STUDY OF AVS CHINA PART 7 JIBEN PROFILE FOR MOBILE APPLICATIONS

Transcription

1 EE 5359 SPRING 2010 PROJECT REPORT STUDY OF AVS CHINA PART 7 JIBEN PROFILE FOR MOBILE APPLICATIONS UNDER: DR. K. R. RAO Jay K Mehta Department of Electrical Engineering, University of Texas, Arlington ID: jay.mehta@mavs.uta.edu 1

2 ACKNOWLEDGEMENT I would like to thank Dr. Rao for all his guidance, support and motivation which led to successful completion of the assigned project. Finally I thank all my friends for helping me throughout the project. 2

3 List of Acronyms AU Access Unit AVS Audio Video Standard AVS-M Audio Video Standard for mobile B-Frame Interpolated Frame CAVLC Context Adaptive Variable Length Coding CBP Coded Block Pattern CIF Common Intermediate Format DIP Direct Intra Prediction DPB Decoded Picture Buffer EOB End of Block HD High Definition HHR Horizontal High Resolution ICT Integer Cosine Transform IDR Instantaneous Decoding Refresh I-Frame Intra Frame IMS IP Multimedia Subsystem ITU-T International Telecommunication Union MB Macroblocks MPEG Moving Picture Experts Group MPM Most Probable Mode MV Motion Vector NAL Network Abstraction Layer 3

4 P-Frame Predicted Frame PIT Prescaled Integer Transform PPS Picture Parameter Set QCIF Quarter Common Intermediate Format QP Quantization Parameter RD Cost Rate Distortion Cost SAD Sum of Absolute Differences SD Standard Definition SEI Supplemental Enhancement Information SPS Sequence Parameter Set VLC Variable Length Coding 4

5 CONTENTS 1 Introduction to AVS Standard 2 Profiles and Levels 3 Data Formats Used in AVS 3.1 Layered Structure Picture Slice Macroblock Block 4 AVS Encoder 5 AVS-M Codec 6 AVS Decoder 7 Major and Minor Tools of AVS-M 7.1 Network Abstraction Layer (NAL) 7.2 Transform 7.3 Quantization 7.4 Intra Prediction Intra_4x Content-based Most Probable Intra Mode Decision Direct Intra Prediction 8 Interframe Prediction 9 Deblocking Filter 10 Entropy Coding 10.1 Context Based Adaptive 2 Dimensional Variable length Coding 11 Error Concealment 12 Error Resilience 13 SSIM 5

6 14 Comparison between AVS Part 2 and AVS Part 7 15 Applications 16 Simulation Results 17 Conclusions and Outcome 18 References 6

7 List of Figures FIGURE 1: HISTORY OF A/V CODING STANDARD FIGURE 2: STANDARD STRUCTURE OF AVS-VIDEO FIGURE 3: LAYERED DATA STRUCTURE FIGURE 4: PICTURE TYPES IN AVS PART 7 FIGURE 5: SLICE STRUCTURE FOR AVS P7 FIGURE 6: MACROBLOCK PARTITIONING FIGURE 7: BLOCK DIAGRAM OF AVS-M ENCODER FIGURE 8: BLOCK DIAGRAM OF AVS-M DECODER FIGURE 9: INTRA_4X4 PREDICTION FIGURE 10: EIGHT DIRECTIONAL PREDICTION MODES OF AVS P7 FIGURE 11: NINE INTRA_4 4 PREDICTION MODES OF AVS P7 FIGURE 12: RELATIONSHIP BETWEEN VARIABLE POSITIONS AND REFERENCE SAMPLE FIGURE 13: THE POSITION OF INTEGER, HALF AND QUARTER PIXEL SAMPLES FIGURE 14: LUMA AND CHROMA BLOCK EDGES FIGURE 15: HORIZONTAL OR VERTICAL EDGE OF 4 4 BLOCK FIGURE 16: FLOW DIAGRAM OF ENTROPY CODING IN AVS 7

8 List of Tables TABLE 1: PROFILES OF AVS CHINA STANDARD TABLE 2: DIFFERENT PARTS OF AVS STANDARD TABLE 3: NAL UNIT TYPES TABLE 4: MACROBLOCK TYPES OF P PICTURE TABLE 5: CONTEST BASED MOST PROBABLE INTRA MODE DECISION TABLE 6: KTH ORDER GOLOMB CODE TABLE 7: COMPARISON BETWEEN AVS PART 2 AND AVS PART 7 TABLE 8: ESULTS FOR QCIF FOREMAN TABLE 9: RESULTS FOR QCIF CAR PHONE TABLE 10: RESULTS FOR QCIF AKIYO TABLE 11: RESULTS FOR CIF TEMPETE 8

