COST 211 ter work on the Simulation Model for Object-based Coding (SIMOC)

While the COST 211 ter work on block-based hybrid coding migrated from SIM3 to H.263 by being accepted as starting point for its development within the ITU-T, a new work item on second generation coding techniques was started in 1993, aiming at an improved image quality for low bit rate video transmission. As starting point for this activity, the approach of object-based analysis-synthesis coding [1][8] was chosen by the COST 211 ter SIM group. Thus, the test m

The general structure of the SIMOC algorithm is depicted in the following block diagram:

As can be seen in the block diagram, in a first step the input image is analysed, i.e. the shape and motion parameters of 2D objects in the image are estimated. Then, these parameters are coded and transmitted to the receiver. At the receiver side, the parameters are decoded and used to reconstruct the image by image synthesis. At the encoder side, the parameters are decoded and the image is reconstructed for analysis of the next input image; additionally, the decoded parameters are stored in a memory

The main properties of the SIMOC approach can be summarised as follows:

• Automatic segmentation of the input images in order to estimate the 2D-shape of moving objects in the scene
• Object-based motion compensated prediction in order to reduce prediction errors especially at boundaries of moving objects
• Motion compensation with dense displacement vector field (generated by interpolation of the actually transmitted sparse displacement vectors) in order to avoid blocking artifacts
• Efficient 2D-shape coding by polygon-approximation and transmission of vertex points
• Allowing subjectively non visible artifacts (geometrical distortions) and concentrate texture update on areas with high errors
• Texture coding by DCT- and VQ-based techniques, taking into account the arbirary shape of the objects

The SIMOC was implemented as a software package in a collaborative approach by many members of the group. Then, new proposals were made in order to improve the algorithm under development. During that time, the ISO/MPEG group initiated their new work item MPEG-4 [3][9], which aimed at the development of an efficient multimedia coding standard providing, among others, functionalities like improved coding

Parts of these proposals as well as parts of other proposals like many H.263 based techniques were then used to form the first MPEG-4 Verification Model (VM) [7]. Of course, the SIMOC is not identical with the now nearly finished final MPEG-4 standard Version 1, but all the experience, some of the techniques and especially the idea of object-based coding, all rooting to the SIMOC work of COST 211 ter, had a large impact on this new multimedia standard

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References

[1] H.G. Musmann, M. Hötter, J. Ostermann, "Object-oriented analysis-synthesis coding of moving images", Signal Processing: Image Communication, Vol. 1, No. 2, pp. 117-138, October 1989.

[2] COST 211ter Simulation Subgroup, DCU (Editor), "Simulation model for object-based coding (SIMOC)", Doc. SIM(93)34, Kjeller, June 1993.

[3] MPEG group, "MPEG-4 project description", Doc. ISO/IEC JTC1/SC29WG11 N1177, Munich, January 1996.

[4] P. Gerken, M. Wollborn, S. Schulz, "An object-based layered codec as proposal for MPEG-4 scalability and compression tests - Technical Description", Doc. ISO/IEC JTC1/SC29WG11 M359, Dallas, November 1995.

[5] P. Gerken, M. Wollborn, S. Schulz, "Polygon/spline approximation of arbitrary image region shapes as proposal for MPEG-4 tool evaluation - Technical Description", Doc. ISO/IEC JTC1/SC29WG11 M360, Dallas, November 1995.

[6] J. DeLameilleure, "Segmentation based coding scheme for object scalable and quality scalable coding of video", Doc. ISO/IEC JTC1/SC29WG11 M415, Dallas, November 1995.

[7] MPEG Video Group, "MPEG-4 Video Verification Model - Version 1.0", Doc. ISO/IEC JTC1/SC29WG11 N1172, Munich, January 1996.

[8] P. Gerken, "Object-based analysis-synthesis coding of image sequences at very low bit rates", IEEE Transactions on Circuits and Systems for Video Technology: Special Issue on Very Low Bit Rate Video Coding", Vol. 4, No. 3, pp. 228-235, June 1994.

[9] MPEG group, "Overview over the MPEG-4 Version 1 standard", Doc. ISO/IEC JTC1/SC29WG11 N1909, Fribourg, October 1997.