KR100932727B1 - Video stream switching device and method - Google Patents

Abstract

Disclosed are a video stream switching apparatus and method. A video stream switching method for generating a switching bitstream switched from a first bitstream to a second bitstream, wherein the decoding step decodes the first bitstream and the second bitstream, respectively, so that the first image frame and the second image frame are decoded. Are respectively calculated. The switching frame calculating step calculates a plurality of switching frames supporting switching from the first bitstream to the second bitstream based on the calculated first image frame and the second image frame. The switching bitstream generating step generates a switching bitstream including the calculated switching frame. According to the apparatus and method for converting a video stream according to the present invention, switching between bitstreams compressed at different bit rates without increasing the overall bit rate prevents an increase in bitrate that may occur at the time of switching and maintains stable bitstream transmission. It is possible to quickly switch the bitstream to match the bandwidth of the various networks or the variable bandwidth of the network.

Description

Apparatus and method for switching video stream

The present invention relates to an apparatus and method for switching video streams, and more particularly, to an apparatus and method for switching between different streaming bitstreams.

In a bitstream, an image composed of a plurality of image frames is compressed in an MPEG format. There are several standard formats that are standardized in the MPEG format for compressing such images. Standard formats include MPEG-1 (reference number ISO / CEI 11172) for applications that store digital audiovisual data, MPEG-2 (reference number ISO / CEI 13818) for distribution of television programs, and interactive management of multimedia data. MPEG-4 (reference number ISO / CEI 14496), etc. dedicated to uses. Each standard is for a different purpose, but all of them use temporal and spatial redundancies that exist within a sequence of pictures, based on a block encoding technique. In general, to remove spatial redundancy, a discrete cosine transform (DCT) is applied to blocks of eight lines of eight samples of the video signal.

In addition, with regard to the method for eliminating temporal redundancy, the MPEG standard defines three types of pictures. First, an intra-coded picture or I picture is encoded by information derived only from the pictures themselves in a frame encoded in the intra mode and used to facilitate random access to the sequence. Secondly, a predictive-coded picture or P picture is encoded by motion compensated prediction based on a previous I or P reference picture in display order in a frame encoded in inter mode. Third, a bi-prediction-coded picture or B picture is encoded by motion compensated prediction based on a previous or subsequent I or P reference picture.

MPEG standards include motion compensation processing based on displacement detection of a picture to be encoded to include a minimum error on the preceding picture. However, the encoding unit in which spatial redundancies can be reduced is a block, and motion compensation is two, four, or eight according to chrominance formats (4: 2: 0, 4: 2: 2 or 4: 4: 4), respectively. Macroblocks, which are a group of four color difference blocks and four luminance blocks, are generated from a sector of 16x16 elements of the luminance component of the picture.

1 is a diagram illustrating a motion estimation process in the background art.

Referring to FIG. 1, motion compensation prediction first maps the macroblock 12 of the current picture 11 to the macroblock of the preceding picture. When the most promising position 14 of the macroblock in the preceding picture 13 is found, the displacement vector 15 associated with the macroblock of the current picture is determined. Then, the predicted macroblock corresponding to the difference between the current macroblock and the most promising macroblock, and the associated motion vector are encoded.

Various prediction methods are possible, and the picture type defines a prediction method that can be used to encode each macroblock. For example, the macroblock may be forward predicted based on the reference macroblock belonging to the previous picture, and may also be backward predicted based on the reference macroblock belonging to the later picture in the display sequence. Another option is that no prediction is applied in the same way that blocks of macro blocks of the current picture are encoded directly. Such macroblocks are called intra macroblocks.

The technical problem of the present invention is to perform switching between bitstreams compressed at different bitrates without increasing the overall bitrate, thereby preventing possible bitrate increase and maintaining stable bitstream transmission. The present invention provides a video stream switching device and a method for converting a bitstream quickly according to a bandwidth of a network or a variable bandwidth of a network.

Another technical problem to be achieved by the present invention is to perform a switch between bitstreams compressed at different bit rates without increasing the overall bit rate, thereby preventing possible bitrate increase during the conversion and maintaining stable bitstream transmission. The present invention provides a computer-readable recording medium that records a program for executing a method in which a bitstream can be quickly switched to various network bandwidths or variable bandwidths of a network.

