KR20160096754A - Method and System for Managing Power Utilizing Time Scale of Hierarchical Video Coding - Google Patents

Abstract

A power management method and system using temporal scalability of hierarchical video coding are presented. A power management method using time scalability of hierarchical video coding, the method comprising: dividing frames of an image into a plurality of segments; Calculating Temporal Information (TI) values for determining the degree of motion through comparison between consecutive frames in the plurality of segments; And changing a frame rate of the image to be reproduced using the calculated TI value.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power management method and system using temporal scalability of hierarchical video coding,

The present invention relates to a power management method and system that utilizes time scalability of hierarchical video coding, and more particularly, to a threshold-based frame rate modification method and system for energy saving in a portable media player.

The widespread use of video playback devices, including smartphones, makes it possible to watch videos on a regular basis, regardless of time. However, video applications require numerous operations involving high power consumption of the CPU. An effective way to reduce CPU power consumption is to use dynamic voltage regulation (DVFS) techniques that dynamically change the processor's voltage and frequency depending on the CPU's workload. Also, the video codec uses a compression scheme and the frames are decoded at the playback time. The frame skipping technique alleviates the CPU power consumption used in such a decoding operation, but the perceived quality perceived by the user is reduced. Therefore, it is important to solve the tradeoff between the quality of the experience and energy consumption.

A video quality parameter, called TI (Temporal Information) introduced by ITU-T, can be used to express the degree of motion of successive pictures and to determine the rate of frame skipping. Quality degradation due to frame skipping is more easily perceived on a screen with many changes of motion, but can be overlooked on a static screen. However, there are actually two issues to consider when using this technique. First, the TI value can only be obtained after two decoded successive frames are decoded. Second, this computation requires all pixel-by-pixel comparisons, resulting in many operations.

Korean Patent No. 10-0631768 describes an inter-frame prediction method and a video encoder, a video decoding method, and a video decoder in such video coding.

The present invention relates to a power management technique and system that utilizes time scalability of hierarchical video coding, and more particularly, to a power management technique and system using time scalability of hierarchical video coding, And more particularly, to a power management method and system using scalability.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for estimating a TI value by comparing a brightness value of a sample pixel of a frame in order to estimate a degree of change of motion with a low cost operation, A power management method and system using time scalability of hierarchical video coding that applies a high frame skipping ratio in a static scene and adjusts a frame rate to apply a small frame skipping rate in a dynamic scene.

According to an aspect of the present invention, there is provided a power management method using temporal scalability of hierarchical video coding proposed by the present invention, comprising: dividing frames of an image into a plurality of segments; Calculating Temporal Information (TI) values for determining the degree of motion through comparison between consecutive frames in the plurality of segments; And changing a frame rate of the image to be reproduced using the calculated TI value.

According to another aspect, calculating the TI value for determining the degree of motion through inter-pixel comparison between consecutive frames in the plurality of segments may include sampling the pixel according to a frame rate of the image to be reproduced And performing a comparison operation on only the selected pixels to calculate the TI value.

According to another aspect of the present invention, the step of extracting a pixel according to a frame rate of the image and performing a comparison operation on only the selected pixels to calculate the TI value may include calculating a pixel sampling ratio The TI value can be calculated.

According to another aspect, the step of changing the frame rate of the image reproduced using the TI value includes: setting a threshold value; Converting the TI value into a value representing a degree of motion; And selecting a low frame skipping rate when the threshold value is lower than a threshold value and selecting a high frame skipping rate when the threshold value is higher than the threshold, And changing the rate.

