JP2000134630A - Device and method for image encoding, image input device and computer readable storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently encode an image which is inputted from an image input device such as a camera having a luminance correction function and is illumination corrected. SOLUTION: An image input device 5 luminance corrects a picked up image, inputs a corrected image to an image encoder 8 as an input image 6 and, at the same time, inputs a luminance correction parameter 7 used for the luminance correction. In the image encoder 8, an encoding controller 11 decides an encoding system such as an INTRA/INTER every macro-block of the input image on the basis of a luminance correction parameter 7 and a difference value 10 between a current frame and a previous frame, the encoder 10 uses the decided encoding system, encodes the input image 6, and outputs its code sequence 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for an image encoding device and method for encoding an input image signal, an image input device such as a camera for inputting an image signal to the image encoding device, and an image encoding process. The present invention relates to a computer-readable storage medium.

[0002]

2. Description of the Related Art Conventionally, H.264, which has been established by the ITU, as a moving picture coding system for realizing a TV telephone or a TV conference at a low bit rate. 261 and H.E. 263. This divides the image into macroblocks of 16x16 pixels,
In each macroblock, an image is encoded by performing DCT, motion compensation, variable length encoding, and the like. The coding apparatus must determine whether to transmit or not transmit each macroblock, and when transmitting, must determine INTRA (transmit all data) or INTER (transmit only difference information). .

In the prior art, an image input device such as a camera is independent of an encoding device, and the encoding device determines an encoding method only by an image to be encoded. As a determination method, the difference is calculated by calculating the difference between the previous claim and the macroblock of the current frame, and comparing this difference value with a fixed threshold. In addition, many recent image input devices have a function of correcting the luminance of the entire image.

[0004]

The brightness correction function of the conventional image input apparatus is to change the brightness of the entire image uniformly. For example, as shown in FIG. Image 1 is captured by the image input device,
At time n + 1, image 2 containing object B having high brightness
Is captured, the luminance of the entire image increases, and the image input apparatus operates to reduce the luminance.
However, the brightness of the background portion A other than the object B is reduced by the brightness correction function even though it has not changed.

As a result, as shown in FIG.
In the input image whose luminance has been corrected, the input images 3 and 4 having different luminances are input to the encoding device at time n and time n + 1 even if the background image B has not changed. In such a case, when the coding apparatus determines the coding method based on the difference from the previous frame, the difference value becomes large, and the block with little change is actually coded as having large change. As a result, there is a problem that the code string becomes long.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and it is an object of the present invention to change the coding method according to the degree of luminance correction of an image input device so that coding can be performed efficiently. It is an object.

[0007]

In order to achieve the above object, in an image coding apparatus according to the present invention, a deciding means for deciding an encoding method in accordance with an input luminance correction parameter; Encoding means for encoding the image signal input together with the parameters using the determined encoding method.

Further, in the image encoding method according to the present invention, a determining procedure for determining an encoding method in accordance with the input luminance correction parameter, and an image signal input together with the luminance correction parameter are converted into the determined code. And an encoding procedure for encoding using an encoding scheme.

In the image input apparatus according to the present invention, there is provided a correction means for correcting the luminance of the image signal, and an output means for outputting the luminance correction parameter used for the luminance correction and the corrected image signal. ing.

Further, in the storage medium according to the present invention, a deciding process for deciding an encoding method in accordance with the inputted luminance correction parameter, and an image signal inputted together with the luminance compensation parameter are converted into the decided encoding method. And a program for executing an encoding process of encoding by using.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an image encoding device according to the present invention. In FIG. 1, the image input device 5 is provided with a correction unit that performs luminance correction of a captured image signal, and an output unit that outputs a luminance correction parameter used for luminance correction together with the corrected image signal. .

From the image input device 5 having the brightness correction function to the encoder 9 and the encoding controller 11 in the image encoding device 8
To the input image 6 as the corrected image signal
And the brightness correction parameter 7 are input. In addition, a difference value 10 between the image of the previous frame and the image of the current frame is sent from the encoder 9 to the encoding controller 11. The image encoding device 8 determines an encoding method for each macroblock according to the luminance correction parameter 7, encodes the image, and outputs a code sequence 12.

