3-D images transmission in a way which is compliant with traditional 2-D representations can be done through the embedding of disparity maps within the 2-D signal. This approach enables the transmission of stereoscopic video sequences or images on traditional analogue TV channels (PAL or NTSC) or printed photographic images. The aim of this work is to study the achievable performances of such a technique. The embedding of disparity maps has to be seen as a global rate-distortion problem. The embedding capacity through steganography is determined by the transmission channel noise and by the bearable distortion on the watermarked image. The distortion of the 3-D image displayed as two stereo views depends on the rate allocated to the complementary information required to build those two views from one reference 2-D image. Results from the works on the scalar Costa scheme are used to optimize the embedding of the disparity map compressed bit stream into the reference image. A method for computing the optimal trade off between the disparity map distortion and embedding distortion as a function of the channel impairments is proposed. The goal is to get a similar distortion on the left (the reference image) and the right (the disparity compensated image) images. We show that in typical situations the embedding of 2 bits/pixels in the left image, while the disparity map is compressed at 1 bit per pixel leads to a good trade-off. The disparity map is encoded with a strong error correcting code, including synchronisation bits.
The present paper introduces a very specific and pragmatic approach to segmentation. It is driven by a particular application context: in the framework of mixed-reality, Tranfiction (“transportation into fictional spaces”) is designed to mix synthetic and natural images in real time while allowing users to interact in these input/output screens. Segmentation is therefore used to provide both the immersion and interaction capabilities. The former aspect is achieved by composing the image of the user within the projected virtual scenes, while the later is achieved thanks to basic body/gesture analysis on the segmented silhouettes. According to indoor or outdoor usages, two real-time techniques are developed. Results are analyzed with respect to the overall application, not only in terms of absolute quality but also in terms of perception by the users.