Class: MP4::Metadata::Memoize::Stbl::CompositionOffsetCalculator

Inherits:
Object
  • Object
show all
Defined in:
lib/mp4/metadata/memoize/stbl/composition_offset_calculator.rb

Instance Method Summary collapse

Constructor Details

#initialize(ctts_table) ⇒ CompositionOffsetCalculator

Returns a new instance of CompositionOffsetCalculator.



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# File 'lib/mp4/metadata/memoize/stbl/composition_offset_calculator.rb', line 5

def initialize(ctts_table)
  @ctts_table = ctts_table.dup
  @ctts_table_dup = ctts_table.dup
  @cached_total_samples = 0
  @cached_composition_offset = nil
end

Instance Method Details

#find_composition_offset(sample_number) ⇒ Object 



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# File 'lib/mp4/metadata/memoize/stbl/composition_offset_calculator.rb', line 12

def find_composition_offset(sample_number)
  return nil if @ctts_table.nil?

  return @cached_composition_offset if sample_number <= @cached_total_samples

  while (entry = @ctts_table.shift)
    @cached_total_samples += entry.sample_count

    if sample_number <= @cached_total_samples
      @cached_composition_offset = entry.fetch(:composition_offset)
      return @cached_composition_offset
    end
  end

  raise "Sample Composition offset not found for sample index: #{sample_number}"
end