Streaming Live View

Live view function enables us to get images of every frame without capturing. While getting the sequence of live view images, we can still access to all shooting functions without any restriction. You can use #start_liveview_thread to create new thread to start streaming live view images to your client PC.

#start_liveview_thread receives a block that is called each time the new live view image arrives. The block parameter is the LiveviewImage class instance, which contains a sequence number, timestamp, and JPEG data. This example continues to save live view images to the current directory.

th = cam.start_liveview_thread do |img|
  filename = "#{img.sequence_number}.jpg"
  File.write filename, img.jpeg_data
  puts "wrote #{filename}."
end
th.join

Using Live View Frame Information

Live view frame information provides the information of the several frames, e.g. focus frames, tracking frames and face frames. If your camera supports Liveview Frame API group, live view frame information is automatically enabled. You can get live view frame information as LiveviewFrameInformation class instance by the second block parameter. This example continues to take a picture only if a face detection frame exists.

face_detected = false
th = cam.start_liveview_thread do |img, info|
  face_frame = info.frames.find { |f| f.category == 4 }
  if face_frame
    puts "  top-left     = (#{face_frame .top_left.x}, #{face_frame .top_left.y})"
    puts "  bottom-right = (#{face_frame .bottom_right.x}, #{face_frame .bottom_right.y})"
    face_detected = true
  else
    puts 'No face!'
    face_detected = false
  end
end

loop do
  if face_detected
    cam.capture_still
  end
  sleep 1
end