A Comparative Study of the Whitening Methods in Linear Video Coding and Transmission Schemes
Résumé
Linear Video Coding and Transmission (LVCT) schemes, pioneered by the SoftCast architecture, have been recently proposed as an alternative solution for wireless broadcast applications where users may experience severe channel quality fluctuations. LVCT schemes offer a graceful video quality adaptation to the user experienced channel quality. This is made possible by relying on linear operators only (decorrelation transform, power allocation, whitening). The LVCT whitening process aims at reducing the impact of slice loss in presence of fades. It is mainly performed by Hadamard transform which is not adapted to all input sizes. Although alternatives to the Hadamard transform have been proposed in the literature, no performance comparison has been performed. In this paper, we compare the performance of SoftCast using three different whitening matrices, namely, Hadamard, Inverse Discrete Cosine Transform (IDCT) and Random matrices. Three scenarios are considered for the comparison: no packet loss, random packet losses and bursty packet losses. Simulation results confirm that these matrices offer similar reconstructed video quality in a lossless scenario, while whitening using a random orthogonal matrix outperforms whitening using Hadamard or IDCT matrices in all lossy scenarios.