9 Abstract Audio video standard for Mobile (AVS-M) [1] is the seventh part of the most recent video coding standard which is developed by AVS workgroup of China which aims for mobile systems and devices with limited processing and power consumption. This project provides an insight into the AVS-M video standard, architecture of AVS-M codec, features it offers and various data formats it supports. The project mainly focuses on providing an understanding of the AVS-M video encoder and decoder, while detailing various logical components within these systems. A performance comparison is made with the other popular standards, and its major applications are discussed. A study is done on the key techniques such as Intra prediction, quarter-pixel interpolation, motion compensation modes, transform and quantization, entropy coding, In-loop deblocking filter, profile and tools that are used in this standard, and the various methods of implementing each key technique are explored. 9

10 1. Introduction to AVS Standard Over the past 20 years, analog based communication around the world has been sidetracked by digital communication. The modes of digital representation of information such as audio and video signals have undergone much transformation in leaps and bounds. With the increase in commercial interest in video communications, the need for international image and video compression standards arose. Many successful standards of audio-video signals have been released which have advanced a plethora of applications, the largest of which is the digital entertainment media. Products have been developed which span a wide range of applications and have been enhanced by the advances in other technologies such as the internet and digital media storage. Figure 1: HISTORY OF A/V CODING STANDARD Moving Picture Experts Group (MPEG) was the first group who formed the format, which quickly became the standard for audio and video compression and transmission. Soon after MPEG-2, was released, being broader in scope, supported interlacing and high definition video formats. Soon later, MPEG-4 uses further coding tools with additional complexity to achieve higher compression factors than MPEG-2. MPEG-4 is very efficient in terms of coding, being almost 1/4th the size of MPEG-1. Although, the MPEG standards had monopoly over most of the video signal formats, several other formats also gave close competition in terms of efficiency, complexity, and storage requirements. 10

11 AVS China [1] was developed by the AVS workgroup, and is currently owned by China. This audio & video standard was initiated by the Chinese government in order to counter the monopoly of the MPEG standards, which were costing it dearly. AVS China clearly seeked to cut down on dependence of audio-video information formatting based on the MPEG formats, thereby providing China with a standard, that helped save millions of dollars of Chinese money being lost to the MPEG group. Figure 2: STANDARD STRUCTURE OF AVS-VIDEO AVS objective was to create a national audio-video standard for broadcasting in China and further extend this technology across the globe. 11

12 2. Profiles and Levels Audio-video coding standard (AVS) is a working group of audio and video coding standard in China, which was established in AVS-China consists of four profiles namely: Jizhun (base) profile, Jiben (basic) profile, Shenzhan (extended) profile and Jiaqiang (enhanced) profile, defined in AVS-video targeting to different applications [16]. Profiles Jizhun profile Jiben profile Shenzhan profile Jiaqiang profile Key Applications Television broadcasting, HDTV, etc. Mobility applications, etc. Video surveillance, etc. Multimedia entertainment, etc. Table 1 PROFILES OF AVS CHINA STANDARD [16] AVS is a set of integrity standard system system video, audio and media copyright management. AVS M is the 7 th part of the video coding standard developed by the AVS Workgroup of China which aims for mobile systems and devices. Part Category 1 System 2 Video 3 Audio 4 Conformance Test 5 Reference Software 6 Digital Media Rights Management 7 Mobile Video 8 Transmit AVS via IP Network 9 AVS File Format 10 Mobile Speech and Audio Coding Table 2 DIFFERENT PARTS OF AVS STANDARD [5] 12

13 In AVS M a Jiben Profile has been defined which has 9 different levels. Profiles and Levels AVS M defies Jiben profile which has 9 levels. 1.0: up to QCIF and 64 kbps 1.1: up to QCIF and 128 kbps 1.2: up to CIF and 384 kbps 1.3: up to CIF and 768 kbps 2.0: up to CIF and 2 Mbps 2.1: up to HHR and 4 Mbps 2.2: up to SD and 4 Mbps 3.0: up to SD and 6 Mbps 3.1: up to SD and 8 Mbps 13

