runner.rb

require 'open3'

RTSP_USER = 'user'
RTSP_PASSWORD = 'password'
RTSP_HOST = '192.168.1.100'
RTSP_PATH = '/live2'

RTSP_PROXY_URI = 'rtmp://127.0.0.1/live/test'

SCREENSHOT_FILE_NAME = 'screenshot.png'
SCREENSHOT_FPS = 1

SEND_COLOR_CMD = "ffmpeg -f lavfi -i color=green:1920x1080:d=1:r=15,format=yuv420p -vcodec libx264 -f flv \"#{RTSP_PROXY_URI}\""
SEND_SCREENSHOT_CMD = "ffmpeg -loop 1 -i #{SCREENSHOT_FILE_NAME} -vcodec libx264 -t 6 -r 15 -f flv \"#{RTSP_PROXY_URI}\""
SEND_CAMERA_FEED_CMD = "ffmpeg -y -f rtsp -rtsp_transport tcp -i rtsp://#{RTSP_USER}:#{RTSP_PASSWORD}@#{RTSP_HOST}#{RTSP_PATH} -filter_complex 'split=2[pic][vid];[pic]fps=#{SCREENSHOT_FPS}[png]' -map '[vid]' -an -preset ultrafast -vcodec libx264 -f flv \"#{RTSP_PROXY_URI}\" -map '[png]' -update 1 #{SCREENSHOT_FILE_NAME}"
ERROR_EXPECTED = "404 Stream Not Found"

def screenshot_or_still_img()
  # If we previously captured a screenshot from the camera that's what we send
  if File.exists?(SCREENSHOT_FILE_NAME)
    SEND_SCREENSHOT_CMD
  else
    # Otherwise we send a solid color image
    SEND_COLOR_CMD
  end
end

def send_screenshot_or_still_img()
  cmds = screenshot_or_still_img()
  puts cmds

  _color_stdout_str, color_stderr_str, color_status = Open3.capture3(*cmds)
  
  if !color_status.success?
    puts "Error while sending secondary command: #{color_stderr_str}"
    exit 1
  end
end

loop do
  puts SEND_CAMERA_FEED_CMD
  _stdout_str, stderr_str, status = Open3.capture3(*SEND_CAMERA_FEED_CMD)

  if !status.success?
    # We send only a replacement of the camera feed when we get a 404 back
    if stderr_str.include?(ERROR_EXPECTED)
      send_screenshot_or_still_img()
    else
      puts "Unhandled error: #{stderr_str}"
      exit 1
    end
  end 
  
  sleep 1
end