## 2 Related Works
### Cross-Layer Oriented Video Streaming  
The cross-layer-based video streaming in vehicular networks is discussed considering the different works performed based on routing, MAC and/or application layer solutions. For example, a V2V video streaming based on Cross-layer Optimization for Overtaking (VCO2) assistance is proposed in order to reduce delay in video packet transmission while improving on-road overtaking safety [12]. A pre-recorded video streaming transmission between vehicles is suggested as a maneuvering system for overtaking assistance. It optimizes video streams such that, redundant video frames are skipped, transcoded and the frame rate are reduced for achieving efficient overtaking. The VCO2 is based on the IEEE 802.11p Enhanced Distributed Channel Access (EDCA). Nonetheless, the quality of the video content is not considered, since the PSNR and SSIM are not measured. Further, a mechanism which is Multi-flow and multi-driven for Video DElivery (MVIDE) is suggested to support pre-recorded video streaming over VANETs [13]. The mechanism performs the function of choosing best paths for pre-recorded video stream series. MVIDE is incorporated into the routing protocol to select paths by considering some characteristics, including application needs, multiple routes and dynamicity of vehicles.  
In addition, cross-layer Techniques for grading the potential paths using Order Preference level by SImilarity type to Ideal Solution (TOPSIS) is introduced. MVIDE is further merged with Greedy Perimeter Stateless Routing protocol with Movement Awareness (GPSR-MA) [14; 15] (GPSR-MA-MVIDE). Moreover, a real-world assessment of video transmission using IEEE 802.11p has been presented to explore the video content delivery challenges in VANETs (RMVT) [16]. The work is to measure the graphics quality of transmitted video using IEEE 802.11p V2V communication channel. Further, a scheme for measuring anticipated end-to-end delay in the graphics quality of the transmitted video information is suggested. In addition, a real-time scalable video codec is also proposed. A selective Rebroadcast mechanism for Video streaming over VANETs (ReViV) is proposed to relieve overloaded channels and assist in delivering video content in sparse network settings [17]. The mechanism chooses a fewer subset of rebroadcasting vehicles so as to reduce interference and attain higher video quality. The vehicles are grouped and graded based on their estimated positions and ability to reach out to other vehicles in the network by employing centrality parameters.  
A Measurement-based analysis of Multi-hop pre-recorded video streaming Transmission (MTRM) using dedicated short-range communication devices is presented [18]. The performance of multi-hoptransmission is measured to overcome the problem of high packet loss rate. High packet loss causes video quality degradation. The measurement also considers interference of the communication channel. Further, startup catching and retransmission strategies are introduced to enhance the video application. In addition, performance measurement of the retransmission strategy and analysis of the strategy are conducted. While the retransmission strategy adopted might lead to delay in the video transmission. However, the proposed video codec has not been adequately validated, because other validation parameters are not considered for ascertaining quality of the video. In addition, the road-based multi-metric is not considered in the aforementioned proposed works. Further, Section 2.2 discusses the related works in multi-metric oriented video steaming over vehicular network.