JPH0750814A - Video frame rate conversion system - Google Patents

Abstract

PURPOSE: To obtain a simplified frame rate conversion system, without 12 Hz judders by combining a pixel of a first signal frame which are superposed on a period of a present frame of a second signal with the second signal, converting a video signal of a certain frame rate into a signal of lower frame rate. CONSTITUTION: A video signal of a 60 Hz 2:1 skip format is inputted from an input circuit 2 to a processor 4 under the control of a system controller 10, and a series of frames which are displayed with 24 frames per second from a 60 Hz signal are generated there. These frames are transmitted to an EBR film transfer unit 8 through an EBR preprocessor, and a gamma corrector 6 and a complete color film frame is generated. In the processor 4, an input signal of 60 fields (F) per second is divided into two streams, and an odd number F is transmitted to a converter 42 by a memory 40. On the other hand, N and N+2 of an even number F are processed simultaneously, N+2 is transmitted to a multiplier 46, N is transmitted to a multiplier 48 by way of a circuit 44, 1/3 and 2/3 factors are multiplied respectively, added by an adder 50, transmitted to the converter 42 and a signal having lower rate is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to video frame rate conversion, and more specifically, from 60 Hz 2: 1 interlace format video signals to 2 per second commonly used in movies.
The present invention relates to a conversion system (system and device) for converting to a 4-frame (comma) film.

[0002]

Transferring video information of a 60Hz 2: 1 interlaced format signal to a 24Hz non-interlaced film using an electron beam recorder (EBR)
It is known. However, this method requires creating a 24 Hz frame from a 60 Hz field. 2 per second
Comparing a 4 frame signal to an input signal of 60 fields per second, there are 5 60 Hz input fields that occupy 2.5 video frames during the period allocated to the two 24 Hz frames, or 1/12 seconds.

One known conversion scheme is to create a first output frame from a first two input fields, ie, those corresponding to the original video frame, and a second two input field,
That is, after the second output frame is created from the one corresponding to the next original video frame, the fifth input video field is simply omitted (or ignored). The process is repeated.

In this known system, the fifth field is omitted from the original video signal, so that a 12 Hz judder (vibration) which is particularly noticeable in a moving image is generated.

In order to solve this problem, a conversion system including "motion correction time interpolation" has been proposed. This requires the production of progressive scan frames of 60 frames per second, each frame being created from one or three of the input fields. Then, an output frame of 24 frames per second is made up of a pair of progressive scan frames, and an output pixel causes a temporal misalignment between the output frame and the pair of progressive scan frames in which it was created. Calculated by interpolation to correct.

While this approach gives good results, it requires complex equipment and is therefore expensive.

Alternatively, forming a first frame from the weighted combination of the first and second progressive scan frames, a second frame from the weighted combination of the third and fourth progressive scan frames, and skipping the fifth progressive scan frame. Was proposed. The proper weighting puts the temporal centroid of the output video frame between the temporal centroids of the input fields, thus mitigating the 12 Hz judder motion resulting from skipping the fifth field or progressive scan frame. be able to.

[0008]

The above scheme is still complex, and it is an object of the invention to provide a simple frame rate conversion apparatus and method.

[0009]

SUMMARY OF THE INVENTION The present invention is a method of converting an interlaced or non-interlaced first video signal of one frame rate to another second video signal of a lower frame rate. A) weighting the pixel data of the second signal with a) weighting corresponding pixel data of a certain number of consecutive frames or fields of the first signal that temporally overlaps the period of the current frame of the second signal. B) deriving the pixel data of the second signal by adding the weighting values obtained in step a), and i) normalizing the weighting and adding steps to avoid luminance flicker, and ii) A method is provided in which all the data of the first signal is involved in the derivation of the pixel data of the second signal.

That is, of the input signal consisting of either a series of fields or a series of frames, the field (frame) related to the period of the output frame is used to create the pixels of the output frame. In that case, the pixels in each field (frame) are used to create at least one output frame, facilitating fading of the weighted pixel data of adjacent input fields (frames) from one output frame into the next. , Thereby reducing judder.

Weight (degree) applied to each corresponding pixel
Can be determined according to the amount by which the first signal frame or field of the pixel temporally overlaps the period of the current second frame.

