JP3200196B2 - Motion vector detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a motion vector in a moving picture coding system.

[0002]

2. Description of the Related Art Video coding is performed as follows. FIG. 7 is a block diagram of a system for encoding and decoding moving images. With the input device 21,
Moving image signals of various formats such as Y, Cb, and Cr are input. The preprocessor 22 converts the data into a format required by the encoder. The encoder 23 generates a bit stream by reducing the data amount without deteriorating the input moving image as much as possible.

[0003] The storage device 24 is composed of a CD, DAT, hard disk or the like, and stores the generated bit stream. The decoder 25 receives the bit stream and creates a reproduced image. The post-processor 26 performs processing such as line interpolation, pixel interpolation, rate conversion, frame field conversion, and conversion of the pixel aspect ratio according to the specifications of the output display. The output device 27 displays and outputs the reproduced moving image.

FIG. 8 shows a block diagram of the encoder 23. As shown in FIG. Before describing the encoder 23, the encoding mode will be briefly described. Encoding modes are roughly classified into two modes: (1) intra-encoding mode and (2) non-intra-encoding mode.

In the intra coding mode, an input image is coded as it is. On the other hand, in the non-intra coding mode, that is, in the predictive coding mode, a predicted image is referred to by referring to an image that has already been coded in one of three predictive modes: forward, backward, or interpolation between them. Generated and a difference image from the predicted image is encoded.
At this time, in the case of the prediction mode and the motion compensation prediction, the motion vector is also coded at the same time.

[0006] The encoder 23 will be described. The input image data (ID) does not pass through the differentiator 301 if it is in the intra-coding mode according to the coding mode.
In the case of a non-intra coding mode, that is, a mode in which a prediction is performed and coding is performed, the prediction image (PI
D) is obtained by a differentiator 301, and the difference image (SID) is input to the DCT 302.

[0007] The transform coefficient (C) resulting from the discrete cosine transform performed by the DCT unit 302 is quantized by the quantizer 303, variable-length coded by the VLC unit 304, and stored in the buffer 305. The encoded data stored in the buffer 305 is read out at a constant rate,
M (digital storage media) and the like.

[0008] A predicted image in the non-intra coding mode is generated by the predictor from the locally decoded image stored in the frame memory of the frame memory & predictor 309. The local decoded image is encoded by the encoder at the same time as encoding.
This is an image locally decoded by performing a reverse decoding process. This is because, at the time of encoding, the data (QC) quantized by the quantizer 303 is inversely quantized by the inverse quantizer 306 and inverse DCT by the inverse DCT unit 307, and this is already stored in the frame memory 309. It is added to the predicted image generated by the predictor 309 from another local decoded image being generated by the adder 308, and is stored in the frame memory 309.

The two switches in FIG. 8, that is, a switch 311 between the difference unit 301 and the DCT unit 302
And the output of the frame memory & predictor 309 and the adder 30
The switch 312 between the inputs to 8 operates as follows.

In the intra coding mode, the switch 3
11 is connected to the lower side, ie, the ID side, and the switch 312 is connected to the upper side, ie, “0”. In the non-intra coding mode, the switch 311 is connected to the upper side, ie, the SID side, and the switch 312 is connected to the lower side, ie, the PID.

The prior art of this type is disclosed, for example, in JP-A-61-169969 and JP-A-2-11.
No. 8884 discloses a technique.

[0012]

The above-described conventional method for detecting a motion vector in the predictive coding mode employs a method for obtaining a motion vector for every pixel block. More. Therefore, there is a problem that the load on the encoder increases.

An object of the present invention is to provide a motion vector detecting method in which an image is separated into a moving area and a still area, thereby limiting a pixel block for obtaining a motion vector and reducing the load on an encoder. .

[0014]

According to the first aspect of the present invention, an independent frame is set at an arbitrary interval from a continuous frame of an input image signal, and the independent frame is set in the frame. Independently encoded, the signal of the non-independent frame between the independent frames, the motion vector detection method in the inter-frame predictive coding system to predict and code based on the signals of the previous and subsequent independent frames and their motion vectors, Separates the image of the current frame into a moving area and a still area, and separates it from the images of the previous frame and the current frame.
A moving object is detected using the extracted line images, and the moving object is detected.
A background portion is detected from the moving area based on the detection of the body, and the background is detected.
Motion vector of each block in the motion area excluding the scenery
It is characterized by seeking .

[0015]

The image input from the image input unit is stored in the current frame memory, and the previous frame image is stored in the previous frame memory. The moving area determination unit calculates the difference between the pixel values of the two blocks read from the current frame memory and the previous frame memory, and determines the moving area when the difference value is larger than a certain threshold. The motion vector detection unit obtains a motion vector for each block in the moving area.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram of a first embodiment of the present invention. In FIG. 1, 1 is an image input unit, 2
Is a current frame memory for storing a current frame, 3 is an address generator for generating an address of the current frame memory, 4 is a previous frame memory for storing a previous frame,
5 is an address generator for generating an address of the previous frame memory, 6 is a moving area determining unit that determines a moving area with reference to the current frame memory and the previous frame memory, and 7 is
A motion vector detecting unit 8 for detecting a motion vector from each block in the moving area, and an encoding unit 8 for encoding the motion vector and block data of the current frame.

