| 1. |
- Engelke, Ulrich, et al.
(författare)
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Perceptual Evaluation of Motion JPEG2000 Quality over Wireless Channels
- 2006
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Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate the applicability of perceptual image quality metrics for quality assessment of Motion JPEG2000 (MJ2) video streams over wireless channels. A performance evaluation of MJ2 quality for different levels of source compression and channel coding settings is provided. This reveals insights into the characteristics and suitability of the considered perceptual quality metrics for wireless video quality assessment. In particular, a reduced-reference hybrid image quality metric (HIQM) is identified as the most favorable metric with respect to supporting real-time applications. The findings obtained from the considered scenarios may also guide the design of efficient physical layer functions for wireless video systems.
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| 2. |
- Engelke, Ulrich, et al.
(författare)
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Perceptual Quality Assessment of Wireless Video Applications
- 2006
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Konferensbidrag (refereegranskat)abstract
- The rapid evolution of wireless networks is driven by the growth of wireless packet data applications such as interactive mobile multimedia applications, wireless streaming services, and video-on-demand. The largely heterogeneous network structures, severe channel impairments, and complex traffic patterns make the wireless networks much more unpredictable compared to their wired counterparts. One of the major challenges with the roll-out of these services is therefore the design of wireless networks that fulfill the stringent quality of service requirements of wireless video applications. In this paper, the applicability of perceptual image quality metrics for real-time quality assessment of Motion JPEG2000 (MJ2) video streams over wireless channels is investigated. In particular, a reduced-reference hybrid image quality metric (HIQM) is identified as suitable for an extension to video applications. It outperforms other known metrics in terms of required overhead and prediction performance.
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| 3. |
- Engelke, Ulrich, et al.
(författare)
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Reduced-reference metric design for objective perceptual quality assessment in wireless imaging
- 2009
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Ingår i: Signal Processing-Image Communication. - : ELSEVIER. - 0923-5965. ; 24:7, s. 525-547
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Tidskriftsartikel (refereegranskat)abstract
- The rapid growth of third and development of future generation mobile systems has led to an increase in the demand for image and video services. However, the hostile nature of the wireless channel makes the deployment of such services much more challenging, as in the case of a wireline system. In this context, the importance of taking care of user satisfaction with service provisioning as a whole has been recognized. The related user-oriented quality concepts cover end-to-end quality of service and subjective factors such as experiences with the service. To monitor quality and adapt system resources, performance indicators that represent service integrity have to be selected and related to objective measures that correlate well with the quality as perceived by humans. Such objective perceptual quality metrics can then be utilized to optimize quality perception associated with applications in technical systems. In this paper, we focus on the design of reduced-reference objective perceptual image quality metrics for use in wireless imaging. Specifically, the Normalized Hybrid Image Quality Metric (NHIQM) and a perceptual relevance weighted L_p-norm are designed. The main idea behind both feature-based metrics relates to the fact that the human visual system (HVS) is trained to extract structural information from the viewing area. Accordingly, NHIQM and L_p-norm are designed to account for different structural artifacts that have been observed in our distortion model of a wireless link. The extent by which individual artifacts are present in a given image is obtained by measuring related image features. The overall quality measure is then computed as a weighting sum of the features with the respective perceptual relevance weight obtained from subjective experiments. The proposed metrics differ mainly in the pooling of the features and amount of reduced-reference produced. While NHIQM performs the pooling at the transmitter of the system to produce a single value as reduced-reference, the L_p-norm requires all involved feature values from the transmitted and received image to perform the pooling on the feature differences at the receiver. In addition, non-linear mapping functions are developed that relate the metric values to predicted mean opinion scores (MOS) and account for saturations in the HVS. The evaluation of prediction performance of NHIQM and the L_p-norm reveals their excellent correlation with human perception in terms of accuracy, monotonicity, and consistency. This holds not only for the prediction performance on images taken for the training of the metrics but also for the generalization to unknown images. In addition, it is shown that the NHIQM approach and the perceptual relevance weighted L_p-norm outperform other prominent objective quality metrics in prediction performance.
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| 4. |
- Engelke, Ulrich, et al.
