JPH07288808A - Image coder - Google Patents

Abstract

PURPOSE:To realize proper coding processing to image data for coding processing by setting the coding control method to each area with different image quality for a moving image and a still image or the like. CONSTITUTION:A control section 4 sets the coding mode and a coding control parameter to 1st-3rd coding control sections 8-10. The INTER+noMC mode is set to the control section 8, the INTER+MC mode is set to the control section 9, and the INTRA mode is set to the control section 10. The control section 4 sets discrimination information to a discrimination section 5. The discrimination section 5 discriminates coding control to image data fed to the coding section 6 from a memory control part 3 and gives the result of discrimination to a selection section T. The selection section 7 selects one of the control sections 8-10 based on the discrimination result to control the coding method of the coding section 6 thereby coding the image data. The coded image data are sent to a communication opposite party via a transmission IF section 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image coding apparatus for selecting a coding suitable for an image.

[0002]

2. Description of the Related Art In recent years, the development of image compression coding technology and the spread of digital communication lines have been remarkable, and TV (Televisi)
communication devices such as telephones and TV conference systems have been proposed.

However, in order to directly digitally transmit TV image data by this type of communication terminal device, a transmission speed of several hundred Mbps is required. Therefore, a method of compressing and coding and transmitting TV image data is adopted for the purpose of reducing the transmission speed and the transmission cost.

FIG. 4 is a block diagram showing a schematic configuration of a conventional image coding apparatus. In the figure, the image data input from the image input device 41 or the data created by the control unit 44 is stored in the memory 42 via the memory control unit 43. Further, the image data stored in the memory 42 passes through the memory control unit 43 and the encoding unit 4
5 is supplied. The encoding unit 45 is used by the memory control unit 4
The image data supplied from 3 is compressed and encoded for each macroblock obtained by dividing the image data into a plurality of blocks. At this time,
The encoding unit 45 includes a communication I / F (interface) unit 46.
Control is performed by feeding back the remaining amount of the transmission buffer of to determine the coding parameter.

[0005]

However, in the case of the above-mentioned conventional apparatus, the encoding is controlled by the remaining amount of the transmission buffer. With this method, if the image data to be encoded is wholly similar, the optimization of the encoding parameter is realized, but if the image data requires the encoding control to be changed. In this case, there is a problem in that the coding parameters for the macroblock to be coded are not optimized.

Therefore, as a method of controlling the coding parameter of the macroblock to be coded, a method of controlling the coding parameter based on the coding result of the macroblock several blocks before has been proposed. However, even with this method, good results are obtained when the macroblock to which the coding result is fed back is similar to the image data of the macroblock to be coded. Has a problem that the encoding parameters are not optimized.

Further, since this method is a feedback process, there is a problem that optimum coding control cannot be performed for each macroblock.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an image coding apparatus capable of performing optimized coding control in each macroblock.

[0009]

To achieve the above object, an image coding apparatus of the present invention comprises a plurality of coding control means for performing preset coding control on image data,
Setting means for setting the discrimination standard of the plurality of encoding control means is compared with the image data and the discrimination standard set by the setting means to compare the image data from the plurality of encoding control means with respect to the image data. It is characterized by further comprising: an encoding discriminating means for discriminating an encoding control means for performing the encoding control, and a selecting means for selecting the encoding control means discriminated by the encoding discriminating means. .

Further, in order to achieve the same object, as the plurality of coding control means, a first redundant spatial component is removed.
It is desirable to have the above-mentioned encoding control means, the second encoding control means for removing the temporal redundant component, and the third encoding control means for excluding the spatial redundant component and the temporal redundant component.

In order to achieve the same object, an area designating means for designating a specific area of image data and an encoding control by the encoding control means for the area designated by the area designating means are set. It is desirable to have an encoding setting means.

Further, in order to achieve the same object, a block designating means for designating a minimum unit block of image data coding processing, and coding control by the coding control means for the block designated by the block designating means. It is desirable to have an encoding setting means for performing the setting of.

