KR20060024609A - Apparatus and method for encoding of real-time moving image - Google Patents

Abstract

The present invention relates to an apparatus and method for encoding an analog broadcast signal in real time for recording an analog broadcast in a PVR device capable of recording / reproducing a broadcast signal received by mounting a storage medium in a broadcast reception device on the storage medium. . In particular, the present invention analyzes the number of non-zero DCT coefficients in real time for each GOP section of the video and allocates an appropriate bit amount to the corresponding section, thereby providing an optimal MPEG-2 video bit stream in terms of both image quality and bit efficiency. to provide. In addition, by adaptively changing the quantization coefficients in slice units, it is possible to cope with changes in the picture and to minimize unnecessary bit consumption due to frequent changes in the quantization parameters.

Quantization parameters, real-time coding, non-zero DCT coefficients

Description

Apparatus and method for encoding of real-time moving image}

1 is a block diagram showing an embodiment of analog and digital broadcast recording using a conventional PVR device

2 is a block diagram showing an embodiment of a general MPEG-2 encoding apparatus

3 is a detailed block diagram illustrating an embodiment of a bit rate control unit of a single pass variable bit rate MPEG-2 encoding apparatus according to the present invention;

4 is a diagram illustrating an embodiment of a function for calculating a bit rate for each section based on the number of non-zero DCT coefficients in an MPEG-2 encoding apparatus according to the present invention.

5 is a graph comparing the amount of bits generated when a variable quantization parameter and a fixed quantization parameter are used.

6 is a flowchart illustrating an embodiment of a step-by-step bit rate control process in an MPEG-2 encoding apparatus according to the present invention.

Explanation of symbols for main parts of the drawings

301: line quantizer 302: counter

303: Quantization Parameter Determination Unit

The present invention relates to a digital broadcast receiver, and more particularly, to recording analog broadcasts in a personal video recording apparatus capable of recording / reproducing a broadcast signal received by mounting a storage medium in the broadcast receiving device. An apparatus and method for encoding an analog broadcast signal in real time.

A personal video recorder (hereinafter referred to as a PVR device) provides a function of storing a digital broadcast on an HDD by attaching a hard disk (HDD) to a digital TV or a set-top box. This eliminates the inconvenience that the existing VCR (Video Cassette Recorder) has to replace the video tape at any time for recording, and at the same time enables a large amount of broadcast recording. In addition, the PVR device provides not only a recording function, which is a main function, but also a time-shift, instant replay, and other trick play functions. To provide.

In such a PVR device, a real time MPEG-2 video encoding device is required to convert an NTSC or PAL analog broadcast signal into a moving picture expert group (MPEG) -2 video stream and record it on an HDD.

1 illustrates a path for storing analog and digital broadcasts in an HDD in a PVR device. An analog broadcast signal such as NTSC or PAL is tuned in the analog tuner 101 and then output to the A / D converter 102 to be digitized.                         

In FIG. 1, an analog broadcast signal of the NTSC transmission method is described as an embodiment.

Therefore, the analog broadcast signal digitized by the A / D converter 102 is output to the NTSC decoder 103. The NTSC decoder 103 converts an analog broadcast signal into a 4: 2: 0 format for encoding into MPEG-2 and outputs it to the MPEG-2 encoder 104. The MPEG-2 encoder 104 compresses and encodes a broadcast signal formatted by the MPEG-2 compression algorithm as shown in FIG. 2 and outputs the compressed signal to the PVR module 108.

Meanwhile, the digital broadcast signal is tuned by the digital tuner 105 and then output to the demodulator 106. The demodulator 106 demodulates the inverse of the modulation scheme for the tuned broadcast signal. For example, if the received digital broadcast is a terrestrial broadcast, a VSB (Vestigial Side Band) demodulation is performed, and if the satellite broadcast is a Quadrature Phase Shift Keying (QPSK) demodulation, a TS decoder in the form of a transport stream (TS) is performed. Output to (107). The TS decoder 107 demultiplexes only a desired program and outputs it to the PVR module 108 when a plurality of programs are multiplexed in an input transport stream.

The PVR module 108 multiplexes the data stream including the audio stream and caption information to the analog broadcast stream compressed and encoded by the MPEG-2 encoder 104 or the digital broadcast stream demultiplexed by the TS decoder 107 together. After multiplexing) to store in the HDD (110). In this case, the audio stream and the data stream may also be encoded using a corresponding encoding device.                         

