Khaled Mamou

A skinning approach for dynamic 3D mesh compression

This paper proposes a novel approach for 3D mesh compression, based on a skinning animation technique. The core of the proposed method is a piecewise affine predictor coupled with a skinning model and a DCT representation of the residuals errors. The experimental evaluation shows that the proposed skinning‐based encoder outperforms (with bitrates gains from 47% to 67%) GV, RT, MPEG‐4/AFX‐IC, D3DMC, PCA and Dynapack techniques. Copyright

FAMC: The MPEG-4 standard for Animated Mesh Compression

This paper presents a new compression technique for 3D dynamic meshes, referred to as FAMC - frame-based animated mesh compression, recently promoted within the MPEG-4 standard as Amendment 2 of part 16 AFX (Animation Framework extension). The heart of the method is a skinning model optimally computed from a frame-based representation and exploited for compression purposes within the framework of a motion compensation strategy. The proposed encoder offers high compression performances (gains in bitrate of 60% with respect to the previous MPEG-4 technique and of 20 to 40% with respect to state-of-the-art approaches) and is well suited for compressing both geometric and photometric attributes.

The New MPEG-4/FAMC Standard for Animated 3D Mesh Compression

This paper presents a new compression technique for 3D dynamic meshes, referred to as FAMC - Frame-based Animated Mesh Compression, recently promoted within the MPEG-4 standard as Amen-dement 2 of part 16 (AFX -Animation Framework extension). The FAMC approach combines a model-based motion-compensation strategy with transform/predictive coding of residual errors. First, a skinning motion-compensation model is automatically derived from a frame-based representation. Subsequently, either 1) DCT/lifting wavelets or 2) layer-based predictive coding is employed to exploit remaining spatio-temporal correlations in the residual signal. Both motion model parameters and residual signal components are finally encoded by using context-based adaptive binary arithmetic coding (CABAC). The proposed FAMC encoder offers high compression performance with gains of 60% in terms of bit-rate savings relative to previous MPEG-4 technology and of 20% to 40% relative to state-of-the-art techniques. FAMC is well suited for compressing both geometric and photometric (normal vectors, colors...) attributes. In addition, FAMC also supports a rich set of functionalities including streaming, scalability (spatial, temporal and quality) and progressive transmission.

Frame-based compression of animated meshes in MPEG-4

This paper presents a new compression technique for 3D dynamic meshes, referred to as FAMC - frame-based animated mesh compression, promoted within the MPEG-4 standard as amendment 2 of part 16 AFX (animation framework extension). The FAMC approach combines a model-based motion compensation strategy, with transform/predictive coding of residual errors. First, a skinning motion compensation model is automatically computed from a frame-based representation and then encoded. Subsequently, either 1) DCT/lifting wavelets or 2) layer-based predictive coding is employed to exploit remaining spatio-temporal correlations in the residual signal. The proposed encoder offers high compression performances (gains in bit rate of 60% with respect to the previous MPEG-4 technique and of 20% to 40% with respect to state-of-the-art approaches) and is well suited for compressing both geometric and photometric (normal vectors, colors...) attributes. In addition, the FAMC method supports a rich set of functionalities including streaming, scalability (spatial, temporal and quality) and progressive transmission.

Multi-Chart Geometry Video: A Compact Representation for 3D Animations

This paper introduces a new compression scheme, so- called Multi-Chart Geometry Video (MCGV), for 3D dynamic meshes with constant connectivity and time-varying geometry. The core of the proposed method is a piecewise affine predictor coupled with a Multi-Chart Geometry IMage (MCGIM) representation of the residual errors. The mesh is first partitioned into vertex clusters whose motion can be accurately described by a unique 3D affine transform. The prediction errors are represented as MCGIMs which are compressed by using standardized image encoders such as JPEG and MPEG-4. The performances of our encoder are objectively evaluated on a data set of six animation sequences with various sizes, geometries and topologies, and exhibiting both rigid and elastic motions. The experimental evaluation shows that the proposed MCGV achieves up to 60% lower compression distortions than the geometry video approach, while outperforming (with 30% to 94% lower distortions) the RT, MPEG-4IAFX-IC, D3DMC, PCA and Dynapack techniques.

Shape approximation for efficient progressive mesh compression

This paper introduces an original multi-resolution 3D mesh compression technique, called Shape Approximation-based Progressive Mesh (SAPM). The proposed approach losslessly compresses the mesh connectivity and exploits it in order to build a smooth approximation of the original mesh. The obtained mesh approximation is then decimated yielding a progressive mesh hierarchy. This hierarchy is used to efficiently predict and progressively transmit the geometry approximation errors. The proposed codec supports both spatial and quality scalabilities and offers high rate-distortion performances. Experimental evaluation shows that the SAPM codec is on average 38–57% more efficient than the state-of-the-art connectivity preserving 3D mesh compression techniques.

Two optimizations of the MPEG-4 FAMC standard for enhanced compression of animated 3D meshes

The MPEG-4 standard adopted a novel technology for compression of dynamic 3D meshes with constant connectivity and time-varying geometry, referred to as FAMC - frame-based animated mesh compression. In this paper, we propose two optimizations of the FAMC approach, aiming at improving the compression efficiency. The first one is based on a PCA (principal component analysis) decomposition of the motion compensation error residuals. The second improves the bi-orthogonal (4-2) wavelet coding approach supported by the standard, by introducing an optimal bit allocation procedure, combined with an adapted quantization of wavelet coefficients. Experimental results show that both optimizations lead to significant gains in compression rate (about 20-30%) at low bitrates.

A Skinning Prediction Scheme for Dynamic 3D Mesh Compression

This paper presents a new prediction-based compression technique for dynamic 3D meshes with constant connectivity and time-varying geometry. The core of the proposed algorithm is a skinning model used for motion compensation. The mesh is first partitioned within vertex clusters that can be described by a single affine motion model. The proposed segmentation technique automatically determines the number of clusters and relays on a decimation strategy privileging the simplification of vertices exhibiting the same affine motion over the whole animation sequence. The residual prediction errors are finally compressed using a temporal-DCT representation. The performances of our encoder are objectively evaluated on a data set of eight animation sequences with various sizes, geometries and topologies, and exhibiting both rigid and elastic motions. The experimental evaluation shows that the proposed compression scheme outperforms state of the art techniques such as MPEG-4/AFX, Dynapack, RT, GV, MCGV, TDCT, PCA and RT compression schemes.

Tuned sparse depth map coding using redundant predefined transform domain

Multiview video plus depth is the most popular 3D video representation that would support novel applications including free viewpoint television. These applications highly depend on high quality rendering of interpolated views which, as well, highly depends on the quality of decoded depth images. Therefore, a depth map coding that preserves perceptual quality, particularly on high frequency regions, is primary. In this paper, we propose a coding depth maps method that deals with emerging sparse signal decomposition technique. Depth images are approximated by a linear combination of few nonzero coefficients and dictionary atoms. Selected atoms are elementary signals based on a mixture of discrete cosine and B-splines of first degree. Sparse depth maps coding is tuned using a couple quality criterion such that depth discontinuities are preserved. The results investigated by objective evaluations over several depth maps imply that the proposed depth maps coding achieves better Rate-Distortion than JPEG and JPEG 2000. Subjective evaluation is also presented to stress the visual quality of interpolated views.