[0013]

The discriminating criterion of the plural encoding control means for performing the preset encoding control on the image data is set by the setting means, and the image data is discriminated by the encoding discriminating means from the setting means. By comparing with a reference, an encoding control means for performing encoding control on the image data is discriminated from the plurality of encoding control means, and an encoding discriminated by the encoding discrimination means by the selection means. The control means is selected, and the selected encoding control means performs the encoding control.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing the schematic arrangement of an image coding apparatus according to an embodiment of the present invention. 1 in the figure
Is an image input device and supplies an image to be transmitted to the memory control unit 3. The memory control unit 3 includes the image input device 1
The image data supplied from is stored in the memory 2 and supplied to the encoding unit 6. Reference numeral 4 denotes a control unit, which includes a memory control unit 3, an encoding determination unit 5, and first, second and third encoding control units 8,
9 and 10 are controlled. The encoding determination unit 5 determines the encoding control method by the determination method described below, and supplies the determination result to the selection unit 7. The selection unit 7 determines the first to third encoding control units 8 to 10 based on the determination result of the encoding determination unit 5.
The encoding control of any of the above is supplied to the encoding unit 6. The encoding unit 6 encodes the image data supplied from the memory control unit 3 by the encoding control method selected by the selection unit 7 and sends it to the communication partner via the communication I / F (interface) unit 11. Transmit data.

FIG. 2 illustrates the operation of the device of the present invention having the above-mentioned configuration with reference to FIGS. 1 and 2. FIG. 2 is a flowchart showing the control procedure of the device of the present invention.

ITU-TS Recommendation H.264 In the H.261-compliant image coding apparatus, the motion-compensated interframe coding that uses the correlation in the temporal direction removes the temporal redundant component, and the orthogonal transform coding that uses the correlation in the spatial direction causes the spatial redundancy. A hybrid coding scheme that removes components is used. Discrete cosine transform is adopted as the orthogonal transform.

Further, as an encoding mode, an INTER (inter-frame encoding) mode in which a difference from a prediction value of a previous encoded frame is encoded, and an INTRA (frame in which an encoded frame is encoded as it is without taking a difference. Inner coding)
There are modes.

If the image is a still image in which the difference between the previous frame and the current frame does not occur, it is sufficient to reduce the temporal redundancy component in the INTER mode. Also, for an image with a small difference but a moving object, effective coding can be realized by performing motion compensation (MC).
However, for an image with a lot of movement or an image in which scene changes occur frequently, the INTRA mode must be used for encoding without taking a difference from the previous frame.

These three INTER + noMC, IN
The TER + MC and INTRA modes are adaptively switched to realize optimum coding. Further, by setting the coding control parameter such as quantization or step size to the optimum, more effective coding can be realized.

In step S201 of FIG. 2, the control unit 4 sets the coding mode and the coding control parameter in each of the first to third coding control units 8 to 10. Here, for convenience of explanation, the first encoding control unit 8 has INTER + no.
MC mode, INTER + MC in the second encoding control unit 9
Mode, the INTRA mode is set in the third encoding control unit 10.

Next, at step S202, the control section 4 sets the discrimination information of the coding discrimination section 5 in the coding discrimination section 5.
It is assumed that the image shown in FIG. 3 is transmitted to the communication partner. In the figure, 31 is an image area in which scene changes occur frequently, 32 is an image area with little movement, and 33 is a still image area.

In such a case, the control section 4 sets the coding mode of the area 31 in the coding judgment section 5 so that the coding judgment section 5 judges the third coding control section 10. In addition, the control unit 4 uses the coding determination unit 5 as the second coding control unit 9 as the coding mode of the region 32, and the coding determination unit 5 as the first coding control unit 8 as the coding mode of the region 33. Set to determine.

