JP4781816B2 - Image coding apparatus and image coding method - Google Patents

Description

  The present invention relates to an image encoding device and an image encoding method used for a surveillance camera or the like.

2. Description of the Related Art Conventionally, there is known a camera control device that captures an image of a monitoring area, encodes captured image data as a moving image or a still image, and transmits the encoded data to a monitor or an image storage device via a communication line (for example, see Patent Document 1) ). In this camera control apparatus, monitoring is usually performed using a moving image, and if any change occurs in the image, a still image can be transmitted in accordance with the moving image.
JP 2000-184367 A

  However, in the conventional camera control device, when the moving image encoding process and the still image encoding process are executed exclusively and are executed without considering each other's processing load, the processing load increases locally. As a result, there is a situation in which a sufficient execution time is not given to any of the processes and a local increase in dropped frames occurs. In addition, a time sharing method is known as a method for exclusively executing a plurality of processes. However, since this method does not consider the data generation amount of each encoding process to a communication line, a video code There is a situation in which an imbalance in the amount of data transmission occurs when digitized data is transmitted.

The present invention has been made in view of the above circumstances, and transmits encoded data without causing an imbalance in the amount of data transmission when data encoding by a plurality of encoding units is performed exclusively. Image encoding apparatus, image encoding method, program for executing image encoding method, and computer-readable recording medium on which program for executing image encoding method is recorded Objective.

To achieve the above object, the picture coding apparatus of the present invention is an image encoding device for exclusively executing a plurality of encoding process of encoding an image, a plurality of executing the encoding process An image encoding unit, a code amount monitoring unit that monitors a generated code amount of an image encoded by at least one image encoding unit among the encoding processes by the plurality of image encoding units, and the generated code amount When the at least one image encoding unit is controlled to approach a target code amount set according to the execution ratio of the plurality of image encoding units, and the generated code amount exceeds the target code amount In this configuration, the image encoding unit that executes the encoding process includes an encoding control unit that changes the image encoding unit monitored by the code amount monitoring unit to another image encoding unit.

With this configuration, when data encoding by a plurality of encoding means such as moving image encoding and still image encoding is performed exclusively , encoded data can be communicated without causing an imbalance in the amount of data transmission. It can be transmitted to the line.

In the image encoding device of the present invention, the encoding control unit controls at least one of a quantization parameter and an encoding type .

With this configuration, the amount of generated code can be adjusted by the encoding process, so that a stable encoded data amount can be transmitted to the communication line while performing a plurality of encoding processes exclusively. In addition, since the encoding efficiency can be adjusted by the encoding process, the generated code amount can be adjusted as a result, and a stable encoded data amount can be obtained while exclusively performing a plurality of encoding processes. Can be transmitted .

The present invention relates to an image encoding device and an image encoding device capable of transmitting encoded data without causing an imbalance in data transmission amount when data encoding by a plurality of encoding units is performed exclusively . A program for executing the method and the image encoding method can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment)

  FIG. 1 is a block diagram illustrating a configuration of an image encoding device 100 according to an embodiment of the present invention. In FIG. 1, the image encoding device 100 includes an imaging unit 101, an image input unit 102, a moving image encoding unit 103, a still image encoding unit 104, a transmission unit 105, and an encoding control unit 106. Here, the moving image encoding unit 103 and the still image encoding unit 104 are examples of an image encoding unit. The encoding control unit 106 is an example of a code monitoring unit and an encoding control unit.

  The imaging unit 101 captures a subject image. The image pickup unit 101 includes an image pickup device such as a charge coupled devices (CCD) or a complementary metal oxide semiconductor (CMOS) sensor, an A / D converter that converts a signal input to the image pickup device into digital image data, and the like. is doing. The image input unit 102 includes a buffer such as a RAM (Random Access Memory) that temporarily stores image data. The image input unit 102 captures image data from the imaging unit 101 and performs subsequent stages (the moving image encoding unit 103 and the still image). Image data output to the image encoding unit 104) is performed in parallel.

