KR102337811B1 - Video compression apparatus and video compression method adaptive to a variable network environment - Google Patents

Abstract

The present invention relates to an apparatus for compressing an image, and relates to an encoder for encoding image data based on an adjustable resolution and a frame rate, a buffer for temporarily storing the encoded image data, and the encoded image temporarily stored in the buffer and a communication unit for transmitting data through a network and a control unit for adjusting at least one of the resolution and the frame rate based on a usage rate of the buffer.

Description

VIDEO COMPRESSION APPARATUS AND VIDEO COMPRESSION METHOD ADAPTIVE TO A VARIABLE NETWORK ENVIRONMENT

The present invention relates to an image compression apparatus and an image compression method, and more particularly, to an image compression apparatus and an image compression method capable of providing compressed images optimized according to network conditions in a variable narrowband network environment.

Recently, in various fields, there is an increasing demand for compressing and transmitting a video in high quality. Accordingly, video compression technology has evolved from H.264 to HEVC (High Efficiency Video Coding). HEVC has the advantage of improving the compression rate and picture quality by performing about 5 times as many operations as for encoding and 2 times as much for decoding as compared to H.264.

On the other hand, in an environment in which bandwidth is sufficiently secured and transmission through a server is possible, high-definition/large-capacity compressed video may be transmitted as it is or a technique such as Scalable Video Coding (SVC) may be applied to transmit to the terminal. However, this method cannot be applied in a limited narrowband environment, and there is a problem in that it is more difficult to apply the method to communication between a small terminal and a small terminal.

The technical problem to be solved by the present invention is an image compression apparatus and an image compression method capable of monitoring a compression transmission state between small terminals in a limited narrowband environment, analyzing a network state, and providing an optimal compression setting in response to a network state is to provide The technical problems to be achieved by the embodiments of the present invention are not limited to the above technical problems, and other technical problems may be inferred from the following embodiments.

An image compression apparatus according to an embodiment of the present invention for solving the above technical problem includes an encoder for encoding image data based on an adjustable resolution and a frame rate, a buffer for temporarily storing the encoded image data, and the and a communication unit for transmitting the encoded image data temporarily stored in a buffer through a network, and a control unit for adjusting at least one of the resolution and the frame rate based on a usage rate of the buffer.

In addition, the control unit calculates the use rate of the buffer based on the remaining memory capacity of the buffer, which varies according to a change in the bandwidth of the network.

In addition, the controller adjusts at least one of the resolution and the frame rate so that the buffer usage rate is within a preset optimal range.

In addition, the control unit sets the optimal range to 20% to 60% of the maximum use rate of the buffer.

In addition, the control unit adjusts the resolution while the frame rate is adjusted within a preset adjustment range.

In addition, the control unit obtains the usage rate of the buffer in a state in which the image data is encoded with a preset reference resolution and a reference frame rate, and sets the frame rate when the obtained usage rate is less than a lower limit value of the optimal range. Increase stepwise within the adjustment range, and when the obtained usage rate is greater than the upper limit value of the optimum range, decrease the frame rate stepwise within the adjustment range.

Also, in a state in which the frame rate is increased up to the upper limit of the adjustment range, the controller increases the resolution by a preset size when the buffer usage rate is less than the lower limit of the optimal range.

Also, in a state in which the frame rate is reduced to a lower limit value of the adjustment range, the controller decreases the resolution by a preset size when the buffer usage rate is greater than the upper limit value of the optimal range.

An image compression method according to another embodiment of the present invention for solving the above technical problem includes encoding image data based on an adjustable resolution and a frame rate, temporarily storing the encoded image data in a buffer, the buffer transmitting the encoded image data temporarily stored in a network; and adjusting at least one of the resolution and the frame rate based on a utilization rate of the buffer.

The recording medium according to another embodiment of the present invention for solving the above technical problem can be read by a computer in which a program for executing the above method is recorded in a computer.

The technical problems of the present invention are not limited to the above, and other technical problems can be inferred from the following examples.

