KR100557618B1 - Bit rate control system based on object - Google Patents

Abstract

The present invention is a method of controlling a bit rate by setting different quantization parameters for each macro block according to the importance of an object when transmitting image data.

According to the present invention, when a network-based multimedia communication is performed, a user is interested in separating an important area from an unsegmented area based on an object segmentation result, calculating a quantization parameter, and applying a weight based on the calculated quantization parameter value. The quantization parameter values of an area or an area important to the user (eg, a human area or a face area of the user) and an area of relatively uninterested or non-important area (eg, a background area) are allocated and encoded differently.

Image Coding, Bit Rate Control, Objects, Quantization Parameters

Description

BIT RATE CONTROL SYSTEM BASED ON OBJECT}

1 is a schematic diagram of a general method of controlling a bit rate

Figure 2 is a schematic diagram of the TMN10 bit rate adjustment method

3 is a schematic diagram of a bit rate control apparatus according to the present invention;

4 is a flowchart of a bit rate control method according to the present invention;

5 is a flowchart of a method for allocating quantization parameters for regions in the present invention;

6 illustrates an example of object segmentation of the present invention.

The present invention relates to a method of controlling a bit rate by adaptively setting a quantization parameter (QP) for block coding according to an object region and a background region in a system for encoding an image signal in macroblock units. .

When transmitting video data including a large amount of information through a bandwidth-limited channel, the bit rate is controlled according to network conditions. Bit rate control for image data transmission is generally achieved by a control technique that determines coding parameters. In the bit rate control technique, a forward control technique that allocates a bit rate in consideration of characteristics of an input image and a parameter of an encoder are determined in consideration of characteristics of a rear end of a source encoder such as a buffer state transmission rate. There is a backward control technique.

Video encoders for low speed transmission media such as video communications and video phones should have excellent performance in terms of compression efficiency and low complexity of the encoder. Therefore, most of the bit rate control schemes for the video encoder for a low-speed transmission medium mainly use a backward technique for controlling the bit rate by adjusting the quantization parameter (QP) considering the state of the buffer.

1 is a schematic diagram illustrating a general bit rate control method, comprising: a characteristic analyzer 101 for receiving an input image and analyzing a characteristic; an encoder 102; a buffer 103 for outputting the encoded signal as a bit string; A target bit allocation setter 104 for setting target bits based on the state of the input video signal and the bit string output buffer, and a bit rate adjuster 105 for adjusting the coding rate with the assigned target bits.

The characteristic analyzer 101 analyzes the characteristic of the input image data and provides the characteristic to the target bit allocation setter 104, and the target bit allocation setter 104 provides the characteristic of the input image and the state information of the output buffer 103. It takes input and sets target bit. The bit rate adjuster 105 adjusts the encoding bit rate of the bit rate encoder 102 according to the target bit set in the target bit allocation setter 104, and the encoder 102 adjusts the image data that has passed through the characteristic analyzer 101. The data is encoded in accordance with the bit rate and stored in the output buffer 103. The output buffer adjusts the output bit stream at a constant speed to transmit the variable bit stream through a channel having a limited bandwidth, and also prevents buffer overflow or buffer deficiency that may occur during bit stream recovery. do.

In general, the adjustment of the bit rate can be adjusted by using a coding parameter such as a quantization parameter (QP). For example, when the quantization parameter value is set large, the bit rate is lowered but the image quality is lowered. The higher the bit rate, the better the picture quality. As described above, since the image quality and the bit rate are in mutual relation with each other, the image quality deteriorates when the bit rate drops.

The most well-known method of bit rate adjustment using quantization parameters is the bit rate adjustment method used in the TMN used as a test model in the standard group that established H.263.

The TMN is followed by a number after the TMN, depending on the version of the test model, of which TMN10 uses a variety of information generated from the encoder as a bit rate control method used in H.263 +. 2 is a schematic diagram of a TMN10 bit rate adjustment method.