Next, the operation of the above configuration will be described. The image input device 5 continuously inputs the image signal as the input image 6 to the image encoding device 8. At the same time, the image input device 5 inputs the degree of correction by the luminance correction function to the image encoding device 8 as a luminance correction parameter 7 of 8 bits. That is, 0 when there is no change, and 1 when bright.
When darkening is performed in 127 levels of 〜 to 127, -1 to -12
8 is transmitted to the image encoding device 8 in 128 stages.

An encoder 9 in the image encoding device 8 includes an IT
U.U., which is a video encoding method for low bit rate communication specified by H.U. 261 or H.264. 263 encodes the image. H. 261 and H.E. In H.263, the encoding controller 11
Does not prescribe the coding control method (transmission / non-transmission, INTRA / INTER) of each macroblock in the image performed by the above, but here, coding is performed based on the sum of absolute values of the differences for each corresponding macroblock. Determine the method.

Further, a threshold value 1 for determining transmission / non-transmission is set and compared with the sum of absolute values of the differences. If the sum is smaller than the threshold value 1, non-transmission is determined, and if larger, the transmission is determined. In the case of transmission, a threshold 2 for determining INTRA / INTER encoding is set and compared with the sum of absolute values of the differences. If the sum is smaller than the threshold 2, INTER
Encoding is determined, and if large, INTRA encoding is determined. The initial values of the threshold 1 and the threshold 2 are statistically determined based on the communication rate and the image difference value.

FIG. 2 shows a flow of processing of the image encoding device 8 by the above operation. First, the encoding controller 1
In step 1, the threshold 1 used for the determination of transmission / non-transmission and the threshold 2 used for the determination of INTRA / INTER are changed according to the value of the luminance correction parameter 7 input from the image input device 5. When the luminance correction is working, the macroblock that has not changed may have a large luminance change. Therefore, each threshold is increased in proportion to the correction value. When the luminance correction is not performed, each threshold 1, 2 is set. Make smaller (step S1
~ S4).

Next, an image is input, and the difference between the macroblock of the current frame and the macroblock of the previous frame is calculated (steps S5 and S6). If the difference value is equal to or smaller than the threshold value 1, it is determined that the macro block has not changed from the previous frame and is not transmitted (steps S7 and S8). If the threshold value is larger than the threshold value 1, it is further compared with a threshold value 2 for INTRA / INTER determination.
NTRA encoding is performed, and the code string 12 is output (steps S9 to S12). If the threshold value is 2 or less, INTER
After motion compensation as an R block, only difference data is encoded and output (steps S13, S11, S12).

Next, as another embodiment of the present invention, a case where the present invention is applied to MPEG which is another encoding system will be described. In the MPEG encoding method, H.264 is used. 261 and H.E. 2
As in 63, information compression is performed using the difference between the current frame and the previous frame, and the smaller the difference value, the higher the coding efficiency. For this reason, efficient coding can be performed by using the brightness correction parameter by the brightness correction function of the image input device in the same manner as in the above embodiment.

Next, a storage medium according to the present invention will be described. The system according to each embodiment including FIG. 1 may be configured as hardware, or may be configured as a computer system including a CPU, a memory, and the like. When configured in a computer system, the memory forms a storage medium according to the present invention. The storage medium stores a program for executing the process according to the flowchart of FIG. 2 described above.

Further, as the storage medium, ROM, R
Semiconductor memory such as AM, optical disk, magneto-optical disk,
A magnetic storage medium or the like may be used, and these may be a CD-ROM,
The present invention may be applied to an FD, a magnetic card, a magnetic tape, a nonvolatile memory card, or the like.

Therefore, when the storage medium is used in another system or apparatus other than the system according to each of the above-described embodiments, and the system or the computer reads out and executes the program code stored in the storage medium, The same functions as those of the embodiments described above can be realized, the same effects can be obtained, and the object of the present invention can be achieved.

An OS running on the computer
When performing part or all of the processing, or after the program code read from the storage medium is written to a memory provided in an extended function board or an extended function unit connected to the computer, Even when the CPU or the like provided in the above-mentioned extended function board or extended function unit performs a part or all of the processing based on the instruction of the program code, the same functions as those of the embodiments can be realized and the same effects can be obtained. Can be obtained, and the object of the present invention can be achieved.

[0023]

As described above, according to the present invention,
Since the coding method of the image is determined according to the brightness correction parameter, the coding can be performed using an appropriate coding method according to the actual change of the image. For this reason, it is possible to perform efficient encoding without the output code string becoming unnecessarily long.