FIG. 2 is a block diagram illustrating a typical MPEG-2 encoder, in which encoding is performed on a macroblock basis. That is, if the image input in macroblock units is an intra type, that is, an I picture, it is output to the DCT unit 203 through the switching unit 202 without passing through the subtractor 201. On the contrary, if the input image is an inter type, that is, a P or B picture, the difference image obtained by the subtractor 201, that is, the difference image between the input image and the motion compensated image by the motion compensation MC 212. It outputs to the DCT unit 203 through this switching unit 202.

That is, the signal input to the DCT unit 203 means a residual image signal based on a DC value in the case of an I picture, and a residual image generated during motion estimation in the case of a P or B picture. Means signal.

The output terminal c of the switching unit 202 is switched to the input image terminal a or the output terminal b of the subtractor 201 according to whether the type of the input image is intra or inter.

The DCT unit 203 DCTs the input data in block units and outputs the result to the quantization unit 204. The quantization unit 204 quantizes the DCT coefficient according to the quantization step size determined by the quantization parameter. In this case, the quantization parameter affecting the overall bit rate and the image quality is determined by the bit rate controller 220.

That is, the DCT unit 203 removes the correlation of data through 2D axis transformation. To this end, the picture is divided into macroblock units, and each 16 * 16 macroblock is divided into 8 * 8 block units. After dividing, each divided block is transformed according to DCT equation. The axis-converted data are quantized to a predetermined quantization step size by the quantization unit 204 and rearranged in one dimension according to a predetermined scan method, and then output to the variable length coding (VLC) unit 205. The VLC unit 205 performs entropy coding to reduce the total number of bits by displaying a number of bits that appear frequently and a number of bits that rarely appear for the rearranged quantized DCT coefficients. In this case, not only the DCT coefficient but also picture header information and motion information are encoded.

At this time, the VLC data from the VLC unit 205 is output to the buffer 206, and the buffer 206 temporarily stores the VLC data and then passes through the PVR module 108 to the HDD 110 at a constant speed. The buffer fullness of the buffer is calculated and output to the bit rate controller 220.

The DCT coefficients quantized by the quantization unit 204 are again input to the inverse quantization unit (IQ) unit 207, dequantized, and then output to the IDCT unit 208. The IDCT unit 208 IDCTs the inverse quantized DCT coefficients and outputs them to the adder 209. When the IDCT data is an intra type, the adder 209 is added to the motion compensated value by the motion compensator 212 if it is an inter type, and reconstructed to a complete image which is the final pixel value. Store in

The motion compensator 212 performs motion compensation using a previous frame read from the frame memory 210 according to the estimation result of the motion estimator ME 211 and then switches with the subtractor 201. Output to the unit 213. If the IDCT data is an intra type, the switching unit 213 is turned off, and the motion compensated data from the motion compensator 212 is not output to the adder 209. If the IDCT data is an inter type, the switching unit 213 is turned on, and the motion compensated data in the motion compensator 212 is output to the adder 209 through the switching unit 213.

The motion estimator 211 estimates a motion vector using the input image and the reference image stored in the frame memory 210 and outputs the motion vector to the motion compensator 212.

On the other hand, the most important thing in the real-time MPEG-2 video encoding process is the bit rate and image quality. These two characteristics are trade-off relations with each other, and the rate control is a process for achieving the best result by combining the two characteristics properly.

The bit rate control is a process of setting a buffer model based on a given bit rate and assigning a GOP (Group Of Picture) of video data and a bit amount required for the encoding process in each frame unit.

That is, the bit rate controller 220 calculates the quantization parameter Qp according to the fullness of the buffer 206 and outputs the quantization parameter Qp to the quantization unit 204.

The quantization unit 204 quantizes the DCT coefficient by obtaining the quantization step size from the input quantization parameter Qp. That is, the bit rate controller 220 adjusts the generation amount of data by varying the step size of the quantization unit 204 according to the fullness of the buffer.

For example, if the number of bits generated is greater than or equal to the reference value, the amount of data filled in the buffer 206 is increased. Therefore, the quantization step size is increased to reduce the number of bits to be generated later. The number of bits generated is increased to decrease the number of bits, so that the state of the buffer 206 can be maintained as a whole.