The encoding initialization step S201 initializes the buffer size and the buffer level and initializes the parameters used in the bit rate adjustment model. In the frame layer bit rate adjustment step (S202), the frame is skipped until the frame is smaller than the reference bit rate in order to check the buffer state to prevent the overflow of the buffer and to prevent the delay. For reference, the TMN10 bit rate control method uses a small buffer because it is intended for real-time transmission.

In the MB (macroblock) layer bit rate adjustment steps (S203 and S205), the number of frame bits to be encoded is predicted based on the bit rate adjustment model, and the encoding is performed while performing the bit rate adjustment by adjusting the QP in MB units. Finally, the parameters used as the bit rate adjustment model are updated (S204).

However, the TMN10 bit rate adjustment method uses a parameter that requires a large amount of computation, such as the variance between this frame and the current frame, in using the bit rate adjustment model. In addition, since the quantization parameter is adjusted in MB units, a user may feel awkward due to the heterogeneity of the image quality of a part having good image quality while the other part has a poor image quality even though the same object area is in one frame.

However, the bit rate control method as described above presents one mathematical model (linear model, nonlinear model, replicalin model, exponential model, Gaussian model, etc.) for all images and assigns bits accordingly. However, there is a disadvantage in that an optimal coding parameter cannot be determined for an important part of the input image. In other words, if the bit rate is lowered due to the deterioration of the network environment even in an important area, the image quality may be deteriorated, and even in an unimportant area, the image quality may be higher than that of the important area.

Such correlation between bit rate and image quality is considered in video communication and video phone communication. That is, the user reacts more sensitively to the deterioration of the image quality of the important area or the region of interest than the deterioration of the image quality of the non-region. In other words, the quality of the important region or the region of interest is determined by the user's image quality rather than the image quality of the entire screen. However, in the general bit rate control method, the quantization parameter is adjusted according to the overflow of the output buffer or the lack of the output buffer. Therefore, the image quality is large and the quality deterioration occurs frequently according to the network conditions, so that the user cannot provide sufficient image quality.

An object of the present invention is to provide a method and apparatus for controlling a bit rate by adaptively allocating a quantization parameter in macroblock units to an object region and a background region when transmitting image data through a network.

Particularly, in the system for encoding and transmitting an image in macroblock units, the image is divided into an object region and a background region based on an object segmentation result, and the bit rate is controlled by adaptively assigning quantization parameters to each region. An object of the present invention is to provide an object-based bit rate control method and apparatus for improving image quality of a relatively important and interested area.

It is still another object of the present invention to properly assign quantization parameters of important and non-critical areas to differentiate them, thereby lowering the image quality of non-critical areas preferentially even if the network environment is deteriorated. A bit rate control method and apparatus for maintaining image quality are provided.

It is still another object of the present invention to use the Macroblock Quantization Parameter (QP) AnnexT Modified Quantization mode, which is calculated by a general bit rate control algorithm when an image is divided into an object region and a background region in a video communication or a network communication such as a video phone. As a method of appropriately allocating the object quantization parameter (ROI_QP) and the background quantization parameter (BG_QP) to control the bit rate, a region of interest or an important region of the input image is allocated by encoding a large number of bits using a small quantization parameter. An area of no interest or an area of insignificance is to provide a method and apparatus for controlling a bit rate by allocating a small bit using a large quantization parameter.

In order to achieve the above object, the object-based bit rate control method of the present invention includes: separating an input image into an object region and a background region, calculating a quantization parameter value QP_new, and determining the calculated quantization parameter value QP_new. Allocating a quantization parameter value ROI_QP of the object region and a quantization parameter value BG_QP of a background region according to a range, and corresponding to the object region and the background region according to the assigned quantization parameter values ROI_QP and BG_QP. Quantizing the macro block; Characterized in that comprises a.