In order to achieve the above technical problem, a video stream switching device according to the present invention, in the video stream switching device for generating a switching bitstream switched from the first bitstream to the second bitstream, the first bitstream and And a switching bitstream generator configured to calculate a plurality of switching frames supporting switching from the first bitstream to the second bitstream based on a second bitstream to generate a switching bitstream including the switching frames.

Preferably, the switching bitstream generation unit corresponds to each of the frames of the second bitstream and the corresponding frames of the first bitstream in the reverse direction based on the frames of the second bitstream at the time of switching between the first bitstream and the second bitstream. A switching frame is calculated.

In addition, the video stream switching method according to the present invention for achieving the above another technical problem, in the video stream switching method for generating a switching bitstream switched from the first bitstream to the second bitstream, the first bit Decoding each of the stream and the second bitstream to produce a first image frame and a second image frame, respectively; A switching frame calculating step of calculating a plurality of switching frames supporting switching from the first bit stream to the second bit stream based on the calculated first image frame and the second image frame; And a switching bitstream generating step of generating a switching bitstream including the calculated switching frame.

According to the apparatus and method for converting a video stream according to the present invention, switching between bitstreams compressed at different bit rates without increasing the overall bit rate prevents an increase in bitrate that may occur at the time of switching and maintains stable bitstream transmission. It is possible to quickly switch the bitstream to match the bandwidth of the various networks or the variable bandwidth of the network.

Hereinafter, exemplary embodiments of a video stream switching apparatus and method according to the present invention will be described in detail with reference to the accompanying drawings.

2A is a block diagram illustrating an example of a preferred computing environment suitable for use in one embodiment of the present invention.

Referring to FIG. 2A, the video stream switching apparatus 213 according to the present invention receives a bitstream in which a video signal is compressed in the MPEG format from the media server 211 and accesses the Internet 215 to which the client 217 belongs. The compressed bitstream is transmitted at an appropriate bit rate according to the bandwidth of the network. Here, the media server 211 compresses a video signal to various bit rates and quantization coefficients to generate a bitstream, store and transmit the bitstream. If the bandwidth of the network to which the client 217 belongs is changed according to the communication state, the video stream switching device 213 converts the transmitted bitstream into a compressed bitstream at a bit rate appropriate for the converted bandwidth and transmits the converted bitstream. Specifically, a video viewer (or viewer) operating on a personal computer (hereinafter referred to as a 'PC') that is suitably configured to access the Internet 215 referred to as the client 217 may access the Internet 215. Will be connected to the media server 202, whereby the client 217 accesses the content (bitstream), and the video stream switching device 213 adjusts the appropriate bit rate to the bandwidth of the network to which the client 217 is connected. It converts the bitstream into a compressed bitstream and transmits the bitstream.

The media server 211, the video stream switching device 213 and the client 217 are portable devices such as mobile phones and PDAs, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframes, respectively. It may be implemented in other computer system configurations, including computers, portable communication devices, and the like.

 2B is a block diagram illustrating another example of a preferred computing environment suitable for use in one embodiment of the present invention.

Referring to FIG. 2B, the video stream switching apparatus 223 according to the present invention directly plays the role of the media server 211 and transmits the stored or compressed bitstream to the client 227 through the Internet 225. do. Similarly, when the bandwidth of the network to which the client 227 belongs is changed according to the communication state, the video stream switching device 223 converts the transmitted bitstream into a compressed bitstream at a bit rate appropriate for the converted bandwidth and transmits it.

2C is a block diagram illustrating another example of a preferred computing environment suitable for use in one embodiment of the present invention.

Referring to FIG. 2C, the video stream switching device 233 according to the present invention receives a bitstream in which a video signal is compressed in MPEG format from the media server 231 through the Internet 232. The video stream switching device 233 is connected to the Internet 235 and transmits the compressed bitstream at an appropriate bit rate according to the bandwidth of the network to which the client 237 belongs. Similarly, when the bandwidth of the network to which the client 237 belongs is changed according to the communication state, the video stream switching device 233 converts the transmitted bitstream into a compressed bitstream at a bit rate appropriate for the converted bandwidth and transmits it. .

3 is a block diagram showing the configuration of a preferred embodiment of a video stream switching apparatus according to the present invention.

