# Time Delay Optimization of Compressing Shipborne Radar Digital Video Based on Deep Learning
## 2 Radar Digital Video Coding Depth Division Algorithm Based on Deep Learning
### Characteristics of Radar Images  
In the field of navigation, radar images are formed by radar transmitters transmitting radio waves to obstructions, other ships, coastlines, and other major targets, and the receivers receiving radio echoes. The Maritime Safety Committee (MSC) in MSC.192 (79) stipulates that the radar image, target tracking information, positional data derived from the ship's own position (EPFS), and geo-referenced data (geospatial coordinates and attributes) should be integrated and displayed on the shipboard radar screen. The integration and display of the ship's Automatic Identification System (AIS) information should be provided to complement radar. Meanwhile, selected part of the electronic navigation chart and other vector chart information can be provided in accordance with needs of the ship so that the driver can monitor and navigate the position, resulting a safer navigation of the ship [10], thus improving the pilot's recognition of the target in the radar image and the perception of the ship's surrounding environment [11]. The size of the object mark in the radar image is inversely proportional to the size of the set range. Under normal navigation, the larger the range, the smaller the volume of the object. On the shipboard radar screen, the display color of the background area usually occupies most of the display area of the entire radar image. In addition, in order to facilitate the pilot's view of the contents of the radar screen under different lighting conditions, the brightness value and color of the set background are usually different from the intensity of the target echo display. In contrast to the content refresh of ordinary video, the content refresh of radar digital video changes with the rotation period of antenna scanning. In addition, the image must be updated continuously and smoothly, so that the content of adjacent frames does not produce obvious variation. A large number of repetitive patterns or signs are also an obvious feature in radar videos, and the edges of the patterns are sharper. In the display of target information, the shipborne radar digital video shall be displayed in accordance with the specified performance standards, using the relevant symbols specified by SN/Circ.243 [10]. For small-size ships of less than 500 GT, the diameter of the radar operation display area should not be less than 180 mm, and the total area of the display area is to be no less than 195 mm \(\times\) 195 mm. For medium and large ships of above 500 GT and below 10,000 GT, the diameter of the radar operation display area is required to be no less than 250 mm, and the total area of the display area is to be no less than 270 mm \(\times\) 270 mm. For large-size ships of 10,000 GT and above, the diameter of the radar operation display area shall not be less than 320 mm, and the total area of the display area is required to be no less than 340 mm \(\times\) 340 mm. The resolution of the shipborne radar image is also quite different from that of ordinary video image. The common video image resolutions are 4:3, 16:9, and other mainstream display ratios, whereas radar video image resolutions are mostly 1:1 and 5:4, and other non-mainstream display ratios. The screen size and resolution of shipborne radar are very important parameters to determine the encoding speed, which decides the total number of CTUs in the radar image. Generally speaking, the higher the resolution and the larger the screen size, the more CTUs in the image, and the slower the encoding speed. For the transmission or storage of radar video images, lower bit rate and higher image quality are important indicators for evaluating the performance of compression algorithms. For the distortion of small objects, in particular, encoding radar images is more stringent than encoding common screen images. Before the SCC coding scheme was proposed, AVC and HEVC standards were used to encode and transmit real-time radar video in the maritime field.