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Class: ActiveStorage::Analyzer::AudioAnalyzer

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::ActiveStorage::Analyzer
Instance Chain:
self, ::ActiveStorage::Analyzer
Inherits: ActiveStorage::Analyzer
Defined in: activestorage/lib/active_storage/analyzer/audio_analyzer.rb

Overview

Active Storage Audio Analyzer

Extracts duration (seconds), bit_rate (bits/s), sample_rate (hertz) and tags (internal metadata) from an audio blob.

Example:

ActiveStorage::Analyzer::AudioAnalyzer.new(blob).metadata
# => { duration: 5.0, bit_rate: 320340, sample_rate: 44100, tags: { encoder: "Lavc57.64", ... } }

This analyzer requires the FFmpeg system library, which is not provided by Rails.

Class Attribute Summary

::ActiveStorage::Analyzer - Inherited

.analyze_later?

Implement this method in concrete subclasses.

Class Method Summary

::ActiveStorage::Analyzer - Inherited

.accept?

Implement this method in a concrete subclass.
.new

Instance Attribute Summary

::ActiveStorage::Analyzer - Inherited

#blob

Instance Method Summary

::ActiveStorage::Analyzer - Inherited

#metadata

Override this method in a concrete subclass.
#download_blob_to_tempfile

Downloads the blob to a tempfile on disk.
#instrument, #logger, #tmpdir

Constructor Details

This class inherits a constructor from ActiveStorage::Analyzer

Class Method Details

.accept?(blob) ⇒ Boolean

[ GitHub ] 

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 15



def self.accept?(blob)
  blob.audio?
end


  







Instance Method Details



  

    #audio_stream   (private)
  

  [ GitHub ]


  

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 44



def audio_stream
  @audio_stream ||= streams.detect { |stream| stream["codec_type"] == "audio" } || {}
end


  








  

    #bit_rate   (private)
  

  [ GitHub ]


  

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 29



def bit_rate
  bit_rate = audio_stream["bit_rate"]
  Integer(bit_rate) if bit_rate
end


  








  

    #duration   (private)
  

  [ GitHub ]


  

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 24



def duration
  duration = audio_stream["duration"]
  Float(duration) if duration
end


  








  

    #ffprobe_path   (private)
  

  [ GitHub ]


  

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 73



def ffprobe_path
  ActiveStorage.paths[:ffprobe] || "ffprobe"
end


  








  

    #metadata  
  

  [ GitHub ]


  

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 19



def metadata
  { duration: duration, bit_rate: bit_rate, sample_rate: sample_rate, tags: tags }.compact
end


  








  

    #probe   (private)
  

  [ GitHub ]


  

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 52



def probe
  @probe ||= download_blob_to_tempfile { |file| probe_from(file) }
end


  








  

    #probe_from(file)   (private)
  

  [ GitHub ]


  

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 56



def probe_from(file)
  instrument(File.basename(ffprobe_path)) do
    IO.popen([ ffprobe_path,
      "-print_format", "json",
      "-show_streams",
      "-show_format",
      "-v", "error",
      file.path
    ]) do |output|
      JSON.parse(output.read)
    end
  end
rescue Errno::ENOENT
  logger.info "Skipping audio analysis because ffprobe isn't installed"
  {}
end


  








  

    #sample_rate   (private)
  

  [ GitHub ]


  

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 34



def sample_rate
  sample_rate = audio_stream["sample_rate"]
  Integer(sample_rate) if sample_rate
end


  








  

    #streams   (private)
  

  [ GitHub ]


  

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 48



def streams
  probe["streams"] || []
end


  








  

    #tags   (private)
  

  [ GitHub ]


  

  


# File 'activestorage/lib/active_storage/analyzer/audio_analyzer.rb', line 39



def tags
  tags = audio_stream["tags"]
  Hash(tags) if tags
end