  The moving image encoding unit 103 inputs an image, performs moving image encoding, generates encoded data, and outputs the encoded data to the transmitting unit 105. As an example of the moving image coding processing method, H.264 261, H.H. 263, H.M. H.264, MPEG-1, MPEG-2, MPEG-4 and the like. The still image encoding unit 104 inputs an image, performs still image encoding, generates encoded data, and outputs the encoded data to the transmission unit 105. For the still image encoding, for example, DCT (Discrete Cosine Transform) calculation processing is used. Examples of still image encoding processing methods include JPEG and JPEG2000.

  The transmission unit 105 includes a transmission buffer that temporarily stores the encoded data generated by the moving image encoding unit 103 or the still image encoding unit 104, and transmits the transmission data to a wireless or wired communication line 107. The encoding control unit 106 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM, a timer, and the like. Also, the encoding control unit 106 controls the encoding parameters and encoding execution of the moving image encoding process of the moving image encoding unit 103, and the encoding parameters of the still image encoding process of the still image encoding unit 104 and Encoding execution is controlled, and transmission control of the transmission unit 105 is performed.

  The operation of the image coding apparatus configured as described above will be described with reference to FIG. FIG. 2 is an operation flowchart of the image encoding device 100 according to the embodiment of the present invention.

  First, the subject is photographed by the imaging unit 101 (step S201), converted into image data (step S202), and input to the image input unit. The image data input to the image input unit 102 is input to the moving image encoding unit 103 and the still image encoding unit 104, respectively. The moving image encoding unit 103 and the still image encoding unit 104 are controlled by the encoding control unit 106, and the moving image encoding unit 103 encodes the input image to generate encoded data (step S203). ). The still image encoding unit 104 encodes the input image, and generates encoded data (step S204). The transmission unit 105 transmits the encoded data generated by the moving image encoding unit 103 and the encoded data generated by the still image encoding unit 104 to the communication line 107 (step S205).

  Next, control of the moving image encoding unit 103 and the still image encoding unit 104 performed by the encoding control unit 106 will be described using the flowchart of FIG. FIG. 3 shows that the moving image encoding unit 103 and the still image encoding unit 104 according to the embodiment of the present invention are executed in parallel, and the moving image encoding unit 103 operates with higher execution priority than the still image encoding unit 104. It is an operation | movement flowchart of the image coding apparatus 100 in case the encoding control part 106 controls to do.

  First, the output code amount (= transmission rate) per unit time that can be sent to the communication line 107, the resolution and input interval of the image input from the image input unit 102 to the moving image encoding unit 103, the outside of the image encoding device 100 Alternatively, various settings (for example, image quality settings) instructed from the inside of the image encoding device 100 via the CPU, execution ratio settings of the moving image encoding unit 103 and the still image encoding unit 104, and the moving image encoding unit 103 Based on the trend of the code amount generated so far by the still image encoding unit 104 and the like, the encoding control unit 106 makes a comprehensive determination and the target generated by the moving image encoding unit 103 per frame The code amount is determined (step S301).

  Note that when the execution rate of the moving image encoding unit 103 is decreased and the execution rate of the still image encoding unit 104 is increased, the target code amount is adjusted to be increased. On the other hand, when the execution rate of the moving image encoding unit 103 is increased and the execution rate of the still image encoding unit 104 is decreased, the target code amount is adjusted to decrease.

  Next, the encoding control unit 106 operates the moving image encoding unit 103 at a timing at which image data for one frame received by the image input unit 102 can be input to the moving image encoding unit 103. This timing is preset. At this time, the code amount generated by the moving image encoding unit 103 is sequentially monitored by the encoding control unit 106, and a unit (one frame or less) so that the generated code amount per image approaches the target code amount. For example, the quantization parameter and the coding type are controlled even for a macro block and a block line (step S302).

  Note that the quantization parameter is a parameter for adjusting the amount of generated code and the image quality. Generally, the amount of generated code increases and the image quality improves because the amount of generated code decreases and the quantization distortion decreases. By increasing the quantization parameter, the generated code amount is reduced and the quantization distortion is increased, so that the image quality is lowered.

  The coding type is a parameter for adjusting the coding efficiency. When inter coding (= inter-frame coding) has already been performed on the previous image, generally, the coding type is set to intra code. (= Intra-frame coding) increases the generated code amount and eliminates the prediction error, so that the image quality is improved. By using inter coding, the generated code amount does not change greatly, and the prediction error does not change. It is said that the image quality is not lowered or greatly changed because it is accumulated without being solved.