In this case, referring to the international standardization MPEG-2 data (document number AVC-491, TEST MODEL 5), IS / IEC JTC1 / SC29 / WG11, an organization under ISO (International Organization for Standardization), the bit rate controller 220 Perform the following three steps.

First, the first step is to predict complexity and to allocate target bits. That is, a constant bit rate is allocated in units of GOP (Group Of Picture) according to the transmission bit rate, and bits to be allocated to each picture in the GOP are allocated according to the complexity of each picture (I, P, B frame).

The second step is to adjust the transmission rate (i.e., bit rate), and calculate a reference quantization parameter for each macro block according to the fullness of the virtual buffer 206. The bit rate is controlled so that each picture can be encoded according to the bit allocated in the first step.

Here, it is assumed that each picture has an arbitrary virtual buffer, and a method of adjusting the quantization parameter according to the state of the buffer is used.

The third step is an adaptive quantization step. After obtaining and normalizing the activity of a macroblock to be encoded currently, the normalized quantization parameter to be actually used for quantization is obtained by multiplying the normalized activity by the reference quantization parameter obtained in the second step. In other words, adaptive quantization is a method of increasing the subjective picture quality and changing the reference quantization parameter according to the complexity of the current macroblock.

However, this conventional bit rate control method has a disadvantage in that the optimization of image quality is not satisfactorily achieved by focusing on an effective allocation of a given bit amount. In particular, in the MPEG-2 video encoding process, the deterioration of image quality tends to be intensified for a section composed of an image having a lot of motion or a visually complicated structure. In addition, the degree of deterioration of image quality felt by the image quality imbalance is more pronounced than the difference in numerical value.

Therefore, the realization of uniform picture quality in MPEG-2 video encoding is a very important problem. In particular, it is very important to ensure satisfactory image quality in a complicated area, that is, a difficult part of encoding. Many variable bit rate schemes have been proposed for realizing such a uniform picture quality, but these methods have a problem in that quantitative and systematic measurement methods for image complexity are insufficient.

In addition, the biggest problem of the conventional variable bit rate control method is that there is almost no real-time prediction method for the amount of bits occurring.

Therefore, in the conventional method, bit amount control by the two-pass method is performed. That is, a method of controlling the amount of bits by performing encoding once and then performing encoding again using the result is used. However, there is a problem that such a method cannot be applied to an application field requiring real time encoding.

In the conventional method, the quantization parameter value is changed based on each complexity in units of macro blocks. However, frequent changes of quantization parameter values of adjacent macroblocks have a disadvantage in that performance is degraded in terms of bit efficiency.

The present invention is to solve the above problems, an object of the present invention is to quantitatively measure the complexity of each video section in real time to be applied to the real-time broadcast recording required by the PVR device in real time to determine the appropriate bit amount for the corresponding section A one-pass variable bit-rate MPEG-2 encoder and a method for allocating the same are provided.

Another object of the present invention is to provide a variable bit rate MPEG-2 encoding apparatus and method which are effective in terms of image quality and bit consumption by maximizing bit efficiency.

In order to achieve the above object, a real-time video encoding apparatus according to the present invention, which performs DCT conversion of an image input in macroblock units, quantizes DCT coefficients according to quantization parameters, and then compresses and encodes the input image by variable length coding (VLC). A pre-quantization device for linearly quantizing a DCT coefficient of a current macro block using a preset reference quantization parameter value; A counter for counting and outputting a number of non-zero DCT coefficients among the pre-quantized DCT coefficients of the current macro block; And a quantization parameter determiner that determines a target bit amount for a section to be currently encoded based on the number of non-zero DCT coefficients counted by the counter, and determines a quantization parameter in slice units from the target bit amount. It is characterized in that the configuration.

The quantization parameter determiner obtains a target bit amount for the current GOP based on the number of pre-quantized non-zero DCT coefficients, and obtains a target bit amount for each picture type (I, P, B) from the determined target bit amount, After the target bit amount of each slice is obtained from the target bit amount in each picture, the quantization parameter to be applied to all macroblocks included in the current slice is determined.

The quantization parameter determiner may determine the quantization parameter to perform quantization for all macroblocks in the same slice using the same quantization parameter.