Since the image compression apparatus and the compression method according to an embodiment of the present invention adaptively vary an encoding factor of image data according to a network state, reliability of communication performance is increased.

In addition, since the image compression apparatus and the compression method vary only the encoding factor of image data, there is an advantage in that the reliability of communication performance is improved without additional equipment or additional cost.

In addition, since the video compression apparatus and the compression method automatically vary the encoding factor according to network conditions, it guarantees rapid communication in emergency situations such as wartime.

1 is a diagram for explaining an image compression system according to an embodiment of the present invention.
2 is a flowchart illustrating an image compression method according to an embodiment of the present invention.
3 is a flowchart illustrating a method of adjusting the encoding factor of FIG. 2 .
FIG. 4 is a diagram referenced in the description of FIG. 3 .
5 is a flowchart illustrating a method of adjusting a frame rate within an optimal range of frame rates according to an embodiment of the present invention.
FIG. 6 is a diagram referenced in the description of FIG. 5 .
7 is a flowchart illustrating a resolution adjustment method according to an increase in a frame rate according to an embodiment of the present invention.
8 is a flowchart illustrating a resolution adjustment method according to a frame rate reduction according to an embodiment of the present invention.

Terms used in the embodiments are selected as currently widely used general terms as possible while considering functions in the present invention, but may vary depending on intentions or precedents of those of ordinary skill in the art, emergence of new technologies, and the like. In addition, in a specific case, there is a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the corresponding invention. Therefore, the term used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, rather than the name of a simple term.

In the entire specification, when a part "includes" a certain element, this means that other elements may be further included, rather than excluding other elements, unless otherwise stated. In addition, terms such as "unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software, or a combination of hardware and software. have.

1 is a diagram for explaining an image compression system according to an embodiment of the present invention.

Referring to the drawings, an image compression system 10 according to an embodiment of the present invention may include an image compression apparatus 100 and an image decompression apparatus 200 .

The image compression apparatus 100 includes an encoder 110 for encoding image data, a buffer 120 for temporarily storing the encoded image data, and a communication unit for transmitting the temporarily stored image data to the image decompression apparatus 200 ( 130 ) and the controller 140 for controlling the encoder 110 , the buffer 120 , and the communication unit 130 .

The encoder 110 may encode image data (video). Specifically, the encoder 110 may convert image data, which is an analog signal, into a digital signal and then compress the image data. For example, the encoder 110 may compress an image through H.264 or HEVC (High Efficiency Video Coding) codec, and may compress audio through AAC (Advanced Audio Coding) codec.

The encoder 110 may encode image data based on a resolution and a frame rate. In this case, the resolution means the number of pixels used to express one frame, and may be expressed as a product of the number of horizontal pixels and the number of vertical pixels of the frame. Also, the frame rate may mean the number of frames transmitted per second.

The initial resolution and initial frame rate of the encoder 110 may be preset. For example, the initial resolution of the encoder 110 may be 640X480, and the initial frame rate may be set to 15 FPS (Frame Per Second).

The resolution and frame rate of the encoder 110 may be varied under the control of the controller 140 . In an embodiment, the controller 140 transmits an encoding factor (FPS, resolution) to the encoder 110, and the encoder 110 may change the resolution and frame rate of image data based on the encoding factor. . Also, the encoder 110 may encode image data based on the changed resolution and frame rate.

The buffer 120 may temporarily store encoded image data. To this end, the buffer 120 may include a memory. In one embodiment, the memory may be random access memory (RAM). For example, the memory may be implemented as a first in first out (FIFO) memory, but is not limited thereto.

Meanwhile, the buffer 120 may be implemented as a part of the communication unit 130 .

The communication unit 130 may wirelessly communicate with the image decompression apparatus 200 . To this end, the communication unit 130 may include a wireless communication module.

The communication unit 130 may read the image data temporarily stored in the buffer 120 , and transmit the read image data to the image decompression apparatus 200 in real time.

