High-quality stereoscopic image content must be viewable in a variety of visual environments, from 3-D theaters to 3-D mobile devices. Stereoscopic effects, however, are affected by screen size, viewing distance, and other parameters. In this study, the authors focus on the stereoscopic image quality experience of viewing 3-D content on a mobile device in order to compare it with that of viewing 3-D content on a large screen. The stereoscopic image quality experience was evaluated using Interpretation Based Quality (IBQ) methodology, which combines existing approaches to image quality evaluation, such as the paired comparison and interview, and assesses the viewer experience using both quantitative and qualitative data. Five stereoscopic images were used in the experiment. The results of the experiment suggest that the discomfort felt while viewing stereoscopic images on a 3-D mobile device arise from not only visual fatigue but also the effects of the smaller screen size. The study also revealed the types of stereoscopic images that are suitable for viewing on 3-D mobile devices.
SUMMARYWith the widespread use of the digital transmission of TV signals, it is highly desirable to establish a remote monitoring scheme for video transmission quality. As a monitoring scheme for the digital video quality in the actual transmission, the reduced reference (RR) scheme is considered promising: in this scheme the feature parameters of the original picture are extracted and transmitted for comparison with the parameters in the receiver. Consequently, this paper proposes an RR-type picture quality-monitoring scheme which can provide highly precise remote estimation of the PSNR of the received picture. In the proposed scheme, the sent and received signals are whitened by spectrum spreading, and orthogonal transformation is applied to the results. The transform coefficients are extracted and transmitted through the monitoring link. Due to the whitening process, highly precise PSNR estimation is realized, even though only a small number of coefficients are extracted. In order to make the whitening effective, the degradation must be distributed as uniformly as possible in the transform block. In order to deal with local picture degradation due to channel error and other factors, multiplication by a PN sequence (spatial spreading) and the inverse orthogonal transform are applied in the transform domain, resulting in effective spreading and helping to improve the precision of PSNR estimation. The WalshHadamard transform, which is easy to implement, is used as the orthogonal transform. By using the proposed scheme, a PSNR estimation error of approximately ±0.1 to 0.3 dB for a monitoring link rate of 40 kbit/s is obtained, which meets practical requirements for highly precise estimation.
In IP-based TV distribution, coding degradation is sometimes evident in critical scenes because the bit rate for compression is rather low. Prefiltering is an effective countermeasure since it replaces the coding noise with the degradation more difficult to detect visually, though it has the drawback that excessive smoothing might occur. This paper proposes a scene-adaptive method to control a prefilter separate from the encoder. By calculating block-wise motion-compensated predictive error variances and correlation coefficients, it estimates the coding noise as well as the potential improvement by prefiltering each frame, realizing a control scheme which performs prefiltering only when effective.
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