The quantization parameter determiner calculates a constant C of the current slice by a ratio of the average bit rate obtained in the process of encoding to the previous slice and the number of average non-zero DCT coefficients, and then allocates the constant C value and the target bit amount to the current slice. It is characterized by determining the number of non-zero DCT coefficients to be actually coded in the current slice.

The quantization parameter determiner performs quantization on the DCT coefficients in the slice to be encoded by applying a plurality of quantization parameters previously designated as candidates, extracts histogram data about the number of non-zero DCT coefficients, and then determines among the candidate quantization parameters. A quantization parameter that generates a value closest to the number of non-zero DCT coefficients is determined as a quantization parameter for a slice to be currently encoded.                     

The real-time video encoding method according to the present invention,

(a) pre-quantizing a DCT coefficient of the current macro block using a preset reference quantization parameter value;

(b) counting and outputting the number of non-zero DCT coefficients among the pre-quantized DCT coefficients of the current macroblock;

(c) obtaining a target bit amount for a GOP interval to be currently encoded and a target bit amount for each picture type (I, P, B) based on the number of non-zero DCT coefficients counted in step (b); Obtaining and allocating a target bit amount of each slice from a target bit amount in each picture;

(d) determining a non-zero DCT coefficient to be actually encoded in the current slice based on the target bit amount allocated in the unit of slice in step (c); And

(e) determining a quantization parameter to be equally applied to all macroblocks included in the current slice based on the number of non-zero DCT coefficients determined in step (d).

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described. In particular, the configuration and operation of the present invention shown in the drawings and described by it are described as at least one embodiment, by which the technical spirit of the present invention and its core configuration and operation are not limited. .

The present invention is to real-time encode an analog broadcast signal (e.g., NTSC transmission scheme) into an MPEG-2 video stream with optimal picture quality at a given bit rate. To do this, the complexity of each scene is analyzed to predict the amount of bits generated, and then an effective bit allocation method provides a user with a high-quality video output and controls the average bit rate of the video data so that the storage space can be effectively operated.

As described above, the present invention implements the MPEG-2 encoder by using a one-pass algorithm so that it can be applied to real-time broadcast recording required by the PVR device, thereby maintaining uniform picture quality and simultaneously encoding video data. The amount of bits can be allocated by effectively analyzing the complexity of the

3 is a detailed block diagram of a bit rate controller for determining a quantization parameter in a single pass variable bit rate MPEG-2 video encoding apparatus according to the present invention. Referring to FIG. 3, a line quantizer 301 that receives DCT coefficients and performs pre-quantization and a counter that counts non-zero DCT coefficients among DCT coefficients quantized by the line quantizer 301 ( 302 and a quantization parameter determiner 303 for obtaining a quantization parameter according to the count result of the counter 302.

The linear quantization of the DCT coefficients in the line quantizer 301 predicts the amount of bit generation of video data to be currently encoded, thereby quantitatively measuring the complexity of the corresponding section, and assigning appropriate bits to the current video section. To do this. That is, the linear quantizer 301 is a macro of the current quantization parameter Q _ref when the quantization parameter Q value ranges from 2 to 62 (Q has an even value) in the linear quantization process. Quantization is performed on the DCT coefficients of the block (2 ≦ Q _ref ≦ 62).

The counter 302 counts the number of non-zero DCT coefficients among the quantized DCT coefficients of the current macro block and outputs the number to the quantization parameter determiner 303. The number of non-zero DCT coefficients has a property that is proportional to the complexity and bit generation amount of the macroblock.

In the present invention, for convenience of description, a non-zero DCT coefficient will be referred to as a non-zero DCT coefficient. At this time, a large number of non-zero DCT coefficients means that the difference video signal of the macro block is large. This means that the spatial structure of the picture is very complicated for the I picture, and the motion estimation error is large for the P or B picture. That is, a large motion estimation error means that there is a complex motion or a very large motion in the video data. This means that there is video data that is very difficult to encode relatively. In addition, since the quantized DCT coefficient having a value of zero does not have a significant amount of bit generation compared to non-zero DCT coefficients in the entropy coding process, the control of the number of non-zero DCT coefficients in terms of the actual bit generation is in terms of bit rate control. Has a great meaning.

For this reason, it is assumed in the present invention that the bit amount is proportional to the number of non-zero DCT coefficients as shown in Equation 1 below.