Further, by changing the criterion such as a threshold value for determining the coding method formula for each macroblock, coding can be performed more efficiently in accordance with the communication rate, the image difference value, and the like. . Further, by providing a first threshold for determining transmission / non-transmission of data and a second threshold for determining an encoding method at the time of transmission as this criterion, the efficiency can be further improved.

Further, according to the image input apparatus of the present invention, it is possible to input a luminance correction parameter for performing the above-described encoding to the image encoding apparatus together with the luminance-corrected image signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an image encoding device according to the present invention.

FIG. 2 is a flowchart illustrating processing of the image encoding device.

FIG. 3 is a configuration diagram illustrating an example of an input image.

FIG. 4 is a configuration diagram illustrating an example of an image subjected to a brightness correction function.

[Explanation of symbols]

 Reference Signs List 5 Image input device 6 Input image 7 Brightness correction parameter 8 Image encoding device 9 Encoder 10 Difference value 11 Encoding controller 12 Code sequence

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B057 CA01 CA08 CA12 CA16 CA19 CB01 CB08 CB12 CB16 CC01 CE11 CG02 CG03 CG05 DB02 DB06 DB09 DC22 DC36 5C059 MA00 MA05 MA23 RE15 SS20 TA17 TA60 TA71 TB07 TC00 TC03 TD12 UA02 UA39 UA39

Claims (14)

[Claims] A determining means for determining an encoding method according to the input luminance correction parameter; and an encoding method for encoding an image signal input together with the luminance correction parameter using the determined encoding method. And an image encoding device. 2. An image according to claim 1, wherein said determining means changes a criterion for determining said encoding method in accordance with a value of said luminance correction parameter for each macroblock of said image signal. Encoding device. 3. The criterion has first and second threshold values, and the determining means compares a difference value between a current frame and a previous frame of the image signal with the first threshold value. 3. The transmission method according to claim 2, wherein the transmission / non-transmission of the signal is determined by the following formula, and when the transmission is determined, the encoding method is determined by comparing the difference value with the second threshold value. Image coding device. 4. The encoding method according to claim 1, wherein the encoding method is an INTRA encoding /
2. The image encoding apparatus according to claim 1, wherein the image encoding is any one of INTER encoding. 5. The image encoding apparatus according to claim 1, further comprising image input means for inputting said image signal and a luminance correction parameter. 6. A determining procedure for determining an encoding method according to an input luminance correction parameter, and encoding for encoding an image signal input together with the luminance correction parameter using the determined encoding method. And an image encoding method. 7. The image according to claim 6, wherein in the determining step, a criterion for determining the encoding method is changed for each macroblock of the image signal according to a value of the luminance correction parameter. Encoding method. 8. The criterion includes first and second threshold values, and the determining step includes comparing a difference value between a current frame and a previous frame of the image signal with the first threshold value. 8. The transmission method according to claim 7, wherein transmission / non-transmission of the signal is determined by the following formula, and when the transmission is determined, the encoding method is determined by comparing the difference value with the seventh threshold value. Image coding method. 9. The coding method according to claim 1, wherein the coding method is INTRA coding / coding.
7. The image encoding method according to claim 6, wherein the method is any one of INTER encoding. 10. An image input apparatus, comprising: a correction unit for correcting luminance of an image signal; and an output unit for outputting a luminance correction parameter used for the luminance correction and the corrected image signal. . 11. A determination process for determining an encoding method according to an input luminance correction parameter, and encoding for encoding an image signal input together with the luminance correction parameter using the determined encoding method. And a computer-readable storage medium storing a program for executing the processing. 12. The computer-readable medium according to claim 11, wherein said determination process changes a determination criterion for determining said encoding method in accordance with a value of said correction parameter for each macroblock of said image signal. Possible storage medium. 13. The criterion includes first and second threshold values, and the determining process includes comparing a difference value between a current frame and a previous frame of the image signal with the first threshold value. 13. The transmission method according to claim 12, wherein transmission / non-transmission of a signal is determined by the following formula, and when the transmission is determined, the encoding method is determined by comparing the difference value with the seventh threshold value. Computer readable storage medium. 14. The computer-readable storage medium according to claim 11, wherein said encoding system is one of INTRA encoding and INTER encoding.