serving two RTSP cameras from one installation

[ChrisHeerschap]

Question

Hi-

I had two Logitech C920 cameras on one Raspberry Pi 3 running mediamtx 1.9.2 (Raspbian 12 bookworm) and was able to access both via the unique paths. Here's the config that I was using:

paths:
  xl:
    runOnInit: ffmpeg -s 1920x1080 -f v4l2 -i /dev/video0 -c:v h264_v4l2m2m -pix_fmt yuv420p -preset ultrafast -b:v 600k -f rtsp rtsp://0.0.0.0:$RTSP_PORT/$MTX_PATH
    runOnInitRestart: yes
  mk:
    runOnInit: ffmpeg -s 1920x1080 -f v4l2 -i /dev/video2 -c:v h264_v4l2m2m -pix_fmt yuv420p -preset ultrafast -b:v 600k -f rtsp rtsp://0.0.0.0:$RTSP_PORT/$MTX_PATH
    runOnInitRestart: yes

With this setup I could connect to rtsp://pi3a:8554/xl and rtsp://pi3a:8554/mk and see the two individual camera streams.

Ran into a problem with the Pi3 so I installed Raspbian 12 (bookworm) on a Pi 4, then copied over the mediamtx binary and mediamtx.yaml file along with the systemd startup file. All looked good, but it was only serving one of the streams, even though both streams were visible in the ps output.

If I configure only one stream in the YAML file, that camera works, so I've confirmed that both cameras work on video0 and video2, they just don't work at the same time.

I've tried updating to the current 1.14.0 and copying over just the paths section of the old YAML file to the new one, but that hasn't helped. I've also run it manually (outside of systemd) and that doesn't change anything. Looking at the output, it almost looks like it starts the first stream and never gets around to starting the second.

Any suggestions? Here's what I get when I run it manually:

2025/09/15 13:46:09 INF MediaMTX v1.14.0
2025/09/15 13:46:09 INF configuration loaded from /usr/local/etc/mediamtx.yml
2025/09/15 13:46:09 INF [path xl] runOnInit command started
2025/09/15 13:46:09 INF [path mk] runOnInit command started
2025/09/15 13:46:09 INF [RTSP] listener opened on :8554 (TCP), :8000 (UDP/RTP), :8001 (UDP/RTCP)
2025/09/15 13:46:09 INF [RTMP] listener opened on :1935
2025/09/15 13:46:09 INF [HLS] listener opened on :8888
2025/09/15 13:46:09 INF [WebRTC] listener opened on :8889 (HTTP), :8189 (ICE/UDP)
2025/09/15 13:46:09 INF [SRT] listener opened on :8890 (UDP)
ffmpeg version 5.1.7-0+deb12u1+rpt1 Copyright (c) 2000-2025 the FFmpeg developers
  built with gcc 12 (Debian 12.2.0-14+deb12u1)
  configuration: --prefix=/usr --extra-version=0+deb12u1+rpt1 --toolchain=hardened --incdir=/usr/include/aarch64-linux-gnu --enable-gpl --disable-stripping --disable-mmal --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libglslang --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librist --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sand --enable-sdl2 --disable-sndio --enable-libjxl --enable-neon --enable-v4l2-request --enable-libudev --enable-epoxy --libdir=/usr/lib/aarch64-linux-gnu --arch=arm64 --enable-pocketsphinx --enable-librsvg --enable-libdc1394 --enable-libdrm --enable-vout-drm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-libplacebo --enable-librav1e --enable-shared
  libavutil      57. 28.100 / 57. 28.100
  libavcodec     59. 37.100 / 59. 37.100
  libavformat    59. 27.100 / 59. 27.100
  libavdevice    59.  7.100 / 59.  7.100
  libavfilter     8. 44.100 /  8. 44.100
  libswscale      6.  7.100 /  6.  7.100
  libswresample   4.  7.100 /  4.  7.100
  libpostproc    56.  6.100 / 56.  6.100
ffmpeg version 5.1.7-0+deb12u1+rpt1 Copyright (c) 2000-2025 the FFmpeg developers
  built with gcc 12 (Debian 12.2.0-14+deb12u1)
  configuration: --prefix=/usr --extra-version=0+deb12u1+rpt1 --toolchain=hardened --incdir=/usr/include/aarch64-linux-gnu --enable-gpl --disable-stripping --disable-mmal --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libglslang --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librist --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sand --enable-sdl2 --disable-sndio --enable-libjxl --enable-neon --enable-v4l2-request --enable-libudev --enable-epoxy --libdir=/usr/lib/aarch64-linux-gnu --arch=arm64 --enable-pocketsphinx --enable-librsvg --enable-libdc1394 --enable-libdrm --enable-vout-drm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-libplacebo --enable-librav1e --enable-shared
  libavutil      57. 28.100 / 57. 28.100
  libavcodec     59. 37.100 / 59. 37.100
  libavformat    59. 27.100 / 59. 27.100
  libavdevice    59.  7.100 / 59.  7.100
  libavfilter     8. 44.100 /  8. 44.100
  libswscale      6.  7.100 /  6.  7.100
  libswresample   4.  7.100 /  4.  7.100
  libpostproc    56.  6.100 / 56.  6.100
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 266513.407163, bitrate: 165888 kb/s
  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1920x1080, 165888 kb/s, 5 fps, 5 tbr, 1000k tbn
Codec AVOption preset (Encoding preset) specified for output file #0 (rtsp://0.0.0.0:8554/xl) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (h264_v4l2m2m))
Press [q] to stop, [?] for help
[h264_v4l2m2m @ 0x55911b9d70]  <<< v4l2_encode_init: fmt=0/-1
[h264_v4l2m2m @ 0x55911b9d70] Using device /dev/video11
[h264_v4l2m2m @ 0x55911b9d70] driver 'bcm2835-codec' on card 'bcm2835-codec-encode' in mplane mode
[h264_v4l2m2m @ 0x55911b9d70] requesting formats: output=YU12 capture=H264
2025/09/15 13:46:11 INF [RTSP] [conn 127.0.0.1:35230] opened
2025/09/15 13:46:11 INF [RTSP] [session 06ef8b84] created by 127.0.0.1:35230
2025/09/15 13:46:12 INF [RTSP] [session 06ef8b84] is publishing to path 'xl', 1 track (H264)
Output #0, rtsp, to 'rtsp://0.0.0.0:8554/xl':
  Metadata:
    encoder         : Lavf59.27.100
  Stream #0:0: Video: h264, yuv420p(tv, progressive), 1920x1080, q=2-31, 600 kb/s, 5 fps, 90k tbn
    Metadata:
      encoder         : Lavc59.37.100 h264_v4l2m2m