R = CN _c

In this case, R represents a bit amount, N _c represents the number of non-zero DCT coefficients of the corresponding macroblock, and C represents a constant. That is, it is assumed that a linear relationship exists between the bit amount R and the number N _c of non-zero DCT coefficients.

In addition, the target bit amount R _local for the current interval may be variably allocated according to the number of non-zero DCT coefficients as shown in Equation 2 below.

R _local ∝ N _c

In this case, R _local means a target bit amount for the current section. The R _local is allocated to be proportional to N _c or used to determine a target bit amount of a corresponding interval by using a discontinuous function. In this case, the interval generally means a GOP.

As described above, the present invention can perform quantitative measurement on the complexity of the corresponding GOP interval by using the number of DCT coefficients generated through the line quantization process.

4 illustrates a function modeling a relationship between R _local and N _c used in the single pass variable bit rate MPEG-2 encoding apparatus according to the present invention. In FIG. 4, R _global means overall target bit rate. That is, in the present invention, a larger bit rate is allocated to a section having a high complexity, and an increase in the bit rate generated at this time is solved by reducing the bit rate of a section having a low complexity.

As a result, after measuring the number N _c of non-zero DCT coefficients, the bit amount to be allocated to the corresponding interval is determined using the function defined by FIG. 4.

In general, image quality deterioration occurring in an uncomplicated region is not visually significant compared to image quality deterioration occurring in a complex region. Therefore, it is possible to reduce the bit consumption in the uncomplicated region and use it for encoding the complex region, thereby improving the overall visual quality.

In the single pass variable bit rate MPEG-2 encoding apparatus according to the present invention, more efficient adaptive control of quantization coefficients is performed to maximize encoding efficiency.

In the conventional MPEG-2 encoding apparatus, the quantization parameter Q value is changed based on each complexity in units of macroblocks. However, frequent changes in the quantization parameter Q values of adjacent macro blocks have a disadvantage in that performance is degraded in terms of bit efficiency.

5 shows a graph comparing bit efficiency when the quantization parameter Q value is changed and when it is fixed. In other words, when the average bit amount when the quantization parameter Q is changed in the range between Q1 and Q2 is defined as R0, and the average bit amount when the quantization parameter Q is fixed to the intermediate value between Q1 and Q2 is R1, As shown in FIG. 5, it can be seen that R1 is smaller than R0.                     

Therefore, it can be seen that the method of fixing the quantization parameter Q value is superior in terms of bit efficiency than changing from time to time. However, since the characteristics of the video signal may be significantly different in the same picture as if the characteristics of the background and the object are different, there is a need to recalculate the Q value in a predetermined unit to change the adaptive quantization parameter Q value.

Therefore, in the present invention, the quantization parameter Q value is allocated in units of slices rather than macro blocks in order to simultaneously satisfy the conditions of the two cases described above.

In other words, all macro blocks included in the same slice are quantized using the same quantization parameter.

By doing so, it is possible to at least prevent the bit efficiency degradation that may occur in the adaptive quantization process and to cope with the change in complexity in the frame.

In general, a video standardization standard such as MPEG divides and processes an image into 16 × 16 blocks called macro blocks, and several macro blocks are grouped into slice units. And, one frame includes several slices according to the image size.

6 is a flowchart illustrating a process of calculating a quantization parameter for bit rate control in units of video sections in a single pass variable bit rate MPEG-2 encoding apparatus according to the present invention.

That is, in step 601, a target bit amount for the current section is allocated. The target bit amount is to first determine the bit amount R _GOP for the current interval, that is, the current GOP. At this time, the target bit amount for the current GOP is determined using the function defined by FIG. 4 based on the number of pre-quantized non-zero DCT coefficients as described above. The number of non-zero DCT coefficients uses the number N _c of non-zero DCT coefficients generated when the quantization parameter Q value is _referred to as the reference quantization parameter Q _ref in the dequantization process.

Then, the bit amount to be allocated is determined according to each picture type (I, P, B). As a result, the following relationship is established.

R _GOP = R _I + R _P + R _B

In this case, R _I , R _P , and R _B are bits used by I, P, and B pictures in the current GOP, respectively. In other words, R _P means a sum of bits allocated to all P pictures included in the current GOP. As a result, the bit amount allocated to one P picture is obtained by dividing R _P by N _P , where N _P represents the number of P pictures in the current GOP. The same applies to I and B pictures. Finally, the target bit amount R _slice is determined for each slice. All slices within the same picture allocate bits of the same size.

