The objective approaches of 3D image quality assessment play a key role for the development of compression standards and various 3D multimedia applications. The quality assessment of 3D images faces more new challenges, such as asymmetric stereo compression, depth perception, and virtual view synthesis, than its 2D counterparts. In addition, the widely used 2D image quality metrics (e.g., PSNR and SSIM) cannot be directly applied to deal with these newly introduced challenges. This statement can be verified by the low correlation between the computed objective measures and the subjectively measured mean opinion scores (MOSs), when 3D images are the tested targets. In order to meet these newly introduced challenges, in this paper, besides traditional 2D image metrics, the binocular integration behaviors-the binocular combination and the binocular frequency integration, are utilized as the bases for measuring the quality of stereoscopic 3D images. The effectiveness of the proposed metrics is verified by conducting subjective evaluations on publicly available stereoscopic image databases. Experimental results show that significant consistency could be reached between the measured MOS and the proposed metrics, in which the correlation coefficient between them can go up to 0.88. Furthermore, we found that the proposed metrics can also address the quality assessment of the synthesized color-plus-depth 3D images well. Therefore, it is our belief that the binocular integration behaviors are important factors in the development of objective quality assessment for 3D images.

Quality Assessment of Stereoscopic 3D Image Compression by Binocular Integration Behaviors

Perceptual quality assessment is a challenging issue in 3D signal processing research. It is important to study 3D signal directly instead of studying simple extension of the 2D metrics directly to the 3D case as in some previous studies. In this paper, we propose a new perceptual full-reference quality assessment metric of stereoscopic images by considering the binocular visual characteristics. The major technical contribution of this paper is that the binocular perception and combination properties are considered in quality assessment. To be more specific, we first perform left-right consistency checks and compare matching error between the corresponding pixels in binocular disparity calculation, and classify the stereoscopic images into non-corresponding, binocular fusion, and binocular suppression regions. Also, local phase and local amplitude maps are extracted from the original and distorted stereoscopic images as features in quality assessment. Then, each region is evaluated independently by considering its binocular perception property, and all evaluation results are integrated into an overall score. Besides, a binocular just noticeable difference model is used to reflect the visual sensitivity for the binocular fusion and suppression regions. Experimental results show that compared with the relevant existing metrics, the proposed metric can achieve higher consistency with subjective assessment of stereoscopic images.

Perceptual Full-Reference Quality Assessment of Stereoscopic Images by Considering Binocular Visual Characteristics

With the increasing demand for image-based applications, the efficient and reliable evaluation of image quality has increased in importance. Measuring the image quality is of fundamental importance for numerous image processing applications, where the goal of image quality assessment (IQA) methods is to automatically evaluate the quality of images in agreement with human quality judgments. Numerous IQA methods have been proposed over the past years to fulfill this goal. In this paper, a survey of the quality assessment methods for conventional image signals, as well as the newly emerged ones, which includes the high dynamic range (HDR) and 3-D images, is presented. A comprehensive explanation of the subjective and objective IQA and their classification is provided. Six widely used subjective quality datasets, and performance measures are reviewed. Emphasis is given to the full-reference image quality assessment (FR-IQA) methods, and 9 often-used quality measures (including mean squared error (MSE), structural similarity index (SSIM), multi-scale structural similarity index (MS-SSIM), visual information fidelity (VIF), most apparent distortion (MAD), feature similarity measure (FSIM), feature similarity measure for color images (FSIMC), dynamic range independent measure (DRIM), and tone-mapped images quality index (TMQI)) are carefully described, and their performance and computation time on four subjective quality datasets are evaluated. Furthermore, a brief introduction to 3-D IQA is provided and the issues related to this area of research are reviewed.

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Subjective and Objective Quality Assessment of Image: A Survey

Quality perception of 3-D images is one of the most important parameters for accelerating advances in 3-D imaging fields. Despite active research in recent years for understanding the quality perception of 3-D images, binocular quality perception of asymmetric distortions in stereoscopic images is not thoroughly comprehended. In this paper, we explore the relationship between the perceptual quality of stereoscopic images and visual information, and introduce a model for binocular quality perception. Based on this binocular quality perception model, a no-reference quality metric for stereoscopic images is proposed. The proposed metric is a top-down method modeling the binocular quality perception of the human visual system in the context of blurriness and blockiness. Perceptual blurriness and blockiness scores of left and right images were computed using local blurriness, blockiness, and visual saliency information and then combined into an overall quality index using the binocular quality perception model. Experiments for image and video databases show that the proposed metric provides consistent correlations with subjective quality scores. The results also show that the proposed metric provides higher performance than existing full-reference methods even though the proposed method is a no-reference approach.