14 3. Data Formats used in AVS AVS follows a layered structure for the data and this representation is seen in the coded bitstream. Figure 3: LAYERED DATA STRUCTURE [2] Sequence layer provides an entry point into the coded video. It consists of a set of mandatory and optional downloadable parameters. Picture The picture layer provides the coded representation of a video frame. It comprises a header with mandatory and optional parameters and optionally with user data. There are 3 types of pictures defined by the AVS: I- Pictures P-Pictures B-Pictures 4:2:0 Sub sampling format is used in AVS M. AVS M supports only I picture and P picture which are shown in Figure 1. AVS M supports only progressive video 14

15 sequence. Therefore, one picture is one frame. P picture can have a maximum of two reference frames for forward prediction. Figure 4 PICTURE TYPES IN AVS PART 7 [11] Slice Slice comprises a series of Macro blocks. They must not overlap, must be contiguous, must begin and terminate at the left and right edges of the picture. A single slice can cover the entire picture. Slices are independently coded so no slice can refer to another slice during the decoding process. Figure 5 SLICE STRUTURE FOR AVS PART 7 [13] 15

16 Macroblocks and Blocks Picture is divided into Macroblocks. The upper left sample of each MB should not exceed picture boundary. Macroblock partitioning is used for motion compensation. The number in each rectangle specifies the order of appearance of motion vectors. Figure 6 MACROBLOCK PARTITIONING [6] 16

17 4. AVS M Encoder Figure 7 AVS M ENCODER [5] 17

18 5. AVS M Codec Each and every input MB needs to either intra predicted or inter predicted. In an AVS M Encoder, S0 is used to select the right prediction method for the current MB whereas in the Decoder, the S0 is controlled by the MB type of current MB. The intra predictions are derived from the neighboring pixels in the left and top blocks. The unit size of intra prediction is 4x4 because of the 4x4 integer cosine transform used by the AVS M. The inter predictions are derived from the decoded frames. AVS M employs an adaptive variable length coding (VLC) coding technique. The reconstructed image is the sum of the prediction and current reconstructed error image. AVS M uses the deblocking filter in motion compensation loop. The deblocking process directly acts on the reconstructed reference first across vertical edges and then across horizontal edges. 18

19 6. AVS M Decoder Figure 8 AVS M DECODER [3] 19

20 7. Major and Minor tools of AVS M Network Abstraction layer NAL Supplemental Enhancement Information SEI Transform 4x4 integer transform Quantization and scaling- scaling only in encoder. Intra prediction 9 modes, simple 4x4 intra prediction and direct intra prediction Motion compensation 16x16/16x8/8x16/8x8/8x4/4x8/4x4 modes Quarter pixel interpolation 8 tap horizontal interpolation filter and 4 tap vertical interpolation filter Simplified in loop deblocking filter Entropy coding Error resilience Network Abstraction Layer [NAL] In AVS M Video compression, a compressed video bitstream is made up of Access units (AUs). Table 3 NAL UNIT TYPES [2] 20

21 AU contains information for decoding a picture. AU consists a no. of NAL units, some of them are optional. A NAL unit can be a sequence parameter set(sps), a picture parameter set(pps), an SEI, a picture header, or a slice_layer_rbsp (raw byte sequence payload) which consists of a slice_header followed by slice data. Table 4 MACROBLOCK TYPES OF P PICTURE [7] Transform 4x4 is the unit of transform, intra prediction and smallest motion compensation in AVS M. The 4x4 transform used in AVS M is AVS M uses a prescaled integer transform (PIT) technology; all of the scale related operations have been done in the encoder. The decoder does not need any scale operations. PIT is used in AVS M to reduce complexity. Quantization It is performed by the adaptive uniform quantizer on the transform coefficients. The step size of the quantizer can be varied to provide rate control. The transmitted step size quantization parameter is used directly for luminance coefficients and for chrominance coefficients it is modified on the upper end of its range. The quantization parameter varies from 0 to 63 in steps of one. 21

22 Intra Prediction There are two types of Intra Prediction which are used. [A] Intra _4x4 [B] Direct Intra Prediction (DIP) It significantly reduces the complexity and maintains a comparable performance. Intra_4x4 Each 4x4 block is predicted from spatially neighboring samples. For each 4x4 block, one of the nine predictions modes can be utilized to exploit spatial correlation including eight directional prediction modes (such as Down Left, vertical etc.) and non-directional prediction mode (DC). The 16 samples of the 4x4 block which are labeled as a-p are predicted using prior decoded samples in adjacent block label as A-D, E-H and X. The up right pixels used to predict are expanded by pixel sample D and the down left pixels are expanded by H. Figure 9 INTRA_4X4 PREDICTION 22