That is, in step 602, the constant C of the current slice is calculated as shown in Equation 4 below based on the modeling of Equation 1 described above. In this case, since there is no R value in the slice to be currently encoded, the values of R and N are used based on the values obtained in the process of encoding the previous slice.

C _slice = R _avg / N _avg

In this case, R _avg and N _avg represent the average bit rate and the number of average non-zero DCT coefficients obtained up to immediately before encoding of the current slice in the encoding process, and R _avg and N _avg are initialized in the case of the first slice of each GOP. In this case, Q = Q _fix to _{fix the} quantization parameter. The Q _fix value is determined to be different according to the target bit amount of the current GOP, and Q _fix has a value of 22 when encoding is performed at a bit rate of 4 Mbps. Also, for 8 Mbps bit rate, Q _fix has a value of 12. In the process of encoding a slice, R _avg and N _avg are continuously updated and C values are updated using a slice unit.

In step 603, the number N of non-zero DCTs to be encoded is determined for bit rate control by the set target bit amount. That is, the modeling of R and N is completed by the constant C value, and control of R can be precisely adjusted by adjusting N. Therefore, given the target bit amount of the current slice, the number N of non-zero DCT coefficients to be coded is determined, and the corresponding quantization parameter Q value is determined to control this.

In step 604, the number of non-zero DCT coefficients generated when performing line quantization using the same quantization parameter Q value for all macro blocks included in the current slice is obtained. That is, histogram data about the number of DCT coefficients is extracted for candidates of the quantization parameter Q value. In principle, we extract the number of non-zero DCT coefficients in a slice generated when performing dequantization for each of 31 Q value candidates between 2 and 62.

Then, in step 605, the quantization parameter Q value for generating the value closest to N calculated in step 603 is determined as the final quantization parameter using Equation 5 extracted in step 604.

In Equation 5, Q _slice represents a final quantization parameter for the slice to be currently encoded, and H (Qi) represents a histogram of the candidate quantization parameter Qi, that is, non-slice in the slice generated when performing prequantization with Qi. -zero The sum of the number of DCT coefficients. N _target means the target number of non-zero DCT coefficients for the current slice calculated in step 603.

The final quantization parameter determined in step 605 is input to the quantization unit 204. The quantization unit 204 obtains a quantization step size from an input final quantization parameter and quantizes a DCT coefficient to adjust the amount of data generation.

As described above, the present invention implements the MPEG-2 encoder by using a one-pass algorithm so that it can be applied to real-time broadcast recording required by the PVR device, thereby maintaining uniform image quality and simultaneously encoding the video data to be encoded. The amount of bits can be allocated by effectively analyzing the complexity of the

Accordingly, the present invention enables real-time encoding of an analog broadcast signal (e.g., NTSC transmission scheme) into an MPEG-2 video stream with optimal picture quality at a given bit rate.

Therefore, the present invention can be applied to the field of encoding and storing analog broadcasts such as NTSC and PAL as a digital stream in a PVR device equipped with a hard disk in a digital TV, and besides, an application requiring a real-time variable bit rate MPEG-2 encoding device. Applicable to the field.

On the other hand, the terms used in the present invention (terminology) are terms defined in consideration of the functions in the present invention may vary according to the intention or practice of those skilled in the art, the definitions are the overall contents of the present invention It should be based on.

And the present invention is not limited to the above-described embodiment, and can be modified by those skilled in the art as can be seen from the appended claims and such modifications are within the scope of the present invention. .

The effects of the real-time video encoding apparatus and method according to the present invention described above are as follows.                     

First, in an application field for recording analog broadcasting in real time in a PVR device, by analyzing the number of non-zero DCT coefficients in real time for each section of video and allocating an appropriate bit amount for the corresponding section, In terms of aspect, it provides an optimal MPEG-2 video bit stream.

Second, by adaptively changing the quantization coefficients in units of slices, it is possible to cope with changes in the picture and to minimize unnecessary bit consumption due to frequent changes of quantization parameters. As a result, it shows superior performance in terms of bit efficiency compared to the method for calculating adaptive quantization parameters in macroblock units.

