Guest editorial: online multimedia signal and image processing

In recent years, multimedia has become an essential part of networking and online communication environments. As people connect to the Internet or to one another multimedia content such as photos, video and music, takes the lion’s share of the overall artwork traffic. Multimedia-based applications use a wide range of signal and image processing techniques to enhance user experience. Semantic multi-media retrieval has been a major research focus for the last decade. Recently, a large number of cutting-edge algorithms have been developed performing audio, image and video content extraction and object recognition. Artificial intelligence and machine learning techniques have been also extensively used to connect contextual and conceptual information to multimedia data. The importance of metadata has been boosted by the emergence of high-end devices such as tablets, smartphones, and other hand-held devices. Sematic-aware metadata can further improve intelligence of online multimedia environments. This special issue targets online applications ranging from traditional signal and imageprocessing methods to evolving semantic-based multimedia, audio, image and video technologies. Also, it aims to demonstrate novel, flexible and easy-to-use applications developed for the next generation of devices. This special issue received many submissions from researchers and practitioners working on multimedia signal and image processing. After two rounds of review, eventually seven high quality papers were chosen. The paper titled “Extending the Image Ray Transform for Shape Detection and Extraction” presents a novel approach to image analysis performing feature extraction at low level and complements it with high-level feature extraction to determine structure, exploiting the Hough transform. Authors analyze performance with images from the Caltech-256 dataset and describe how thir approach can select chosen shapes.