Subsequently, when the moving image encoding unit 103 finishes the encoding process of one frame, the encoding processing unit 106 temporarily waits for the operation of the moving image encoding unit 103, and the generated code amount so far and the current frame A generated code amount per unit time (= generated rate) is calculated from the generated code amount (step S303), and compared with the target code amount (step S304).

Here, when the generation rate is lower than the target code amount , the encoding control unit 106 is at a timing at which the image data of the next frame received by the image input unit 102 can be input to the moving image encoding unit 103. 103 is operated again, and the processing after step S302 is repeated. When the generation rate exceeds the target code amount , the encoding control unit 106 does not execute the moving image encoding process for the next frame, and sets the encoding parameter for the still image encoding unit 104. Operate (step S305).

  The still image encoding process is executed until the next timing when the image data of the frame received by the image input unit 102 can be input to the moving image encoding unit 103, and the image data of the frame received by the image input unit 102 is processed. When the timing that can be input to the moving image encoding unit 103 is reached, the still image encoding process is temporarily stopped, the generation rate is calculated again according to the elapsed time (step S306), and the processes after step S304 are continued. Do.

Next, execution in the case of using MPEG-4 and JPEG as an example of a plurality of encoding means will be described.
FIG. 4 is a diagram assuming that MPEG-4 processing and JPEG processing are executed exclusively on the time axis.

  A straight line 401 indicates a time zone in which the MPEG-4 encoding by the moving image encoding unit 103 is executed. A straight line 402 indicates a time zone in which JPEG encoding is performed by the still image encoding unit 104. In FIG. 4, the encoding control unit 106 controls the JPEG encoding process to be performed while the MPEG-4 encoding process is being executed. The encoding process is performed at a rate of 1. Also, in FIGS. 4 to 6, the MPEG-4 encoding process is controlled by the encoding control unit 106 to operate with higher execution priority than the JPEG encoding process.

  Here, as shown in FIG. 5, in the conventional image encoding apparatus, the encoded data amount 502 per unit time generated by the moving image encoding unit 103 and the transmission buffer of the transmission unit 105 are transmitted to the communication line 107. The amount of transmission data to be equalized. FIG. 5 is a diagram showing the amount of generated code and the amount of transmission buffer when the time sharing method is used when executing conventional MPEG-4 and JPEG.

  Since the encoded data amount 502 is equal to the transmission data amount to the communication line 107 during the MPEG-4 encoding process, the transmission buffer residual amount 501 indicates a predetermined threshold regarding the buffer residual amount. It is constant within a range smaller than the frame drop threshold 503. On the other hand, when still image encoding is performed by the still image encoding unit 104, MPEG-4 code is not generated even if moving image encoded data is constantly transmitted to the communication line 107. May become empty (for example, refer to point A), and there may be a state (underflow) in which there is no transmittable moving image encoded data.

  Therefore, in the present embodiment, as shown in FIG. 6, the encoding control unit 106 adjusts the quantization coefficient and the coding type, thereby intentionally generating the normal generated MPEG-4 code amount 602 as shown in FIG. A code is generated with a larger generated code amount 603. FIG. 6 is a diagram showing the amount of generated code and the amount of transmission buffer when MPEG-4 and JPEG are executed in the embodiment of the present invention.

  In this case, since the MPEG-4 code amount is transmitted to the communication line 107 at a predetermined bit rate every hour, some MPEG-4 code remains in the transmission buffer. When the remaining amount 601 of the transmission buffer exceeds the frame drop threshold 604, it is determined that the next frame is not subjected to the MPEG-4 encoding process, and the period during which this MPEG-4 encoding process is not performed is the JPEG encoding process. I do. By not performing the MPEG-4 processing, the transmission buffer residual amount 601 is reduced (for example, refer to point B in FIG. 6), and it is determined that the MPEG-4 processing can be executed after the next frame. The In this way, the transmission buffer and the communication line 107 can be used more effectively.

  Next, with reference to FIG. 7 and FIG. 8, the operation at the time of encoding execution by a plurality of encoding means in the conventional and the embodiments of the present invention will be described.