According to another aspect of the present invention, there is provided a power management system using time scalability of hierarchical video coding proposed by the present invention, the power management system comprising: a division unit dividing frames of an image into a plurality of segments; A TI value calculation unit for calculating TI (Temporal Information) values for understanding the degree of motion through comparison between consecutive frames in the plurality of segments; And a frame rate changing unit for changing a frame rate of the image reproduced using the calculated TI value, wherein the frame rate changing unit sets a threshold value and converts the TI value into a value representing the degree of motion And comparing the threshold value with a value representing the degree of motion to select a lower frame skipping rate when the threshold value is lower than a threshold value and selecting a higher frame skipping rate when the threshold is higher than the threshold value, You can change the frame rate.

According to embodiments of the present invention, the quality of an image can be managed within a range that the user can not recognize or can accept, and an optimal CPU frequency is selected by predicting a decoding time, thereby realizing a high quality and portable medium It is possible to provide a power management method and system utilizing time scalability of hierarchical video coding that can effectively reduce high power consumption in a device.

1 is a block diagram illustrating a power management system that utilizes temporal scalability of hierarchical video coding according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a power management method utilizing time scalability of hierarchical video coding according to an exemplary embodiment of the present invention. Referring to FIG.
FIG. 3 shows a CPU power comparison graph according to an animation reproduction according to an embodiment of the present invention.
FIG. 4 shows a CPU power comparison graph according to the reproduction of sports according to an embodiment of the present invention.
5 is a graph illustrating a CPU power comparison according to playback of a TV show according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention relates to a technique for reducing CPU power consumption in a portable media player based on hierarchical video coding. Specifically, according to the tradeoff relationship between the video frame rate and the power consumption, the video can be encoded to have various frame rates through the time scalability of H.264 / SVC. At this time, when the motion picture is reproduced, when the degree of motion of the continuous frame is static, it is reproduced at a low frame rate, so that the power consumption of the CPU can be lowered. In addition, the power consumption of the CPU can be lowered by reducing the comparison operation through pixel sampling according to the frame rate so as to reduce the number of pixel-based operations that occur in order to grasp the degree of motion of successive frames.

That is, the present invention relates to a selective frame rate application and a pixel sampling policy that effectively reduce the CPU power consumed in the portable media player.

In the following, we propose a method to effectively reduce the new CPU power considering the small amount of computation and motion change by utilizing the time scalability of H.264 / SVC.

First, it reduces the number of operations for predicting the degree of motion of the screen. More specifically, in order to derive a temporal information (TI) value for determining the degree of motion of a continuous screen, the brightness of all the pixels is compared. In the pixel sampling process for reducing the amount of computation, Technique.

Second, the threshold value is set and the frame rate is adjusted according to the degree of motion of the frames. More specifically, when frame-by-segment frames are made up of dynamic screens, lowering the frame rate can further reduce the perceived quality. Therefore, it is possible to use a frame rate adjustment technique which can reduce the decrease in the perceived quality by comparing the degree of motion of the segment with the threshold level line.

For example, if the above method is implemented in two types of smartphones and applied to actual measurement, energy savings of up to about 47% can be confirmed compared with the on-demand governor.

There is Scalable Video Coding (SVC) in which a user can dynamically encode an image so that a user can select services such as resolution and quality of video according to their preferences. Among these multiple hierarchical video coding (SVC) codecs are H.264 / SVC codecs, which provide excellent efficiency and three scalability. H.264 / SVC codecs have spatial scalability to provide various resolutions, temporal scalability to provide multiple frame rates, and quality scalability to allow layers of video to have different quality levels. Among these, time scalability can be used to reduce the user's perceived quality degradation when the video is played back and reduce the power consumption by adjusting the frame rate.

In order to dynamically adjust the frame rate during frame skipping, the temporal scalability of the hierarchical video coding scheme, in which a partial video stream can provide video at a low frame rate, can be utilized.

For example, a moving picture is divided into segments corresponding to 3.2 seconds in length.

Is the number of the frame in the segment when the temporal level is j.

Wow

Represent the number of the temporal level and the number of the segment, respectively.

