In recent years, 3D point clouds have enjoyed a great popularity for representing both static and dynamic 3D objects. When compared to 3D meshes, they offer the advantage of providing a simpler, denser and more close-to-reality representation. However, point clouds always carry a huge amount of data. For a typical example of a point cloud with 0.7 million points per 3D frame at 30 fps, the point cloud raw video needs a bandwidth around 500MB/s. Thus, efficient compression methods are mandatory for ensuring the storage/transmission of such data, which include both geometry and attribute information. In the last years, the issue of 3D point cloud compression (3D-PCC) has emerged as a new field of research. In addition, an ISO/MPEG standardization process on 3D-PCC is currently on-going. In this paper, a comprehensive overview of the 3D-PCC state-of-the-art methods is proposed. Different families of approaches are identified, described in details and summarized, including 1D traversal compression, 2D-oriented techniques, which take leverage of existing 2D image/video compression technologies and finally purely 3D approaches, based on a direct analysis of the 3D data.

https://dl.acm.org/doi/pdf/10.1145/3329714.3338130

3D Point Cloud Compression: A Survey

In order to efficiently archive and transmit large 3D models, lossy and lossless compression methods are needed. We propose a compression scheme for coordinate data of point-based 3D models of surfaces. A point-based model is processed for compression in a pipeline of three subsequent operations, partitioning, parameterization, and coding. First the point set is partitioned yielding a suitable number of point clusters. Each cluster corresponds to a surface patch, that can be parameterized as a height field and resampled on a regular grid. The domains of the height fields have irregular shapes that are encoded losslessly. The height fields themselves are encoded using a shape-adaptive wavelet coder, producing a progressive bitstream for each patch. A rate-distortion optimization provides for an optimal bit allocation for the individual patch codes. With this algorithm design compact codes are produced that are scalable with respect to rate, quality, and resolution. In our encodings of complex 3D models competitive rate-distortion performances were achieved with excellent reconstruction quality at under 3 bits per point (bpp).

Compression of point-based 3D models by shape-adaptive wavelet coding of multi-height fields

We have provided an overview of state-of-the-art ROI coding techniques applied to medical images. These techniques are classified according to the image type they apply to; thus the first class includes ROI coding schemes developed for two-dimensional (2-D) still medical images whereas the second class consists of ROI coding in the case of volumetric images. In the third class, a prototype ROI encoder for compression of angiogram video sequences is presented. ROI coding preserves image quality in diagnostically critical regions by performing advanced image compression, enabling better image examination and addressing issues regarding image handling and transmission in telemedicine systems. The mapping of the ROI from the spatial domain to the wavelet domain is dependent on the used wavelet filters and it is simplified for rectangular and circular regions. Therefore, ROI coding is considered quite important in distributed and networked electronic healthcare.

Region of Interest Coding Techniques for Medical Image Compression

We examine 3-D wavelet coding of video with arbitrary regions of support (AROS). A critically sampled wavelet transform is applied to the AROS and a modified 3-D set partitioning in hierarchical trees (SPIHT) algorithm is used to quantize and code the wavelet coefficients in the AROS only. Experiments show that, for typical MPEG-4 pre-segmented sequences, our proposed method can achieve a gain of up to 5.6 dB in average PSNR at the same rate over 3-D SPIHT coding of regular volumes that embed the AROS of the given video sequences.

/pdf/3-d-wavelet-coding-of-video-with-arbitrary-regions-of-cps90j9elt.pdf

3-D wavelet coding of video with arbitrary regions of support

This paper presents the Secure Shape and Texture SPIHT (SecST-SPIHT) scheme for secure coding of arbitrarily shaped visual objects. The scheme can be employed in a privacy protected surveillance system, whereby visual objects are encrypted so that the content is only available to authorized personnel with the correct decryption key. The secure visual object coder employs shape and texture set partitioning in hierarchical trees (ST-SPIHT) along with a novel selective encryption scheme for efficient, secure storage and transmission of visual object shape and textures. The encryption is performed in the compressed domain and does not affect the rate-distortion performance of the coder. A separate parameter for each encrypted object controls the strength of the encryption versus required processing overhead. Security analyses are provided, demonstrating the confidentiality of both the encrypted and unencrypted portions of the secured output bit-stream, effectively securing the entire object shape and texture content. Experimental results showed that no object details are revealed to attackers who do not possess the correct decryption key. Using typical parameter values and output bit-rates, the SecST-SPIHT coder is shown to require encryption on less than 5% of the output bit-stream, a significant reduction in computational overhead compared to “whole content” encryption schemes.

Privacy Protected Surveillance Using Secure Visual Object Coding

This paper presents a shape-adaptive wavelet coding technique for coding arbitrarily shaped still texture. This technique includes shape-adaptive discrete wavelet transforms (SA-DWTs) and extensions of zerotree entropy (ZTE) coding and embedded zerotree wavelet (EZW) coding. Shape-adaptive wavelet coding is needed for efficiently coding arbitrarily shaped visual objects, which is essential for object-oriented multimedia applications. The challenge is to achieve high coding efficiency while satisfying the functionality of representing arbitrarily shaped visual texture. One of the features of the SA-DWTs is that the number of coefficients after SA-DWTs is identical to the number of pixels in the original arbitrarily shaped visual object. Another feature of the SA-DWT is that the spatial correlation, locality properties of wavelet transforms, and self-similarity across subbands are well preserved in the SA-DWT. Also, for a rectangular region, the SA-DWT becomes identical to the conventional wavelet transforms. For the same reason, the extentions of ZTE and EZW to coding arbitrarily shaped visual objects carefully treat "don't care" nodes in the wavelet trees. Comparison of shape-adaptive wavelet coding with other coding schemes for arbitrarily shaped visual objects shows that shape-adaptive wavelet coding always achieves better coding efficiency than other schemes. One implementation of the shape-adaptive wavelet coding technique has been included in the new multimedia coding standard MPEG-4 for coding arbitrarily shaped still texture. Software implementation is also available.

/pdf/shape-adaptive-discrete-wavelet-transforms-for-arbitrarily-2817q5zqnr.pdf

Shape-adaptive discrete wavelet transforms for arbitrarily shaped visual object coding

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Shape-adaptive discrete wavelet transforms for arbitrarily shaped visual object coding