feat: built-in preset improvements

CHANGELOG

@@ -1,3 +1,16 @@
+== 7.0.0-beta.14 2025-04-25
+
+Improvements:
+* Built-in presets now use the closest standard frame rate to the input file
+  when the input file has lower frame rate than the preset.
+* Increased the keyframe interval of the MPEG-DASH H.264 preset to 2 seconds by default.
+  This results in a more efficient encoding process and smaller file sizes, while
+  still maintaining a good quality.
+
+Fixes:
+* Fixed some audio timeline shifting issues with the MPEG-DASH H.264 preset due to which
+  some players would skip to the end of the video upon loading.
+
 == 7.0.0-beta.13 2025-04-23
 
 Fixes:

lib/ffmpeg/command_args.rb

@@ -15,6 +15,8 @@ module FFMPEG
   #  end
   #  args.to_s # "-map 0:v:0 -c:v:0 libx264 -r 30"
   class CommandArgs < RawCommandArgs
+    STANDARD_FRAME_RATES = [12, 24, 25, 30, 50, 60, 90, 120, 240].freeze
+
     class << self
       # Composes a new instance of CommandArgs with the given media.
       # The block is evaluated in the context of the new instance.
@@ -96,7 +98,10 @@ def audio_bit_rate(target_value, **kwargs)
     # @param target_value [Integer, Float] The target frame rate.
     # @return [Numeric]
     def adjusted_frame_rate(target_value)
-      [media.frame_rate, target_value].compact.min
+      return target_value if media.frame_rate.nil?
+      return target_value if media.frame_rate > target_value
+
+      STANDARD_FRAME_RATES.min_by { (_1 - media.frame_rate).abs }
     end
 
     # Returns the minimum of the current video bit rate and the target value.

lib/ffmpeg/presets/dash/h264.rb

@@ -18,7 +18,7 @@ def h264_360p(
           metadata: nil,
           threads: FFMPEG.threads,
           segment_duration: 4,
-          keyframe_interval: 1,
+          keyframe_interval: 2,
           audio_bit_rate: '128k',
           frame_rate: 30,
           ld_frame_rate: 24,
@@ -48,7 +48,7 @@ def h264_480p(
           metadata: nil,
           threads: FFMPEG.threads,
           segment_duration: 4,
-          keyframe_interval: 1,
+          keyframe_interval: 2,
           audio_bit_rate: '128k',
           frame_rate: 30,
           ld_frame_rate: 24,
@@ -79,7 +79,7 @@ def h264_720p(
           metadata: nil,
           threads: FFMPEG.threads,
           segment_duration: 4,
-          keyframe_interval: 1,
+          keyframe_interval: 2,
           audio_bit_rate: '128k',
           ld_frame_rate: 24,
           sd_frame_rate: 30,
@@ -112,7 +112,7 @@ def h264_1080p(
           metadata: nil,
           threads: FFMPEG.threads,
           segment_duration: 4,
-          keyframe_interval: 1,
+          keyframe_interval: 2,
           audio_bit_rate: '128k',
           ld_frame_rate: 24,
           sd_frame_rate: 30,
@@ -146,7 +146,7 @@ def h264_1440p(
           metadata: nil,
           threads: FFMPEG.threads,
           segment_duration: 4,
-          keyframe_interval: 1,
+          keyframe_interval: 2,
           audio_bit_rate: '128k',
           ld_frame_rate: 24,
           sd_frame_rate: 30,
@@ -181,7 +181,7 @@ def h264_4k(
           metadata: nil,
           threads: FFMPEG.threads,
           segment_duration: 4,
-          keyframe_interval: 1,
+          keyframe_interval: 2,
           audio_bit_rate: '128k',
           ld_frame_rate: 24,
           sd_frame_rate: 30,
@@ -231,7 +231,7 @@ def initialize(
           metadata: nil,
           threads: FFMPEG.threads,
           segment_duration: 4,
-          keyframe_interval: 1,
+          keyframe_interval: 2,
           h264_presets: [Presets.h264_1080p, Presets.h264_720p, Presets.h264_480p, Presets.h264_360p],
           ld_h264_presets: [Presets.h264_240p, Presets.h264_144p],
           &
@@ -292,11 +292,14 @@ def initialize(
                   constant_rate_factor h264_preset.constant_rate_factor, stream_type: 'v', stream_index: index
                   min_keyframe_interval preset.keyframe_interval * frame_rate, stream_index: index
                   max_keyframe_interval preset.keyframe_interval * frame_rate, stream_index: index
+                  force_keyframes "expr:gte(t,n_forced*#{preset.keyframe_interval})", stream_index: index
                 end
               end
             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
             end
           end

lib/ffmpeg/raw_command_args.rb

@@ -580,8 +580,22 @@ def aspect_ratio(value, **kwargs)
       stream_arg('aspect', value, stream_type: 'v', **kwargs)
     end
 
