# Sample-Based Gradient Edge and Angular Prediction for VVC Lossless Intra-Coding
## 4 Results and Analysis  
In order to evaluate the performance of SGAP, we implemented it on the VTM12.3 platform and tested 26 video sequences (six natural scene classes and one screen content class) in the 4:2:0 format specified by the VVC standard. The parameter information of these sequences is shown in Table 1. The tests are run in a lossless All Intra (AI) configuration under the common test conditions [33]. In addition, performance tests for several existing lossless coding optimization methods on the VTM12.3 platform proceeded. In the coding schemes that do not retain block-based intra-prediction, the multiple reference lines (MRL) tool is not enabled. In the coding schemes that retain block-based intra-prediction and in which basic VVC coding is used for comparison, the MRL tool is enabled. Except for the MRL tool, other configurations for all coding schemes are identical. We compare and analyze the experimental results of the proposed SGAP and other optimization methods. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Class** & **Sequence** & **Resolution** & **Frames** & **Frame-Rate/fps** \\ \hline \multirow{4}{*}{A1} & Tango2 & \(3840\times 2160\) & 294 & 60 \\  & FoodMarket4 & \(3840\times 2160\) & 300 & 60 \\  & Campfire & \(3840\times 2160\) & 300 & 30 \\ \hline \multirow{4}{*}{A2} & CatRobot & \(3840\times 2160\) & 300 & 60 \\  & DaylightRoad2 & \(3840\times 2160\) & 300 & 60 \\  & ParkRunning3 & \(3840\times 2160\) & 300 & 50 \\ \hline \multirow{4}{*}{B} & MarketPlace & \(1920\times 1080\) & 600 & 60 \\  & RitualDance & \(1920\times 1080\) & 600 & 60 \\ \cline{1-1}  & Cactus & \(1920\times 1080\) & 500 & 50 \\ \cline{1-1}  & BasketballDrive & \(1920\times 1080\) & 500 & 50 \\ \cline{1-1}  & BQTerrace & \(1920\times 1080\) & 600 & 60 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The parameter information of VVC test sequences. Table 2 shows the bit-rate differences of several coding schemes compared to basic VVC coding. Negative numbers indicate a decrease in the bit rate of the coding schemes compared to basic VVC encoding. It can be observed that BDPCM achieves the lowest average bit-rate savings. BDPCM only applies sample-based angular prediction in horizontal and vertical directions, resulting in limited coding performance gain. SAP and SAP1 both use sample-based angular prediction to replace all conventional angle predictions and achieve close average bit-rate savings. Due to adopting an equidistant prediction method, the average bit-rate savings achieved by SAP1 are slightly higher than that achieved by SAP. LIP-RMED and SAP-E introduce the edge detection method into coding. Compared to coding schemes that only apply sample-based prediction in angular modes, LIP-RMED and SAP-E achieve higher coding performance gains. Since the proposed SGAP can perform accurate prediction on frequently occurring image regions, SGAP saves 7.31% bit-rate, on average, in VVC lossless intra-coding, which is ahead of other experimental coding schemes. Moreover, SGAP provides the highest bit-rate savings for all video sequences except the Campfire sequence.