No-Reference Quality Assessment for Stereoscopic Images Based on Binocular Quality Perception

Quality assessment of 3D images encounters more challenges than its 2D counterparts. Directly applying 2D image quality metrics is not the solution. In this paper, we propose a new full-reference quality assessment for stereoscopic images by learning binocular receptive field properties to be more in line with human visual perception. To be more specific, in the training phase, we learn a multiscale dictionary from the training database, so that the latent structure of images can be represented as a set of basis vectors. In the quality estimation phase, we compute sparse feature similarity index based on the estimated sparse coefficient vectors by considering their phase difference and amplitude difference, and compute global luminance similarity index by considering luminance changes. The final quality score is obtained by incorporating binocular combination based on sparse energy and sparse complexity. Experimental results on five public 3D image quality assessment databases demonstrate that in comparison with the most related existing methods, the devised algorithm achieves high consistency with subjective assessment.

Full-Reference Quality Assessment of Stereoscopic Images by Learning Binocular Receptive Field Properties

In the near future, many conventional video applications are likely to be replaced by immersive video to provide a sense of ldquobeing there.rdquo This transition is facilitated by the recent advancement of 3D capture, coding, transmission, and display technologies. Stereoscopic video is the simplest form of 3D video available in the literature. ldquoColor plus depth maprdquo based stereoscopic video has attracted significant attention, as it can reduce storage and bandwidth requirements for the transmission of stereoscopic content over communication channels. However, quality assessment of coded video sequences can currently only be performed reliably using expensive and inconvenient subjective tests. To enable researchers to optimize 3D video systems in a timely fashion, it is essential that reliable objective measures are found. This paper investigates the correlation between subjective and objective evaluation of color plus depth video. The investigation is conducted for different compression ratios, and different video sequences. Transmission over Internet protocol (IP) is also investigated. Subjective tests are performed to determine the image quality and depth perception of a range of differently coded video sequences, with packet loss rates ranging from 0% to 20%. The subjective results are used to determine more accurate objective quality assessment metrics for 3D color plus depth video.

Quality Evaluation of Color Plus Depth Map-Based Stereoscopic Video

This paper describes a real time prototype implementation of a system, which enables secure voice and data communication over the GSM voice channel. The security of GSM is not guaranteed especially over the core network. The proposed system modulates digital data, which may be encrypted onto speech-like waveforms. The modulated waveform is then transmitted over the GSM voice channel, which can be demodulated and decrypted at the receiver. The real time prototype system has been tested on GSM-to-GSM voice calls, and a proprietary speech codec is used on the real time data channel to produce communication quality speech. A demonstration will be provided at the presentation. (4 pages)

Real time data transmission over GSM voice channel for secure voice and data applications

GSM is the most wide spread mobile communications system in the world. However the security of the GSM voice traffic is not guaranteed especially over the core network. It is highly desirable to have end-to-end secure communications over the GSM voice channel. In order to achieve end-to-end security, speech must be encrypted before it enters the GSM network. A modulation scheme that enables the transmission of encrypted voice and data over the GSM voice channel was designed1. A real-time prototype is implemented demonstrating the end-to-end secure voice communications over the GSM voice channel. The modem technology presented facilitates the transmission of encrypted data and an encryption algorithm is not specified. The users may choose an algorithm and a hardware platform as necessary.

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Real-time end-to-end secure voice communications over GSM voice channel

The GSM speech service is secure up to the point where speech enters the core network but over the core network it has no security. In order to have an end-to-end security, speech must be encrypted before it enters the GSM network. The reason for not using encryption at the input of the GSM handset is that the encrypted speech signal would be randomised and would not exhibit the speech like characteristics on which the GSM speech transcoding principles are based. Hence die encoded signal would be significantly distorted by the GSM transcoding process, making the resultant signal unsuitable for the decryption process. Here we present a method that allows encryption at the input to the GSM terminal by modulating the encrypted data onto speech-like waveforms, so that it goes through the GSM system with sufficient accuracy to be decoded and decrypted at the receiving end. Throughputs of 3 and 4 kb/s have been achieved with the modulation introducing 0.5% and 4% bit error rates (BER) respectively. With the addition of error correcting codes near zero BER has been achieved at 1.8 kb/s, allowing the robust transmission of the bitstream from a modem low-bit rate speech coder. (4 pages)

Secure voice over GSM and other low bit rate systems

A speech coder includes an encoder using an analysis and synthesis approach. The encoder uses a pitch determination algorithm requiring analysis in both the frequency domain and the time domain, a voicing determination algorithm and an algorithm for determining spectral amplitudes and means for quantising the values determined. A decoder is also described.

Stephane Pierre Villette

Papers

Quality Evaluation of Color Plus Depth Map-Based Stereoscopic Video

Real time data transmission over GSM voice channel for secure voice and data applications

Real-time end-to-end secure voice communications over GSM voice channel

Secure voice over GSM and other low bit rate systems

Split band linear prediction vocoder with pitch extraction