As a discrimination method of the encoding discriminating section 5, the area designation information from the control section 4 and the encoding control section designation information for the area are held in advance, and the memory control section 2 to the encoding section 6 are held. There is a method of determining which region the image data is in based on the position information of the image data supplied to the device and determining the encoding control unit. This method is suitable for designating a rectangular area. Further, as another determination method, there is a method of holding mapping information designated by the coding mode for all macroblocks. This method can increase the degree of freedom in the distribution of coding modes as compared with the above method.

Returning to FIG. 2 again, in steps S203 and S204, the coding determination unit 5 causes the memory control unit 3 to operate.
To determine the encoding control for the image data supplied to the encoding unit 6, and supply the determination result to the selecting unit 7. The selection unit 7 is based on the determination result of the encoding determination unit 5,
Any one of the third encoding control units 8 to 10 is selected to control the encoding method executed by the encoding unit 6. The encoding unit 6 encodes image data under the control of the encoding control unit selected by the selection unit 7 in steps S205, S206, and S207.

The processing steps will be described in detail. In step S203, the control unit 4 determines whether the determination result of the encoding determination unit 5 is the first encoding control. If it is the first coding control, the coding by the first coding control unit 8 is executed in step S207, and then step S described later.
Proceed to 208.

If it is not the first encoding control in step S203, the control unit 4 determines in step S204 whether the determination result of the encoding determination unit 5 is the second encoding control. If it is the second coding control, the coding by the second coding control unit 9 is executed in step S206, and then the process proceeds to step S208.

If it is not the second encoding control in step S204, the third encoding control unit 10 executes the encoding in step S205, and then the process proceeds to step S208.

In step S208, the encoded image data is transmitted to the communication partner via the communication I / F unit 11. Next, in step S209, the control unit 4 determines whether or not the transmission is stopped.
Return to 203. If the transmission is stopped, step S21
At 0, the control unit 4 determines whether or not the setting has been changed,
If the setting is changed, the process returns to step S201. If the setting is not changed, this processing operation ends.

In the above embodiment, ITU-TS Recommendation H.264 is used. Regarding the image coding apparatus conforming to H.261, only the case where the motion of the image data to be coded is used as the discrimination standard has been described, but the discrimination standard of the coding system and the coding control is not limited to this.

[0031]

As described above, according to the image coding apparatus of the present invention, the coding control method is set in advance for each region having different image quality such as a moving image region and a still image region. It is possible to achieve the optimum encoding process for the image data to be encoded.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image coding apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of the device.

FIG. 3 is a diagram showing an example of image data transmitted by the apparatus.

FIG. 4 is a block diagram showing a configuration of a conventional image encoding device.

[Explanation of symbols]

4 control unit (setting unit, region designating unit, coding setting unit, block designating unit) 5 coding discriminating unit (coding discriminating unit) 7 selecting unit (selecting unit) 8 first coding control unit (encoding control) Means) 9 Second encoding control unit (encoding control unit) 10 Third encoding control unit (encoding control unit)

Claims (4)

[Claims] 1. A plurality of encoding control means for performing preset encoding control on image data, a setting means for setting a discrimination criterion of the plurality of encoding control means, the image data and the setting. Encoding discrimination means for comparing the discrimination criterion set by the means to discriminate the encoding control means for performing the encoding control on the image data from the plurality of encoding control means, and the encoding discrimination An image coding apparatus comprising: a selection unit that selects the coding control unit that is discriminated by the unit. 2. As the plurality of coding control means, a first coding control means excluding a spatial redundant component, a second coding control means excluding a temporal redundant component, and a spatial redundancy. The image coding apparatus according to claim 1, further comprising a third coding control unit that removes a component and a temporal redundant component. 3. An area specifying means for specifying a specific area of image data, and an encoding setting means for setting encoding control by the encoding control means for the area specified by the area specifying means. The image coding apparatus according to claim 1, wherein: 4. A block designating means for designating a block of a minimum unit of image data coding processing, and a coding setting means for setting coding control by the coding control means for the block designated by the block designating means. The image coding apparatus according to claim 1, further comprising: