SRT in and out

[JonnyTech]

Question

I am testing locally before trying on a LAN.

Running mediamtx_v1.8.5_linux_amd64 on Debian 11 with default yml config apart from loglevel:

logLevel: debug

$ ./mediamtx 
2024/08/12 17:05:30 INF MediaMTX v1.8.5
2024/08/12 17:05:30 INF configuration loaded from /opt/mediamtx/mediamtx.yml
2024/08/12 17:05:30 DEB path manager created
2024/08/12 17:05:30 INF [RTSP] listener opened on :8554 (TCP), :8000 (UDP/RTP), :8001 (UDP/RTCP)
2024/08/12 17:05:30 INF [RTMP] listener opened on :1935
2024/08/12 17:05:30 INF [HLS] listener opened on :8888
2024/08/12 17:05:30 INF [WebRTC] listener opened on :8889 (HTTP), :8189 (ICE/UDP)
2024/08/12 17:05:30 INF [SRT] listener opened on :8890 (UDP)

Then starting a feed with ffmpeg:

$ ~/ffmpeg -re -f lavfi -i "movie=filename=video.mp4:loop=0" -c:v libx264 -f mpegts srt://localhost:8890?streamid=publish:mystream

The log shows the stream:

2024/08/12 17:05:56 INF [SRT] [conn [::1]:49180] opened
2024/08/12 17:05:56 DEB [path mystream] created
2024/08/12 17:05:58 INF [SRT] [conn [::1]:49180] is publishing to path 'mystream', 1 track (H264)

Then using ffplay to view then stream:

~/ffplay -fs -f mpegts srt://127.0.0.1:8890?streamid=read:mystream

The log shows it receiving:

2024/08/12 17:06:45 INF [SRT] [conn 127.0.0.1:36777] opened
2024/08/12 17:06:45 INF [SRT] [conn 127.0.0.1:36777] is reading from path 'mystream', 1 track (H264)

But nothing is received:

    nan    :  0.000 fd=   0 aq=    0KB vq=    0KB sq=    0B 

Checking that SRT is supported:

$ ~/ffmpeg -protocols |grep -i srt
ffmpeg version N-116557-g1b8d95da3a-20240810 Copyright (c) 2000-2024 the FFmpeg developers
  built with gcc 14.2.0 (crosstool-NG 1.26.0.106_ed12fa6)
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-ffbuild-linux-gnu- --arch=x86_64 --target-os=linux --enable-gpl --enable-version3 --disable-debug --enable-iconv --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-libxml2 --enable-openssl --enable-lzma --enable-fontconfig --enable-libharfbuzz --enable-libvorbis --enable-opencl --enable-libpulse --enable-libvmaf --enable-libxcb --enable-xlib --enable-amf --enable-libaom --enable-libaribb24 --enable-avisynth --enable-chromaprint --enable-libdav1d --enable-libdavs2 --enable-libdvdread --enable-libdvdnav --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-frei0r --enable-libgme --enable-libkvazaar --enable-libaribcaption --enable-libass --enable-libbluray --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librist --enable-libssh --enable-libtheora --enable-libvpx --enable-libwebp --enable-libzmq --enable-lv2 --enable-libvpl --enable-openal --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopenmpt --enable-librav1e --enable-librubberband --disable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --enable-libdrm --enable-vaapi --enable-libvidstab --enable-vulkan --enable-libshaderc --enable-libplacebo --enable-libvvenc --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --enable-libzvbi --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-libs='-ldl -lgomp' --extra-ldflags=-pthread --extra-ldexeflags=-pie --cc=x86_64-ffbuild-linux-gnu-gcc --cxx=x86_64-ffbuild-linux-gnu-g++ --ar=x86_64-ffbuild-linux-gnu-gcc-ar --ranlib=x86_64-ffbuild-linux-gnu-gcc-ranlib --nm=x86_64-ffbuild-linux-gnu-gcc-nm --extra-version=20240810
  libavutil      59. 33.100 / 59. 33.100
  libavcodec     61. 11.100 / 61. 11.100
  libavformat    61.  5.101 / 61.  5.101
  libavdevice    61.  2.100 / 61.  2.100
  libavfilter    10.  2.102 / 10.  2.102
  libswscale      8.  2.100 /  8.  2.100
  libswresample   5.  2.100 /  5.  2.100
  libpostproc    58.  2.100 / 58.  2.100
  srtp
  srt
  srtp
  srt

What am I doing wrong?

[aler9]

The problem here is that you are not using the recommended FFmpeg flags when encoding to H264, and therefore your stream cannot be processed in real time. Flags are available in the README and are:

-c:v libx264 -pix_fmt yuv420p -preset ultrafast -b:v 600k

[JonnyTech]

Thank you very much @aler9