After I hit CTRL-C to stop it, I get the following:

^C2025/09/15 14:04:31 INF shutting down gracefully
2025/09/15 14:04:31 INF [SRT] listener is closing
2025/09/15 14:04:31 INF [WebRTC] listener is closing
2025/09/15 14:04:31 INF [HLS] listener is closing
2025/09/15 14:04:31 INF [RTMP] listener is closing
2025/09/15 14:04:31 INF [RTSP] listener is closing
2025/09/15 14:04:31 INF [RTSP] [conn 127.0.0.1:50732] closed: terminated
2025/09/15 14:04:31 INF [RTSP] [session 92e8ce21] destroyed: terminated
2025/09/15 14:04:31 INF [path xl] runOnInit command stopped
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: 2025/09/15 14:04:31 INF [path mk] runOnInit command stopped
N/A, bitrate: 165888 kb/s
  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1920x1080, 165888 kb/s, 5 fps, 5 tbr, 1000k tbn2025/09/15 14:04:31 INF waiting for running hooks

Codec AVOption preset (Encoding preset) specified for output file #0 (rtsp://0.0.0.0:8554/xl) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (h264_v4l2m2m))
Press [q] to stop, [?] for help
Finishing stream 0:0 without any data written to it.
av_interleaved_write_frame(): Broken pipe
frame=  172 fps=5.0 q=-0.0 Lsize=N/A time=00:00:34.20 bitrate=N/A speed=0.993x
video:2556kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
[h264_v4l2m2m @ 0x55930be7a0]  <<< v4l2_encode_init: fmt=0/-1
[h264_v4l2m2m @ 0x55930be7a0] Using device /dev/video11
[h264_v4l2m2m @ 0x55930be7a0] driver 'bcm2835-codec' on card 'bcm2835-codec-encode' in mplane mode
[h264_v4l2m2m @ 0x55930be7a0] requesting formats: output=YU12 capture=H264
[tcp @ 0x5593051a90] Connection to tcp://0.0.0.0:8554?timeout=0 failed: Connection refused
Could not write header for output file #0 (incorrect codec parameters ?): Connection refused
Error initializing output stream 0:0 --
Exiting normally, received signal 2.
Exiting normally, received signal 2.

The "Connection refused" seems relevant, for sure. The warning about "has not been used for any stream" appears to be related to the h264_v4l2m2m - if I set that back to the libx264 recommended in the docs, that error goes away, but then the stream doesn't work.

I'm at a loss - same OS level, both were kept up to date with routine apt upgrades.