Referring to FIG. 3, the video stream switching apparatus 300 according to the present invention generates a switching bitstream that is switched from the first bitstream to the second bitstream. To this end, a first decoder 310, a second decoder 320, and a switching bitstream generator 330 are provided.

The first decoder 310 receives the first bitstream, decodes the image frame, and outputs the decoded image frame to the switching bitstream generator 330. The output image frame is an image frame located in a reverse direction from the image frame at the time of switching from the first bit stream to the second bit stream, and the number corresponds to the number of times that the switching bit stream generator 330 calculates the switching frame. do. The number of switching frames generated by the switching bit stream generator 330 is determined by a preset value. When the number of switching frames to be calculated increases, the calculation time increases, so that the time required for switching the bit stream is increased. When the number of switching frames is increased and the number of switching frames is reduced, the size of the switching frame may increase and burden the network. Therefore, it is preferable to set a setting value in consideration of this.

Similarly, the second decoder 320 receives the second bit stream, decodes the image frame, and outputs the decoded image frame to the switching bitstream generator 330. The image frame output here is an image frame at the time of switching from the first bit stream to the second bit stream.

4 is a block diagram showing the configuration of an embodiment of a decoder of a video stream switching apparatus according to the present invention.

Referring to FIG. 4, the first decoder 310 and the second decoder 320 may be implemented as, for example, a decoder 400. The decoder 400 includes a variable length decoding block VLD, an inverse quantization block DQ, an adder S1, a quantization block Q, an inverse discrete cosine block IDCT, a buffer BUF, and a motion compensator MC. And a discrete cosine block (DCT).

Referring to the operation of the decoder 400, the variable length decoding block VLD performs a variable length decoding conversion on the input bit stream. The inverse quantization block DQ performs inverse quantization on a frame of a variable length decoded bit stream output by the variable length decoding block VLD. The adder S1 calculates an image frame by adding a reference image frame to the dequantized frame output by the inverse quantization block DQ. The quantization block Q quantizes the image frame calculated by the adder S1. The dequantization block DQ dequantizes an image frame quantized by the quantization block Q. The inverse discrete cosine block IDCT performs inverse discrete cosine transform on an image frame inversely quantized by the inverse quantization block DQ. The buffer BUF stores an inverse discrete cosine transformed image frame output by the inverse discrete cosine block IDCT. The motion compensator MC calculates a reference image frame by performing motion compensation based on the image frame stored in the buffer BUF. The discrete cosine block DCT performs discrete cosine transform on the reference image frame calculated by the motion compensator MC and outputs it to the adder S1. That is, the adder S1 calculates an image frame by adding a reference image frame output by the discrete cosine block DCT to an inverse quantized frame output by the inverse quantization block DQ.

5A is a diagram illustrating a switching frame corresponding to each of frames of a first bitstream and a second bitstream.

Referring to FIG. 5A, the switching bitstream generator 330 calculates a plurality of switching frames supporting switching from the first bitstream to the second bitstream based on a first bitstream and a second bitstream. A switching bitstream including the same is generated. That is, the switching bitstream generation unit 330 is connected to the frame of the second bitstream and the corresponding frame of the first bitstream in the reverse direction based on the frame of the second bitstream at the time of switching between the first bitstream and the second bitstream. Calculate the corresponding switching frame. The apparatus for converting a video stream according to the present invention generates a switching bitstream including a plurality of switching frames, thereby preventing a sudden bit rate sudden increase that occurs when switching between bitstreams compressed at different bit rates, thereby ensuring a stable bitstream. It maintains the transmission and allows the bitstream to switch quickly to match the bandwidth of the various networks or the variable bandwidth of the network.

는 각각 제 1비트스트림으로부터 재구조화된 영상 프레임 즉, 복원된 영상 프레임이고,

는 제 2비트스트림으로부터 재구조화된 영상 프레임 즉, 복원된 영상 프레임이며, k는 k 번째의 영상 프레임을 의미한다. 입력되는 비트스트림(520) 중에서

는 각각 제 1비트스트림에서 인터 모드로 압축된 프레임이고,

는 제 2비트스트림에서 인트라 모드로 압축된 프레임이다. 그리고 출력되는 스트림(530) 중에서

는 제 1비트스트림에서 인터 모드로 압축된 프레임이고,

는 각각 P_K-2,1, P_K-1,1,I_K,2에 대응하는 스위칭 프레임이다.First, each symbol will be described. In the decoded video frame 510,

Are respectively reconstructed image frames, i.e., reconstructed image frames, from the first bitstream,

Denotes an image frame reconstructed from the second bitstream, that is, a reconstructed image frame, and k denotes a k-th image frame. Of the input bitstream 520

Are each compressed frames in the inter mode in the first bitstream,

Is a frame compressed in the intra mode in the second bitstream. From the stream 530 that is output

Is a frame compressed in the inter mode in the first bitstream,

Are switching frames corresponding to P _K-2,1 , P _K-1,1 , I _{K, 2} , respectively.