A frame-level dynamic voltage and frequency control (DVFS) technique may be used to select the smallest frequency value that meets the decoding time limit. Based on the predicted decoding time of the next frame at each frequency, the media player can select the lowest frequency that meets the decoding deadline of the selected temporal level.

1 is a block diagram illustrating a power management system that utilizes temporal scalability of hierarchical video coding according to an embodiment of the present invention.

Referring to FIG. 1, the power management system 100 using time scalability of hierarchical video coding may include a partitioning unit 110, a TI value calculation unit 120, and a frame rate changing unit 130 have.

The division unit 110 may divide the frames of the image into a plurality of segments.

The TI value calculation unit 120 may compute temporal information (TI) values for determining the degree of motion through comparison between consecutive frames in a plurality of segments. In other words, the TI value calculation unit 120 may calculate a TI value by sampling a pixel according to a frame rate of an image to be reproduced, and performing a comparison operation on only selected pixels. At this time, the TI value can be calculated by selecting different pixel sampling rates according to each frame rate of the image.

The frame rate changing unit 130 may change the frame rate of an image to be reproduced using the calculated TI value. The frame rate changing unit 130 sets a threshold value, converts the TI value into a value representing the degree of motion, compares a value expressing the degree of motion with a threshold value, and if the value is lower than a threshold value, The frame rate of the reproduced image can be changed by selecting a skip rate and selecting a high frame skip rate when the skip rate is higher than the threshold value. That is, the threshold value is compared with a value expressing the degree of motion, and the frame skipping rate is selected to be higher than the frame skipping rate when the frame skipping rate when the value representing the degree of motion is higher than the threshold value is lower than the threshold value. The frame rate of the reproduced image can be changed.

FIG. 2 is a flowchart illustrating a power management method utilizing time scalability of hierarchical video coding according to an exemplary embodiment of the present invention. Referring to FIG.

Referring to FIG. 2, a power management method that utilizes time scalability of hierarchical video coding can be specifically described using a power management system that utilizes the time scalability of hierarchical video coding described in FIG. Here, the power management system utilizing the time scalability of the hierarchical video coding may include a division unit, a TI value calculation unit, and a frame rate changing unit.

In step 210, the power management system utilizing the temporal scalability of hierarchical video coding may divide frames of an image into a plurality of segments.

In step 220, the power management system utilizing the temporal scalability of the hierarchical video coding calculates a Temporal Information (TI) value for understanding the degree of motion through comparison between consecutive frames in a plurality of segments .

Here, the step of calculating the TI value for understanding the degree of motion through comparison of pixels between consecutive frames in a plurality of segments is performed by performing a comparison operation on only selected pixels by sampling pixels according to the frame rate of the reproduced image And calculating a TI value. This causes power consumption of the CPU when a large number of calculations are performed, so that power consumption can be minimized by extracting a specific sample and comparing only selected pixels.

Also, in the step of calculating a TI value by performing a comparison operation on only selected pixels by sampling a pixel according to a frame rate of an image, a TI value can be calculated by selecting different pixel sample extraction ratios according to each frame rate of the image .

In step 230, the power management system utilizing the temporal scalability of the hierarchical video coding may change the frame rate of the image to be reproduced using the calculated TI value.

Here, the step of changing the frame rate of an image to be reproduced using the TI value will be described in more detail.

The step of changing the frame rate of an image reproduced using the TI value may first set a threshold value which is a predetermined water level point. Then, the TI value can be converted into a value representing the degree of motion, which is a new indicator. Thereafter, when a value representing the degree of motion is compared with a threshold value, a lower frame skip rate is selected when the threshold value is lower than a threshold value, and a higher frame skip rate is selected when the threshold value is higher than a threshold value. . That is, through the above calculations, it is determined whether the current segment includes dynamic frames or a static screen, and the temporal level is predicted by estimating the degree of motion of the next segment, thereby minimizing the deterioration of the user's perceived quality . That is, the threshold value is compared with a value expressing the degree of motion, and the frame skipping rate is selected to be higher than the frame skipping rate when the frame skipping rate when the value representing the degree of motion is higher than the threshold value is lower than the threshold value. The frame rate of the reproduced image can be changed.

