How to transfer video as rtp stream with least delay by FFmpeg - ffmpeg

Question

I use AXIS M1045-LW supporting rtsp/http access, and my Windows 10 PC can access to the camera through LAN.
I would like to transfer the video as rtp with keeping H.264 codec which is supported by the camera.
Image
[Camera] == (rtsp or http) ==> [FFmpeg on Win10] == (rtp) ==>
When I accessed the camera through Google Chrome on my Win10 PC, there is only 1 or 2 sec delay.
However, when I tried access by the following command, I found over 10 sec delay.
How could I reduce the delay as much as possible?
[Windows Command Prompt A ] (sender)
C:\Users\xxxx\ffmpeg-4.3.1-2020-11-19-full_build\bin>ffmpeg -re -i rtsp://xxx:xxx#xxx.xxx.xxx.xxx/axis-media/media.amp -codec:v copy -f rtp rtp://localhost:30002 -sdp_file stream.sdp
ffmpeg version 4.3.1-2020-11-19-full_build-www.gyan.dev Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 10.2.0 (Rev5, Built by MSYS2 project)
configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-libsnappy --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
libavutil 56. 51.100 / 56. 51.100
libavcodec 58. 91.100 / 58. 91.100
libavformat 58. 45.100 / 58. 45.100
libavdevice 58. 10.100 / 58. 10.100
libavfilter 7. 85.100 / 7. 85.100
libswscale 5. 7.100 / 5. 7.100
libswresample 3. 7.100 / 3. 7.100
libpostproc 55. 7.100 / 55. 7.100
Input #0, rtsp, from 'rtsp://xxx:xxx#xxx.xxx.xxx.xxx/axis-media/media.amp':
Metadata:
title : Session streamed with GStreamer
comment : rtsp-server
Duration: N/A, start: 2.979633, bitrate: N/A
Stream #0:0: Video: h264 (Baseline), yuvj420p(pc, bt709, progressive), 320x240 [SAR 1:1 DAR 4:3], 2 fps, 25 tbr, 90k tbn, 4 tbc
Output #0, rtp, to 'rtp://localhost:30002':
Metadata:
title : Session streamed with GStreamer
comment : rtsp-server
encoder : Lavf58.45.100
Stream #0:0: Video: h264 (Baseline), yuvj420p(pc, bt709, progressive), 320x240 [SAR 1:1 DAR 4:3], q=2-31, 2 fps, 25 tbr, 90k tbn, 2 tbc
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[rtp # 000002da44da33c0] Non-monotonous DTS in output stream 0:0; previous: 0, current: -224986; changing to 0. This may result in incorrect timestamps in the output file.
[rtp # 000002da44da33c0] Non-monotonous DTS in output stream 0:0; previous: 0, current: -178194; changing to 0. This may result in incorrect timestamps in the output file.
[rtp # 000002da44da33c0] Non-monotonous DTS in output stream 0:0; previous: 0, current: -134998; changing to 0. This may result in incorrect timestamps in the output file.
[rtp # 000002da44da33c0] Non-monotonous DTS in output stream 0:0; previous: 0, current: -88201; changing to 0. This may result in incorrect timestamps in the output file.
[rtp # 000002da44da33c0] Non-monotonous DTS in output stream 0:0; previous: 0, current: -45002; changing to 0. This may result in incorrect timestamps in the output file.
frame= 89 fps=2.1 q=-1.0 size= 142kB time=00:00:43.01 bitrate= 27.0kbits/s speed= 1x
[Windows Command Prompt B ] (receiver)
C:\Users\xxx\ffmpeg-4.3.1-2020-11-19-full_build\bin>ffplay -protocol_whitelist "file,udp,rtp" stream.sdp
ffplay version 4.3.1-2020-11-19-full_build-www.gyan.dev Copyright (c) 2003-2020 the FFmpeg developers
built with gcc 10.2.0 (Rev5, Built by MSYS2 project)
configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-libsnappy --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
libavutil 56. 51.100 / 56. 51.100
libavcodec 58. 91.100 / 58. 91.100
libavformat 58. 45.100 / 58. 45.100
libavdevice 58. 10.100 / 58. 10.100
libavfilter 7. 85.100 / 7. 85.100
libswscale 5. 7.100 / 5. 7.100
libswresample 3. 7.100 / 3. 7.100
libpostproc 55. 7.100 / 55. 7.100
[sdp # 000001832f4ecec0] decoding for stream 0 failed 0B f=0/0
Input #0, sdp, from 'stream.sdp':
Metadata:
title : Session streamed with GStreamer
Duration: N/A, bitrate: N/A
Stream #0:0: Video: h264 (Baseline), yuvj420p(pc, bt709, progressive), 320x240 [SAR 1:1 DAR 4:3], 2 fps, 2 tbr, 90k tbn, 4 tbc
[swscaler # 0000018336868d00] deprecated pixel format used, make sure you did set range correctly
127.52 M-V: -0.021 fd= 12 aq= 0KB vq= 11KB sq= 0B f=0/0