  First, FIG. 7 is an operation flowchart for explaining the operation of the encoding control unit when executing conventional MPEG-4 and JPEG. It is determined in advance how many frames are to be continuously executed in MPEG-4. The encoding control unit is activated by an input completion interrupt or the like of one frame of MPEG-4 image data, and determines how many frames of MPEG-4 have been executed continuously (step S701). If the continuous frame execution number has reached the predetermined number of times, the encoding processing unit executes JPEG encoding processing (step S702). If the continuous frame execution number has not reached the predetermined number of times, the encoding processing unit 106 performs MPEG processing. -4 encoding processing is executed (step S703).

  On the other hand, FIG. 8 is an operation flowchart for explaining the operation of the encoding control unit 106 when MPEG-4 and JPEG are executed in the embodiment of the present invention. The encoding control unit 106 is activated by, for example, an input completion interrupt of MPEG-4 image data for one frame, and determines whether or not the MPEG-4 transmission buffer residual amount 601 exceeds a certain frame drop threshold 604 (step S100). S801). If the MPEG-4 transmission buffer residual amount 601 exceeds the frame drop threshold 604, the encoding control unit 106 executes JPEG encoding processing (step S802). If the MPEG-4 transmission buffer residual amount 601 does not exceed the frame drop threshold 604, the encoding control unit 106 adjusts the quantization coefficient or the ratio of intra encoding / inter encoding to adjust the MPEG-4 encoding processing. Is executed (step S803), and the transmission buffer residual amount 601 is updated (step S804).

According to such an image encoding device 100 of the embodiment of the present invention, the image encoding device 100 exclusively executes a plurality of encoding processes for encoding an image , and executes the plurality of encoding processes. Of the plurality of encoding processes performed by the moving image encoding unit 103 and the still image encoding unit 104, and the moving image encoding unit 103 and the still image encoding unit 104. A code amount monitoring unit that monitors the code amount of an image encoded by the processing, and, as a result of monitoring by the code amount monitoring unit, if the code amount exceeds a predetermined amount, By including a coding control unit 106 that changes from the moving image coding unit 103 monitored by the code amount monitoring unit to the still image coding unit 104, moving image coding and still image coding When performing data coding by a plurality of encoding means, such as exclusively, it is possible to transmit without causing imbalance data transmission amount encoded data to a communication line.

  The image encoding device 100 according to the embodiment of the present invention is based on the premise that encoded data generated by the moving image encoding process and the still image encoding process is transmitted to the outside via the communication line 107. Further, the recording unit may be configured to store in an internal or external recording medium of the encoding unit (the moving image encoding unit 103 or the still image encoding unit 104).

  The image encoding device 100 according to the embodiment of the present invention has been described on the assumption that the plurality of image encoding units are the moving image encoding unit 103 and the still image encoding unit 104. Even if both are the moving image encoding unit 103 or the still image encoding unit 104, the same effect is obtained.

  In addition, MPEG-4 is assumed as the moving image encoding process, and JPEG is assumed as the still image encoding process. Of course, other encoding processes are performed as the moving image encoding process and the still image encoding process. Has the same effect.

As described above, the image encoding apparatus according to the present invention transmits encoded data without causing an imbalance in data transmission amount when data encoding by a plurality of encoding units is performed exclusively. In addition, when moving picture coding and still picture coding are performed exclusively, the respective encoding parameters of the moving picture coding process and still picture coding process are controlled, and the generated code amount of the coding process and An image used for a surveillance camera or the like that can transmit a stable amount of moving image encoded data to a communication line while exclusively performing moving image encoding processing and still image encoding processing by controlling execution timing This is useful as an encoding device or the like.

The block diagram of the image coding apparatus in embodiment of this invention Operation flow diagram for explaining the operation of the image coding apparatus according to the embodiment of the present invention. Operation flow diagram for explaining the operation of the encoding control unit in the embodiment of the present invention Conceptual diagram regarding execution of MPEG-4 and JPEG in an embodiment of the present invention The figure which showed the amount of generated codes and the amount of transmission buffers when the time sharing method was used at the time of execution of conventional MPEG-4 and JPEG The figure which showed the generated code amount at the time of execution of MPEG-4 and JPEG in embodiment of this invention, and the amount of transmission buffers Operation flow diagram for explaining the operation of the encoding control unit at the time of execution of conventional MPEG-4 and JPEG Operation flow diagram for explaining the operation of the encoding control unit when MPEG-4 and JPEG are executed in the embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image coding apparatus 101 Image pick-up part 102 Image input part 103 Moving image coding part 104 Still image coding part 105 Transmission part 106 Encoding control part 107 Communication line

