I pushed the stream all the way to the SRS server. After decoding the SRS video stream using the FFmpeg code, I found that there was a lag every 11 frames.

ffmpeg -re -stream_loop -1 -i .\test.mp4 -c:v h264_nvenc -bf 0 -c:a aac -b:v 4000k -f flv rtmp://192.168.1.200:1935/live/test1

if (av_read_frame(mSrcFmtCtx, &srcPkt) >= 0)
{
auto end_ = std::chrono::steady_clock::now();
auto elapsed_ = std::chrono::duration_caststd::chrono::milliseconds(end_ - start).count();
std::cout<<"av_read_frame time: "<<elapsed_<<std::endl;

av_read_frame time: 0
srcframe: 42387, id: 1273, img_queue: 1
av_read_frame time: 256
srcframe: 42420, id: 1274, img_queue: 1
av_read_frame time: 0
srcframe: 42453, id: 1275, img_queue: 1
av_read_frame time: 0
srcframe: 42487, id: 1276, img_queue: 1
av_read_frame time: 0
srcframe: 42520, id: 1277, img_queue: 1
av_read_frame time: 0
srcframe: 42553, id: 1278, img_queue: 1
av_read_frame time: 0
srcframe: 42587, id: 1279, img_queue: 1
av_read_frame time: 0
srcframe: 42620, id: 1280, img_queue: 1
av_read_frame time: 0
srcframe: 42653, id: 1281, img_queue: 1
av_read_frame time: 0
srcframe: 42687, id: 1282, img_queue: 1
av_read_frame time: 0
srcframe: 42720, id: 1283, img_queue: 1
av_read_frame time: 0
srcframe: 42753, id: 1284, img_queue: 1
av_read_frame time: 276
srcframe: 42787, id: 1285, img_queue: 1
av_read_frame time: 0
srcframe: 42820, id: 1286, img_queue: 1
av_read_frame time: 0