On the other hand, the usage rate of the buffer 120 may be higher as the network state is unstable. If the usage rate of the buffer 120 exceeds the maximum usage, image data may be lost.

The control unit 140 may indirectly grasp the state of the network by calculating the usage rate of the buffer 120 . For example, when the usage rate of the buffer 120 is 20% to 60% of the maximum usage rate of the buffer 120 , the controller 140 may determine that the network state is good. Also, when the usage rate of the buffer 120 is less than 20% of the maximum usage rate of the buffer 120 , the controller 140 may determine that there is room in the network bandwidth. Also, when the usage rate of the buffer 120 exceeds 60% of the maximum usage rate of the buffer 120 , the controller 140 may determine that the network is unstable.

The controller 140 may calculate the usage rate of the buffer 120 based on the remaining memory capacity of the buffer 120 . The remaining memory capacity may mean the size of memory areas in which encoded image data is not stored. For example, the maximum usage rate of the buffer 120 may mean a case in which the remaining memory capacity of the buffer 120 is 0. Also, the meaning that the buffer 120 is using 20% of the maximum usage rate may mean that the remaining memory capacity of the buffer 120 is 80% of the total memory capacity of the buffer 120 . Also, the meaning that the buffer 120 is using 40% of the maximum usage rate may mean that the remaining memory capacity of the buffer 120 is 60% of the total memory capacity of the buffer 120 .

The image compression apparatus 100 according to the embodiment of the present invention sees the network state through the remaining memory capacity of the buffer 120 rather than a complicated method of calculating the round trip time (eg, Round Trip Time) of packets. It has the advantage of being able to make a simple judgment.

In addition, the image compression apparatus 100 according to the embodiment of the present invention is not a complicated method of determining the state of the buffer 120 through the packet data rate of the buffer 120 , but the remaining amount of the buffer 120 . There is an advantage that the state of the network can be more simply determined through the memory capacity.

The controller 140 may adjust at least one of a compression resolution of the encoder 110 and a compressed frame based on the usage rate of the buffer 120 .

The controller 140 may adjust at least one of a resolution and a frame rate so that the usage rate of the buffer 120 is included within a preset optimal range. The optimal range may be set to 20% to 60% of the maximum usage rate of the buffer 120 .

The controller 140 may adjust the frame rate before the resolution. The controller 140 may adjust the resolution while the frame rate is adjusted within a preset adjustment range.

Although the control unit 140 adjusts the frame rate within a preset adjustment range, when the usage rate of the buffer 120 is not within the optimal range, the controller 140 may adjust the resolution. For example, the control range may be set to 5 FPS to 30 FPS.

When the usage rate of the buffer 120 is less than the lower limit value of the optimal range, the controller 140 may increase the frame rate stepwise within the adjustment range. For example, the controller 140 may increase the frame rate in steps of 3 FPS.

When the usage rate of the buffer 120 is smaller than the lower limit of the optimal range while the frame rate is increased up to the upper limit of the adjustment range, the controller 140 may increase the resolution by a preset size.

When the usage rate of the buffer 120 is greater than the upper limit value of the optimal range, the controller 140 may reduce the frame rate in stages within the adjustment range. For example, the controller 140 may decrease the frame rate in steps of 5 FPS.

The controller 140 may increase the resolution by a preset size when the usage rate of the buffer 120 is less than the lower limit of the optimal range while the frame rate is increased up to the upper limit of the adjustment range.

Meanwhile, the image compression apparatus 100 of FIG. 1 may be disposed in an autonomous driving device such as an unmanned vehicle or a drone. In addition, the image compression apparatus 100 may be disposed in various mobile or non-mobile computing devices, such as a smart phone, a mobile phone, a personal digital assistant (PDA), a laptop, and a PC. In addition, the image data may be provided by a camera provided in the devices.

The image decompression apparatus 200 may include a communication unit 210 and a decoder 220 .

The communication unit 210 may wirelessly communicate with the image compression apparatus 100 . To this end, the communication unit 210 may include a wireless communication module. The communication unit 210 may receive encoded image data.