23 Figure 10 EIGHT DIRECTIONAL PREDICTION MODES OF AVS PART 7 1 of the 9 prediction modes shown below is used for spatial correlation. Figure 11 NINE INTRA_4X4 PREDICTION MODES OF AVS PART 7 Content based Most Probable Intra Mode Decision A statistical model is used to determine the most probable intra mode of current block based on video characteristics and content correlation. A look up table is used to predict the most probable intra mode decision of current block. Irrespective 23

24 of whether Intra_4x4 or DIP is used, the most probable mode decision method is described as follows: Get the intra mode of up block and left block. If the up (or left) block is not available for intra mode prediction, the mode up (or left) block is defined as -1. Use the up intra mode and left intra mode to find the most probable mode in the table. If the current MB is coded as Intra_4x4 mode, the intra prediction mode is coded as follows: If the best mode equals to the most probable mode, 1 bit of flag is transmitted to each block to indicate the mode of current block is its most probable mode. Table 5 CONTENT BASED MOST PROBABLE INTRA MODE DECISION If the best mode is not the most probable mode, the 1 bit flag is to indicate the mode of current block is not the most probably mode, and then a 3 bit mode information is transmitted. Thus mode information of each block can be presented in 1 bit or 4 bits. 24

25 Direct Intra Prediction When direct intra prediction is used, a new method is followed to code the intra prediction mode information. A rate distortion based direct intra prediction mainly contains 5 steps. Step 1: All 16 4x4 blocks in a MB use their most probable modes to do Intra_4x4 prediction and calculate RDCost(DIP) of this MB. RDCost(mode)=D(mode) + λ.r(mode) (11) Step 2: Mode search of Intra_4x4, find the best intra prediction mode of each block, and calculate RDCost(Intra_4x4). Step 3: Compare RDCost(DIP) and RDCost(Intra_4x4). If RDCost(DIP) is less than the RDCost(Intra_4x4), DIP flags equals to 1 then go to step 4, else DIP flags equals to 0 and go to step 5. Step 4: Encode the MB using DIP and finish the encoding of this MB. Step 5: Encode the MB using ordinary Intra_4x4 and finish the encoding of this MB. 25

26 8. Interframe Prediction AVS M defines I picture and P picture. P picture uses forward motion compensated prediction. The maximum number of reference pictures used by a P picture is 2. It also specifies nonreference P pictures. If the nal_ref_idc of a P picture is equal to 0, the P picture shall not be used as a reference picture. The nonreference P pictures can be used for temporal scalability. The reference pictures are identified by the reference picture number, which is 0 for IDR picture. After decoding current picture, if nal_ref_idc of current picture is not equal to 0, then current picture is marked as used for reference. If current picture is an IDR picture, all reference pictures except current picture shall be marked as unused for reference. Otherwise, if nal_unit_type of current picture is not equal to 0 and the total no. of reference pictures excluding current picture is equal to the num ref frames, the foll. applies: If num ref frames is 1, reference pictures excluding current picture in DBP shall be marked as unused for reference. If num ref frames is 2 and sliding window size is 2, the reference picture excluding the current picture in DPB with smaller reference picture number shall be marked as unused for reference. Otherwise, id num ref frames is 2 and sliding window size is 1, the reference picture excluding the current picture in DBP with larger reference picture number shall be marked as unused for reference. The size of motion compensation block can be 16x16, 16x8, 8x16, 8x8, 8x4, 4x8, and 4x4. If the half_pixel_mv_flag is equal to 1, the precision of the motion vector is up to ½ pixels; otherwise the precision of motion vector is up to ¼ pixels. When half_pixel_mv_flag is not present in the bitstream, it shall be inferred to be

27 The interpolated values at half sample positions can be obtained using 8 tap filter F1 = (-1/4, -12, 41, 41, -12, 4, -1) and 4 tap filter F2 = (-1, 5, 5, -1). The positions of the integer, half and quarter pixel samples are shown in the figure 8. Capital letters indicate integer sample positions, while small letters indicate half and quarter sample positions. Figure 12 RELATIONS BETWEEN VARIALBLE POSITIONS AND REFERENCE SAMPLES Figure 13 THE POSITION OF INTEGER, HALF, AND QUARTER PIXEL SAMPLES 27