Third, by continuously updating the number of bits and non-zero DCT coefficients and applying them to the next coding unit, it is possible to prepare for sudden changes in the screen or other unexpected situations that may occur during bit rate tuning.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (11)

A real-time video encoding apparatus for DCT transforming an image input in macroblock units, and then quantizing a DCT coefficient according to a quantization parameter and then compressing and encoding an input image by variable length coding (VLC). A pre-quantization device for linearly quantizing a DCT coefficient of the current macro block using a preset reference quantization parameter value; A counter for counting and outputting a number of non-zero DCT coefficients among the pre-quantized DCT coefficients of the current macro block; And And a quantization parameter determiner for determining a target bit amount for a section to be currently encoded based on the number of non-zero DCT coefficients counted by the counter, and determining a quantization parameter in units of slices from the target bit amount. Real-time video encoding apparatus, characterized in that. The method of claim 1, wherein the quantization parameter determiner Obtain a target bit amount for the current GOP based on the number of pre-quantized non-zero DCT coefficients, obtain a target bit amount for each picture type (I, P, B) from the determined target bit amount, and set a target bit in each picture. And determining a quantization parameter to be applied to all macroblocks included in the current slice after obtaining a target bit amount of each slice from the amount. The method of claim 2, wherein the quantization parameter determiner And all the slices in the same picture are allocated target bit amounts of the same size. The method of claim 2, wherein the quantization parameter determiner And determining the quantization parameter to perform quantization using the same quantization parameter for all macroblocks in the same slice. The method of claim 2, wherein the quantization parameter determiner After calculating the constant C of the current slice by the ratio of the average bit rate obtained in the process of encoding to the previous slice and the number of average non-zero DCT coefficients, the current slice using the constant C value and the target bit amount allocated to the current slice And a number of non-zero DCT coefficients to be actually encoded within the real-time video encoding apparatus. The method of claim 5, wherein the quantization parameter determiner Quantization is performed on the DCT coefficients in the slice to be encoded by applying a plurality of previously designated quantization parameters, and histogram data about the number of non-zero DCT coefficients is extracted, and then non-zero DCT coefficients are determined among the candidate quantization parameters. And determining a quantization parameter that generates a value closest to the number of s as a quantization parameter for a slice to be currently encoded. In the real-time video encoding method of DCT transform the input image in macroblock unit, and then quantize the DCT coefficient according to the quantization parameter and then compression-coding the input image by variable length coding (VLC), (a) pre-quantizing a DCT coefficient of the current macro block using a preset reference quantization parameter value; (b) counting and outputting the number of non-zero DCT coefficients among the pre-quantized DCT coefficients of the current macroblock; (c) obtaining a target bit amount for a GOP interval to be currently encoded and a target bit amount for each picture type (I, P, B) based on the number of non-zero DCT coefficients counted in step (b); Obtaining and allocating a target bit amount of each slice from a target bit amount in each picture; (d) determining a non-zero DCT coefficient to be actually encoded in the current slice based on the target bit amount allocated in the unit of slice in step (c); And (e) determining a quantization parameter to be equally applied to all macroblocks included in the current slice based on the number of non-zero DCT coefficients determined in step (d). Coding method. 8. The method of claim 7, wherein step (c) The real-time video encoding method, characterized in that the target bit amount of the same size is allocated to all slices in the same picture. 8. The method of claim 7, wherein step (d) Calculating a constant C (= R _avg / N _avg ) of the current slice using the average bit rate R _avg and the number of average non-zero DCT coefficients N _avg obtained in the previous slice encoding; And determining the number of non-zero DCT coefficients to be encoded in the current slice by using the constant C value and the target bit amount of the current slice in the step (c). The method of claim 9, wherein step (d) R _avg and N _avg are continuously updated in a slice encoding process, and the constant C value is further updated in slice units. The method of claim 7, wherein step (e) Extracting histogram data for the number of non-zero DCT coefficients for each candidate quantization parameter by performing quantization on DCT coefficients in a slice to be encoded with a plurality of quantization parameters previously designated as candidates; Real-time video encoding comprising the step of determining a quantization parameter that generates a value closest to the number of non-zero DCT coefficients determined in step (d) among the candidate quantization parameters as a quantization parameter for a slice to be currently encoded. Way.

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