The decoder 220 may decode the encoded image data and provide the decoded image data to a predetermined display means (not shown).

2 is a flowchart illustrating an image compression method according to an embodiment of the present invention.

Referring to the drawings, in step S210 , the encoder 110 may encode image data based on an adjustable resolution and frame rate.

The initial resolution and initial frame rate of the encoder 110 may be preset. For example, the controller 140 may set the initial resolution of the encoder 110 to 640X480 and set the initial frame rate of the encoder 110 to 15 FPS (Frame Per Second).

In operation S220 , the buffer 120 may temporarily store the encoded image data. In an embodiment, the buffer 120 may be implemented as a part of the communication unit 130 .

In step S230 , the communication unit 130 may transmit the encoded image data temporarily stored in the buffer 120 over the network.

The communication unit 130 may read the image data temporarily stored in the buffer 120 , and transmit the read image data to the image decompression apparatus 200 through a wireless network.

In operation S240 , the controller 140 may adjust at least one of a resolution and a frame rate based on the usage rate of the buffer 120 . The usage rate of the buffer 120 may be calculated based on the remaining memory capacity of the buffer 120 .

A method of adjusting the resolution and frame rate of the controller 140 will be described in more detail below with reference to FIG. 3 .

FIG. 3 is a flowchart for explaining a method of adjusting the encoding factor of FIG. 2 , and FIG. 4 is a diagram referred to in the description of FIG. 3 .

Referring to the drawings, in step S310 of FIG. 3 , the controller 140 may calculate the usage rate of the buffer 120 based on the remaining memory size of the buffer 120 that varies according to a change in the bandwidth of the network.

Specifically, the bandwidth of the network may change frequently due to various factors, such as the surrounding environment and the distance between the terminals, between the terminal and a small terminal for which sufficient bandwidth and equipment such as a separate streaming server are not provided. In addition, such a change in the bandwidth of the network affects the usage rate of the buffer 120 . For example, as the bandwidth of the network decreases, the usage rate of the buffer 120 may increase. Conversely, as the bandwidth of the network increases, the usage rate of the buffer 120 may decrease.

Accordingly, the control unit 140 may indirectly grasp the state of the network by calculating the usage rate of the buffer 120 . For example, when the usage rate of the buffer 120 is 20% to 60% of the maximum usage rate of the buffer 120 , the controller 140 may determine that the network state is good. Also, when the usage rate of the buffer 120 is less than 20% of the maximum usage rate of the buffer 120 , the controller 140 may determine that there is room in the network bandwidth. Also, when the usage rate of the buffer 120 exceeds 60% of the maximum usage rate of the buffer 120 , the controller 140 may determine that the network is unstable.

The controller 140 may calculate the usage rate of the buffer 120 based on the remaining memory capacity of the buffer 120 . The remaining memory capacity may mean the size of memory areas in which encoded image data is not stored. For example, when the remaining memory capacity of the buffer 120 is 80% of the total memory capacity of the buffer 120 , the controller 140 may determine that the usage rate of the buffer 120 is 20% of the maximum usage rate. Also, when the remaining memory capacity of the buffer 120 is 40% of the total memory capacity of the buffer 120 , the controller 140 may determine that the usage rate of the buffer 120 is 60% of the maximum usage rate.

The total memory capacity of the buffer 120 may be preset. 4 shows various examples of the memory size of the buffer 120 . As shown in FIG. 4 , the total memory capacity of the buffer 120 may be determined by a resolution, a frame rate, a size per pixel, and a buffering time. The memory of the buffer 120 may be designed with any one of the buffer sizes of FIG. 4 .

Again in step S320 of FIG. 3 , the controller 140 may adjust at least one of a resolution and a frame rate so that the usage rate of the buffer 120 is included within a preset optimal range.

The optimal range may be experimentally set to 20% to 60% of the maximum use rate of the buffer 120 .