28 9. Deblocking Filter AVS M makes use of a simplified deblocking filter, wherein boundary strength is decided at MB level. Filtering is applied to the boundaries of luma and chroma blocks except for the boundaries of the pictures or slice. Intra prediction MB usually has more and bigger residuals than that of inter prediction MB, which leads to very strong blocking artifacts at the same QP. A stronger filter is applied to intra predicted MB and a weak filter is applied to inter predicted MB. When QP is not very large, the distortion caused by the quantization is relatively small, henceforth no filtering is required. If the following three conditions hold good then the filtering process is applied otherwise the filtering process is bypassed. p0-q0 <α (IndexA) p1-p0 <β (IndexB) q1-q0 <β (IndexB) Figure 14 LUMA AND CHROMA BLOCK EDGES Where α and β can be calculated by IndexA, IndexB. p1, p0, q1, q0 are samples across every sample level boundary. Figure 15 HORIZONTAL AND VERTICAL EDGE OF 4X4 BLOCK 28

29 10. Entropy Coding Entropy coding involves mapping from a video signal after prediction and transforming to a variable length coded bitstream. Figure 15 FLOW DIAGRAM OF ENTROPY CODING IN AVS PART 7 29

30 AVS M uses Exp-Golomb code, as shown in the table below to encode syntax elements such as quantized coefficients, macroblock coding type, and motion vectors. 18 coding tables are used in quantized coefficients encoding. The encoder uses the run and the absolute value of the current coefficient to select the table. Table 6 KTH ORDER GOLOMB CODE Context based Adaptive 2-D Variable Length Coding In AVS an efficient context based adaptive 2D variable length coding is designed for coding transform coefficients in a 4x4 block. The transform coefficients are mapped into one dimensional (level, run) sequence by the reverse zigzag scan. It employs 2D joint VLC to remove the redundancy between the levels and runs in transform coefficient blocks. It employs multiple conditionally trained 2D VLC tables to better match different (level, run) s probability distributions at different coding phases by automatic table switching. It makes use of an improved table switching method and an improved escape coding method. Also, it employs a new Coded Block Pattern (CBP), CBP_4x4 to be compatible better with the 4x4 transform. The transform block size in AVS is 4x4, so a new 4- bit syntax element CBP_4x4 is introduced. 30

31 11. Error Concealment To deal with the transmission error problem numerous techniques have been specified which are: Forward Error Concealment: Encoder plays the primary role. Backward error Concealment: estimation of lost information due to transmission errors in which the decoder fulfills the error concealment task. Interactive error Concealment: best reconstruction quality, but difficult to implement. 31

32 12. Error Resilience With the purpose of error concealment, scene signaling in SEI illustrates two kinds of information: (1) Frames in which the short change starts and ends. (2) The type of the scene transition. If a part of the current picture with which a scene information SEI message is associated is lost or corrupted, the decoder may apply a spatial error concealment algorithm to construct the lost or corrupted parts of the current picture if the scene has changed since the previous received picture. Otherwise the decoder may use a spatiotemporal error concealment algorithm. 32

33 13. SSIM The structural similarity (SSIM) index is a method for measuring the similarity between two images. The SSIM index is a full reference metric. In other words, the measuring of image quality based on an initial uncompressed or distortion-free image as reference. SSIM is designed to improve on traditional methods like Peak to peak Signal to Noise ratio (PSNR) and Mean Squared Error (MSE), which have proved to be inconsistent with human eye perception. 33

34 14. Comparison between AVS Part 2 and AVS Part 7 Table 7 Comparison between AVS Part 2 and AVS Part 7 [2] 34

35 15. Applications AVS Part-7: Mobile video Jiben Profile Record and local playback on mobile devices Multimedia Message Service (MMS) Streaming and broadcasting Real-time video conversation 35

36 16. Simulation Results Input Sequence: QCIF Foreman QCIF sequence: Foreman (4:2:0 format) Total No: of frames: 300 frames. Width: 176. Height: 144. Frame rate: 20 fps. 36

37 PSNR v/s Bitrate for Foreman QCIF Table 8: Results for QCIF Foreman QP Original File Size [Kb] Compressed File Size [Kb] Compression Ratio Bit Rate [Kbps] Y-PSNR [db] : : : : : : : : : :

38 Input Sequence: QCIF Car Phone QCIF sequence: Car Phone (4:2:0 format) Total No: of frames: 300 frames.. Width: 176. Height: 144. Frame rate: 20 fps. 38

39 PSNR v/s Bitrate for QCIF Car Phone Table 9: Results for QCIF Car phone QP Original File Size [Kb] Compressed File Size [Kb] Compression Ratio Bit [Kbps] Rate Y-PSNR [db] : : : : : : : : : :

