ruby-ffmpeg/lib/ffmpeg/presets/aac.rb at 6a11692258bf830ee3d2403bbec3d6fa9fb02302 · instructure/ruby-ffmpeg · GitHub

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# frozen_string_literal: true

require_relative '../preset'

module FFMPEG
  # rubocop:disable Style/Documentation
  module Presets
    # rubocop:enable Style/Documentation
    class << self
      def aac_128k(
        name: 'AAC 128k',
        filename: '%<basename>s.m4a',
        metadata: nil,
        threads: FFMPEG.threads,
        audio_sample_rate: 48_000,
        audio_channels: 2,
        &
      )
        AAC.new(
          name:,
          filename:,
          metadata:,
          threads:,
          audio_sample_rate:,
          audio_channels:,
          audio_bit_rate: '128k',
          &
        )
      end

      def aac_192k(
        name: 'AAC 192k',
        filename: '%<basename>s.m4a',
        metadata: nil,
        threads: FFMPEG.threads,
        audio_sample_rate: 48_000,
        audio_channels: 2,
        &
      )
        AAC.new(
          name:,
          filename:,
          metadata:,
          threads:,
          audio_sample_rate:,
          audio_channels:,
          audio_bit_rate: '192k',
          &
        )
      end

      def aac_320k(
        name: 'AAC 320k',
        filename: '%<basename>s.m4a',
        metadata: nil,
        threads: FFMPEG.threads,
        audio_sample_rate: 48_000,
        audio_channels: 2,
        &
      )
        AAC.new(
          name:,
          filename:,
          metadata:,
          threads:,
          audio_sample_rate:,
          audio_channels:,
          audio_bit_rate: '320k',
          &
        )
      end
    end

    # Preset to encode AAC audio files.
    class AAC < Preset
      attr_reader :threads, :audio_bit_rate, :audio_sample_rate, :audio_channels

      # @param name [String] The name of the preset.
      # @param filename [String] The filename format of the output.
      # @param metadata [Object] The metadata to associate with the preset.
      # @param audio_bit_rate [String] The audio bit rate to use.
      # @param audio_sample_rate [Integer] The audio sample rate to use.
      # @param audio_channels [Integer, nil] The number of audio channels to use (nil to preserve source).
      # @yield The block to execute to compose the command arguments.
      def initialize(
        name: nil,
        filename: nil,
        metadata: nil,
        threads: FFMPEG.threads,
        audio_bit_rate: '128k',
        audio_sample_rate: 48_000,
        audio_channels: 2,
        &
      )
        @threads = threads
        @audio_bit_rate = audio_bit_rate
        @audio_sample_rate = audio_sample_rate
        @audio_channels = audio_channels
        preset = self

        super(name:, filename:, metadata:) do
          threads preset.threads if preset.threads
          format_name 'mp4'
          brand 'M4A '
          muxing_flags '+faststart'
          map_chapters '-1'
          audio_codec_name 'aac'

          instance_exec(&) if block_given?

          map media.audio_mapping_id do
            audio_bit_rate preset.audio_bit_rate
            audio_sample_rate preset.audio_sample_rate
            audio_channels preset.audio_channels if preset.audio_channels
          end
        end
      end
    end
  end
end