extract_keyframes_worker.rb

class ExtractKeyframesWorker
  include Sidekiq::Worker

  def perform(video_id, grinder_id)
    video       = Video.find(video_id)
    download_as = video.tmp_file.path

    # Destroy all present keyframes
    video.keyframes.destroy_all

    # Convert duration to integer
    duration = video.file_meta['duration'].to_i

    # Load video file
    movie = FFMPEG::Movie.new(download_as)

    # Determine how many keyframes should be extracted
    # based on movie duration.
    if duration > 60
      frames_to_extract = 9
    elsif 60 > duration && duration > 30
      frames_to_extract = 6
    else
      frames_to_extract = 3
    end

    # Extract the keyframes and save them to db
    for i in 1..(frames_to_extract)
      seek_time = (duration / frames_to_extract) * i

      image = movie.screenshot(
        Rails.root.join('tmp', seek_time.to_s + '.jpg'),
        seek_time: seek_time
      )

      Rails.logger.debug "Taking screenshot from #{seek_time}s"

      Keyframe.create(video_id: video.id, file: File.open(image.path))

      # Destroy image
      File.delete(image.path)
    end

    # Destroy downloaded video
    # File.delete(Rails.root.join('tmp', download_as))

    logger.info "Keyframes extracted!"
  end
end