diff --git a/app/services/waveform_service.rb b/app/services/waveform_service.rb
index fc0ce6f93b..4100443a87 100644
--- a/app/services/waveform_service.rb
+++ b/app/services/waveform_service.rb
@@ -75,33 +75,37 @@ def empty_waveform(master_file)
 
   def get_normalized_peaks(uri)
     wave_io = get_wave_io(uri.to_s)
-    peaks = gather_peaks(wave_io)
+    peaks = []
+    reader = nil
+    abs_max = 0
+    begin
+      reader = WaveFile::Reader.new(wave_io)
+      reader.each_buffer(@samples_per_pixel) do |buffer|
+        sample_min, sample_max = buffer.samples.minmax
+        peaks << [sample_min, sample_max]
+        abs_max = [abs_max, sample_min.abs, sample_max.abs].max
+      end
+    rescue WaveFile::InvalidFormatError
+      # ffmpeg generated no wavefile data
+    end
     return [] if peaks.blank?
-    max_peak = peaks.flatten.map(&:abs).max
     res = 2**(@bit_res - 1)
-    factor = max_peak.zero? ? 1 : res / max_peak.to_f
-    peaks.map { |peak| peak.collect { |num| (num * factor).to_i } }
+    factor = abs_max.zero? ? 1 : res / abs_max.to_f
+    peaks.each do |peak|
+      peak[0] = (peak[0] * factor).to_i
+      peak[1] = (peak[1] * factor).to_i
+    end
+    peaks
   ensure
-    Process.wait(wave_io.pid) if wave_io&.pid
+    reader&.close
+    wave_io&.close
   end
 
   def get_wave_io(uri)
     headers = "-headers $'Referer: #{Rails.application.routes.url_helpers.root_url}\r\n'" if uri.starts_with? "http"
     normalized_uri = uri.starts_with?("file") ? Addressable::URI.unencode(uri) : uri
     timeout = 60000000 # Must be in microseconds. Current value = 1 minute.
-    cmd = "#{Settings.ffmpeg.path} #{headers} -rw_timeout #{timeout} -i '#{normalized_uri}' -f wav -ar 44100 - 2> /dev/null"
+    cmd = "#{Settings.ffmpeg.path} #{headers} -rw_timeout #{timeout} -i '#{normalized_uri}' -f wav -ar 44100 -ac 1 - 2> /dev/null"
     IO.popen(cmd)
   end
-
-  def gather_peaks(wav_file)
-    peaks = []
-    begin
-      WaveFile::Reader.new(wav_file).each_buffer(@samples_per_pixel) do |buffer|
-        peaks << [buffer.samples.flatten.min, buffer.samples.flatten.max]
-      end
-    rescue WaveFile::InvalidFormatError
-      # ffmpeg generated no wavefile data
-    end
-    peaks
-  end
 end
diff --git a/spec/fixtures/meow.json b/spec/fixtures/meow.json
index 468602d53d..9506de99d7 100644
--- a/spec/fixtures/meow.json
+++ b/spec/fixtures/meow.json
@@ -14,4 +14,4 @@
  * ---  END LICENSE_HEADER BLOCK  ---
 */
 
-{"sample_rate":44100,"bits":8,"samples_per_pixel":1024,"length":54,"data":[-75,72,-113,106,-109,104,-117,112,-128,127,-122,114,-105,86,-81,76,-81,76,-93,88,-108,105,-112,108,-99,96,-91,91,-77,77,-63,70,-49,55,-39,45,-36,40,-36,40,-30,31,-30,29,-28,25,-24,16,-17,16,-10,8,-7,7,-4,4,-3,3,-2,2,-2,2,-2,2,-1,1,-2,2,-2,2,-2,2,-1,1,-1,1,-1,1,-1,1,-1,1,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]}
+{"sample_rate":44100,"bits":8,"samples_per_pixel":1024,"length":54,"data":[-75, 72, -113, 106, -109, 104, -117, 112, -127, 128, -122, 114, -105, 87, -81, 75, -80, 76, -94, 88, -108, 105, -111, 108, -98, 96, -90, 87, -76, 76, -63, 70, -47, 53, -37, 44, -34, 38, -34, 39, -29, 31, -29, 27, -27, 25, -24, 16, -15, 13, -9, 8, -6, 5, -3, 4, -2, 3, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]}
diff --git a/spec/fixtures/meow.mono.wav b/spec/fixtures/meow.mono.wav
new file mode 100644
index 0000000000..3384815280
Binary files /dev/null and b/spec/fixtures/meow.mono.wav differ
diff --git a/spec/services/waveform_service_spec.rb b/spec/services/waveform_service_spec.rb
index 3d230993fe..c145cfb4a8 100644
--- a/spec/services/waveform_service_spec.rb
+++ b/spec/services/waveform_service_spec.rb
@@ -18,7 +18,7 @@
   let(:service) { WaveformService.new }
 
   describe "get_waveform_json" do
-    let(:wav_path) { File.join(Rails.root, "spec/fixtures/meow.wav") }
+    let(:wav_path) { File.join(Rails.root, "spec/fixtures/meow.mono.wav") }
 
     it "should return waveform json from file" do
       allow(service).to receive(:get_wave_io).and_return(open(wav_path))
@@ -67,7 +67,7 @@
 
     context "http file" do
       let(:uri) { "http://domain/to/video.mp4" }
-      let(:cmd) {"#{Settings.ffmpeg.path} -headers $'Referer: http://test.host/\r\n' -rw_timeout 60000000 -i '#{uri}' -f wav -ar 44100 - 2> /dev/null"}
+      let(:cmd) {"#{Settings.ffmpeg.path} -headers $'Referer: http://test.host/\r\n' -rw_timeout 60000000 -i '#{uri}' -f wav -ar 44100 -ac 1 - 2> /dev/null"}
 
       it "should call ffmpeg with headers" do
         service.send(:get_wave_io, uri)
@@ -77,7 +77,7 @@
 
     context "local file" do
       let(:uri) { "file:///path/to/video.mp4" }
-      let(:cmd) {"#{Settings.ffmpeg.path}  -rw_timeout 60000000 -i '#{uri}' -f wav -ar 44100 - 2> /dev/null"}
+      let(:cmd) {"#{Settings.ffmpeg.path}  -rw_timeout 60000000 -i '#{uri}' -f wav -ar 44100 -ac 1 - 2> /dev/null"}
 
       it "should call ffmpeg without headers" do
         service.send(:get_wave_io, uri)
@@ -87,7 +87,7 @@
       context 'with spaces in filename' do
         let(:uri) { 'file:///path/to/special%20video%20file.mp4' }
         let(:unencoded_uri) { 'file:///path/to/special video file.mp4' }
-        let(:cmd) {"#{Settings.ffmpeg.path}  -rw_timeout 60000000 -i '#{unencoded_uri}' -f wav -ar 44100 - 2> /dev/null"}
+        let(:cmd) {"#{Settings.ffmpeg.path}  -rw_timeout 60000000 -i '#{unencoded_uri}' -f wav -ar 44100 -ac 1 - 2> /dev/null"}
 
         it "should call ffmpeg without url encoding" do
           service.send(:get_wave_io, uri)