1. Add three-way audio and video real-time invigilation function
-- Added three-way video invigilation function: computer main camera & computer screen recording & mobile phone secondary camera
-- Modify the invigilation interface on the management side, and support enlarged video viewing;
-- Increase the code scanning and debugging of the sub-camera on the mobile terminal, and video transmission (PC terminal + mobile terminal);
-- Increase the video playback function after the test (main camera, screen recording, secondary camera);
-- Adjust and optimize the camera debugging before the test, and increase the three-way debugging function;
-- Add invigilation configuration, support configuration invigilation definition (480P/720P/1080P)
2. Other optimizations & adjustments
-- Modify the sys_ prefix table to el_sys_, the table name is more standardized and easy to distinguish, and the prefix of Yunfan test table is all unified as el_;
-- The front-end url is changed to history mode;
-- Optimize the reading function of video courseware duration, and speed up the download speed of temporary files;
-- Remove the mock test function;
