Objective image quality assessment (IQA) aims to predict human judgment on an image’s visual quality. This computational model is applicable in various scenarios, such as monitoring, image compression and image restoration. However, the research in this area began with natural scenes while image contents has become much more diverse. Remote computing and screen sharing applications led to the prevalence of screen content images (SCIs), which are full of texts, flat areas, and also natural scenes. Due to their different characteristics, traditional methods for IQA are insufficient for SCIs. In this paper, we show that capturing the distortions in the horizontal and vertical structures of an SCI is effective for predicting its quality. We also take into account the human visual system’s trend to analyze a scene in a multi-scale fashion. Based on these observations, we propose wavelet analysis as a means to accomplish the mentioned strategies. Experimental results on three SCI quality datasets show that plausible predictions can be made by the proposed full-reference method, while having an acceptable time complexity.

This paper proposes a new method for digital video watermarking in compressed domain. Both the embedding and extracting phases are performed after entropy decoding. Consequently, fully decompressing the compressed video is not necessary making this scheme an appropriate choice for real-time application. Furthermore, taking the structural information into account leads to presenting a robust watermarking scheme along with less quality degradation. To select suitable coefficients for embedding the watermark, three different aspects, imperceptibility, security, and bit rate increase, have been considered. These performance factors are adjusted by defining three priority matrices. In addition, a content based key is proposed in order to overcome the collusion attack. The flexibility of our method to provide desired characteristic can be expressed as another advantage.

In this paper, a new blind and readable H.264 compressed domain watermarking scheme is proposed in which the embedding/extracting is performed using the syntactic elements of the compressed bit stream. As a result, it is not necessary to fully decode a compressed video stream both in the embedding and extracting processes. The method also presents an inexpensive spatiotemporal analysis that selects the appropriate submacroblocks for embedding, increasing watermark robustness while reducing its impact on visual quality. Meanwhile, the proposed method prevents bit-rate increase and restricts it within an acceptable limit by selecting appropriate quantized residuals for watermark insertion. Regarding watermarking demands such as imperceptibility, bit-rate control, and appropriate level of security, a priority matrix is defined which can be adjusted based on the application requirements. The resulted flexibility expands the usability of the proposed method.