In other words, in order to reduce the power consumed by the CPU at the time of video reproduction in the portable media device, the video to which the time scalability of H.264 / SVC is applied is divided into segments, and the comparison between consecutive frames is performed The TI (Temporal Information) value can be derived.

This value is converted to a value representing the degree of motion, and if it is lower than a certain threshold value, a lower frame skipping rate is selected. Otherwise, a higher frame skipping rate can be selected.

In addition, other pixel samples may be extracted according to the frame rate in order to reduce the amount of numerous operations between the pixels of two consecutive frames. This minimizes the power consumption in the portable media device.

Hereinafter, a pixel sampling method will be described in detail.

A pixel sampling technique can be used to derive TI (Temporal Information) values and to reduce the computer's burden on algorithms for selecting different frame rates according to segment motion.

Can be done pixel by pixel between two consecutive frames of computation intensive that have a disadvantageous power consumption.

To reduce this burden, a method of comparing only selected pixels between successive two frames can be used. Here, it is assumed that all the pixels are classified according to the laster scanning order, and all the pixels in each frame at the temporal level j

One of the pixels is selected,

May represent a result set of row and column pairs of pixels used for comparison at temporal level j.

Also,

May represent the mean standard deviation of the difference of the sampled pixel values between two consecutive frames in the brightness region of segment m at temporal level j. Such,

Can be expressed by the following equation.

here,

In column < RTI ID = 0.0 > I < / RTI &

Lt; / RTI >

Can represent the standard deviation over all the pixels above.

The value is a new indicator

, Which can be expressed in dB.

Can be expressed by the following equation. .

here,

The value usually represents the degree of motion variation. Thus, a segment with a dynamic picture is low

High as a result of value

Value, and in contrast, a segment having a static screen has a high

Low as a result of the value

Value. ≪ / RTI >

In addition, since the low frame rate makes the difference in the brightness value between two consecutive frames larger

Lt; RTI ID = 0.0 > j. ≪ / RTI >

If the segment is made up of dynamic screens, lowering the frame rate can further reduce the quality of the visual perception compared to when it consists of static screens. From this point, we can specify the minimum and maximum water level points

Values are retained, and dynamic screens use a high frame rate, whereas static screens use a low frame rate.

Represents a threshold value,

Is initialized to the highest temporal level

, It can represent the temporal level selected for segment m. However, in the next segment m + 1

It is possible to repeat the following three steps to select the temporal level of segment m

.

1) Using equations (1) and (2) at the end of each segment m

Can be calculated.

2) Current

If the value is below the lowest level point, the temporal level

Since the next segment of the screen is expected to be static screens,

Can be reduced by one step.

3) Current

If the value is above the highest point, the temporal level

Since the next segment of the picture is expected with dynamic pictures,

Can be increased by one step.

FIG. 3 shows a CPU power comparison graph according to an animation reproduction according to an embodiment of the present invention.

FIG. 4 shows a CPU power comparison graph according to the reproduction of sports according to an embodiment of the present invention.

5 is a graph illustrating a CPU power comparison according to playback of a TV show according to an embodiment of the present invention.

Referring to Figures 3 to 5, when three videos of animation, sports, and TV show are played back with a high frame rate and on-demand governor,

) And the energy consumed when playing back using an optimal CPU can be compared and plotted as a graph. At this time, power consumption can be measured by using the technique implemented in two types of smartphones having different CPU frequency bands in order to evaluate energy saving.

Below, an example implemented in two smartphones with different CPUs according to the invention presented above can be shown.

First, one smartphone has 12 frequencies between 245MHz and 998MHz, and the other has 13 frequencies between 200MHz and 1400MHz. To allow real-time application of frame rate, H.264 / SVC decoders can be ported to smartphones.