In a preferred embodiment, the switching bitstream generator 330 calculates the switching frame by the following equation (1).

는 제 2비트스트림의 k번째 영상 프레임이 재구조화된 영상 프레임이며, S_k,12는 상기 제 2비트스트림의 프레임에 대응하는 스위칭 프레임이고, S_k-1,12는 S_k,12의 전 스위칭 프레임이고

는 제 1비트스트림의 k-2번째 영상 프레임이 재구조화된 영상 프레임이다. 그리고 Inter(a, b)는 기준 영상 프레임 b로 하여 영상 프레임 a를 인터 모드로 인코딩하는 것을 의미하고, Inter^-1(a, b)은 기준 프레임 b로 하여 인터 모드로 인코드된 프레임 a를 디코딩하는 것을 의미한다.Where k is the sequence number of the frame of the second bitstream at the time of switching between the first bitstream and the second bitstream,

Is a picture frame in which the k-th picture frame of the second bitstream is restructured, S _{k, 12} is a switching frame corresponding to the frame of the second bitstream, and S _k-1,12 is a previous frame of S _{k, 12} . Is a switching frame

Denotes an image frame in which the k-2nd image frame of the first bitstream is restructured. Inter (a, b) denotes encoding of image frame a in inter mode using reference frame b, and Inter- ¹ (a, b) denotes frame a encoded in inter mode using reference frame b. Means to decode.

 5B is a block diagram showing the configuration of an embodiment of a switching bitstream generator of a video stream switching device according to the present invention.

Referring to FIG. 5B, the switching bitstream generator 500 selectively receives the first image frame and the second image frame output by the first decoder 310 and the second decoder 320 to calculate a switching frame. do. To this end, the switching bitstream generator 500 includes a discrete cosine block (DCT), a quantization block (Q), an inverse quantization block (DQ), an adder (S1), a variable length encoding block (VLC), a buffer (BUF), and a motion. The prediction unit ME and the motion compensation unit MC are provided.

을 입력받아 이산 코사인 변환을 수행한다. 양자화 블록(Q)은 이산 코사인 블록(DCT)이 출력한 이산 코사인 변환된

을 양자화 한다. 역양자화 블록(DQ)은 양자화 블록(Q)이 양자화 한

을 역양자화 한다. 움직임 예측부(ME)는 역양자화 블록(DQ)이 역양자화 한

에 대한 움직임 예측을 하여 움직임 벡터를 산출한다. 움직임 보상부(MC)는 움직임 예측부(ME)가 산출한 움직임 벡터 및 재구조화된

을 기초로 움직임 보상을 수행하여 기준 영상 프레임을 산출한다.Referring to the operation of the switching bitstream generator 500, the discrete cosine block (DCT) is

Input to perform discrete cosine transform. The quantization block Q is a discrete cosine transformed by the discrete cosine block DCT.

Quantize Inverse quantization block (DQ) is a quantization block (Q)

Dequantize The motion predictor ME performs inverse quantization by the inverse quantization block DQ.

The motion vector is computed by performing the motion prediction on. The motion compensator MC may include a motion vector and a restructured motion vector calculated by the motion predictor ME.

Based on the motion compensation, a reference image frame is calculated.

에 음직임 보상부(MC)가 산출한 기준 영상 프레임을 감산하여 스위칭 프레임인 S_k-2,12를 산출한다. 양자화 블록(Q)은 가산기(S1)가 산출한 스위칭 프레임 S_k-2,12를 양자화 한다. 가변길이인코딩 블록(VLC)은 양자화 블록(Q)이 양자화 한 S_k-2,12에 대해 가변 길이 인코딩 변환을 수행한다. 가변 길이 인코딩 변환된 S_k-2,12는 스위칭 비트 스트림으로서 출력된다. 그리고 역양자화 블록(DQ)은 양자화 블록(Q)이 양자화 한 산출한 스위칭 프레임 S_k-2,12를 역양자화 한다. 버퍼(BUF)는 역양자화 블록(DQ)이 역양자화 한 S_k-2,12를 저장한다.The adder S1 is an inverse quantized block by the inverse quantization block DQ.

