Slide 1Motivation:Brief overview of the thesis:Table of contents:Introduction to AVS-M[24]Different parts of AVS [10]Key tools of AVS-M[31]:Layered Data StructureAVS-M Codec[10]EncoderDecoderIntra adaptive directional prediction [25]Intra predictionIntra predictionInter-frame predictionInter frame block sizes [9]:sub-pixel motion estimation by interpolation[15][16]:Complexity calculation for AVS-MContinued…Various techniques to reduce complexityIntroduction to machine learning [32]:Machine learning algorithm C4.5[33]Proposed encoder:Implementation steps [2]:-Continued…Decision tree used in encoder:Slide 27Comparison of the encoding time:Bar chart comparing encoding time (sec.):Comparison of the PSNR (Y- dB)Bar chart comparing PSNR (Y in dB)Comparison of the PSNR (U in dB)Bar chart comparing PSNR (U in dB)Comparison of the PSNR (V in dB)Bar chart comparing PSNR (V in dB)Comparison of PSNR (YUV in dB)Bar chart comparing PSNR(YUV in dB)Comparison of number of bits usedBar chart comparing # of bits:Comparison of performances of AVS-M and proposed encoderContinued…Conclusions:Future work:References:Continued…Continued…Continued…Continued…Continued…Low complexity AVS-M by implementing machine learning algorithm C4.5By :- Ramolia Pragnesh R.Guided by :- Dr. K.R.Rao. Term :- Spring 2011.1Motivation:Increase in demand of multimedia contents over internet and wireless networks. Bandwidth is the too expensive resource to increase it in proportion to the increase in demand of data.Video codec plays an important role here, compressing the data with high efficiency tools.Complexity comes along with high efficiency in codecs.Implementing hardware solutions for low end devices like mobile, is very expensive and also creates problem of over heating and power consumption.2Brief overview of the thesis:3Figure 1: Proposed encoder with C4.5Table of contents:Overview of AVS-M.Complexity calculation in AVS-M.Various approaches to reduce complexity.Introduction to machine learning and algorithm C4.5Proposed encoder.Results.Future work.References.4Introduction to AVS-M[24]AVS-M is the seventh part of video coding standard developed by AVS working group of China targeting mobile applications.It has 9 different levels for different formats [16].It supports only progressive video coding hence codes frames only[22].It uses only 4:2:0 chroma sub-sampling format[22].It uses only I and P frames[22].5Different parts of AVS [10]Part Name 1 System2 Video3 Audio4 Conformance test5 Reference software6 Digital media rights management7 Mobile video8 Transmit AVS via IP network9 AVS file format10 Mobile speech and audio codingTable 1: Different parts of AVS 6Key tools of AVS-M[31]:Network abstraction layer (NAL).Supplemental enhancement information (SEI).Transform –4x4 integer transform.Adaptive quantization of step size varying from 0-63.Intra prediction –9 modes (Fig. 5 ), simple 4x4 intra prediction and direct intra prediction[25].Inter prediction –16x16, 16x8, 8x16, 8x8, 8x4, 4x8, and 4x4 block sizes for ME/MC(Fig. 7).Quarter pixel accuracy in motion estimation.Simplified in-loop de-blocking filter.Entropy coding.Error resilience.7Layered Data StructureSequencePictureSliceMacro BlockBlockSequenceG.O.P.PictureSliceMacro blockBlock8Figure 2: Layered data structure of AVS-MAVS-M Codec[10]Each MB needs to be intra or inter predicted.Switch S0(Fig. 3 ) is used to decide between inter and intra based type of MB.Unit size for intra prediction is block size of 4x4, and predictions are derived based on left and upper blocks.Inter predictions are derived from blocks of varying sizes: 16x16, 16x8, 8x16, 8x8, 8x4, 4x8, and 4x4 from locally reconstructed frames .Transform coefficients are coded by VLC.Deblocking filter is applied on reconstructed image.9Encoder Figure 3: Encoder of AVS-M [10] 10DecoderFigure 4: Decoder of AVS-M [10]11Intra adaptive directional prediction [25]Figure 5: Intra adaptive directional prediction12Intra predictionIntra prediction scheme in AVS-M brings much simplicity as compared to H.264 baseline profile of H.264.It uses 4x4 block as the unit for intra-prediction.It uses 2 modes of prediction in intra prediction: intra_4x4 and direct intra prediction.Intra_4x4 uses content based most probable intra mode decision as shown in Table 2 to save bits, where U and L represents the upper ad left blocks as shown in Fig. 6. Direct intra prediction brings much of the compression based on trade-off decision.Upper block[U]Left block[L]Current blockFig. 6 : Current block and neighboring block representation [16]13Intra prediction U L -1 0 1 2 3 4 5 6 7 8-1 8 8 8 8 8 8 8 8 8 8 0 8 0 0 2 0 0 0 2 0 2 1 8 2 1 2 2 2 2 2 2 2 2 8 2 2 2 2 2 2 2 2 2 3 8 2 1 2 3 4 5 2 7 2 4 8 4 4 2 4 4 4 6 4 4 5 8 5 5 2 5 5 5 6 5 5 6 8 6 6 6 6 6 6 6 6 6 7 8 7 7 2 7 7 7 6 7 7 8 8 0 1 2 3 4 5 6 7 8Table 2: Content based most probable mode decision table [25]Mode ‘-1’ is assigned to ‘L’ or “U’ when the current block does not have ‘Left’ or ‘Upper’ block respectively. 14Inter-frame predictionSize of the blocks in inter-frame prediction can be 16x16, 16x8, 8x16, 8x8, 8x4, 4x8, and 4x4 depending on the amount of information present within the macro-block[9].Motion is predicted up to ¼ pixel accuracy. If the half_pixel_mv_flag is 1 then it is up to ½ pixel accuracy.Half pixel and quarter pixel accurate motion vectors are calculated by interpolating the reference frame, by applying filters. (Fig. 8)15Inter frame block sizes [9]:7 block sizes are present in AVS-M for inter frame prediction .Figure 7: Inter frame prediction block sizes16sub-pixel motion estimation by interpolation[15][16]:Figure 8: interpolation of sub-pixels (hatched lines show half-pixels, empty circles are quarter-pixels, and capital letters represent full-pixels.)17Complexity calculation for AVS-M Variable 7 block sizes in Inter Mode.It supports 9 intra_4*4 mode and 1 Direct_intra prediction mode.Full search for motion estimation gives the optimum result, but that comes along with implementation complexity.For example, assuming FS(full search) and M block types, N reference frames and a search range for each reference frame and block type equal to +/- W, check for N x M x (2W + 1)^2 positions, to find out inter prediction mode and its motion vector, that too inter
View Full Document
Unlocking...