一种基于小波四叉树的无线视频组播方案

摘要

无线视频组播在视频传输领域应用越来越多，如何让异构的组播用户接收到与其信道特性相匹配的视频质量，是现今无线视频组播面临的一个难题。论文提出一个基于小波四叉树（ QuadTree）的无线视频组播方案。首先，编码端对视频帧进行离散小波变换，并按照四叉树格式选取每一级每一子带相应位置的小波系数，将其合并为一列；然后，对每一列数据进行能量分配、白噪化以减少随机丢包对重要信息的影响；最后，数据被打包成相同重要性的包并传入有噪声信道。解码端利用最小线性均方估计对接收到的数据包进行去噪并重构视频帧。实验结果表明，基于小波四叉树的视频组播比具有相同应用目标的SoftCast性能提高将近1 dB.%Wireless video multicast is becoming more and more popular in applications of video transmission. Here, one major challenge is to offer heterogeneous users with a graceful degradation against varying packet loss ratios and channel noise. In this paper,a QuadTree-based multicast scheme in wavelet domain is proposed. In encoder side,a discrete wavelet transform( DWT)is performed on each frame;and then the obtained coefficients are arranged by QuadTrees across all levels from the same wavelet subband,with each QuadTree arranged into a column. After that, power allocation and whitening are performed on these columns in order to obtain equal-importance packets. Final-ly,packets are transmitted to noise channel. In decoder side,linear least square estimation(LLSE)is used to recover the original packets from the noise data. Experimental results show that wavelet QuadTree-based scheme outperforms the state-of-art SoftCast by 1 dB in PSNR at different channel SNR or different packet loss ratio.