JPH06105969B2 - Image encoding / decoding transmission device - Google Patents

Description

The present invention relates to an image coding / decoding transmission apparatus, and more particularly to an improvement of an image coding / decoding transmission apparatus that transmits input image information at a low bit rate.

[Prior Art] As a conventional technology, for example, the image coding / decoding disclosed in "A Study on Image Quality Improvement of Low Bit Rate Video Image Transmission" in Proceedings of the 1986 National Conference of the Television Society of Japan 6-19 (page 155). There is an integrated transmission device.

FIG. 5 is a block diagram showing a configuration of a transmitting section of a conventional image coding / encoding / decoding transmission apparatus, and FIG. 6 is a block diagram showing a configuration of a receiving section.

In FIG. 5, (1) is a block divider, (2) is a frame memory, (3) is a motion compensation circuit, (4) is a motion adaptive filter, (5) coding and decoding circuit, and (6) is transmission. It is a buffer memory.

Further, FIG. 6 shows a receiving unit corresponding to the transmitting unit, and (7)
Is a reception buffer memory (8) is a decoding circuit, (9) is a frame memory, (10) is a motion compensation circuit, and (11) is a reception motion adaptive filter.

Next, the operation will be described. The A / D converted digital image signal (100) is divided by the block divider (1) into blocks of a certain size M × N (M and N are integers) to generate an input block signal (101). .

On the other hand, the frame memory (2) stores the previous frame decoded signal.

Then, the motion compensation circuit (3) generates a predicted image signal (103a) for the block input image signal (101) using the preceding frame decoded block signal (102), and inputs it in the unit of M × N blocks. Block signal (10
1) and the previous frame decoded block signal (102) are pattern-matched, and the previous frame decoded block signal (10
2) is used as the predicted image signal (103a) at the input block position, and the displacement of the block position of the preceding frame decoded block signal (102) with the minimum matching distortion with respect to the input block is a motion vector (103b). To detect as. This motion vector (103b) is transmitted to the receiving side, and the receiving side generates a predicted image signal (110) using the received motion vector information (107b).

The pattern matching method will be described below.

The input block signal is X = {x _l ... x _L }, and the previous frame decoding block signal is X '= {x _l ' ... x _L '} (L = M
XN), and the matching distortion D is defined by the following equation.

However, due to the entropy control of the motion vector information, the matching distortion D between the input block and the preceding frame block at the same position is set to a threshold value T _D (when the motion vector information is smaller than a fixed value, the motion vector is set to 0. The previous frame decoded block signal is used as a prediction signal.

Next, the prediction signal (10
Smoothing processing in 3a) is performed as follows. The predicted image signal (103a) generated by the motion compensation circuit (3) is smoothed by a motion adaptive filter (4) for the purpose of removing high frequency component noise. FIG. 7 shows the arrangement of pixels used for the filter. The value of the pixel of interest is X, and adjacent pixel 4
When the values of the points are A, B, C and D, respectively, the filter output X ′ is given by

Here, the smaller the filter coefficient α, the stronger the smoothing effect, and the larger the α, the weaker the smoothing effect.

FIG. 8 shows the characteristic of the motion adaptive filter. When the size of the motion vector amount (the motion vector (103b) detected by the motion compensation circuit (3) is small, the block can be regarded as a still region. In the still region, the difference between frames is originally a small value but smooth. Since the difference between frames is increased by applying the smoothing filter to the prediction signal, the coefficient α is increased so that the smoothing characteristic is weakened when the motion vector amount is small. Is regarded as a moving region, noise is removed with a strong smoothing characteristic.

Then, the difference between the predicted image signal (104) smoothed by the motion adaptive filter (4) and the input signal (100) is calculated, and the difference signal is calculated in pixel unit or size in the block coding / decoding circuit (5). Encoding and decoding are performed for each block of size m × n (m and n are integers) in blocks obtained by subdividing the M × N block. At this time, in the encoding / decoding circuit (5), whether or not encoding is to be performed in block units by comparing the degree of difference representing the magnitude of the difference signal in block units with a preset threshold value. After that, only the effective block described below is encoded. The determination method is shown below.

The block of the input signal is S = {S ₁ ... S _K } (K = m ×
n), the block of the predicted image signal is S ′ = {S _l ′ ...
S _K ′}, the dissimilarity d indicating the magnitude of the difference signal, and the block identification threshold value Th, the determination is made as follows.

If d ≧ Th, valid block (block for encoding) If d> Th, invalid block (block for pixel supplementation) Block coding information output from the coding / decoding circuit (5) and the block The coded information (105a) including the pixel supplement information indicating the determination result of (1) is temporarily stored in the transmission buffer memory (6) and sent out at a constant speed. On the other hand, the block coding information is decoded in the coding / decoding circuit (5) and is added to the smoothed predicted image signal (104) to generate a reproduced image signal (105b) to generate a frame. Store in memory (2).

