention configured as described above will be described below.

In the telecine signal (Vin) input from the input terminal 100, a duplicate field is detected by the duplicate field detection means 400, and duplicate field identification information is output. Further, the input telecine signal is delayed by one frame in the duplicated field detecting means 400 and then input to the duplicated field removing means 600. The output of the telecine signal input to the duplicated field remover 600 is controlled by the duplicated field remover 600 in accordance with the duplicated field identification information output from the duplicated field detector 400, and output from the output terminal 200.

FIGS. 2 (a) and 2 (b) show a detailed block diagram of the duplicated field detecting means 400 and the noise amount estimating means 500 and a timing chart of each signal. In the figure, a telecine signal input from an input terminal 100 is directly subtracted by a subtracter 440.
At the same time, the signal is input to the subtractor 440 via a serial circuit (one frame delay) of the field memory constituting the delay means 430 and 431, and at the same time, from the telecine signal output terminal 410 to the overlap field removing means 600 in FIG. Output to The subtractor 440 calculates the difference between the telecine signal (Vin) input from the input terminal 100 and the output of the delay means. After the absolute value is calculated by the absolute value means 441, the one-field accumulative addition means 442 calculates the difference signal for one field. Cumulative addition of minutes is performed. The output of the one-field accumulative adding means 442 is input to the duplicated field determining means 470, and at the same time, the D-type flip-flops 450, 4
52 is input. The cumulative addition result output from the D-type flip-flop 450 is input to the D-type flip-flop 451. Match. Comparison means 510 compares the cumulative addition result of the first field and the cumulative addition result of the second field in the same frame. Comparison means 510
Then, the cumulative addition result of the first field is multiplied by a coefficient greater than 1, and the result is compared with the cumulative addition result of the second field. If the comparison result is smaller than a predetermined value, the first field is determined to be a duplicate field, The cumulative addition result of the two fields is multiplied by a coefficient greater than 1, and the result is compared with the cumulative addition result of the first field. If the comparison result is smaller than a predetermined value, the second field is determined to be a duplicate field. If each of the comparison results is larger than a predetermined value, it is determined that the field is not a duplicate field. In the figure, when an overlap field exists, the output signal from the comparison means 510 is set to low level, and when no overlap field exists, the output signal from the comparison means 510 is set to high level, and the comparison output (N
cmp) to the duplicated field determination means 470. In addition, a duplicate field selection signal (dup) indicating whether a duplicate field exists in the first field or the second field in the same frame, when a duplicate field exists in the first field, a frame of the frame in which the duplicate field exists exists. The low level is maintained from the next frame, and the low level is maintained until the duplicate field comes in the second field. When the duplicate field exists in the second field, the high level starts from the frame next to the frame in which the duplicate field exists, and This signal is maintained at a high level until a duplicate field comes in one field, and is output to the duplicate field determination means 470. The comparing means 510 outputs the result of the cumulative addition in the detected overlapping field as the amount of noise included in the telecine signal to the threshold value determining means 520. Threshold value determining means 520
Now, the duplicated field determination means 470 according to the noise amount
Is determined as a threshold value (Th) to be input.

