Module: MP4::Nolan::Service

Defined in:
lib/mp4/nolan/service.rb

Defined Under Namespace

Modules: Sound, Track, Video

Class Method Summary collapse

Class Method Details

.compile_segment(cache, segment_index, _from_keyframe, _to_keyframe, segment_start_timestamp, segment_end_timestamp, _duration, previous_chunk_end_delta_sum, sample_timescale) ⇒ Object 



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# File 'lib/mp4/nolan/service.rb', line 25

def compile_segment(cache, segment_index, _from_keyframe, _to_keyframe, segment_start_timestamp, segment_end_timestamp, _duration, previous_chunk_end_delta_sum, sample_timescale)
  cache.tracks.each do |track|
    case track['handler_type']
    when 'vide'
      Video.compute(cache, segment_index,
                    track: track,
                    from_timestamp: segment_start_timestamp,
                    to_timestamp: segment_end_timestamp,
                    sample_timescale: sample_timescale,)
    when 'soun'
      Sound.compute(cache, segment_index,
                    track: track,
                    from_timestamp: previous_chunk_end_delta_sum,
                    to_timestamp: segment_end_timestamp,
                    sample_timescale: sample_timescale,)
    else
      MP4.logger.warn "Nolan::Service: skipping unsupported track #{track['handler_type']}"
    end
  end
end

.compute_segments(cache) ⇒ Object 



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# File 'lib/mp4/nolan/service.rb', line 15

def compute_segments(cache)
  track_id = cache.first_video_track_id
  return [] if track_id.nil?

  video_track = cache.track(track_id)
  timescale = video_track.fetch('timescale')

  divide_video_by_keyframes(cache, track_id, timescale)
end

.divide_into_segments(cache) ⇒ Object 



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# File 'lib/mp4/nolan/service.rb', line 5

def divide_into_segments(cache)
  segments = compute_segments(cache)

  segments.each_with_index do |segment_args, segment_index|
    compile_segment(cache, segment_index, *segment_args)
  end

  nil
end

.divide_video_by_keyframes(cache, track_id, timescale) ⇒ Object 



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# File 'lib/mp4/nolan/service.rb', line 46

def divide_video_by_keyframes(cache, track_id, timescale)
  first_keyframe   = cache.first_sample(track_id)
  latest_keyframe  = cache.last_sample(track_id)
  return [] if first_keyframe.nil? || latest_keyframe.nil?

  original_keyframes = cache.keyframes_grouped_by_second(track_id)
  return [] if original_keyframes.empty?

  chunks = []
  last_index = original_keyframes.size - 1

  original_keyframes.each_with_index do |keyframe, idx|
    keyframes =
      if idx == last_index
        [keyframe.fetch('sample_index'), latest_keyframe.fetch('sample_index')]
      elsif idx.zero? && keyframe.fetch('delta_sum').to_i.nonzero?
        [first_keyframe.fetch('sample_index'), keyframe.fetch('sample_index')]
      else
        [keyframe.fetch('sample_index'), original_keyframes[idx + 1].fetch('sample_index') - 1]
      end

    previous_chunk_end_delta_sum = chunks.dig(-1, 3)
    duration = cache.sum_delta_between(track_id, keyframes.first, keyframes.last).to_f

    chunks << [
      keyframes.fetch(0),
      keyframes.fetch(1),
      cache.sample_delta_sum_ms(track_id, keyframes.first).to_i,
      cache.sample_delta_sum_ms(track_id, keyframes.last).to_i,
      (duration / timescale.to_f).round(3),
      previous_chunk_end_delta_sum,
      timescale,
    ]
  end

  chunks
end