S _{k-2, 12} , which is a switching frame, is calculated by subtracting the reference video frame calculated by the sound compensation compensator MC. The quantization block Q quantizes the switching frames S _{k-2 and 12} calculated by the adder S1. The variable length encoding block VLC performs a variable length encoding transform on S _k-2,12 quantized by the quantization block Q. The variable length encoded transform S _k-2,12 is output as a switching bit stream. The inverse quantization block DQ inversely quantizes the calculated switching frames S _{k-2, 12} quantized by the quantization block Q. The buffer BUF stores S _k-2 , 12 which are inversely quantized by the inverse quantization block DQ.

을 입력받아 이산 코사인 변환을 수행한다. 양자화 블록(Q)은 이산 코사인 블록(DCT)이 출력한 이산 코사인 변환된

을 양자화 한다. 역양자화 블록(DQ)은 양자화 블록(Q)이 양자화 한

을 역양자화 한다. 움직임 예측부(ME)는 역양자화 블록(DQ)이 역양자화 한

에 대한 움직임 예측을 하여 움직임 벡터를 산출한다. 움직임 보상부(MC)는 움직임 예측부(ME)가 산출한 움직임 벡터 및 재구조화된

을 기초로 움직임 보상을 수행하여 기준 영상 프레임을 산출한다. 가산기(S1)는 역양자화 블록(DQ)이 역양자화 한

에 음직임 보상부(MC)가 산출한 기준 영상 프레임을 감산하여 스위칭 프레임인 S_k-1,12를 산출한다.In the same way, the discrete cosine block (DCT)

Input to perform discrete cosine transform. The quantization block Q is a discrete cosine transformed by the discrete cosine block DCT.

Quantize Inverse quantization block (DQ) is a quantization block (Q)

Dequantize The motion predictor ME performs inverse quantization by the inverse quantization block DQ.

The motion vector is computed by performing the motion prediction on. The motion compensator MC may include a motion vector and a restructured motion vector calculated by the motion predictor ME.

Based on the motion compensation, a reference image frame is calculated. The adder S1 is an inverse quantized block by the inverse quantization block DQ.

S _{k-1, 12} , which is a switching frame, is calculated by subtracting the reference video frame calculated by the sound compensation compensator MC.

을 입력받아 이산 코사인 변환을 수행한다. 양자화 블록(Q)은 이산 코사인 블록(DCT)이 출력한 이산 코사인 변환된

을 양자화 한다. 역양자화 블록(DQ)은 양자화 블록(Q)이 양자화 한

을 역양자화 한다. 움직임 예측부(ME)는 역양자화 블록(DQ)이 역양자화 한

에 대한 움직임 예측을 하여 움직임 벡터를 산출한다. 움직임 보상부(MC)는 움직임 예측부(ME)가 산출한 움직임 벡터 및 재구조화된

을 기초로 움직임 보상을 수행하여 기준 영상 프레임을 산출한다. 가산기(S1)는 역양자화 블록(DQ)이 역양자화 한

에 음직임 보상부(MC)가 산출한 기준 영상 프레임을 감산하여 스위칭 프레임인 S_k,12를 산출한다.In the same way, the discrete cosine block (DCT)

Input to perform discrete cosine transform. The quantization block Q is a discrete cosine transformed by the discrete cosine block DCT.

Quantize Inverse quantization block (DQ) is a quantization block (Q)

Dequantize The motion predictor ME performs inverse quantization by the inverse quantization block DQ.

The motion vector is computed by performing the motion prediction on. The motion compensator MC may include a motion vector and a restructured motion vector calculated by the motion predictor ME.

Based on the motion compensation, a reference image frame is calculated. The adder S1 is an inverse quantized block by the inverse quantization block DQ.

Subtract the reference video frame calculated by the sound compensation compensator MC to calculate the switching frames S _{k and 12} .

