Figure 1.a AVS China encoder [3]

Video

Bit stream

Figure 1.b AVS China decoder [3]

Encoded bit stream

Video output

+

Intra

Motion Compensation

Mode decision

Inverse DCT

Forward Frame Buffer

Figure 1.b.1 Correction to be made at the AVS China decoder showing the intra prediction block connected to +

Major blocks in AVS China [3]:•16-bit 8x8 integer transform.•Quantization and scaling and the scaling is pre-performed in the encoder itself as compared to H.264•Intra prediction 5 modes•Motion compensation 4 modes 8x8, 8x16, 16x8, 16x16•Quarter pixel interpolation•De-blocking •Entropy coding•Minor blocks in AVS China [3]•Motion vector prediction•Adaptive scan

Bit stream flow structure•Sequence•Frame•Slice•Macro Block•Block

Figure 1.c Bit stream flow structure [2]

8X8 Integer cosine transform [2]•AVS adopts a pre-scaled Integer transform technique that is performed in the encoder itself. The forward transform is given as [2],

where f8x8, C8x8 stands for the input pixel matrix and the transformed coefficient matrix respectively•After forward transform and combined scaling is performed [2],

Figure 1.d 8x8 Integer cosine transform and the transformed coefficient matrix [2]

Different prediction and compensation modesIntra frame prediction mode [2]•Spatial prediction technique is implemented in AVS China

•The intra prediction is based on 8x8 block structure.

•AVS China implements 5 luminous intra prediction technique and 4 chrominance intra prediction technique.

•The reconstructed pixels of neighboring block before the De-blocking filtered is used as a reference pixels to current block.

Figure 1.e Neighboring pixels in luminance intra prediction [3]

Figure 1.f Five different luminance intra prediction modes [3]

Inter frame prediction [3]•There are 4 macro blocks specification for the inter frame prediction namely,8x8,8x16,16x8,16x16.•In p-picture there are 5 inter prediction modes namely P_skip (16x16), P_ 8x8, P_8x16, P_16x8, P_16x16.•For the last 4 modes of inter prediction, each partition of macro block is predicted from one of the two reference frames which are latest decoded I or P frame.•There are two kinds of Bi-Predictions in AVS China namely the symmetric and the direct prediction.•In symmetric, only one forward motion vector is transmitted for each partition.•In direct forward and backward motion vectors are derived from motion vector of the collocated block.

Figure 2.a Symmetric mode in AVS China [1]

Interpolation [1]• A quarter pixel interpolation named as Two Step four Tap (TFST) method is implemented in AVS China.

•½ pixel samples are interpolated in step-1 and ¼ pixel samples are interpolated in step 2.

•½ pixel Interpolation method is a 4 Tap filter H1 (-1/8,5/8,5/8,-1/8).•For ordinary ¼ pixel samples a,c,d,f,I,k,n and q in the below shown Figure 2.b 4-Tap filter H2 (1/16, 7/16, 7/16, 1/16) is applied, and four special ¼ pixel samples e,g,p and r are filtered by two-Tap bilinear filter H3 (1/2,1/2).

Figure 2.b Position of integer pixels, ½ pixels and ¼ pixels wherein a, c, d, f, l, k, n and q are ordinary ¼ pixels , e, g, p and r are special ¼ pixels [1]

Performance analysis of AVS China [6]•In MPEG-1, MPEG-2, MPEG-4 the transform block size is 8x8 and their smallest motion compensation block size are 16x16, 16x8 and 8x8 respectively.•In H.264 AVC the smallest transform and intra and inter compensation block size are of 4x4.•The smaller the block size, the more precise is the inter and intra compensation and the smaller the residuals are.•The smaller the block size is, more bits are required for motion vectors and intra prediction modes.•Hence a series of experiment which compares the coding efficiency of block sizes 4x4 and 8x8 have been tabulated.

Figure 2.c Experimental results showing the performance comparison between AVS China and H.264 AVC [6]

Figure 2.d showing the PSNR gain at the same bit rate of 8x8 block size in AVS China over the 4x4 block size in H.264 and the bit rate increase at the same PSNR of the 8x8 block size in AVS China over the 4x4 block size in H.264 for different sequences [6]

Figure 3.a comparison of AVS China with MPEG-2 and H.264/AVC [4], [6]

Figure 3.b comparison of AVS China, H.264/AVC and MPEG-2 on HD sequence [4], [6]

AVS China encoder

AVS China to VP6 transcoder

Internet (Flash Media VP6 )

VP6 decoderVideo

An overview on VP6 coding technique [7]•VP6 is the coding technique developed by On2 Technologies. Flash Media is emerging as the new preferred solution over the existing Windows Media Player, Apple QuickTime, and Real Network Player for providing video services over the Internet. Macromedia adopted VP6 as their video coding algorithm for its Flash player in 2005 [7]. VP6 on Flash8 provides better performance than the existing standards with smoother streaming and low color contrast video images [7]. •Hence forth this creates an opening for developing an AVS to VP6 transcoder to transmit the AVS coded signals over the internet. Proposed ResearchBased on the available reference materials like H.263 to VP6 transcoder [8], AVS to MPEG-2 transcoder [5], performance comparison of AVS and H.264/AVC video coding standard [6], a new method can be proposed to develop the AVS to VP6 transcoder as shown in the figure 4.a .

Figure 4.a showing the implementation of AVS to VP6 transcoder

References1] L. Yu et al. “An Overview of AVS-Video: tools, performance and complexity”, Visual Communications and Image Processing 2005, Proc. of SPIE, vol. 5960, pp.596021, July 31, 2006.2] Zhang, L. Yu “An area-efficient VLSI architecture for AVS intra frame encoder” Visual Communications and Image Processing 2007, Proc. of SPIE-IS & T Electronic Imaging, SPIE vol. 6508, pp. 650822, Jan. 29, 2007. 3] W. Gao et al. “AVS - The Chinese Next-Generation Video Coding Standard” NAB, Las Vegas, 2004. 4] T. Wiegand, J. Sullivan “Overview of the H.264/AVC Coding Standard” IEEE Trans. Circuits Syst. Video Technol., vol.13, pp.560-576, July 2003. 5] J. Wang et al. “An AVS-to-MPEG2 Transcoding System” China Proceedings of 2004 International Symposium on Intelligent Multimedia, Video and Speech Processing , Hong Kong, pp. 302-305, October 20-22, 2004.6] X. Wang, D. Zhao “Performance comparison of AVS and H.264/AVC video coding standards” J. Comput. Sci. & Technol., Vol.21, No.3, pp.310-314 J, May 2006.7] On2 Technologies, Inc. “WHITE PAPER On2 VP6 for Flash8 Video” Sept. 12, 2005.8] C. Holder and H. Kalva , “H.263 to VP6 transcoder”, SPIE, vol.6822 (VCIP) , pp. 68222B, San Jose, CA, Jan. 2008.

Web References:AVS China software1] http://www.avs.org.cn/en.2]http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=199900715 3] ftp://159.226.42.57/public/avs_doc/avs_software

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