SCAST: Wireless Video Multicast Scheme Based on Segmentation and Softcast

Analog transmission schemes for wireless video multicast, especially SoftCast, have gained great attention recently. SoftCast can overcome the “cliff effect” by delivering the linear transformations of video pixels, which is unavoidable for digital schemes. Considering the fact that different parts of image/video have diverse importances to the human perception, in this paper, a new analog video multicast scheme named SCAST is proposed. SCAST is based on SoftCast and the image segmentation technology, designed to improve the video subjective visual quality. Firstly, SCAST employs the Otsu segmentation algorithm to decompose the video source into the foreground part and the background part. Then a power allocation method is presented to provide strong protection for the foreground part, which is the region of interest (ROI) of video for the human visual system (HVS). The two parts are both encoded in the analog way by SoftCast and mapped into a complex signal before transmitted. Results show that the proposed scheme SCAST outperforms SoftCast, H.264/AVC and WSVC in both the metrics, i.e., peak signal-to-noise ratio (PSNR) and structural similarity (SSIM), which reflect the objective and subjective video qualities separately. Especially, SCAST performs excellently under bad channel condition.