The controller 140 may adjust the frame rate before the resolution. The controller 140 may adjust the resolution while the frame rate is adjusted within a preset adjustment range.

5 is a flowchart for explaining a method of adjusting a frame rate within an optimal range of a frame rate according to an embodiment of the present invention, and FIG. 6 is a diagram referred to in the description of FIG. 5 .

Referring to the drawings, in step S510 of FIG. 5 , the controller 140 may obtain the usage rate of the buffer 120 in a state in which image data is encoded with a reference resolution and a reference frame rate.

The reference resolution is a preset value and may have the same meaning as the initial resolution. Similarly, the reference frame rate is a preset value and may have the same meaning as the initial frame rate.

The reference resolution and reference frame rate may be initially set based on the theoretical bandwidth of the network. 6 is a diagram for explaining a reference resolution and a reference frame rate according to a theoretical bandwidth.

As shown in FIG. 6 , the controller 140 may set the reference resolution to 176X144 when the theoretical bandwidth is less than 64 kbps. Also, when the theoretical bandwidth is 64 kbps to 256 kbps, the controller 140 may set the reference resolution to 352X288. Also, when the theoretical bandwidth is 256 kbps to 512 kbps, the controller 140 may set the reference resolution to 640X480. In addition, the controller 140 may set the reference resolution to 1280X720 when the theoretical bandwidth is 1024 kbps or more. For convenience of control, in FIG. 6 , the controller 140 sets the reference frame rate to 15 FPS, but may adjust the frame rate in the range of 5 FPS to 30 FPS.

In step S520 of FIG. 5 again, the controller 140 may determine whether the usage rate of the buffer 120 is included in the optimal range. The optimal range may be set to 20% to 60% of the maximum usage rate of the buffer 120 .

In step S530 , when the usage rate of the buffer 120 is within the optimum range, the controller 140 may determine the reference frame rate as the optimum frame rate.

In operation S540 , the controller 140 may encode the image data based on the optimal frame rate. The encoded image may be temporarily stored in the buffer 120 and then transmitted to the image decompression apparatus 200 by the communication unit 130 .

Meanwhile, in step S550 , when the usage rate of the buffer 120 is not included in the optimal range, the controller 140 may adjust the frame rate. In other words, when the usage rate of the buffer 120 is not within the optimal range, the controller 140 may increase or decrease the reference frame rate. A method of adjusting the frame rate will be described in more detail below with reference to FIG. 7 .

7 is a flowchart illustrating a resolution adjustment method according to an increase in a frame rate according to an embodiment of the present invention.

In more detail, FIG. 7 is a flowchart illustrating a method of adjusting the frame rate and resolution when the usage rate of the buffer 120 is smaller than the lower limit of the optimal range.

Referring to the drawings, in step S710 , when the usage rate of the buffer 120 is less than the lower limit value (eg, 20%) of the optimal range, the control unit 140 increases the frame rate stepwise within a preset adjustment range. can do it The control range may range from 5 FPS to 30 FPS.

In an embodiment, the controller 140 may increase the frame rate in steps of 3 FPS within the adjustment range.

In step S720 , the controller 140 may calculate whether the usage rate of the buffer 120 obtained while the frame rate is increased by one step (3 FPS) is within an optimal range.

In step S730 , when the usage rate of the buffer 120 is within the optimum range, the controller 140 may determine the frame rate increased by one step (3 FPS) from the reference frame rate as the optimum frame rate.

In operation S540 , the controller 140 may encode the image data based on the optimal frame rate. The encoded image may be temporarily stored in the buffer 120 and then transmitted to the image decompression apparatus 200 by the communication unit 130 .

On the other hand, in step S750 , when the usage rate of the buffer 120 obtained while the frame rate is increased by one step (3 FPS) is not within the optimal range, the frame rate reaches the upper limit value of the adjustment range It can be determined whether or not

The controller 140 may increase the frame rate in stages when the usage rate of the buffer 120 obtained while the frame rate is increased by one step (3 FPS) does not reach the upper limit value of the adjustment range. In other words, the controller 140 may increase the frame rate in stages until the frame rate reaches the upper limit value of the adjustment range.

