Class: Captive::VTT

Inherits:
Object
  • Object
show all
Includes:
Base
Defined in:
lib/captive/formats/vtt.rb

Constant Summary collapse

VTT_HEADER =

Standard VTT Header

'WEBVTT'
VTT_METADATA =

VTT METADATA Regex

/^NOTE|^STYLE/.freeze

Instance Attribute Summary

Attributes included from Base

#cues

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Base

#as_json, included, #initialize, #method_missing, #respond_to_missing?, #save_as

Dynamic Method Handling

This class handles dynamic methods through the method_missing method in the class Captive::Base

Class Method Details

.integer?(val) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/captive/formats/vtt.rb', line 103

def self.integer?(val)
  val.to_i.to_s == val
end

.metadata?(text) ⇒ Boolean

VTT Metadata tag matcher

Returns:

  • (Boolean) 


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# File 'lib/captive/formats/vtt.rb', line 94

def self.metadata?(text)
  !!text.match(VTT_METADATA)
end

.parse(blob:) ⇒ Object

Parse VTT blob and return array of cues

Raises:



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# File 'lib/captive/formats/vtt.rb', line 14

def self.parse(blob:)
  cue_list = []
  lines = blob.split("\n")
  cue_count = 1
  state = :new_cue
  cue = nil
  raise InvalidSubtitle, 'Invalid VTT Signature' unless validate_header(lines.shift)

  lines.each_with_index do |line, index|
    line.strip!

    case state
    when :new_cue
      next if line.empty?

      if metadata?(line)
        state = :metadata
        next
      end

      # If its not metadata, and its not an empty line, it should be a timestamp or an identifier
      unless time?(line)
        # If this line is an identifier the next line should be a timecode
        next if time?(lines[index + 1])

        raise InvalidSubtitle, "Invalid Time Format at line #{index + 1}" unless time?(line)
      end

      elements = line.split
      start_time = elements[0]
      end_time = elements[2]
      cue = Cue.new(cue_number: cue_count, start_time: start_time, end_time: end_time)
      cue_count += 1
      state = :text
    when :text
      if line.empty?
        ## end of previous cue
        cue_list << cue
        cue = nil
        state = :new_cue
      else
        cue.add_text(line)
      end
    when :metadata
      next unless line.empty?

      # Line is empty which means metadata block is over
      state = :new_cue
    end
  end

  # Check to make sure we add the last cue if for some reason the file lacks an empty line at the end
  cue_list << cue unless cue.nil?

  # Return the cue_list
  cue_list
end

.time?(text) ⇒ Boolean

VTT Timecode matcher

Returns:

  • (Boolean) 


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# File 'lib/captive/formats/vtt.rb', line 99

def self.time?(text)
  !!text.match(/^(\d{2}:)?\d{2}:\d{2}.\d{3}.*(\d{2}:)?\d{2}:\d{2}.\d{3}/)
end

.validate_header(line) ⇒ Object

VTT Header tag matcher



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# File 'lib/captive/formats/vtt.rb', line 88

def self.validate_header(line)
  # Make sure BOM does not interfere with header detection
  !!line.force_encoding('UTF-8').delete("\xEF\xBB\xBF").strip.match(/^#{VTT_HEADER}/)
end

Instance Method Details

#to_s ⇒ Object

Dump contents to String



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# File 'lib/captive/formats/vtt.rb', line 73

def to_s
  string = VTT_HEADER.dup
  string << "\n\n"
  cues.each do |cue|
    string << milliseconds_to_timecode(cue.start_time)
    string << ' --> '
    string << milliseconds_to_timecode(cue.end_time)
    string << "\n"
    string << cue.text
    string << "\n\n"
  end
  string
end