Class: AlprCam::FrameCapture

Inherits:
Object
  • Object
show all
Defined in:
lib/alpr_cam/frame_capture.rb

Constant Summary collapse

CAPTURE_TIMEOUT = 
10

Instance Method Summary collapse

Constructor Details

#initialize(device: "/dev/video0") ⇒ FrameCapture

Returns a new instance of FrameCapture.



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# File 'lib/alpr_cam/frame_capture.rb', line 11

def initialize(device: "/dev/video0")
  @device = device
end

Instance Method Details

#capture ⇒ Object 



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# File 'lib/alpr_cam/frame_capture.rb', line 15

def capture
  tmpfile = Tempfile.new(["alpr_frame_", ".jpg"])
  path = tmpfile.path
  tmpfile.close

  cmd = [
    "gst-launch-1.0",
    "v4l2src", "device=#{@device}", "num-buffers=1",
    "!", "videoconvert",
    "!", "jpegenc",
    "!", "filesink", "location=#{path}"
  ]

  begin
    _stdout, stderr, status = Timeout.timeout(CAPTURE_TIMEOUT) do
      Open3.capture3(*cmd)
    end
  rescue Timeout::Error
    raise CaptureError, "Frame capture timed out after #{CAPTURE_TIMEOUT}s for device #{@device}"
  end

  unless status.success?
    raise CaptureError, "Frame capture failed (exit #{status.exitstatus}): #{stderr}"
  end

  unless File.exist?(path) && File.size(path) > 0
    raise CaptureError, "Frame capture produced no output file"
  end

  path
end