Here, the quantization block Q and the inverse dequantization block DQ are quantization coefficients for quantizing or dequantizing an image frame, and are quantization coefficients of the first bitstream, quantization coefficients of the second bitstream, or other third parties. Quantization coefficients can be used.

6 is a block diagram showing the configuration of another preferred embodiment of a video stream switching apparatus according to the present invention.

Referring to FIG. 6, the apparatus 600 for converting a video stream according to the present invention is a quantization coefficient different from a quantization coefficient of a first bitstream and a second bitstream in a switching bitstream switched from a first bitstream to a second bitstream. Create using To this end, a first decoder 610, a second decoder 620, a switching bitstream generator 630, and a quantization coefficient calculator 640 are provided.

The first decoder 610, the second decoder 620, and the switching bitstream generator 630 are respectively the first decoder 310, the second decoder 320, and the video stream switching device 300 according to the present invention. As a component corresponding to the switching bitstream generator 330, detailed description thereof will be omitted.

The quantization coefficient calculator 640 calculates a quantization coefficient for quantizing the switching bitstream. In a preferred embodiment, the quantization coefficient calculator 640 calculates a value satisfying Equation 2 below and outputs the value to the switching bitstream generator 630 as a quantization coefficient.

Where Q _k is a quantization coefficient and D _k (Q _k ) and R _k (Q _k ) are distortion and rate functions, respectively, N _ps is the number of switching streams and R _T is the target bit rate.

The distortion function of the switching frame is composed of the sum of the quantum distortion function and the propagation distortion function of the reference video frame as shown in Equation 3 below.

양자화에 의한 왜곡함수이고

는 전파에 의한 왜곡 함수 있다.here,

Distortion function by quantization

Has a distortion function due to propagation.

The distortion function by quantization may be defined as a two-dimensional function model as shown in Equation 4 below.

Where a ₁ and a ₂ are constant values.

The distortion function propagated from the reference video frame is represented by Equation 5 below.

Where μ _prop is a value representing the degree of propagation.

If Q _H and Q _L represent the quantization step sizes of the high bit rate and the low bit rate, respectively, it can be assumed that the initial distortion function of the bit stream compressed with different quantization coefficients is expressed by Equation 6 below.

The overall distortion function may be defined as in Equation 7 below.

The rate function R _k (Q _k ) is defined as in Equation 8 below.

는

및

사이에 차이의 절대값을 의미한다.Where b ₁ and b ₂ are constant values

Is

And

The absolute value of the difference between.

The quantization coefficient calculator 640 calculates a quantization coefficient that satisfies Equation 2 based on Equations 3 and 8. Then, the switching bitstream generator 630 quantizes the switching frame using the quantization coefficients calculated by the quantization coefficient calculator 640 to generate the switching bitstream. For example, the quantization block Q and the inverse inverse quantization block DQ of the switching bitstream generator 630 may use quantization coefficients output by the quantization coefficient calculator 640 as quantization coefficients for quantizing or dequantizing an image frame. use. As a result, the apparatus for converting a video stream according to the present invention can prevent an increase in bitrate that may occur during the conversion by performing the switching between bitstreams compressed at different bit rates without increasing the overall bit rate of the image.

7 is a flowchart illustrating a process of performing a preferred embodiment of the image switching method according to the present invention.

Referring to FIG. 7, the first decoder 610 and the second decoder 620 decode the first bit stream and the second bit stream, respectively, to calculate a first image frame and a second image frame, respectively (S710). The quantization coefficient calculator 640 calculates a quantization coefficient for quantizing the switching frame (S720). The switching bitstream generator 630 supports switching from the first bitstream to the second bitstream based on the first image frame and the second image frame calculated by the first decoder 610 and the second decoder 620. A switching frame for calculating a plurality of switching frames is calculated (S730). The switching bitstream generator 630 generates a switching bitstream including the calculated switching frame (S740).

FIG. 8 is a diagram illustrating a result of generating a switching stream such that 10 switching for each of Foreman, News, and Stefan images is performed by the video stream switching method and the conventional video stream switching method according to the present invention. Referring to FIG. 8, the video stream switching method 830 according to the present invention compares Total Bits and PSNRs for each of Foreman, News, and Stefan images, compared to Periodic I-frames 810, which is one of the conventional video stream switching methods. It can be seen that the value is small or similar. In addition, it can be seen that the video stream switching method 830 according to the present invention has smaller Total Bits and PSNRs values for Foreman, News, and Stefan images than S-frames 820, which is one of the conventional video stream switching methods. have.

