# Time Delay Optimization of Compressing Shipborne Vision Sensor Video Based on Deep Learning
## 2 SVSV Image Characteristics
### Shipborne Infrared Camera Video Image Features  
The infrared camera is a kind of infrared induction imaging camera, which main principle is to form the contour shape of the object on the image through the different areas of radiation infrared energy variations, and reflectivity variations. Unlike the visible light camera, the infrared camera has a very strong detection capability in the dark or bad weather and other poor visibility climate conditions, while its imaging system will not be disturbed. The working band of the infrared ray is divided into near-infrared, short-wave infrared, infrared, long-wave infrared, far infrared, etc. The working band in the long wave of SIRC is also known as an onboard thermal imager, whose main function is to convert the temperature difference signal into video image. That is, detecting the thermal radiation emitted by the target in the waters around the ship by the infrared detector, and after processing and conversion into a video signal, the target in the waters around the ship will be imaged. Since there is usually a temperature difference between the target on the water and the water surface, the SIRC can detect the target existing on the water surface more easily than the visible light camera in the environment of poor visibility. During navigation, the video content captured by the SIRC is similar to that of the visible camera, both with the sea and sky as the background. The main distinction is that the visual effect of the infrared video (IR video) image is relatively blurred, the signal-to-noise ratio is low, and it is easily affected by the external environment, making the target and background contrast not high and the edges are blurred.  
The SIRC video, similar to the SVLC video, also has a large amount of redundant data in the spatial and temporal domains. As shown in Figure 4a, the IR image has a uniform background with limited color information, and the main content of the camera consists of the infrared radiation from the water surface, sky, the target, and the ambient noise together. Since the infrared intensity of the water surface is much lower than that of the sky, and it will lead to a large variation between the grayscale values of the water surface and those of the sky. Therefore, the video image generated by the SIRC has a more obvious middle sea antenna. In order to visualize the energy distribution characteristics in the SIRC video, the SIRC image is transformed into a grayscale histogram Figure 4b, which shows that the energy distribution of the image is more concentrated, and this energy distribution characteristic is very favorable for its processing using the intra-frame PC technique. The movement characteristics of the target and background in the IR video are also the same as in the visible light video. Figures 5 and 6 show the intra-frame pixel variation probability density and inter-frame pixel variation statistics of the SIRC video. Showing that the intra-frame pixel variation probability density and inter-frame pixel variation are more concentrated compared to the visible light camera video. Therefore, it is also more efficient to use HEVC PC algorithm to reduce the redundant data in the null and temporal domain in IR video.  
Figure 3: Inter pixel difference statistics of shipborne visible light camera video.