class Lolcommits::CaptureLinuxAnimated

Public Instance Methods

capture() click to toggle source
# File lib/lolcommits/capturer/capture_linux_animated.rb, line 3
def capture
  # make a fresh frames directory
  FileUtils.rm_rf(frames_location)
  FileUtils.mkdir_p(frames_location)

  # capture the raw video with ffmpeg video4linux2
  system_call "ffmpeg -v quiet -y -f video4linux2 -video_size 320x240 -i #{capture_device_string} -t #{capture_duration} \"#{video_location}\" > /dev/null"
  return unless File.exist?(video_location)
  # convert raw video to png frames with ffmpeg
  system_call "ffmpeg #{capture_delay_string} -v quiet -i \"#{video_location}\" -t #{animated_duration} \"#{frames_location}/%09d.png\" > /dev/null"

  # use fps to set delay and number of frames to skip (for lower filesized gifs)
  fps   = video_fps(video_location)
  skip  = frame_skip(fps)
  delay = frame_delay(fps, skip)
  debug "Capturer: anaimated gif choosing every #{skip} frames with a frame delay of #{delay}"

  # create the looping animated gif from frames (picks nth frame with seq,
  # quotes output and concats to a single line with tr)
  seq_command = "seq -f \"\\\"#{frames_location}/%09g.png\\\"\" 1 #{skip} #{Dir["#{frames_location}/*"].length} | tr '\\n' ' '"
  seq_frame_files = system_call(seq_command, true)
  # convert to animated gif with delay and gif optimisation
  system_call "convert -layers OptimizeTransparency -delay #{delay} -loop 0 #{seq_frame_files} -coalesce \"#{snapshot_location}\""
end

Private Instance Methods

capture_delay_string() click to toggle source
# File lib/lolcommits/capturer/capture_linux_animated.rb, line 63
def capture_delay_string
  " -ss #{capture_delay}" if capture_delay.to_i > 0
end
capture_device_string() click to toggle source
# File lib/lolcommits/capturer/capture_linux_animated.rb, line 59
def capture_device_string
  capture_device || '/dev/video0'
end
capture_duration() click to toggle source
# File lib/lolcommits/capturer/capture_linux_animated.rb, line 67
def capture_duration
  animated_duration.to_i + capture_delay.to_i
end
frame_delay(fps, skip) click to toggle source
# File lib/lolcommits/capturer/capture_linux_animated.rb, line 35
def frame_delay(fps, skip)
  # calculate frame delay
  delay = ((100.0 * skip) / fps.to_f).to_i
  delay < 6 ? 6 : delay # hard limit for IE browsers
end
frame_skip(fps) click to toggle source
# File lib/lolcommits/capturer/capture_linux_animated.rb, line 47
def frame_skip(fps)
  # of frames to skip depends on movie fps
  case fps
  when 0..15
    2
  when 16..28
    3
  else
    4
  end
end
system_call(call_str, capture_output = false) click to toggle source
# File lib/lolcommits/capturer/capture_linux_animated.rb, line 30
def system_call(call_str, capture_output = false)
  debug "Capturer: making system call for \n #{call_str}"
  capture_output ? `#{call_str}` : system(call_str)
end
video_fps(file) click to toggle source
# File lib/lolcommits/capturer/capture_linux_animated.rb, line 41
def video_fps(file)
  # inspect fps of the captured video file (default to 29.97)
  fps = system_call("ffmpeg -i \"#{file}\" 2>&1 | sed -n \"s/.*, \\(.*\\) fp.*/\\1/p\"", true)
  fps.to_i < 1 ? 29.97 : fps.to_f
end