9 is a diagram illustrating a result of generating a switching stream without switching for each of the Foreman, News, and Stefan images by using the video stream switching method and the existing video stream switching method according to the present invention. Referring to FIG. 9, the video stream switching method according to the present invention uses Total Bits and PSNRs for respective Foreman, News, and Stefan images as compared to Periodic I-frames 910, which is one of the conventional video stream switching methods 930. It can be seen that the value is small. In addition, the video stream switching method 930 according to the present invention shows that the Total Bits and PSNRs for the Foreman, News, and Stefan images are the same as compared to the S-frames 920, which is one of the conventional video stream switching methods. have.

FIG. 10A is a graph comparing the change of each bit rate in the case where the bitstreams from the low bit rate to the high bit rate are respectively switched by the video stream switching method and the conventional video stream switching method according to the present invention. FIG. 10B is a graph comparing the change of each bit rate in the case where the bitstreams from the high bit rate to the low bit rate are respectively switched by the video stream switching method and the conventional video stream switching method according to the present invention.

10A and 10B, the video stream switching method 1020 and 1070 according to the present invention has a low bit rate and a high bit rate compared to the S-frames 1010 and 1060 which is one of the conventional video stream switching methods. It can be seen that the bit rate of each frame at the time of switching the bitstream and the bitstream from the high bit rate to the low bit rate is gradual.

FIG. 11A is a graph comparing the change of each PSNR in the case where the bitstreams from the low bit rate to the high bit rate are respectively switched by the video stream switching method and the conventional video stream switching method according to the present invention. FIG. Is a graph comparing the change of each PSNR in the case of switching the bitstream from the high bit rate to the low bit rate by the video stream switching method and the conventional video stream switching method according to the present invention.

11A and 11B, the video stream switching methods 1120 and 1170 according to the present invention have a low bit rate and a high bit rate compared to the S-frames 1110 and 1160 which are one of the conventional video stream switching methods. It can be seen that the PSNR value of each frame at the time of performing the bitstream switching and the bitstream switching from the high bit rate to the low bit rate is small.

The invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer device is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer devices so that the computer readable code is stored and executed in a distributed fashion.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the above-described specific preferred embodiments, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

Recently, the Internet has experienced a rapid quantitative expansion in real-time multimedia transmission, mainly in the form of streamed audio visual content such as live transmission or transmission from a pre-recorded source. Moreover, conventional multimedia forms such as streaming and video conferencing are followed by more rich content applications such as Internet multi-channel television and complex immersive environments. This increase in traffic will put a strain on the network and therefore require an application designed to respond to the congestion of the network in order to maintain network stability.

Also, because the current Internet is essentially the best network of the kind and dynamic, the channel bandwidth typically varies in the range of data bit rates from 64 kbps to 1 Mbps. In particular, in order to transmit a video signal through a wireless network that varies in bandwidth as a wireless communication service supporting heterogeneous networks is executed, it is necessary to transmit a video stream in accordance with the bit rate of the bandwidth of each wireless network. This poses a significant problem for video coding and streaming techniques in providing the user with a smooth playback experience and the most useful picture quality. Therefore, it is necessary to monitor the conditions of the network and to ensure that the output bit rate adjusts to the available bandwidth.

The apparatus and method for converting video streams according to the present invention can be used to adaptively adjust and transmit a bit rate of a bitstream in accordance with an Internet environment composed of a network having such diverse and dynamic bandwidths.

1 is a diagram showing a motion estimation process of a background art;

2A is a block diagram illustrating an example of a preferred computing environment suitable for use in one embodiment of the present invention;

2B is a block diagram illustrating another example of a preferred computing environment suitable for use in one embodiment of the present invention;

2C is a block diagram illustrating another example of a preferred computing environment suitable for use in one embodiment of the present invention;

3 is a block diagram showing the configuration of a preferred embodiment of a video stream switching apparatus according to the present invention;

4 is a block diagram showing the configuration of an embodiment of a decoder of a video stream switching apparatus according to the present invention;

FIG. 5A illustrates a switching frame corresponding to each of frames of a first bitstream and a second bitstream; FIG.