In addition, for measurement, three different H.264 / SVC videos (animation, sports, TV show) were used, each supporting four frame rates (3.75, 7.5, 15, 30 fps). For each temporal level, pixel sampling rates may be selected differently

. Linux's Userspace governor is used to support DVFS, and the power consumption of a smartphone can be measured by an external digital multimeter that receives a DC current input.

As shown in Fig. 5, it can be seen that the frame rate adjustment technique is effective for energy saving by using less energy between 24% and 47% than the on-demand governor.

Table 1 is a table showing the comparison in each pixel according to an embodiment of the present invention.

Referring to Table 1, when comparing all the pixels

By showing the difference of the average ratio of the values, it can be confirmed that the pixel sampling method is accurate.

Thus, a new technique for adjusting the frame rate due to the overshoot of the TI value obtained by comparing recently sampled pixels of the brightness region between two consecutive frames can be devised and implemented. Furthermore, it is also possible to support a video player that does not have the SVC capability to use the remaining battery effectively to minimize the deterioration of the quality of the experience.

Therefore, according to embodiments of the present invention, the quality of an image can be managed within an acceptable or unacceptable range by a user, and an optimal CPU frequency can be selected by predicting a decoding time, The high power consumption in the portable media device can be effectively reduced.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the apparatus and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, controller, arithmetic logic unit (ALU), digital signal processor, microcomputer, field programmable array (FPA) A programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing apparatus may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device , Or may be permanently or temporarily embodied in a transmitted signal wave. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.

The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (5)

A power management method using time scalability of hierarchical video coding,
Dividing frames of an image into a plurality of segments;
Calculating Temporal Information (TI) values for determining the degree of motion through comparison between consecutive frames in the plurality of segments; And
Changing a frame rate of the image reproduced using the calculated TI value
A power management method utilizing temporal scalability of hierarchical video coding. The method according to claim 1,
Calculating the TI value for determining the degree of motion through pixel-by-pixel comparison between consecutive frames in the plurality of segments
Calculating the TI value by sampling the pixel according to a frame rate of the image to be reproduced and performing a comparison operation only on the selected pixel
A power management method utilizing temporal scalability of hierarchical video coding. 3. The method of claim 2,
Calculating a TI value by performing a comparison operation only on the selected pixel by sampling a pixel according to a frame rate of the image,
And calculating the TI value by selecting different pixel sample extraction ratios according to each frame rate of the image
Wherein the power management method utilizes temporal scalability of hierarchical video coding. The method according to claim 1,
Wherein changing the frame rate of the image reproduced using the TI value comprises:
Setting a threshold value;
Converting the TI value into a value representing a degree of motion; And
Comparing the value representing the degree of motion with the threshold value to determine whether the frame skipping rate when the frame skipping rate when the value expressing the degree of motion is higher than the threshold value is higher than the frame skipping rate when the frame skipping rate is lower than the threshold value And changing a frame rate of the image to be reproduced
A power management method utilizing temporal scalability of hierarchical video coding. A power management system utilizing time scalability of hierarchical video coding,
A dividing unit dividing frames of an image into a plurality of segments;
A TI value calculation unit for calculating TI (Temporal Information) values for understanding the degree of motion through comparison between consecutive frames in the plurality of segments; And
And a frame rate changing unit for changing a frame rate of the image reproduced using the calculated TI value,
Lt; / RTI >
Wherein the frame rate changing unit comprises:
A threshold value is set, the TI value is converted into a value representing the degree of motion, and a value representing the degree of motion is compared with a value expressing the degree of motion, The frame skipping rate when the frame skipping rate is higher than the threshold skipping rate when the frame skipping rate is higher than the threshold skipping rate is higher than the frame skipping rate when the frame skipping rate is higher than the threshold,
A power management system utilizing time scalability of hierarchical video coding.

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