Efficient Coding of Shape and Transparency for Video Objects

Abstract

Abstract-A novel scheme for coding gray-level alpha planes in object-based video is presented. Gray-level alpha planes convey the shape and the transparency information, which are required for smooth composition of video objects. The algorithm proposed is based on the segmentation of the alpha plane in three layers: binary shape layer, opaque layer, and intermediate layer. Thus, the latter two layers replace the single transparency layer of MPEG-4 Part 2. Different encoding schemes are specifically designed for each layer, utilizing cross-layer correlations to reduce the bit rate. First, the binary shape layer is processed by a novel video shape coder. In intra mode, the DSLSC binary image coder presented in [3] is used. This is extended here with an intermode utilizing temporal redundancies in shape image sequences. Then the opaque layer is compressed by a newly designed scheme which models the strong correlation with the binary shape layer by morphological erosion operations. Finally, three solutions are proposed for coding the intermediate layer. The knowledge of the two previously encoded layers is utilized in order to increase compression efficiency. Experimental results are reported demonstrating that the proposed techniques provide substantial bit rate savings coding shape and transparency when compared to the tools adopted in MPEG-4 Part 2.Index Terms-Alpha plane, MPEG-4, object-based video, shape coding, transparency coding.

Highly efficient contour-based predictive shape coding

“…To further demonstrate the performance of the proposed scheme, some comparison results against some well-known methods, including JBIG, JBIG2, MPEG-4 CAE and DSLSC [14,15], are given in Table 3. Table 3 Comparison results (bits/frame) with the existing methods with N L = 8, a = −31 and b = 32 .…”

“…However, it is a lossy coding scheme and can't be used for lossless applications. In [14,15], a context-based lossless coding scheme (DSLSC) for bilevel-images was proposed. It is based on a local analysis of the digital straightness of the causal part of object boundary, which is used in context definition for arithmetic encoding.…”

“…It is based on a local analysis of the digital straightness of the causal part of object boundary, which is used in context definition for arithmetic encoding. Experimental results show that it outperforms most of the existing techniques [14,15]. In [16], a block-based scheme that combines a quad-tree structure with context-based arithmetic coding was proposed.…”

Edge-Based Reduced-Reference Quality Metric for 3-D Video Compression and Transmission

“…However, the number of bits required for the binary depth edge mask is still high. Therefore, in order to further reduce the overhead, the reference data (i.e., binary edge mask) can be compressed, e.g., through run-length encoding or by considering techniques for binary maps encoding such as those used for MPEG4 [29], [30]. Since the binary edge mask of the depth map is composed of a high number of zero values, a high compression rate is achievable.…”

Binary document image compression using a three-symbol grouped code dictionary

“…This standard allowed a substantial size reduction without loss of information. [10][11][12][13][14][15][16][17][18][19][20][21] Currently, JBIG2 performs the best compression for bilevel and halftone images where a great amount of noise exists. The research of better compression algorithms continued and in 1993, the Joint Bi-level Image Experts Group (JBIG) produced a new standard called the International Organization for Standardization/International Electro-technical Commission (ISO/IEC 11544).…”