The overlap field determination means 470 uses the comparison output (Ncmp) of the comparison means 510, the overlap field selection signal (dup) and VF, VF = low level, N
Assume that a duplicate field exists in the first field when cmp = low level, dup = high level, and that a duplicate field exists in the second field when VF = high level, Ncmp = low level, and dup = low level.
When VFNcmp and dup are in other states, a first duplicate field determination that no duplicate field exists is performed. The threshold value (Th) output from the threshold value determining means 520 and the output (s
If um) is equal to or less than the threshold value, a duplicate field is determined. A determination as to whether or not a field is a duplicate field is made based on the first and second duplicate field determinations, and a duplicate field identification signal is output to an output terminal 420.
To the duplicated field removing means 600 of FIG. In the duplicate field removing means 600, output control is performed according to the duplicate field identification information, and the output terminal 2
Output from 00.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing a second embodiment of the television signal converter according to the present invention. 3, reference numeral 1100 denotes a telecine signal input terminal 1200 denotes a selection signal input terminal, 1300 denotes a threshold input terminal, 140
0 is an output terminal of the telecine signal. Memory control means 1
Reference numeral 500 denotes a selection signal input from the input terminal 1200, which controls writing or reading to or from the memory 1600. In the figure, when the selection signal is 1, the memory control means 15
00 is controlled to perform writing to the memory 1600, and when the selection signal is 0, reading from the memory 1600 is performed. First, 1 is input to the input terminal 1200 as a selection signal, and the memory 1600 is set to the write mode. Thereafter, the telecine signal is input from the input terminal 1100 to the duplicated field detecting means 17.
00 to detect duplicate fields. The duplicate field identification signal output from the duplicate field detection means 1700 is recorded in the memory 1600 and at the same time is input to the duplicate field removal means 1800 to delete the duplicate field according to the signal. When the same telecine signal is input again, 0 is input from the input terminal 1200 of the selection signal, the memory controller 1500 is set to the reading mode, the signal of the memory 1600 is read, and the memory 1600 is read.
Is deleted by the duplicated field elimination means 1800 in accordance with the output of, and output to the output terminal 1400.

[0030]

As is apparent from the above embodiments, the television signal converter according to the present invention determines whether or not a field is an overlapping field according to the amount of conversion noise generated when converting a motion picture film into a telecine signal. By changing the threshold value used as an identification reference, it is possible to detect a duplicated field more accurately than in the conventional method where the threshold value is fixed.

By storing the identification result of the duplicated field in the storage device, the duplicated field is always stored at the same position without being affected by noise generated during reproduction of the recording medium, even if the same video signal is input again. Can be deleted.

Further, according to the present invention, it is possible to provide an efficient image encoding device and image decoding device using a 30 Hz television signal telecine-converted from a movie film or the like as an input signal source.

[Brief description of the drawings]

FIG. 1 is a block diagram of a television signal conversion device according to a first embodiment of the present invention.

FIG. 2A is a block diagram of a noise amount detecting unit and a noise amount estimating unit. FIG. 2B is a timing diagram of each signal.

FIG. 3 is a block diagram of a television signal conversion device according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the principle of a 2-3 pull-down method.

FIG. 5 is a block diagram of a conventional television signal conversion device.

FIG. 6 is an explanatory diagram showing the operation.

[Explanation of symbols]

 Reference Signs List 100 input terminal 200 output terminal 300 VF generating means 400 duplicate field detecting means 401 VF signal input terminal 430, 431 field memory 440 subtractor 441 absolute value means 442 one-field accumulative adding means 450, 451, 452 D-type flip-flop 453 not circuit 500 noise amount estimating means 510 comparing means 520 threshold value determining means 600 duplicate field removing means

Claims (2)

[Claims] 1. A television signal in which a field identical to a field corresponding to a frame immediately before a current field is periodically inserted as an overlapping field, and
An image encoding apparatus that detects a field of the duplicated television signal and performs encoding by thinning out the duplicated field, and a duplicated field detection unit that detects a field in which an input television signal is repeated. A storage unit capable of storing at least one frame of the input television signal; and a control unit that controls reading of the storage unit based on a detection result of the overlapping field detection unit. Is controlled by stopping the encoding of the television signal for one frame period when the duplicated field is detected at least once in each of the first field and the second field and decimating the duplicated field. Is configured to stop the encoding process during the period of The image coding apparatus according to claim. 2. An image decoding apparatus for forming a television signal by inserting a duplication field into a signal transmitted at a frame number smaller than a normal frame number per second of a television signal and decoding the television signal. When at least one duplication field is inserted at least once between the first field and the second field forming the television signal,
Stop decoding the television signal during a frame period,
An image decoding apparatus, characterized in that decoding processing during a period of data that becomes temporally extra due to the insertion of the duplicate field is stopped.