5B is a block diagram showing the configuration of an embodiment of a switching bitstream generator of a video stream switching device according to the present invention;

6 is a block diagram showing the configuration of another preferred embodiment of a video stream switching apparatus according to the present invention;

7 is a flowchart illustrating a process of performing an embodiment of an image switching method according to the present invention;

FIG. 8 is a view illustrating a result of generating a switching stream such that 10 switching for each of Foreman, News, and Stefan images is performed by the video stream switching method and the conventional video stream switching method according to the present invention;

9 is a view showing a result of generating a switching stream without switching for each of the Foreman, News, and Stefan images by the video stream switching method and the existing video stream switching method according to the present invention;

FIG. 10A is a graph comparing the change of each bit rate in the case where the bitstreams from the low bit rate to the high bit rate are respectively switched by the video stream switching method and the conventional video stream switching method according to the present invention; FIG.

FIG. 10B is a graph comparing the change of each bit rate in the case where the bitstreams from the high bit rate to the low bit rate are respectively switched by the video stream switching method and the conventional video stream switching method according to the present invention; FIG.

11A is a graph comparing the change of each PSNR in the case where the bitstreams from the low bit rate to the high bit rate are respectively switched by the video stream switching method and the conventional video stream switching method according to the present invention; and

FIG. 11B is a graph comparing the change of each PSNR in the case where the bitstreams from the high bit rate to the low bit rate are respectively switched by the video stream switching method and the conventional video stream switching method according to the present invention.

Claims (8)

An apparatus for converting a video stream for generating a switching bitstream switched from a first bitstream to a second bitstream, A switching bitstream generator configured to generate a switching bitstream including a plurality of switching frames supporting switching from the first bitstream to the second bitstream based on the first bitstream and the second bitstream Including, The switching bitstream generator, Calculating a switching frame corresponding to each of the frames of the second bit stream and the corresponding frames of the first bit stream in the reverse direction based on the frames of the second bit stream at the switching time point between the first bit stream and the second bit stream. A video stream switching device. delete The method of claim 1, The switching bitstream generator, And the switching frame is calculated by the following equation.

Where k is the sequence number of the frame of the second bitstream at the time of switching between the first bitstream and the second bitstream,

Is a picture frame in which the k-th picture frame of the second bitstream is restructured, S _{k, 12} is a switching frame corresponding to the frame of the second bitstream, and S _k-1,12 is a previous frame of S _{k, 12} . Is a switching frame

Denotes an image frame in which the k-2nd image frame of the first bitstream is restructured. The method according to claim 1 or 3, The switching bitstream generator, And generating the switching bitstream by quantizing the switching frame with a quantization coefficient different from the quantization coefficients of the first and second bitstreams. The method according to claim 1 or 3, The video stream switching device, Further comprising: a quantization coefficient calculator for calculating a quantization coefficient based on the following equation, And the switching bitstream generator generates the switching bitstream by quantizing the switching frame using the calculated quantization coefficients.

Where Q _k is a quantization coefficient and D _k (Q _k ) and R _k (Q _k ) are distortion and rate functions, respectively, N _ps is the number of switching streams and R _T is the target bit rate. A video stream switching method for generating a switching bitstream switched from a first bitstream to a second bitstream, Decoding the first bitstream and the second bitstream, respectively, and calculating a first image frame and a second image frame, respectively; A switching frame calculating step of calculating a plurality of switching frames supporting switching from the first bit stream to the second bit stream based on the calculated first image frame and the second image frame; And And a switching bitstream generating step of generating a switching bitstream including the calculated switching frame. The plurality of switching frames are calculated by the following equation.

Where k is the sequence number of the frame of the second bitstream at the time of switching between the first bitstream and the second bitstream,

Is a picture frame in which the k-th picture frame of the second bitstream is restructured, S _{k, 12} is a switching frame corresponding to the frame of the second bitstream, and S _k-1,12 is a previous frame of S _{k, 12} . Is a switching frame

Denotes an image frame in which the k-2nd image frame of the first bitstream is restructured. delete The method of claim 6, The video stream switching method, And a quantization coefficient calculating step of calculating a quantization coefficient for quantizing the calculated switching frame based on the following equation.

Where Q _k is a quantization coefficient and D _k (Q _k ) and R _k (Q _k ) are distortion and rate functions, respectively, N _ps is the number of switching streams and R _T is the target bit rate.

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