feat: add audio channels to presets

* Also fixes some issues with MPEG-DASH timings (uses avoid_negative_ts
  'make_zero' instead of the asetpts filter).
* Also adds some new methods to check for the FFmpeg and FFprobe
  binary versions.

Refs: ARC-11152

Author: bajankristof

lib/ffmpeg.rb

@@ -100,6 +100,7 @@ def ffmpeg_binary=(path)
       end
 
       @ffmpeg_binary = path
+      @ffmpeg_version = nil
     end
 
     # Get the path to the ffmpeg binary.
@@ -110,6 +111,27 @@ def ffmpeg_binary
       @ffmpeg_binary ||= which('ffmpeg')
     end
 
+    # Get the version of the ffmpeg binary.
+    #
+    # @return [String] The version string (e.g., "4.4.6", "8.0")
+    def ffmpeg_version
+      @ffmpeg_version ||= begin
+        stdout, = FFMPEG::IO.capture3(ffmpeg_binary, '-version')
+        stdout[/ffmpeg version (\d+\.\d+(?:\.\d+)?)/i, 1]
+      end
+    end
+
+    # Check if the ffmpeg version matches the given pattern.
+    #
+    # @param pattern [String, Regexp] The version pattern to match.
+    # @return [Boolean] True if the ffmpeg version matches the pattern, false otherwise.
+    def ffmpeg_version?(pattern)
+      return false unless ffmpeg_version
+      return pattern.match?(pattern) if pattern.is_a?(Regexp)
+
+      ffmpeg_version.start_with?(pattern.to_s)
+    end
+
     # Safely captures the standard output and the standard error of the ffmpeg command.
     #
     # @param args [Array<String>] The arguments to pass to ffmpeg.
@@ -198,6 +220,28 @@ def ffprobe_binary=(path)
       end
 
       @ffprobe_binary = path
+      @ffprobe_version = nil
+    end
+
+    # Get the version of the ffprobe binary.
+    #
+    # @return [String] The version string (e.g., "4.4.6", "8.0")
+    def ffprobe_version
+      @ffprobe_version ||= begin
+        stdout, = FFMPEG::IO.capture3(ffprobe_binary, '-version')
+        stdout[/ffprobe version (\d+\.\d+(?:\.\d+)?)/i, 1]
+      end
+    end
+
+    # Check if the ffprobe version matches the given pattern.
+    #
+    # @param pattern [String, Regexp] The version pattern to match.
+    # @return [Boolean] True if the ffprobe version matches the pattern, false otherwise.
+    def ffprobe_version?(pattern)
+      return false unless ffprobe_version
+      return pattern.match?(ffprobe_version) if pattern.is_a?(Regexp)
+
+      ffprobe_version.start_with?(pattern.to_s)
     end
 
     # Safely captures the standard output and the standard error of the ffmpeg command.

lib/ffmpeg/presets/aac.rb

@@ -13,6 +13,7 @@ def aac_128k(
         metadata: nil,
         threads: FFMPEG.threads,
         audio_sample_rate: 48_000,
+        audio_channels: 2,
         &
       )
         AAC.new(
@@ -21,6 +22,7 @@ def aac_128k(
           metadata:,
           threads:,
           audio_sample_rate:,
+          audio_channels:,
           audio_bit_rate: '128k',
           &
         )
@@ -32,6 +34,7 @@ def aac_192k(
         metadata: nil,
         threads: FFMPEG.threads,
         audio_sample_rate: 48_000,
+        audio_channels: 2,
         &
       )
         AAC.new(
@@ -40,6 +43,7 @@ def aac_192k(
           metadata:,
           threads:,
           audio_sample_rate:,
+          audio_channels:,
           audio_bit_rate: '192k',
           &
         )
@@ -51,6 +55,7 @@ def aac_320k(
         metadata: nil,
         threads: FFMPEG.threads,
         audio_sample_rate: 48_000,
+        audio_channels: 2,
         &
       )
         AAC.new(
@@ -59,6 +64,7 @@ def aac_320k(
           metadata:,
           threads:,
           audio_sample_rate:,
+          audio_channels:,
           audio_bit_rate: '320k',
           &
         )
@@ -67,12 +73,14 @@ def aac_320k(
 
     # Preset to encode AAC audio files.
     class AAC < Preset
-      attr_reader :threads, :audio_bit_rate, :audio_sample_rate
+      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,
@@ -81,11 +89,13 @@ def initialize(
         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
@@ -101,6 +111,7 @@ def initialize(
           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

lib/ffmpeg/presets/dash.rb

@@ -31,6 +31,7 @@ def initialize(
           use_template 1
           use_timeline 1
           segment_duration preset.segment_duration
+          avoid_negative_ts 'make_zero'
 
           muxing_flags 'frag_keyframe+empty_moov+default_base_moof'
           map_chapters '-1'

lib/ffmpeg/presets/dash/aac.rb

@@ -15,6 +15,7 @@ def aac_128k(
           threads: FFMPEG.threads,
           segment_duration: 4,
           audio_sample_rate: 48_000,
+          audio_channels: 2,
           &
         )
           AAC.new(
@@ -24,6 +25,7 @@ def aac_128k(
             threads:,
             segment_duration:,
             audio_sample_rate:,
+            audio_channels:,
             audio_bit_rate: '128k',
             &
           )
@@ -36,6 +38,7 @@ def aac_192k(
           threads: FFMPEG.threads,
           segment_duration: 4,
           audio_sample_rate: 48_000,
+          audio_channels: 2,
           &
         )
           AAC.new(
@@ -45,6 +48,7 @@ def aac_192k(
             threads:,
             segment_duration:,
             audio_sample_rate:,
+            audio_channels:,
             audio_bit_rate: '192k',
             &
           )
@@ -57,6 +61,7 @@ def aac_320k(
           threads: FFMPEG.threads,
           segment_duration: 4,
           audio_sample_rate: 48_000,
+          audio_channels: 2,
           &
         )
           AAC.new(
@@ -66,6 +71,7 @@ def aac_320k(
             threads:,
             segment_duration:,
             audio_sample_rate:,
+            audio_channels:,
             audio_bit_rate: '320k',
             &
           )
@@ -74,12 +80,14 @@ def aac_320k(
 
       # Preset to encode DASH AAC audio files.
       class AAC < DASH
-        attr_reader :audio_bit_rate, :audio_sample_rate
+        attr_reader :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,
@@ -89,10 +97,12 @@ def initialize(
           segment_duration: 4,
           audio_bit_rate: '128k',
           audio_sample_rate: 48_000,
+          audio_channels: 2,
           &
         )
           @audio_bit_rate = audio_bit_rate
           @audio_sample_rate = audio_sample_rate
+          @audio_channels = audio_channels
           preset = self
 
           super(
@@ -111,6 +121,7 @@ def initialize(
             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

lib/ffmpeg/presets/dash/h264.rb

@@ -308,10 +308,9 @@ def initialize(
             end
 
             map media.audio_mapping_id do
-              # Reset the audio stream's timestamps to start from 0.
-              filter Filter.new(:audio, 'asetpts', expr: 'PTS-STARTPTS')
               audio_bit_rate h264_presets.first.audio_bit_rate
               audio_sample_rate h264_presets.first.audio_sample_rate
+              audio_channels h264_presets.first.audio_channels if h264_presets.first.audio_channels
             end
           end
         end