With reference to recent experiences in movies targeted to reproduce sensory stimulation (thermal and olfactory) in combination with audio-visual contents, this paper describes a line of research developed aimed at testing a possible integration of multisensorial systems into multimedia streams. In particular, a demonstration 4D platform and its main components are presented by highlighting both their architectural and technological main features. The transport of control signals to the actuators is a crucial point, because one must consider both current standards and possible future developments. Therefore, we identified two strategies for data transport in local systems, first using a single file and then using multiple separate files, and we have analyzed three transmission modes for ancillary data in communication networks in order to select the most appropriate for our application. To encode sensory effects data related to control signals we propose the use of MPEG-V standard.

Conventional 3D-TV codecs processing one down-compatible (either left, or right) channel may optionally include the extraction of the disparity field associated with the stereo-pairs to support the coding of the complementary channel. A two-fold improvement over such approaches is proposed in this paper by exploiting the three-dimensional features retained in the stereo-pairs to reduce the redundancies in both channels, and according to their visual sensitiveness. Through an apriori disparity field analysis, our coding scheme separates a region of interest from the foreground/background in the volume space reproduced in order to code them selectively based on their visual relevance. Such a region of interest is here identified as the one which is focused by the shooting device. By suitably scaling the DCT coefficients in such a way that precision is reduced for the image blocks lying on less relevant areas, our approach aims at reducing the signal energy in the background/foreground patterns, while retaining finer details on the more relevant image portions. From an implementation point of view, it is worth noticing that the system proposed keeps its surplus processing power on the encoder side only. Simulation results show such improvements as a better image quality for a given transmission bit rate, or a graceful quality degradation of the reconstructed images with decreasing data-rates.

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