Add experimental Pocketsphinx::CMNDecoder (relates to #10)

lib/pocketsphinx.rb

@@ -3,6 +3,7 @@
 require "pocketsphinx/version"
 
 # Pocketsphinx FFI API
+require "pocketsphinx/api/sphinxbase/cmn"
 require "pocketsphinx/api/sphinxbase"
 require "pocketsphinx/api/sphinxad"
 require "pocketsphinx/api/pocketsphinx"
@@ -22,6 +23,7 @@
 require "pocketsphinx/audio_file"
 require "pocketsphinx/microphone"
 require "pocketsphinx/decoder"
+require "pocketsphinx/cmn_decoder"
 require "pocketsphinx/speech_recognizer"
 require "pocketsphinx/live_speech_recognizer"
 require "pocketsphinx/audio_file_speech_recognizer"

lib/pocketsphinx/api/pocketsphinx.rb

@@ -26,6 +26,7 @@ def self.ps_init(*args)
       attach_function :ps_unset_search, [:decoder, :string], :int
       attach_function :ps_get_search, [:decoder], :string
       attach_function :ps_set_search, [:decoder, :string], :int
+      attach_function :ps_get_feat, [:decoder], :pointer
 
       typedef :pointer, :seg_iter
 
@@ -35,6 +36,11 @@ def self.ps_init(*args)
       attach_function :ps_seg_frames, [:seg_iter, :pointer, :pointer], :void
       attach_function :ps_seg_prob, [:seg_iter, :pointer, :pointer, :pointer], :int32
       attach_function :ps_seg_free, [:seg_iter], :void
+
+      def self.get_cmn_values(ps_decoder)
+        feature = Sphinxbase::Feature.new(ps_get_feat(ps_decoder))
+        feature[:cmn_struct][:cmn_mean].get_array_of_float32(0, feature[:cmn_struct][:veclen])
+      end
     end
   end
 end

lib/pocketsphinx/api/sphinxbase.rb

@@ -4,6 +4,8 @@ module Sphinxbase
       extend FFI::Library
       ffi_lib "libsphinxbase"
 
+      include Cmn
+
       class Argument < FFI::Struct
         layout :name, :string,
           :type, :int,

lib/pocketsphinx/api/sphinxbase/cmn.rb

@@ -0,0 +1,40 @@
+module Pocketsphinx
+  module API
+    module Sphinxbase
+      module Cmn
+        extend FFI::Library
+
+        enum :cmn_type, [:none, 0, :current, :prior]
+        enum :agc_type, [:none, 0, :max, :emax, :noise]
+
+        class CmnData < FFI::Struct
+          layout :cmn_mean, :pointer,
+            :cmn_var, :pointer,
+            :sum, :pointer,
+            :nframe, :int32,
+            :veclen, :int32
+        end
+
+        class Feature < FFI::Struct
+          layout :refcount, :int,
+            :name,  :string,
+            :cepsize, :int32,
+            :n_stream, :int32,
+            :stream_len, :pointer,
+            :window_size, :int32,
+            :n_sv, :int32,
+            :sv_len, :pointer,
+            :subvecs, :pointer,
+            :mfcc_t, :pointer,
+            :sv_dim, :int32,
+            :cmn, :cmn_type,
+            :varnorm, :int32,
+            :agc, :agc_type,
+            :compute_feat, :pointer,
+            :cmn_struct, CmnData.ptr,
+            :agc_struct, :pointer
+        end
+      end
+    end
+  end
+end

lib/pocketsphinx/cmn_decoder.rb

@@ -0,0 +1,29 @@
+module Pocketsphinx
+  class CMNDecoder < Decoder
+    CMN_TOLERANCE_DEFAULT = 20
+
+    attr_writer :cmn_tolerance
+
+    def cmn_tolerance
+      @cmn_tolerance || CMN_TOLERANCE_DEFAULT
+    end
+
+    def decode_raw(audio_file, max_samples = 2048)
+      repeat_if_cmn_sum_exceeds { super }
+    end
+
+    private
+
+    def repeat_if_cmn_sum_exceeds(tolerance = cmn_tolerance)
+      before = cmn_values
+      result = yield
+      after = cmn_values
+
+      cmn_sum(before, after) > tolerance ? yield : result
+    end
+
+    def cmn_sum(before, after)
+      before.zip(after).inject(0) { |sum, a| sum + (a.last - a.first).abs }
+    end
+  end
+end

lib/pocketsphinx/decoder.rb

@@ -66,6 +66,7 @@ def decode(audio_path_or_file, max_samples = 2048)
     # @param [IO] audio_file The raw audio stream to decode as a single utterance
     # @param [Fixnum] max_samples The maximum samples to process from the stream on each iteration
     def decode_raw(audio_file, max_samples = 2048)
+      audio_file.rewind
       start_utterance
 
       FFI::MemoryPointer.new(:int16, max_samples) do |buffer|
@@ -147,6 +148,10 @@ def words
       words
     end
 
+    def cmn_values
+      ps_api.get_cmn_values(ps_decoder)
+    end
+
     # Adds new search using JSGF model.
     #
     # Convenience method to parse JSGF model from string and create a search.