Class: Subconv::Scc::Transformer

Inherits:
Object
  • Object
show all
Defined in:
lib/subconv/scc/transformer.rb

Overview

Transform an array of caption grids parsed from SCC into an array of captions with the caption content converted to a tree of text and style nodes

Instance Method Summary collapse

Instance Method Details

#combine_paint_on_captions(captions) ⇒ Object

Transform paint-on captions to pop-on captions by combining successive captions that only add text. As soon as text is removed or text that is already on-screen is changed, a caption is produced.



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# File 'lib/subconv/scc/transformer.rb', line 64

def combine_paint_on_captions(captions)
  first_paint_on_caption = nil
  last_paint_on_caption = nil
  # Insert nil pseudo-element at end for flushing
  (captions + [nil]).each_with_object([]) do |caption, result_captions|
    if caption&.paint_on_mode?
      first_paint_on_caption ||= caption
      # Detect when characters disappear/change; until then: skip all paint-on captions (that just add text).
      # At the same time, always produce a cue for empty grids so explicit display clears do not get lost.
      # Simple character replacement cues that replace standard characters with extended ones should also never trigger a new caption.
      if !last_paint_on_caption.nil? && !caption.char_replacement? && (!require_grid_object(last_paint_on_caption.grid).without_identical_characters(require_grid_object(caption.grid)).empty? || last_paint_on_caption.grid.nil?)
        # Take timecode from the first caption of the current batch, but the grid from the current caption
        result_captions << Scc::Caption.new(timecode: first_paint_on_caption.timecode, grid: last_paint_on_caption.grid, mode: :pop_on)
        # Caption produced, so this marks a new segment
        first_paint_on_caption = caption
      end
      last_paint_on_caption = caption
    else
      # Flush out last paint-on caption if necessary
      result_captions << Scc::Caption.new(timecode: first_paint_on_caption.timecode, grid: last_paint_on_caption.grid, mode: :pop_on) unless first_paint_on_caption.nil?
      first_paint_on_caption = nil
      last_paint_on_caption = nil
      result_captions << caption unless caption.nil?
    end
  end
end

#transform(captions) ⇒ Object

Perform the transformation Continuous text blocks are collected in each caption grid and merged Empty grids will end the previously displayed caption



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# File 'lib/subconv/scc/transformer.rb', line 14

def transform(captions)
  transformed_captions = []
  return [] if captions.empty?

  # Use fps from Scc
  fps = captions.first.timecode.fps
  last_time = Timecode.new(0, fps)

  captions_open = []
  captions.each do |caption|
    if caption.grid.nil? || !captions_open.empty?
      # Close any captions that might be displayed
      captions_open.each do |caption_to_close|
        caption_to_close.timespan = Utility::Timespan.new(last_time.dup, caption.timecode.dup)
      end
      transformed_captions.concat captions_open
      # All captions are closed now
      captions_open = []
    end

    # Collect text chunks in each row and create captions out of them
    caption.grid&.each_with_index do |row, row_number|
      chunks = collect_chunks(row)
      chunks.each_pair do |start_column, chunk|
        content = transform_chunk(chunk)
        position = position_from_grid(row_number, start_column)
        captions_open.push(Subconv::Caption.new(
          align:    :start,
          position: position,
          content:  content
        ))
      end
    end

    last_time = caption.timecode
  end

  unless captions_open.empty?
    # Close any captions that are still open at the end
    captions_open.each do |caption_to_close|
      caption_to_close.timespan = Utility::Timespan.new(last_time.dup, last_time + Timecode.from_seconds(5, fps))
    end
    transformed_captions.concat captions_open
  end

  transformed_captions
end