# Video Error-Resilience Research Based on Error-Resilient Screen Content
## 3 Proposed Method  
Traditional error-resilient coding algorithms are based on a single error suppression mechanism and do not adaptively consider different error-resilient coding methods according to the application environment. For this reason, this section proposes an algorithm based on a frame-level error-resilient coding selection mechanism for the transmission security of screen content sequences. If the complexity of the current frame is greater than three times the average encoded frames, the current frame defined as a mutation (abrupt) frame. Due to the lack of correlation with the encoded frames, the mutation frame is often encoded by intra prediction, which consumes a lot of bits. By judging the mutation frame, the abrupt frame is regarded as a more important frame and more redundancy is assigned to it to achieve adaptive frame-level video error-resilient coding algorithm.  
Note that the total end-to-end rate-distortion is optimized by virtue of number adjustment of coded redundant frames in this paper. In consequence, error prevention coding varies adaptively in the process of video transmission. In addition, the abrupt frames are determined based on SCC characteristics and the region of interest is considered as a redundant allocation for the proposed scheme. The flowchart of the proposed scheme is described in Figure 1. According to Figure 1, the detailed operations are concluded as follows.  
1. The proposed algorithm first creates and initializes a sliding window with size 5.
2. Then the complexity of the current frame is analyzed and compared with the threshold to determine whether the current frame is an abrupt frame.
3. If the current frame is not an abrupt frame, the original model of HEVC is used to control the bit rate.
4. If the current frame is an abrupt frame, the algorithm will judge whether the redundancy (frame) count in the slice header is greater than 0. Note that the information of the redundant frame count is in the slice header in the process of error-resilient encoding. A slice contains part or all of the data of a frame image [17]. In other words, a frame of a video image can be encoded into one or more slices. Each slice is composed of two parts, where one part is the slice header and is used to save the overall information of the slice. During the encoding process, the information of the redundant frame count is included in the slice header.
5. When a slice with a redundancy count is greater than 0, the slice is identified as a redundant slice, otherwise, it will be identified as a primary slice. In the encoding process, the encoding of the current frame is divided into two phases: primary frame encoding and redundant frame encoding.  
Figure 1: The flowchart of the proposed scheme.  
6. The primary slice will be encoded by the primary frame encoding. The ROI of the redundant slice will be divided, then the redundant slice will be encoded with the adaptive frame-level video error-resilient coding algorithm based on ROI.
7. If the current frame is not the last frame, repeat step 2 to step 6, otherwise, the algorithm will terminate.