Therefore, at the time of creating the pixels of the output frame, every input pixel is converted into the input field (frame).
Involve (contribute) directly related to the relationship between the period and the output period.

The weighting may be proportional to the amount by which the first signal frame or field of the pixel in question temporally overlaps the duration of the current second frame.

That is, the contribution of the input pixel is determined according to the relationship between the output period and the input period.

The weighting may be chosen such that it differs from the rate at which the first signal frame or field of the pixel temporally overlaps the duration of the current second frame, to alter the subjective effect. Thus, the involvement of the input pixel at the beginning of the output period is more than proportional to the output pixel, for example when the first and third fields are combined together to form the output frame. It can be weighted to contribute more or less. The first and third fields are 60%-
A 40% weighting may be applied and combined.

The method is also applicable when the first video signal is a series of non-interlaced frames produced by progressive scan conversion of a series of original interlaced fields.

From another aspect, the present invention is an apparatus for converting an interlaced or non-interlaced first video signal of a certain frame rate into a second video signal of another lower frame rate, A weighting means for weighting corresponding pixel data of a certain number of consecutive frames or fields of the first signal that overlaps in time with the current frame of the second signal, and a weighting value obtained from the weighting means are added. And then the second
Weighting means for deriving pixel data of the signal, wherein the weighting and addition means performs normalization in order to avoid luminance flicker in use, and all pixel data of the first signal is converted to pixel data of the second signal. An apparatus is provided which is used for derivation.

This second side shares the same advantages and preferred features as the first side described above.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the present invention. Under the control of the system controller 10, in the apparatus shown in the figure, a video signal of 60 Hz 2: 1 interlace format is sent from the input circuit 2 to the processor 4, where the 6
A series of frames displayed at 24 frames per second is created from the 0 Hz signal. These frames are then E
It is sent to the EBR film transfer unit 8 via the BR preprocessor (preprocessor) and the gamma corrector 6. In the case of a complete color frame, the EBR film transfer unit 8 is supplied with three color-specific frames corresponding to, for example, red, green and blue of the frame. The EBR film transfer unit drives the electron beam to scan three consecutive frames corresponding to the three color components and uses the resulting three film frames to create a full color film frame.

Looking at the timing diagram of FIG. 6, five 60
Hz fields N, N + 1, N + 2, N + 3 and N + 4
It will be appreciated that only two 24 Hz frames can be used to convey the same information within the moving period of the video involved.

In the above-mentioned "skip field" method,
Frame F1 is made of fields N and N + 1, frame F2 is made of fields N + 2 and N + 3, and field N + 4 is omitted (ignored). Similarly, frame F
3 and F4 are fields N + 5, N + 6 and N + 7, N
Made from +8, field N + 9 is dropped.

However, now in FIG. 6, a combination of fields N, N + 1 and N + 2 is used to form frame F1 and a combination of frames N + 2, N + 3 and N + 4 is used to form frame F2 and no fields are omitted. I suggest that. That is, for each 24 Hz output frame, all fields associated with the period for that output frame are used in its creation.

The output frame F1 has fields N and N + 1.
And the process of using N + 2 will be considered in more detail. Of these fields, N and N + 1 are the first and second fields of the original video frame, while N + 2 is the first field of the next original video frame. Thus, the fields N and N + 2 are combined, resulting in an "intermediate"
The output frame F1 can be created by combining the field with the field N + 1.

The process will be described with reference to FIG. The figure is a functional block diagram showing the operation of the processor 4 (FIG. 1) for the five fields of the input signals N, N + 1, N + 2, N + 3 and N + 4.

As shown in FIG. 6, for the frame F1, only half of the time allocated to the field N + 2 is in the period relating to the frame F1, whereas the time allocated to the field N + 1 is Are all within that period. Therefore, according to this scheme, the field N + 2 should contribute only 1/2 of the frame F1 compared to the field N. This alone creates an "intermediate" field from the combination of N and 1/2 (N + 2), but normalizes the participation rate (contribution) so that it does not affect the overall image brightness and Try to make the field from a combination of 2 / 3N and 1/3 (N + 2).

