Performance assessment of three-dimensional video codecs in mobile terminals

Understanding the most relevant factors influencing the end user experience is key to design and manage multimedia services in mobile networks. Thus, user demand can be dealt with efficient strategies of resource management. In this paper, a comprehensive analysis is carried out to evaluate the Quality of Experience (QoE) obtained by three-dimensional (3D) video codecs in mobile terminals. The analysis covers the most widespread 3D video coding formats, namely the frame-compatible Side-by-Side (SbS) and Multiview Video Coding (MVC) schemes. The analysis considers both subjective and objective measurements over compression strategies that combine bit rate reduction and frame-rate dropping. Subjective tests are done by presenting 3D video sequences with different coding parameters to users who judge image quality, depth perception and visual comfort. For this purpose, a mobile phone with autostereoscopic screen is used. Then, mean opinion scores are compared with objective measurements obtained by a video quality measurement tool. Results show that MVC outperforms SbS in terms of image quality. However, when internal parameter settings are set to very restrictive configurations, the impairment of the original image are similar for both codecs. Likewise, results show that the reduction of the video bit rate is the key parameter controlling video quality, and that the use of frame-rate dropping is not enough to counteract the impairment introduced by bit rate reduction. Finally, it is confirmed that a simple QoE indicator for 3D video can be obtained from objective measurements.