In step S760 , when the frame rate reaches the upper limit of the adjustment range, the controller 140 may increase the reference resolution by a preset size. For example, when the reference resolution is 640X480 and the frame rate reaches the upper limit value of the adjustment range, the controller 140 may decrease the reference resolution by one step from 640X480 to 1280X720. The increase size of the reference resolution may be set in consideration of the frame standard.

The controller 140 may determine the optimal frame rate by adjusting the frame rate at the increased reference resolution. In other words, the controller 140 may re-perform steps S710 to S760 according to the increased reference resolution.

8 is a flowchart illustrating a resolution adjustment method according to a frame rate reduction according to an embodiment of the present invention.

In more detail, FIG. 8 is a flowchart for explaining a method of adjusting the frame rate and resolution when the usage rate of the buffer 120 is greater than the upper limit value of the optimal range.

Referring to the drawings, in step S810 , when the usage rate of the buffer 120 is greater than the upper limit value (eg, 60%) of the optimal range, the control unit 140 reduces the frame rate stepwise within a preset adjustment range. can do it The control range may range from 5 FPS to 30 FPS.

The absolute value of the decrease in the frame rate may be set to be larger than the absolute value of the increase in the frame rate in FIG. 7 . In an embodiment, the controller 140 may decrease the frame rate in steps of 5 FPS within the adjustment range. This is by setting a large increase in the frame rate when the bandwidth is relaxed, so there is no need to decrease the communication reliability due to the weight of the buffer 120 , and when the bandwidth is larger than the upper limit of the optimal range, the decrease in bandwidth is insufficient This is because it is necessary to prevent frame dropping or transmission loss occurring due to the limited memory capacity of the buffer 120 by setting the value to be large.

In step S820 , the controller 140 may calculate whether the usage rate of the buffer 120 obtained while the frame rate is reduced by one step (5 FPS) is within an optimal range.

In operation S830 , when the usage rate of the buffer 120 is within the optimal range, the controller 140 may determine a frame rate reduced by one step (3 FPS) from the reference frame rate as the optimal frame rate.

In operation S840, the controller 140 may encode the image data based on the optimal frame rate. The encoded image may be temporarily stored in the buffer 120 and then transmitted to the image decompression apparatus 200 by the communication unit 130 .

On the other hand, in step S850 , when the use rate of the buffer 120 obtained while the frame rate is reduced by one step (5 FPS) is not included within the optimal range, the frame rate reaches the lower limit of the adjustment range. It can be determined whether or not

When the usage rate of the buffer 120 obtained while the frame rate is reduced by one step (5 FPS) does not reach the lower limit of the adjustment range, the controller 140 may decrease the frame rate in stages. In other words, the controller 140 may decrease the frame rate in stages until the frame rate reaches the lower limit of the adjustment range.

In operation S860 , when the frame rate reaches the lower limit of the adjustment range, the controller 140 may decrease the reference resolution by a preset size. For example, when the reference resolution is 640X480 and the frame rate reaches the lower limit of the adjustment range, the controller 140 may decrease the reference resolution by one step from 640X480 to 352X288. The reduction size of the reference resolution may be set in consideration of the frame standard.

The controller 140 may determine the optimal frame rate by adjusting the frame rate at the reduced reference resolution. In other words, the controller 140 may re-perform steps S810 to S860 according to the reduced reference resolution.

As described above, the image compression apparatus 100 of the present invention can encode image data at an optimal frame rate and optimal resolution by adaptively varying encoding factors (resolution and frame rate) in a variable narrowband network. have.

The embodiment according to the present invention described above may be implemented in the form of a computer program that can be executed through various components on a computer, and such a computer program may be recorded in a computer-readable medium. In this case, the medium includes a hard disk, a magnetic medium such as a floppy disk and a magnetic tape, an optical recording medium such as CD-ROM and DVD, a magneto-optical medium such as a floppy disk, and a ROM , RAM, flash memory, etc., a hardware device specially configured to store and execute program instructions.