Therefore, as shown in FIG. 2, the corresponding pixels in fields N and N + 2 are 2/3 and 1 respectively.
Multiply the factor (factor) of / 3 and add them together to create the "middle" field. The "middle" field is
It is then combined with field N + 1 to form frame F1.

Similarly, the field N + 2 has only 50% contribution to the frame F2 as compared to the field N + 4. Therefore, combining the weighted combination of fields N + 2 and N + 4 with field N + 3, frame F2
make.

A more practical realization of the operation of the processor 4 of FIG. 1 is shown in FIG. Field division memory 4
0 acts as a buffer for an input signal of 60 fields per second and splits the signal into two streams of the same polarity, for example, odd fields directly to the field frame converter 42 and even fields to intermediate field creation processing. Supply for. A frame period delay (delay circuit) 44 is provided so that, for example, the fields N and N + 2 are simultaneously processed, and the field N + 2 is multiplied by the multiplier 46.
Then, the field N is sent to the multiplier 48. The multipliers 46 and 48 use factors of 1/3 and 2/3, which are controlled to alternate. Ie fields N and N +
For 2, multipliers 48 and 46 are 2/3 and 1/3 respectively
However, the factors of 1/3 and 2/3 are used for the fields N + 2 and N + 4, respectively. The outputs of multipliers 46 and 48 are then provided to field frame converter 42 via adder 50.

Although it has been described that the combination (combination) of the intermediate fields is performed in the processor 4 and the frame is sent to the EBR equipments 6 and 8, the fields may be sent to the EBR equipments and combined there. In this case, "same polarity"
The polarities of the video fields must be taken into account so that only the fields of the are actually electrically coupled. When printing on film, the interlaced fields are combined into one frame so that the field pairs are visible at the same time when viewed later.

Since the output frame obtained by this method includes the video information regarding the field that was ignored by the previous "skipping field" method, the transition from frame to frame is smooth and "judder" is reduced. To do. Also, since the output frames of the present scheme each contain consecutive fields of the original video frame and the combined fields are seen at the same time, the temporal field inversions that occur in frames F3 and F4 etc. are no longer a problem.

FIG. 6 also shows the video fields N, N +.
1 shows a general series of film frames (frames) F1 'to F4' which are out of phase with each other by δ.

When the proportional contribution of each field to the obtained frame is considered and its value is normalized, the following equation is obtained.

[0033]

[Equation 1] However, the period for 2u = 1 field (u = 8.3
3 ° ms), deviation between δ = 0 and the start of field N.

In the case of frames F1, F2, ..., The value δ
Since = 0, the above formula is simplified as follows.

[0035]

[Equation 2]

In the latter case, since the contribution is small, 1 /
The 5 × (N + 2) and 1/5 × (N + 5) values may be ignored, and the formula for F2 ′ then becomes simple: Combination of F2 '= N + 3 and N + 4

An example of this case is shown in FIG. In the figure, frame 1 is composed of fields N and N + 1, frame 2 is composed of a combination of fields N + 3 and N + 2 and N + 4, and frame 3 is composed of fields N + 5 and N + 6.
Consists of The same applies hereinafter.

According to the above equation, "intermediate" of frame F1 '
The field consists of a combination of 50% N and 50% N + 2. However, it is not proportional to the overlap of fields N and N + 2 with F1 ', but gives a special subjective effect.
Weightings such as a percentage of 40% can also be used.

Considering various concrete examples, the method of FIG.
Although advantageous in that it is simple in shape and requires the least amount of processing, the dynamic resolution from film frame to film frame may change. On the other hand, the δ = 0 method requires slightly more complicated processing, but has the advantage that there is no change in dynamic resolution between frames, which may lead to improved quality.

A variation of the above scheme is to first create a frame from a field by progressive scan conversion using linear interpolation or motion compensation techniques, and then rate combine the frames in the same manner as described above for the field.

In general, the video input is the previously recorded signal,
For example, a signal in the format of SMPTE 240M, which has 1125 lines per frame and 60 per second.
High definition format with field and 2: 1 interlace. Each frame has 1035 active lines and its field has 517 or 518 lines.

In this system, a Sony SIPS processor, which is a high-performance parallel processor capable of performing video processing in real time, can be used as the processor 4.