In addition, the object-based bit rate control apparatus of the present invention for achieving the above object, the means for setting the target number of bits for bit rate calculation and control according to the network environment, means for separating the input image into the object area and the background area, Means for calculating the quantization parameter value QP_new in consideration of the set target bit number, the quantization parameter value ROI_QP of the object region and the quantization parameter value of the background region according to the calculated range of the quantization parameter value QP_new. Means for allocating BG_QP), and means for quantizing an input image by applying a corresponding quantization parameter value for each macroblock corresponding to each of the allocated areas; Characterized in that comprises a.

Hereinafter, an object-based bit rate control scheme of the present invention will be described with reference to the accompanying drawings.

[Object-based bit rate control device embodiment]

3 shows a schematic diagram of a technique for controlling a bit rate by adjusting a quantization parameter value based on an object of the present invention. The target bit setter 302 sets the target bit amount from the result 301 of performing object segmentation and the result of checking the state of the output buffer 306. The quantization parameter setter 303 inputs the target bit amount and the object segmentation result set by the target bit setter 302 to adaptively apply the quantization parameter ROI_QP of the object region and the quantization parameter BG_QP of the background region, respectively. Set to. The quantization mode setter 304 determines whether the macroblock to be quantized belongs to the boundary between the object region and the background region, and sets the quantization using the arbitrary QUANT selection mode at the region boundary. The quantizer 305 performs quantization on the input image according to the quantization parameter QP set according to the background region, the object region, the boundary region, and the like, and the output buffer 306 outputs the quantized image signal as a bit stream. do.

The bit rate control technique based on object / background separation information using the quantization parameter of FIG. 3 sets a target bit based on a result from an output buffer and performs image segmentation based on an object segmentation result. As a technique of specifying different quantization parameters in macroblock units according to an important region and a non-critical region, it is based on the following technique.

According to a moving picture standard such as H.263 or MPEG1 / 2, each frame of a given picture is encoded in macroblock units, which are 16 × 16 sub-regions. The brightness component and the color component of each macro block go through a discrete cosine transform (DCT) and quantize coefficient values to represent N bits. The quantized value is again encoded by Variable Length Coding (VLC). At this time, determining the method of performing the quantization is a quantization parameter, the number of coefficients smaller than the quantization parameter is '0'. Therefore, if the value of the quantization parameter is large, the coefficient converted to '0' is increased, resulting in a loss of information due to quantization instead of a small number of bits as a result of encoding by the VLC. Information loss due to quantization is reduced and image quality is improved, but the burden of data transmitted over a limited bandwidth network is increased.

Accordingly, in the present invention, the region of interest or the important region of the image to be transmitted is separated, and the quantization parameter value is set relatively small for the region of interest or important to enhance the image quality, while the quantization parameter is relatively relatively for the region of no interest or importance. We propose a technique that reduces the burden of data transmission by setting a large value.

The segmentation result 301 for the input image provides information on important and non-important regions of the input image. Object segmentation is a technique of separating an object from an image input image, and is a technique of separating each object when there is a user and a background or several objects. When such a technique is provided, the separated object and the background area have different importance in separating the objects. Subjective picture quality, which is usually felt by a person, is object dependent rather than background, and especially in a video communication system, the user (object) image contributes more to recognition than the background image. Allocating relatively fewer bits to the background can improve subjective picture quality.

Therefore, based on the information imparted with importance in the object region and the background region, the quantization parameter setter 303 and the quantization mode setter 304 appropriately set different quantization parameter values for each region (macro block). By performing the quantization based on the quantizer 305, the overall subjective image quality can be improved by increasing the quality of the region that is important and of interest to the user and lowering the image quality of the region that is not of interest to the user.

[Object based bit rate control method]

Fig. 4 illustrates a method of classifying quantization parameters into important regions (in this case, macro blocks of object regions) and insignificant regions (in this case, macro blocks of background regions) to assign quantization parameters and control quantization modes, respectively. Shows.