Meanwhile, the computer program may be specially designed and configured for the present invention, or may be known and used by those skilled in the computer software field. Examples of the computer program may include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like.

A person of ordinary skill in the art related to this embodiment will understand that it can be implemented in a modified form without departing from the essential characteristics of the above description. Therefore, the disclosed methods are to be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

10: video compression system
100: video compression device
110: encoder
120: buffer
130: communication department
200: decompression device

Claims (10)

A video compression apparatus adaptive to a variable narrowband network environment, comprising:
an encoder for encoding image data based on an adjustable resolution and frame rate;
a buffer for temporarily storing the encoded image data;
a communication unit for transmitting the encoded image data temporarily stored in the buffer through a network; and
A control unit that adjusts at least one of the resolution and the frame rate based on the buffer usage rate;
the control unit
In a state in which the frame rate is adjusted within a preset adjustment range, the resolution is adjusted,
The resolution means the number of pixels used to represent one frame,
the control unit
In a state in which the image data is encoded with a preset reference resolution and a reference frame rate, the buffer usage rate is obtained,
When the obtained usage rate is less than the lower limit of the optimum range, the frame rate is increased stepwise within the adjustment range, and when the obtained usage rate is greater than the upper limit of the optimum range, the frame rate is adjusted to the adjustment range Step-by-step reduction within
In a state in which the frame rate is increased up to the upper limit of the adjustment range and the buffer usage rate is less than the lower limit of the optimal range, the resolution is increased by a preset size;
When the use rate of the buffer is greater than the upper limit of the optimal range in a state in which the frame rate is reduced to the lower limit of the adjustment range, the resolution is reduced by a preset size;
and an absolute value of a decrease in the frame rate when the frame rate is decreased in steps is set to be larger than an absolute value of an increase in the frame rate when the frame rate is increased in stages. According to claim 1,
the control unit
An image compression apparatus for calculating a usage rate of the buffer based on the remaining memory capacity of the buffer, which varies according to a change in the bandwidth of the network. According to claim 1,
the control unit
An image compression apparatus for adjusting at least one of the resolution and the frame rate so that the buffer usage rate is within a preset optimal range. 4. The method of claim 3,
the control unit
An image compression apparatus for setting the optimal range to 20% to 60% of the maximum use rate of the buffer. delete delete delete delete A video compression method adaptive to a variable narrowband network environment, the method comprising:
encoding the image data based on the adjustable resolution and frame rate;
temporarily storing the encoded image data in a buffer;
transmitting the encoded image data temporarily stored in the buffer through a network; and
Including; adjusting at least one of the resolution and the frame rate based on the buffer usage rate;
The adjusting step is
obtaining a utilization rate of the buffer in a state in which the image data is encoded with a preset reference resolution and a reference frame rate; and
In a state in which the frame rate is adjusted within a preset adjustment range, adjusting the resolution,
The resolution means the number of pixels used to represent one frame,
In a state in which the frame rate is adjusted within a preset adjustment range, adjusting the resolution includes:
When the obtained usage rate is less than the lower limit of the optimum range, the frame rate is increased stepwise within the adjustment range, and when the obtained usage rate is greater than the upper limit of the optimum range, the frame rate is adjusted to the adjustment range Step-by-step reduction within
In a state in which the frame rate is increased up to the upper limit of the adjustment range and the buffer usage rate is less than the lower limit of the optimal range, the resolution is increased by a preset size;
When the use rate of the buffer is greater than the upper limit of the optimal range in a state in which the frame rate is reduced to the lower limit of the adjustment range, the resolution is reduced by a preset size;
and an absolute value of a decrease in the frame rate when the frame rate is decreased in steps is set to be greater than an absolute value of an increase in the frame rate when the frame rate is increased in stages. A computer-readable recording medium recording a program for executing the method of claim 9 on a computer.

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