(författare)
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Subjective Quality Assessment for Wireless Image Communication : The Wireless Imaging Quality Database
- 2010
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Konferensbidrag (refereegranskat)abstract
- Mean opinion scores (MOS) obtained in image quality experiments are a key component in the transition from subjective to objective measures of perceived quality. In this respect, MOS are widely used to validate objective quality prediction models. To facilitate comparison between models from different laboratories it is desirable to have publicly available image quality databases. Several databases were made available in recent years. In this paper, we introduce the Wireless Imaging Quality (WIQ) database which, unlike any of the previous databases, takes into account the complex nature of a wireless communications link. The database is thus considered as a valuable complement to the existing databases. The distortion model, the test images, and two quality experiments that we conducted are explained in this paper. A number of contemporary objective quality metrics are tested for their quality prediction performance on the database. The WIQ database including test images and MOS is made freely available to the research community.
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| 5. |
- Kusuma, Tubagus Maulana, et al.
(författare)
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Objective Hybrid Image Quality Metric for In-Service Quality Assessment
- 2005
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Ingår i: Signal Processing for Telecommunications and Multimedia. - Berlin : Springer. - 9780387228471 ; , s. 44-55
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Bokkapitel (refereegranskat)abstract
- User-oriented image quality assessment has become a key factor in multimedia communications as a means of monitoring perceptual service quality. However, existing image quality metrics such as Peak Signal-to-Noise Ratio (PSNR) are inappropriate for in-service quality monitoring since they require the original image to be available at the receiver. Although PSNR and others are objective metrics, they are not based on human visual perception and are typically designed to measure the fidelity. On the other hand, the human visual system (HVS) is more sensitive to perceptual quality than fidelity. In order to overcome these problems, we propose a novel objective reduced-reference hybrid image quality metric (RR-HIQM) that accounts for the human visual perception and does not require a reference image at the receiver. This metric is based on the combination of several image artifact measures. The result is a single number, which represents overall image quality.
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| 6. |
- Kusuma, Tubagus Maulana, et al.
(författare)
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On the Development of a Reduced-Reference Perceptual Image Quality Metric
- 2005
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Konferensbidrag (refereegranskat)abstract
- User-oriented image quality assessment has be- come a key factor in wireless multimedia commu- nications. In particular, perceptual quality assess- ment methods are required to measure the overall perceived service quality based on the grading given by human subjects. This paper focuses on the de- velopment of a reduced-reference perceptual image quality metric, which can be applied for in-service quality monitoring and link adaptation purposes. In contrast to the conventional image ¯delity metrics such as the peak signal-to-noise ratio (PSNR), the proposed hybrid image quality metric (HIQM) takes the human perception into account. In addition, HIQM does not rely on the availability of the full reference of the original image at the receiver.
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| 7. |
- Kusuma, Tubagus Maulana, et al.
(författare)
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Utilizing Perceptual Image Quality Metrics for Link Adaptation Based on Region of Interest
- 2005
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Konferensbidrag (refereegranskat)abstract
- An implicit link adaptation technique based on hybrid automatic repeat request (H-ARQ) and soft-combining is considered for transmission of Joint Photographic Experts Group 2000 (JPEG2000) images over wireless channels. Adaptation is carried out utilizing an objective perceptual image quality metric that takes into account the human perception. Retransmissions focus on the Region of Interest (ROI) part of the JPEG2000 image to efficiently utilize the bandwidth. Numerical results show that the combination of the proposed perceptual image quality metric with link adaptation provides robust link performance while meeting satisfactory quality constraints.
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| 8. |
- Yatawara, Yeshan, et al.
(författare)
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Unequal Error Protection for ROI Coded Images over Fading Channels
- 2005
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Konferensbidrag (refereegranskat)abstract
- Region of interest (ROI) coding is a feature supported by the Joint Photographic Experts Group 2000 (JPEG2000) image compression standard and allows particular regions of interest within an image to be compressed at a higher quality than the rest of the image. In this paper, unequal error protection (UEP) is proposed for ROI coded JPEG2000 images as a technique for providing increased resilience against the effects of transmission errors over a wireless communications channel. The hierarchical nature of an ROI coded JPEG2000 code-stream lends itself to the use of UEP whereby the important bits of the code-stream are protected with a strong code while the less important bits are protected with a weaker code. Simulation results obtained using symbol-by-symbol maximum a posteriori probability (MAP) decoding demonstrate that the use of UEP offers significant gains in terms of the peak signal to noise ratio (PSNR) and the percentage of readable files. Moreover, the use of ROI-based UEP leads to reduced computational complexity at the receiver.
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