The image input from the image input unit 1 is taken into the current frame memory 2. It is assumed that the image of the previous screen has been captured in the previous frame memory 4. The data blocks of the addresses generated by the address generators 3 and 5 are read from the current frame memory 2 and the previous frame memory 4, respectively, and input to the moving area determination unit 6.

The moving area determining section 6 determines a moving area. In this determination, the difference between the pixel values of the two blocks is calculated, and if the difference value is larger than a predetermined threshold value h, the block is determined to be a moving area. The data block of the current frame is input to the motion vector detection unit 7.

The motion vector detecting section 7 gives the moving area information to the address generators 3 and 5 based on the judgment result of the moving area judging section 6 (that is, designates the search range of the motion vector), and The block is read from the current frame memory 2 and the previous frame memory 4, and a motion vector is obtained. The motion vector detected by the motion vector detector 7 and the data block of the current frame are input to the encoder 8.

FIG. 2 shows images of the previous frame a and the current frame b. In the current frame b, the image of the circle indicated by the broken line (the image of the previous frame a) has moved to the position of the circle indicated by the solid line. FIG. 3 shows the moving regions 31 and 32 (hatched portions) determined by the moving region determining unit 6. The motion vectors are obtained for all the blocks determined to be the moving areas 31 and 32, but the motion vectors are not obtained for the other blocks.

As described above, in this embodiment, the image is divided into the moving area and the still area, and the motion vector is obtained only for the blocks constituting the moving area. Therefore, the load on the encoder can be reduced.

FIG. 4 is a block diagram of the second embodiment. In this embodiment, a current frame edge map memory 9, a previous frame edge map memory 10, and a moving object detection unit 11 are added to the configuration of the first embodiment. The current frame edge map memory 9 is a memory that stores a binary line image obtained by extracting an edge from the image of the current frame memory 2. Similarly, the previous frame edge map memory 10 is a memory that stores a binary line image obtained by extracting an edge from the image of the previous frame memory 4.

FIG. 5 shows an edge map a 'of the previous frame and an edge map b' of the current frame. Circles and triangles in the figure indicate line images, respectively.

The moving body detecting section 11 refers to the current frame edge map memory 9 and the previous frame edge map memory 10 to extract an object in each frame, and the correspondence between the extracted object in the current frame and the previous frame. To detect a moving object.

This embodiment is similar to the first embodiment described above.
A moving area and a still area are separated, and a motion vector of only a block in the moving area is obtained. At this time, the moving body detection unit 11
Detects a moving object from the edge map memory 9 of the current frame and the edge map memory 10 of the previous frame, and sends a detection signal to the motion vector detection unit 7.

The motion vector detecting section 7 includes the moving body detecting section 1
1, a background called an uncovered background is detected from the moving regions determined by the moving region determining unit 6, and a motion vector of each block of the moving region portion excluding the background portion is calculated. Ask.

FIG. 6 shows the background called the uncovered background in the moving area determined by the moving area determining unit 6 by a hatched portion. As described above, this uncovered background is obtained by detecting a moving object.

Further, in this embodiment, the motion vector of each object is obtained using the edge map information of the previous frame and the current frame, and the motion vector is set as the motion vector of each block belonging to each object.

As described above, when the motion vector of each block in the moving area is obtained, the motion of the image is not smooth. In contrast, the object of the motion vector is a large block size, by a representative of the motion vector of each block in the mobile, i.e. by aligning the motion vector in the moving body, the movement of the image smoothly In addition, the amount of calculation of the motion vector of the object is smaller than the amount of calculation of the motion vector of each block.

[0030]

As described above, according to the present invention , the image of the current frame is separated into a moving area and a still area, and the pixel blocks for which a motion vector is to be obtained are limited.
Since the load on the encoder can be reduced and the motion vector of the still region is not obtained, the fluctuation caused by encoding the still region as the moving region is reduced.

Further , by detecting a moving object, it is possible to detect a background portion from within a moving area, and since the motion vector of the object is representative of the motion vector of each block, the motion of the image is smooth. And the amount of calculation of the motion vector of the object is further reduced.

[Brief description of the drawings]

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

FIG. 2 shows images of a previous frame and a current frame.

FIG. 3 shows a moving area determined by a moving area determining unit.

FIG. 4 is a block diagram of a second embodiment.

FIG. 5 is a diagram showing an edge map of a previous frame and an edge map of a current frame.

FIG. 6 is a diagram in which a background called an uncovered background in a moving area is indicated by hatching.

FIG. 7 is a block diagram of a system for encoding and decoding moving images.

FIG. 8 is a block diagram of an encoder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image input part 2 Current frame memory 3, 5 Address generator 4 Previous frame memory 6 Moving area determination part 7 Motion vector detection part 8 Encoding part 9 Current frame edge map memory 10 Previous frame edge map memory 11 Moving body detection part

Claims (1)

(57) [Claims] 1. An independent frame is set at an arbitrary interval from a continuous frame of an input image signal, the independent frame is independently encoded within the frame, and a signal of a non-independent frame between the independent frames is In a motion vector detection method in an inter-frame prediction coding method of predicting and coding based on a signal of an independent frame and its motion vector, an image of a current frame is separated into a moving region and a still region, A moving object is detected by using the line images extracted from the images, a background portion is detected from the moving region based on the detection of the moving object, and each block in the moving region excluding the background portion is detected. A method for detecting a motion vector, comprising determining a motion vector.