Claims (10)

An image encoding device that exclusively executes a plurality of encoding processes for encoding an image,
A plurality of image encoding unit for executing the coding process,
A code amount monitoring unit that monitors a generated code amount of an image encoded by at least one image encoding unit among the encoding processes by the plurality of image encoding units;
The at least one image encoding unit is controlled so that the generated code amount approaches a target code amount set according to an execution ratio of the plurality of image encoding units, and the generated code amount is the target code amount. An image encoding unit that executes an encoding process when the code amount is exceeded, an encoding control unit that changes the image encoding unit monitored by the code amount monitoring unit to another image encoding unit. Image encoding device. An image encoding apparatus that exclusively executes a plurality of encoding processes for encoding an image and transmits encoded data via a buffer,
A plurality of image encoding units for performing the encoding process;
A code amount monitoring unit that monitors a buffer residual amount of the buffer that holds an image encoded by at least one image encoding unit among the encoding processes by the plurality of image encoding units;
Image encoding for controlling the at least one image encoding unit so that the buffer residual amount approaches the frame drop threshold value, and executing an encoding process when the buffer residual amount exceeds the frame drop threshold value A coding control unit that changes the image coding unit monitored by the code amount monitoring unit to another image coding unit;
An image encoding device having: The image encoding device according to claim 1 , wherein:
The plurality of image encoding units are image encoding devices including a moving image encoding unit and a still image encoding unit . The image encoding device according to any one of claims 1 to 3 ,
The image encoding device, wherein the encoding control unit controls at least one of a quantization parameter and an encoding type . An image encoding method for exclusively executing a plurality of encoding processes for encoding an image,
A code amount monitoring step of monitoring a generated code amount of an image encoded in at least one of the plurality of encoding processes;
The at least one encoding process is controlled so that the generated code amount approaches a target code amount set according to an execution ratio of the plurality of encoding processes, and the generated code amount exceeds the target code amount In such a case, the image encoding method includes a step of changing the encoding process to be executed from the encoding process in which the generated code amount is monitored to another encoding process. An image encoding method for exclusively executing a plurality of encoding processes for encoding an image and transmitting encoded data via a buffer,
A code amount monitoring step of monitoring a buffer residual amount of the buffer that holds an image encoded in at least one of the plurality of encoding processes; and
The at least one encoding process is controlled so that the buffer residual amount approaches the frame drop threshold, and when the buffer residual amount exceeds the frame drop threshold, the encoding process to be executed Changing from the encoding process whose residual amount was monitored to another encoding process;
An image encoding method comprising: The image encoding method according to claim 5 or 6 , comprising:
The plurality of encoding processes is an image encoding method including a moving image encoding process and a still image encoding process. The image encoding method according to any one of claims 5 to 7 , comprising:
An image encoding method comprising a step of controlling at least one of a quantization parameter and an encoding type in the encoding process. A computer, a plurality of encoding process of encoding an image comprising a program for executing exclusively, the computer,
Image encoding means for executing the plurality of encoding processes;
Code amount monitoring means for monitoring a generated code amount of an image encoded by at least one of the plurality of encoding processes;
The at least one encoding process is controlled so that the generated code amount approaches a target code amount set according to an execution ratio of the plurality of encoding processes, and the generated code amount exceeds the target code amount If so, an encoding control means for changing the encoding process to be executed from the encoding process monitored by the code amount monitoring means to another encoding process;
Program to make it function . A program for causing a computer to exclusively execute a plurality of encoding processes for encoding an image and transmitting encoded data via a buffer, the computer comprising:
Image encoding means for executing the plurality of encoding processes;
Code amount monitoring means for monitoring a buffer residual amount of the buffer that holds an image encoded by at least one of the plurality of encoding processes; and
The at least one encoding process is controlled so that the residual amount of the buffer approaches the frame drop threshold, and when the residual amount of the buffer exceeds the frame drop threshold, the encoding process to be executed is Encoding control means for changing from the encoding process monitored by the code amount monitoring means to another encoding process;
Program to make it function .

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