Extract sample rate in audio analyzer

activestorage/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Add `sample_rate` to `ActiveStorage::Analyzer::AudioAnalyzer` output
+
+    *Matija Čupić*
+
 *   Remove deprecated `purge` and `purge_later` methods from the attachments association.
 
     *Rafael Mendonça França*

activestorage/lib/active_storage/analyzer/audio_analyzer.rb

@@ -1,12 +1,12 @@
 # frozen_string_literal: true
 
 module ActiveStorage
-  # Extracts duration (seconds) and bit_rate (bits/s) from an audio blob.
+  # Extracts duration (seconds), bit_rate (bits/s) and sample_rate (hertz) from an audio blob.
   #
   # Example:
   #
   #   ActiveStorage::Analyzer::AudioAnalyzer.new(blob).metadata
-  #   # => { duration: 5.0, bit_rate: 320340 }
+  #   # => { duration: 5.0, bit_rate: 320340, sample_rate: 44100 }
   #
   # This analyzer requires the {FFmpeg}[https://www.ffmpeg.org] system library, which is not provided by Rails.
   class Analyzer::AudioAnalyzer < Analyzer
@@ -15,7 +15,7 @@ def self.accept?(blob)
     end
 
     def metadata
-      { duration: duration, bit_rate: bit_rate }.compact
+      { duration: duration, bit_rate: bit_rate, sample_rate: sample_rate }.compact
     end
 
     private
@@ -29,6 +29,11 @@ def bit_rate
         Integer(bit_rate) if bit_rate
       end
 
+      def sample_rate
+        sample_rate = audio_stream["sample_rate"]
+        Integer(sample_rate) if sample_rate
+      end
+
       def audio_stream
         @audio_stream ||= streams.detect { |stream| stream["codec_type"] == "audio" } || {}
       end

activestorage/test/analyzer/audio_analyzer_test.rb

@@ -12,6 +12,7 @@ class ActiveStorage::Analyzer::AudioAnalyzerTest < ActiveSupport::TestCase
 
     assert_equal 0.914286, metadata[:duration]
     assert_equal 128000, metadata[:bit_rate]
+    assert_equal 44100, metadata[:sample_rate]
   end
 
   test "instrumenting analysis" do