+    # Sets a force keyframe interval in the command arguments.
+    #
+    # @param value [String, Numeric] The force keyframe interval to set.
+    # @param kwargs [Hash] The stream specific arguments to use (see stream_arg).
+    # @return [self]
+    #
+    # @example
+    #  args = FFMPEG::RawCommandArgs.compose do
+    #    force_keyframes 'expr:gte(t,n_forced*2)'
+    #  end
+    #  args.to_s # "-force_key_frames expr:gte(t,n_forced*2)"
+    def force_keyframes(value, **kwargs)
+      stream_arg('force_key_frames', value, **kwargs)
+    end
+
     # Sets a minimum keyframe interval in the command arguments.
-    # This is used for adaptive streaming.
     #
     # @param value [String, Numeric] The minimum keyframe interval to set.
     # @param kwargs [Hash] The stream specific arguments to use (see stream_arg).
@@ -598,7 +612,6 @@ def min_keyframe_interval(value, **kwargs)
 
     # Sets a maximum keyframe interval in the command arguments.
     #
-    # This is used for adaptive streaming.
     # @param value [String, Numeric] The maximum keyframe interval to set.
     # @param kwargs [Hash] The stream specific arguments to use (see stream_arg).
     # @return [self]
@@ -613,7 +626,6 @@ def max_keyframe_interval(value, **kwargs)
     end
 
     # Sets a scene change threshold in the command arguments.
-    # This is used for adaptive streaming.
     #
     # @param value [String, Numeric] The scene change threshold to set.
     # @param kwargs [Hash] The stream specific arguments to use (see stream_arg).

lib/ffmpeg/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module FFMPEG
-  VERSION = '7.0.0-beta.13'
+  VERSION = '7.0.0-beta.14'
 end

spec/ffmpeg/command_args_spec.rb

@@ -5,11 +5,19 @@
 module FFMPEG
   describe CommandArgs do
     describe '#frame_rate' do
-      context 'when the media frame rate is lower than the target value' do
-        it 'sets the frame rate to the media frame rate' do
+      context 'when the target value is nil' do
+        it 'does not set the frame rate' do
           media = instance_double(Media, frame_rate: 30)
+          args = CommandArgs.compose(media) { frame_rate nil }
+          expect(args.to_a).to eq(%w[])
+        end
+      end
+
+      context 'when the media frame rate is nil' do
+        it 'sets the frame rate to the target value' do
+          media = instance_double(Media, frame_rate: nil)
           args = CommandArgs.compose(media) { frame_rate 60 }
-          expect(args.to_a).to eq(%w[-r 30])
+          expect(args.to_a).to eq(%w[-r 60])
         end
       end
 
@@ -21,11 +29,19 @@ module FFMPEG
         end
       end
 
-      context 'when the target value is nil' do
-        it 'does not set the frame rate' do
-          media = instance_double(Media, frame_rate: 30)
-          args = CommandArgs.compose(media) { frame_rate nil }
-          expect(args.to_a).to eq(%w[])
+      context 'when the media frame rate is lower than the target value' do
+        it 'sets the frame rate to the closest standard value' do
+          {
+            0 => 12,
+            21 => 24,
+            26 => 25,
+            29.94 => 30,
+            480 => 240
+          }.each do |media_frame_rate, expected_value|
+            media = instance_double(Media, frame_rate: media_frame_rate)
+            args = CommandArgs.compose(media) { frame_rate 1000 }
+            expect(args.to_a).to eq(%W[-r #{expected_value}])
+          end
         end
       end
     end

spec/ffmpeg/raw_command_args_spec.rb

@@ -169,6 +169,7 @@ module FFMPEG
       frame_rate: 'r',
       pixel_format: 'pix_fmt',
       resolution: 's',
+      force_keyframes: 'force_key_frames',
       min_keyframe_interval: 'keyint_min',
       max_keyframe_interval: 'g',
       scene_change_threshold: 'sc_threshold',