In step S401, the quantization parameter QP is calculated by using the TMN10 bit rate adjustment algorithm. A next step (S402) is a step of allocating the quantization parameter ROI_QP of the object region and the quantization parameter BG_QP of the background region based on the quantization parameter value calculated by the TMN10 bit rate adjustment algorithm. The next step S403 is to determine whether the current macroblock belongs to a boundary area between the background area and the object area. If the current macro block belongs to the boundary area between the background area and the object area, the process proceeds to step S404a to perform quantization using the Arbitrary QUANT selection mode (S404a, S405, S406), otherwise, step S404b. In step S404b, S405, and S406, quantization is performed using the small-step QUANT alteration mode.

The basic concept of the bit rate adjustment method shown in Fig. 4 is that the state information from the output buffer, i.e., when the network's bit rate is low, the high importance portion decreases the quantization parameter, and the low importance portion increases the quantization parameter so that the important object has a bit rate. Even if it is lowered, it allocates a relatively large number of bits and lowers the bit rate of an unimportant object as much as possible, thereby distinguishing an important part from an important part while maintaining the target bit number. This makes the user feel less deterioration in image quality. That is, the encoder separates the important areas from the object segmentation results into macroblock units and performs encoding according to the object importance-based quantization parameter value, thereby reducing the degradation of image quality while maintaining the target number of bits. The bandwidth burden can be solved.

[Object based bit rate control method embodiment]

The operation of bit rate control by adjusting the importance-based quantization parameter values of the object / background region described above will be described in more detail.

In a video communication environment, an important area generally may be a human area or a face area or an eye or mouth area, and may be composed of one or two or more thereof. In addition, in designating the importance of the object, the importance of the human area, the face area, and the eye or mouth area may be set higher than that of the background area.

Object separation is a process of separating a human and a background area or a face and a background area. In fact, when the face region appears in high quality, the user may not feel the quality deterioration even if the other peripheral region is degraded by the quantization parameter. This is because the user's eyes are mainly focused on the face part of the image, so the sensitivity of the image quality is also focused on the face part.

5 is a diagram illustrating a method of classifying quantization parameters into important and non-important regions and assigning them, respectively. First, ROI separation information is input from the object segmentation result (S501), and then a quantization parameter value QP_new is calculated using the TMN10 bit rate adjustment algorithm (S502).

In a next step S503, the quantization parameter ROI_QP of an important region (object region) and the quantization parameter BG_QP of an insignificant region (background region) based on the quantization parameter value QP_new calculated by the TMN10 bit rate adjustment algorithm. ) Will be assigned.

Here, it is divided into several areas according to the size of the quantization parameter value (QP_new) calculated by the TMN10 bit rate adjustment algorithm. That is, when QP_new> 25, 20 <QP_new <25, 10 <QP_new <20, QP_new <10.

The ROI_QP and BG_QP values are determined in the next step S504 according to the range of the quantization parameter value QP_new calculated as TMN10. In the method of allocating ROI_QP and BG_QP, weights are set according to importance, and usually ROI_QP is set at about half of QP_new and BG_QP is set at 1,5 times. However, if QP_new exceeds 25, lowering ROI_QP as usual would result in a lot of frame skipping due to a sudden increase in data, resulting in poor temporal image quality. Therefore, in this case ROI_QP prevents frame skipping by assigning a relatively high quantization parameter. In addition, when QP_new is less than 10, even if the quantization parameter is further lowered, the degree of image recognition that humans can recognize is very small, so in this case, the overall image quality can be maintained by increasing the quality of non-essential areas.

That is, if QP_new> 25, ROI_QP = QP_new * 0.8 (weighted), BG_QP = 31, and if 20 <QP_new <25, ROI_QP = QP_new * 0.5 (weighted), BG_QP = 31, and 10 <QP_new < In case of 20, ROI_QP = QP_new * 0.5 (weighted) and BG_QP = QP_new * 1.5 (weighted), and when QP_new <10, ROI_QP = QP_new and BG_QP = QP_new.

The next step S505 is adjusting the quantization parameter value. That is, the quantization parameter dquant of the macro block is adjusted by dquant = prev_QP-(ROI_QP or BG_QP). Where prev_QP is the previous quantization parameter value, ROI_QP is the set object quantization parameter value, and BG_QP is the set background quantization parameter value.