The EBR preprocessor operates at one frame per second and allows a slow transfer rate of 1/30 of the real time rate to give processor 4 sufficient time to process the video signal "without a break". .

Therefore, the digital video tape recorder in the input circuit 2 performs the reproduction operation at the slow motion speed of 1/30 and repeats each video frame 30 times. Processor 4 operates to capture one frame from each of these repeats in synchronism with this successive repeat and to assemble the series of video field sequences shown in FIG. 6 in its internal video buffer memory.

To eliminate the need for buffers in the video data path between the input circuit (DVTR) 2 and the processor 4 and between the processor 4 and the EBR preprocessor 6, 30 frames per second instead of 24 frames per second required for film.
It is preferable to operate both data paths in the repeating frame. This is accomplished by repeating one false field every two frame outputs from processor 4 and making the number of field inputs and outputs to processor 4 the same.

This "fake" field is 2 for film.
When recorded in the 4 Hz mode, it is later ejected by the EBR preprocessor 6 and the EBR film transfer unit 8. It is essential that the system controller 10 synchronize the creation and destruction of false fields.

FIG. 4 is a block diagram showing a second embodiment of the present invention. This example operates as a real-time transfer machine (tape-to-tape) that pre-processes signals before EBR conversion. As described above, the signal is input from the tape player at 60 fields per second (fps), but since the EBR system requires a "direct frame" transfer mode, that is, a signal of 24 frames per second in one-to-one frame correspondence,
The recorder at the output of the system records at 24 frames per second. Unfortunately, this system is not very practical because 24 Hz recorders are hard to come by.

FIG. 5 is a block diagram showing a practical third embodiment of the present invention using a standard video tape recorder of 60 fields per second. In this system, a buffer for receiving a signal output from a processor is used, and a video tape recorder periodically records a video signal of 24 frames per second in a "burst intermittent" operation. clearly,
If we simply replay the recorded signal, it will appear to be sped up by 30/24, ie operating at 1.25 times standard speed. However, if the signal is EB
When transferred to R equipment in 30 fps mode (ie, direct 1: 1 frame transfer), the film made will appear at the correct speed when it is finally viewed at 24 frames per second.

[0049]

As described above, according to the present invention, 1
It is possible to obtain a video frame rate conversion system in which the 2 Hz judder is reduced, the transition of the image from frame to frame is smooth, the required processing amount is small, and the configuration is simple.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a functional block diagram showing an operation of a first processor.

FIG. 3 is a block diagram showing an actual configuration of the processor of FIG.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a block diagram showing a third embodiment of the present invention.

FIG. 6 is a timing diagram showing the time relationship between a 60 Hz video input signal and a 24 frame per second output signal.

FIG. 7 is an explanatory diagram showing the relationship between a 60 fps video signal and an output of 24 frames per second according to the simplified method of the present invention.

[Explanation of symbols]

 46, 48 Weighting means 50 Addition means 42 Field frame converter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Milan Cruz Janin United Kingdom Hampshire, Basingstoke, Chinaham, Greenwood Drive 18 (72) Inventor James Bernard Pearman West Wilson Avenue 620 (72) Invention, Glendale, California, USA John William Richards Hampshire, UK Stockstock Chilbolton, Dernford Close 17

Claims (20)