The decoding operation of the receiving unit is the same as the operation after the encoding / decoding circuit on the transmission side.

[Problems to be Solved by the Invention] Since the motion compensation circuit of the conventional image coding / decoding / transmitting apparatus is configured as described above, in a region having a monotonous pattern in which an erroneous determination of a motion vector is likely to occur. Actually, the motion vector amount becomes large due to an erroneous determination at the time of detecting the motion vector even though it is a still region, and the smoothing is applied to the predicted image signal. Therefore, there is a problem that the difference signal increases, the amount of generated information increases as a result, and the convergence of the reproduced image becomes slower or does not converge.

The present invention has been made to solve the above problems, and reduces erroneous determination of motion compensation in a still region of an input image, and reduces image deterioration due to a smoothing filter and unnecessary amount of generated information. It is an object of the present invention to obtain an image coding / decoding transmission device capable of performing the above.

[Means for Solving the Problems] In the image coding / decoding / transmitting apparatus according to the present invention, the motion of the value having the matching distortion between the input signal block of the motion compensation circuit and the preceding frame signal block located at the same position of the block. If it is smaller than the vector detection threshold, the motion vector detection threshold and the characteristics of the motion adaptive smoothing filter are determined according to the amount of information generated at the time of frame coding under the method of setting the motion vector of the block to 0. To control.

[Operation] The amount of motion of the input image is estimated by the amount of generated information,
When the generated information amount is small, it is regarded as a stationary state, and the motion vector detection threshold for matching distortion in the motion compensation circuit is set higher than when the generated information amount is large. as a result,
The motion vector detected in the still area tends to be 0, and the smoothing action of the motion adaptive filter is weakened in the block in which the motion vector is 0. Further, at this time, even when the motion vector is erroneously determined, the smoothing characteristic of the motion adaptive filter is weakened, and the adverse effect of the smoothing filter on the still area is reduced.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show block configurations of a transmission unit and a reception unit of the image coding / decoding transmission apparatus according to the present invention.

In FIGS. 5 and 6, the same parts as those in the conventional example are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 1, in the transmitter, the amount of generated information (106b) temporarily stored in the transmission buffer memory (6) is transferred to the motion compensation circuit (3) and the motion adaptive filter (4) to generate the previous frame generated information. Latch circuit (20) that outputs as a quantity (120)
Is provided.

Then, in the motion compensation circuit (3), threshold control is performed so that the threshold value becomes higher as the previous frame generation information amount (120) becomes smaller, and the motion adaptive filter (4) controls the previous frame generation information. Based on the amount (120), the smoothing characteristic is controlled so that the smoothing action becomes weaker as the magnitude of the motion vector (103b) becomes smaller, and the smoothing becomes smoother as the preceding frame generated information amount (120) becomes smaller. It is configured to control the action to be weak.

Next, the operation will be described. In FIG. 1, the transmission buffer memory counts the generated information amount (106b) generated in (6) encoded frames, and the latch circuit (20) performs motion compensation as the previous frame generated information amount (120) at the next encoding. Output to the circuit (3) and the motion adaptive filter (4).
FIG. 3 shows an embodiment of motion vector threshold value control for matching distortion in the motion compensation circuit.

In FIG. 3, the smaller the generated information B (120) is, the higher the motion threshold value T _D is set so that the motion vector detected in the motion compensation circuit (3) easily becomes zero. In the block in which the motion vector is 0, the smoothing characteristic of the motion adaptive filter (4) is weak, or the smoothing is not performed, so the difference signal from the input signal does not increase. The motion adaptive filter (4) switches the motion vector amount vs. smoothing coefficient characteristic according to the generated information amount (120).

FIG. 4 shows an embodiment of the motion adaptive filter characteristic. When the generated information amount (120) is small, the smoothing characteristic is weak. As a result, even in the block of the still region in which the motion vector detected by the motion compensation circuit (3) becomes a larger vector due to erroneous determination, the smoothing characteristic becomes weak, and the increase of the differential signal between the block and the input signal is suppressed. be able to.

In the above operation, when the amount of generated information (120) is small, the effect of the motion compensating circuit (3) and the motion adaptive filter (4) is reduced, so that the image quality is deteriorated in the moving area.
When the input image can be regarded as a still state, most of it is a still region, and the advantage of speeding up the suppression of the generated information amount and the convergence of the reproduced image due to invalid block formation in this still region is greater.