40 Input Sequence: QCIF Akiyo QCIF sequence: Akiyo (4:2:0 format) Total No: of frames: 300 frames.. Width: 176. Height: 144. Frame rate: 20 fps. 40

41 Table 10: Results for QCIF Akiyo QP Original File Size [Kb] Compressed File Size [Kb] Compression Ratio Bit Rate [Kbps] Y-PSNR [db] Y-SSIM : : : : : : : : : :

42 Input Sequence: CIF Tempete CIF sequence: Tempete (4:2:0 format) Total No: of frames: 260 frames. Width: 352. Height: 288. Frame rate: 20fps 42

43 Table 11: Results for CIF Tempete QP Original File Size [Kb] Compressed File Size [Kb] Compression Ratio Bit Rate [Kbps] Y-PSNR [db] Y-SSIM : : : : : : : : : :

44 17. Conclusions and Outcome AVS M is an application driven coding standard with well optimized and efficient techniques. AVS part 7 targets low complexity and low picture resolution mobility applications. The AVS encoder and decoder are implemented using AVS M software. Tests are carried out on various QCIF and CIF sequences. The Bit rate, PSNR and SSIM values are tabulated. The performance of AVS-china was analyzed by varying the quantization parameter. The PSNR, Bit rate, SSIM are calculated. Here at higher QP the performance is degraded and vice versa. The project helped in increasing familiarity in working with this codec. The experimental results gave an insight into the efficiency of this codec. The different aspects of simulation of this codec such as the following was learned and understood like Modes of Configuration, Modification of Parameters, Input sequence specifications, Analyze the codec output, Efficient use of time and re-use of knowledge. 44

45 18. References [1] AVS working group official website, [2] AVS Project and AVS-Video Techniques Lu Yu, Zhejiang University, Dec.13, 2005 ISPACS, [3] L.Yuet al., Overview of AVS-Video: Tools, performance and complexity, SPIE VCIP, vol. 5960, pp ~ , Beijing, China, July [4] W.Gaoet al., AVS the Chinese next-generation video coding standard, National Association of Broadcasters, Las Vegas, [5] L.Fan, Mobile Multimedia Broadcasting Standards, ISBN: , Springer US, [6] F.Yi et al., Low-Complexity Tools in AVS Part 7, J. Comput. Sci. Technol, vol.21, pp , May [7]L.YU, S.Chenand J.Wang, Overviewof AVS-video coding standards, Signal Process: Image Commun, vol. 24, Issue 4, pp , April [8] W.Gao, AVS A project towards to an open and cost efficient Chinese national standard, ITU-T VICA workshop, ITU Headquarters, Geneva, July [9] Z.Zhang et al., Improved Intra Prediction Mode-decision Method, Proc. of SPIE,Vol. 5960, pp W-1~ 59601W-9, Beijing, China, July [10] Z.Ma et al., Intra Coding of AVS Part 7 Video Coding Standard, J. Comput. Sci. Technol, vol.21, Feb.2006 [11] W.Gao and T.Huang AVS Standard -Status and Future Plan, Workshop on Multimedia New Technologies and Application, Shenzhen, China, Oct [12] Y.Cheng et al., Analysisand application of error concealment tools in AVS-M decoder, Journal of Zhejiang University Science A, vol. 7, pp 54-58, Jan [13] M.Liuand Z.Wei A fast mode decision algorithm for intra prediction in AVS- M video coding Volume 1, ICWAPR apos;07, Issue, 2-4, pp , Nov

46 [14] Q.Wang et al., Context-Based 2D-VLC for Video Coding, IEEE Int l Conf. on Multimedia and Expo (ICME), vol.1, pp , June [15] Audio Video Coding Standard (AVS) of China, King Ngi Ngan, Department of Electronic Engineering, The Chinese University of Hong Kong, 11/19/2009. [16] W.Gao,K.N. NganandL.Yu Special issue on AVS and its applications: Guest editorial, Signal Process: Image Commun, vol. 24, Issue 4, pp , April [17] S.W.Maand W.Gao, Low Complexity Integer Transform and Adaptive Quantization Optimization, J. Comput. Sci. Technol, vol.21, pp , May [18] S.Hu, X.Zhangand Z.Yang, Efficient Implementation of Interpolation for AVS, Image and Signal Processing, Congress on Volume 3, Issue, May 2008, pp [19] R. Schafer and T. Sikora, Digital video coding standards and their role in video communications, Proc. of the IEEE, vol. 83, pp , June