[Claims] 1. A method of converting an interlaced or non-interlaced first video signal of a certain frame rate into a second video signal of another lower frame rate, the pixel data of the second signal being converted. a) weighting corresponding pixel data of a certain number of consecutive frames or fields of the first signal that temporally overlaps the period of the current frame of the second signal; and b) the weighting obtained in step a). Deriving the pixel data of the second signal by adding values, and i) normalizing the weighting and adding steps to avoid luminance flicker; ii) all the data of the first signal is A video frame rate conversion method, wherein the video frame rate conversion method is performed so as to be involved in deriving pixel data of two signals. 2. The weight applied to each corresponding pixel is determined according to the amount by which the first signal frame or field of the pixel temporally overlaps the duration of the current second frame. the method of. 3. The method of claim 2, wherein the weighting is proportional to the amount by which the first signal frame or field of the pixel temporally overlaps the duration of the current second frame. 4. The weighting is selected to be different from the rate at which the first signal frame or field of the pixel temporally overlaps the duration of the current second frame to alter the subjective effect. Item 2 method. 5. The method of claim 1, 2 or 3 wherein said second signal is an interlaced signal and field pairs of pixel data are combined to form a second signal frame. 6. The method of claim 1, wherein the first video signal is a non-interlaced signal and is produced by progressive scan conversion of the interlaced signal. 7. A method for converting 60 fields per second 2: 1 interlaced digital video signal to 24 frames per second signal, wherein first and third fields of an input 6 field sequence are combined to form a first intermediate field, The first output field is formed by combining the first intermediate field with the second field of the input 6-field sequence, and the second intermediate field is created by combining the third and fifth fields of the input 6-field sequence. 7. The method according to claim 5, wherein the fourth and sixth fields of the six-field sequence are combined to form a third intermediate field, and the second intermediate field and the third intermediate field are combined to form a second output frame. 8. The method of claim 7, wherein the first and second output frames are calculated according to the relationship: Where u = 8.33 ° ms, δ is the offset between 0 and the start of N, F1 is the matrix representing the pixels of the first output frame, and F2 is the matrix representing the pixels of the second output frame. , N, N + 1, N + 2,
N + 3, N + 4, N + 5 = input 6 field sequence. 9. With the value δ = 0, the above equation is 9. The method of claim 8 simplified to. 10. The above N + 1 and N + 5, where δ = u / 2.
The contribution of a field with respect to the second output frame is ignored and the frame is determined according to the equation:
the method of And a combination of | N + 1 | and F2 '= N + 3 and N + 4. 11. An interlaced or non-interlaced device for converting a first video signal of a certain frame rate into a second video signal of another lower frame rate, said device for converting the current frame of said second signal. Weighting means for weighting corresponding pixel data of a certain number of consecutive frames or fields of the first signal that overlaps in time with a period, and weighting values obtained from the weighting means are added to add pixels of the second signal The weighting and weighting means performs normalization to avoid luminance flicker when used, and uses all the pixel data of the first signal for deriving the pixel data of the second signal. A video frame rate conversion device characterized by: 12. The weighting applied by the weighting means to each corresponding pixel is determined according to the amount by which the first signal frame or field of the pixel temporally overlaps the duration of the current second frame. The device of claim 11. 13. The weighting is the first of the pixels.
13. The apparatus of claim 12, wherein the signal frame or field is proportional to the amount of time overlap of the current second frame period. 14. The weighting is applied to the first pixel of the pixel.
13. The apparatus of claim 12, wherein the signal frame or field is chosen to have a different temporal overlap with the current second frame period to alter the subjective effect. 15. The apparatus of claim 11, 12 or 13 wherein said second signal is an interlaced signal and including means for combining field pairs of said second signal to form a second signal frame. 16. The apparatus of claim 11, 12 or 13 wherein said first video signal is a non-interlaced signal and is produced by progressive scan conversion of the interlaced signal. 17. A device for converting 60 fields per second 2: 1 interlaced digital video signal into 24 frames per second signal, wherein first and third fields of an input 6 field sequence are combined to form a first intermediate field, The first output field is formed by combining the first intermediate field with the second field of the input 6-field sequence, and the second intermediate field is created by combining the third and fifth fields of the input 6-field sequence. 17. The apparatus of claim 15 or 16, wherein the fourth and sixth fields of the six field sequence are combined to form a third intermediate field and the second intermediate field and the third intermediate field are combined to form a second output frame. 18. The apparatus of claim 17, wherein the first and second output frames are calculated according to the relationship: Where u = 8.33 ° ms, δ is the offset between 0 and the start of N, F1 is the matrix representing the pixels of the first output frame, and F2 is the matrix representing the pixels of the second output frame. , N, N + 1, N + 2,
N + 3, N + 4, N + 5 = input 6 field sequence. 19. With the value δ = 0, the above equation is 19. The apparatus of claim 18, simplified to. 20. Where δ = u / 2, the above N + 1 and N + 5
The contribution of a field with respect to the second output frame is ignored and the frame is determined according to
8 devices And a combination of | N + 1 | and F2 '= N + 3 and N + 4.