On the other hand, in FIG. 2, the reception buffer memory detects the frame delimiter from the transmission control information using the reception information and counts the generated information amount (107c) in frame units. The generated information amount is stored in the latch circuit (21) and is input to the reception unit motion adaptive filter (11) as the previous frame generated information amount (121) at the next reception frame, so that the same operation as the transmitting side is performed.

Although the generated information amount is used for controlling the motion compensation circuit and the motion adaptive filter in the above embodiment, a method using a combination of the encoding / decoding circuit conditional pixel supplementation determination threshold value and the generated information amount is also possible. Alternatively, the number of intra-frame encoded pixels may be used instead of the generated information amount.

As described above, according to the present invention, the motion vector detection threshold value of the motion compensation circuit and the smoothing coefficient of the motion adaptive filter are controlled by using the generated information amount. This has the effect of reducing the occurrence of the amount of wasted information and speeding up the convergence in the reproduced image.

[Brief description of drawings]

In FIG. 1, FIG. 1 is a block diagram of a transmitting section of an image coding / decoding apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of a receiving section of an image coding / decoding apparatus according to an embodiment of the present invention. FIG. 3 is a motion vector detection threshold characteristic diagram of a motion compensation circuit according to an embodiment of the present invention, and FIG. 4 is a smoothing coefficient characteristic diagram of a motion adaptive filter according to an embodiment of the present invention.
FIG. 6 is a configuration diagram of a transmission unit of a conventional image encoding / decoding device,
FIG. 7 is a block diagram of a receiving unit of a conventional pixel encoding / decoding device.
The figure is a layout diagram of reference pixels of a conventional motion adaptive filter,
The figure is a characteristic diagram of the smoothing coefficient of the conventional motion adaptive filter. In the figure, (3) and (10) are motion compensation circuits, and (4)
And (11) are motion adaptive filters, and (20) and (21) are latch circuits. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

[Claims] 1. An image coding / decoding transmission apparatus comprising: a transmitter for encoding and transmitting a digital image input signal; and a receiver corresponding to the transmitter, wherein the transmitter receives a digital image input for each frame. A block divider that divides a signal into blocks of a predetermined amount (M × N pixel units) (where M and N are integers) and outputs an input block signal for each block, and decoding of the current input signal block one frame before A frame memory that stores a signal for one frame and a decoded block signal at the same position as the current input block are read from the frame memory, the degree of difference between the decoded block signal and the current input block signal is calculated, and the difference is calculated. Degree is compared with a preset threshold value, and when the difference degree is less than or equal to the threshold value, the degree of positional deviation of the previous frame decoding block with respect to the current input block is detected. A vector is set to 0, a prediction signal is generated using a decoded block signal, and when the dissimilarity is larger than a threshold value, a pre-frame decoding block within a predetermined range from the position of the current input block is generated. From among the decoded block signals having the smallest dissimilarity, a prediction signal is generated and a motion compensation circuit that calculates a motion vector of the selected block, and the motion vector is subjected to smoothing processing of the prediction signal. The motion adaptive filter to be performed, and the difference signal between the input signal and the smoothed prediction signal are encoded, and the encoded information is output as transmission data, the encoded information is decoded, and the decoded signal is stored in the frame memory. An encoding / decoding circuit for outputting, a transmission buffer memory for temporarily storing the encoded signal and outputting it as transmission data for each frame,
Including a reception buffer memory that temporarily stores a reception signal, a reception unit motion compensation circuit that generates a prediction signal based on the received motion vector, and the received motion vector for the prediction signal, A receiver motion adaptive filter that performs a smoothing process by using a decoding circuit that generates a reproduction signal based on the smoothed prediction signal and the received coding information,
A frame memory for storing the reproduction signal, wherein the transmitting unit counts the encoded information amount temporarily stored in the transmission buffer memory for each frame, and the generated information amount is used as a previous frame generated information amount. A latch circuit that outputs to a motion compensation circuit and a motion adaptive filter is provided, and the motion compensation circuit performs the threshold value control on a frame-by-frame basis so as to increase the threshold value as the previous frame generation information amount decreases, The motion adaptive filter performs smoothing processing characteristic control so that the smoothing action becomes weaker as the motion vector and the previous frame generated information amount are smaller, and the reception information amount temporarily stored in the reception buffer memory in the receiving unit. A latch circuit that counts the received information amount and outputs the received information amount to the reception unit motion adaptive filter. Data image encoding decoding transmission apparatus and performing smoothing processing based on the received motion vector and the received information amount to the prediction signal. 2. A motion compensation circuit and a motion adaptive filter of the transmitter and the receiver, wherein the number of coded pixels is used instead of the information amount or the received information amount. ) The image encoding / decoding transmission device according to the item.