Next steps S506a and S506b are steps of adjusting the dquant value according to the macroblock type, Pre_MBType represents the previous macroblock quantization type, and Cur_MBType represents the current macroblock quantization type. The next step S507a is to use the previous quantization parameter value prev_QP as ROI_QP or BG_QP when dquant is in the ± 3 range, and step S507b uses the current ROI_QP or BG_QP when dquant> 3 or dquant <3 It means to use.

Next step (S508) is to perform the final quantization (Quantization) using the quantization parameter set as described so far.

In the present invention, in order to greatly change the quantization parameters of ROI_QP and BG_QP, H.263 + AnnexT (Modified Quantization Parameter) is used. In the existing H.263, the quantization parameter can be adjusted from +2 to 2 of the quantization parameter value of the previous macroblock in macroblock units. That is, the degree of change of the quantization parameter for changing the bit rate is possible only within ± 2 of the value of the quantization parameter in the previous macro block. As a result, it is difficult to adapt to sudden network environments, and it is difficult to make a significant change between major and non-primary domains. However, in Annex T, the quantization parameter is adjusted using the difference of the QUANT specified in Table 1 using 2 bits in 'small-step QUANT alteration mode', or 6 bits in 'arbitrary QUANT selection mode'. It has been extended to adjust the quantization parameter value from 1 to 31 regardless of the value.

By using this function, if the network's bit rate is lowered, the DCT coefficients of macro blocks determined to be insignificant areas are quantized to a large value to reduce the amount of data, and the DCT coefficients of macro blocks determined to be important areas are quantized to small values. Thus, even when the bit rate is low, relatively good image quality can be maintained for the region of interest.

When the user separates an image based on an object and tries to quantize differently by determining the importance, an easy and fast way to adjust the bit rate is to use the 'arbitrary QUNAT selection mode'. 6 shows an example of object segmentation and shows that it can be divided into an object region and a background region. When the background region and the user region are separated by object segmentation in video communication, as shown in FIG. 6, the two portions may be separated and encoded using different quantization parameters.

In case of using 'Arbitrary QUANT selection mode', users can select any quantization parameter from 1 to 31 for each macroblock regardless of the quantization parameter value of previous macroblock. The bit rate can be adjusted while quantizing the object region and the background region differently. If the image is divided into an object and a background region as shown in FIG. 6, when controlling the bit rate using this information, the user region (object region) is quantized using a small quantization parameter to leave much DCT coefficient information, and the background region is The bit rate is controlled by quantizing using a relatively large quantization parameter to discard DCT coefficient information. In this way, areas of interest or interest can be represented with relatively good image quality, while areas of interest or relative interest are notably low.

However, when both areas use the 'arbitrary QUANT selection mode' of Annex T, the number of header bits added increases, which may be a burden on the bit rate control. In other words, when using a quantization parameter in a general manner, a 2-bit header is required per macroblock. When using an 'arbitrary QUANT selection mode' of Annex T, a 6-bit header is required. Since this additional bit is added for each macro block, the overhead may be large.

However, when the image is separated and input based on the object, the difference between the quantization parameter is large only in the boundary region (boundary macroblock) of the background region and the object region, and the difference in the quantization parameter is small within each region. It will be very different. When the object and the background are separated from the image using this property, the arbitrary quantization parameter desired by the user is determined using the 'arbitrary QUANT selection mode' only for the macroblock of the object's boundary region, and in the same region, the previous quantization parameter is determined. If the difference in value is within the range of ± 3, the same quantization parameter is used so that 6-bit headers are used only for the border region and 2 bits are used for the rest, so that the header bits are more than 6-bit headers for the entire frame. You can adjust the bit rate on a per-object basis with much reduction.

As described above, if the current macroblock is a boundary macroblock of an object when quantizing based on importance information imposed in macroblock units in bit rate control, the quantization parameter is largely adjusted using the 'arbitrary QUANT selection mode' and the current macro If the block is a macro block within an object, the quantization parameter can be adjusted to a small width using the 'small-step QUANT alteration mode', so that the number of bits can be adjusted in units of objects. By imposing a large number of bits, even in low bit rate transmissions, the image quality can be prevented while adjusting the bit rate.

In FIG. 6, the boundary region using the arbitrary QUANT selection mode is a portion denoted by a dot, and the macroblock or the important region in the macroblock coding sequence that passes from the non-essential region to the important region in the macroblock coding order is not important. It becomes a macro block that goes into an area. The coding order of a macroblock of one frame is made from the upper left to the lower right in line units.

[Spatial and temporal image quality and its adjustment]

There are two main picture quality. It refers to spatial and temporal picture quality, and the degree to which the overall picture quality is felt varies from person to person. Spatial image quality refers to the image quality that is felt when viewing a frame of a video, and temporal image quality refers to the extent to which video movement is naturally felt when playing a video. For example, if the number of frames displayed per second is small, the movement is not natural and thus the temporal image quality deteriorates. In other words, some people are more sensitive to spatial image quality, while others are more sensitive to spatial image quality.

The present invention can also control spatial and temporal image quality, which depends on how many bits are allocated to the critical area. In other words, if ROI_QP is made smaller, the spatial quality of the region of interest is increased, but the probability of frame skipping is relatively increased. Therefore, we propose a quantization parameter value that best satisfies the spatial and temporal image quality. Table 2 shows each quantization parameter value according to the range of QP_new for this purpose.

QP_new> 25 20 <QP_New <25 15 <QP_new <20 10 <QP_new <15 QP_new <10 ROI_QP 25 15 13 10 8 BG_QP 31 31 25 25 20

As shown in Table 2, in the present invention, the quantization parameter value QP_new calculated according to the TMN10 bit rate adjustment algorithm is divided into five regions (ranges), and the object region quantization parameter ROI_QP and the background region quantization parameter BG_QP are respectively determined. Assigned. Referring to Table 2, ROI_QP = 25 and GB_QP = 31 for QP_new> 25, and ROI_QP = 15 and BG_QP = 31 for 20 <QP_New <25, and ROI + _QP = for 15 <QP_New <20. 13, BG_QP = 25, ROI_QP = 10, BG_QP = 25 when 10 <QP_New <15, ROI_QP = 8, BG_QP = 20 when QP_new <10.

Thus far, the present invention has described a method for adaptively assigning quantization parameters to important and non-critical areas for effective bit rate control in a real-time communication environment.

The present invention is an algorithm for adaptively assigning quantization parameters to each region based on information about an important region and an insignificant region of an image segmented in units of objects. As a result, the image quality that a person feels at the same bit rate can be improved.

According to the present invention, when a video is segmented based on an object in a video communication or video phone transmission, the user can greatly set the importance of a specific object, thereby improving the image quality of the video because the user intuitively feels in the video communication. have. In low bit rate communication, the quality of the transmitted video is not constant and the quality deterioration occurs frequently according to the bandwidth of the network. This is because when controlling the bit rate, the quantization parameter is used according to the instantaneous bit rate rather than the object in the video to control the overflow of the output buffer. Because it is determined. However, in video communication or video phone communication, the user is sensitive to the image quality of the region of interest. Therefore, when controlling the bit rate, sending more information of the region of interest and less information of the region of less interest may be useful in controlling the bit rate. In addition, it can provide a satisfactory picture quality to the user.

The present invention can be particularly useful in wireless mobile communication, such as IMT 2000. Since wireless mobile communication uses a lower network environment than wired mobile communication, it is very important to obtain high image quality at a low bit rate.

In addition, the present invention can be effectively applied to the video mail image acquired by the mobile terminal and the like. That is, by coding the video mail image without deteriorating the image quality in a small size, there is an effect that enables a low fee for the user.

In other words, the technique proposed in the present invention can be usefully used as a video encoding method such as a video mail. That is, when the image acquired by the mobile terminal or the like is encoded by the method proposed in the present invention, the size of the entire encoded image may be small and high image quality may be maintained. In general, since video services are charged by the number of packets, the size of a video will be a very important factor, and the present invention works very advantageously in that it can maintain high image quality while reducing the size of an encoded video.

Claims (11)

Separating the input image into an object region and a background region, calculating a quantization parameter value QP_new, and a quantization parameter value ROI_QP and a background region of the object region according to the range of the calculated quantization parameter value QP_new. Assigning each of the quantization parameter values BG_QP; Quantize the corresponding macroblocks of the object region and the background region according to the allocated access. If the current macroblock is the boundary region of the background and the object, the quantization parameter value is changed using the 'arbitrary QUANT selection mode' in the AnnexT mode of H.263. Quantizing corresponding macro blocks of the object region, the background region, and the boundary region according to the assigned quantization parameter values (ROI_QP, BG_QP) using the same quantization parameter values if the current macro block is the same region; Object-based bit rate control method characterized in that made. delete The method of claim 1, wherein the quantization parameter value lower than the calculated quantization parameter value QP_new is allocated to the object region based on the calculated quantization parameter value QP_new, and the calculated quantization parameter value is assigned to the background region. (QP_new) An object-based bit rate control method characterized by allocating a higher quantization parameter value. The arbitrary QUANT selection mode of claim 1, wherein the calculated quantization parameter value QP_new compares the previous quantization parameter value prev_QP and the current quantization parameter value cur_QP even if the difference is greater than a predetermined value. And updating the quantization parameter value using the method. The object of claim 1, wherein weights of the quantization parameter value ROI_QP of the object region and the quantization parameter value BG_QP of the background region are set differently according to the calculated range of the quantization parameter value QP_new. Based bit rate control method. The method of claim 1, wherein the weights of the quantization parameter value ROI_QP of the object region and the quantization parameter value BG_QP of the background region are set differently according to the calculated range of the quantization parameter value QP_new, respectively. And adjusting the weights in consideration of the image quality. The method according to claim 1, wherein the ROI_QP = QP_new x 0.8 and the BG_QP = 31 when the calculated quantization parameter value QP_new is QP_new> 25, and the ROI_QP = QP_new x 0.5 when 20 <QP_new <25, Set BG_QP = 31, set ROI_QP = QP_new × 0.5 when 10 <QP_new <20, set BG_QP = QP_new × 1.5, and set ROI_QP = QP_new, BG_QP = QP_new when QP_new <10 An object-based bit rate control method. The method of claim 1, wherein the calculated quantization parameter value QP_new is set to ROI_QP = 25 and BG_QP = 31 when QP_new> 25, and ROI_QP = 15 and BG_QP = 31 when 20 <QP_new <25. If ROI_QP = 13 and BG_QP = 25 if 15 <QP_new <20, set ROI_QP = 10 and BG_QP = 25 if 10 <QP_new <15, and ROI_QP if QP_new <10 = 8, BG_QP = 20, the object-based bit rate control method. Means for setting a target bit number for calculating and controlling a bit rate to be transmitted according to a network environment, means for separating an input image into an object region and a background region, and means for calculating a quantization parameter value (QP_new) in consideration of the set target bit number. Means for assigning a quantization parameter value ROI_QP of the object region and a quantization parameter value BG_QP of a background region according to the calculated quantization parameter value QP_new, and a macroblock corresponding to each of the allocated regions. Means for quantizing the input image by applying a corresponding quantization parameter value for each time; Based on the separation information of the object region and the background region, it is determined whether the current macroblock is an area boundary, and according to the determination result, a quantization mode according to the assigned quantization parameter value is determined for macroblocks that are area boundaries and macroblocks that are not. Means for selectively applying differently; object-based bit rate control device comprising a. delete 10. The apparatus of claim 9, wherein the quantization mode applied to the macroblock that is the region boundary is an arbitrary QUANT selection mode in AnnexT of H.263 +.

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