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diff --git a/third_party/libwebrtc/modules/audio_processing/test/py_quality_assessment/quality_assessment/echo_path_simulation.py b/third_party/libwebrtc/modules/audio_processing/test/py_quality_assessment/quality_assessment/echo_path_simulation.py
new file mode 100644
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+++ b/third_party/libwebrtc/modules/audio_processing/test/py_quality_assessment/quality_assessment/echo_path_simulation.py
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+# Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+"""Echo path simulation module.
+"""
+
+import hashlib
+import os
+
+from . import signal_processing
+
+
+class EchoPathSimulator(object):
+    """Abstract class for the echo path simulators.
+
+  In general, an echo path simulator is a function of the render signal and
+  simulates the propagation of the latter into the microphone (e.g., due to
+  mechanical or electrical paths).
+  """
+
+    NAME = None
+    REGISTERED_CLASSES = {}
+
+    def __init__(self):
+        pass
+
+    def Simulate(self, output_path):
+        """Creates the echo signal and stores it in an audio file (abstract method).
+
+    Args:
+      output_path: Path in which any output can be saved.
+
+    Returns:
+      Path to the generated audio track file or None if no echo is present.
+    """
+        raise NotImplementedError()
+
+    @classmethod
+    def RegisterClass(cls, class_to_register):
+        """Registers an EchoPathSimulator implementation.
+
+    Decorator to automatically register the classes that extend
+    EchoPathSimulator.
+    Example usage:
+
+    @EchoPathSimulator.RegisterClass
+    class NoEchoPathSimulator(EchoPathSimulator):
+      pass
+    """
+        cls.REGISTERED_CLASSES[class_to_register.NAME] = class_to_register
+        return class_to_register
+
+
+@EchoPathSimulator.RegisterClass
+class NoEchoPathSimulator(EchoPathSimulator):
+    """Simulates absence of echo."""
+
+    NAME = 'noecho'
+
+    def __init__(self):
+        EchoPathSimulator.__init__(self)
+
+    def Simulate(self, output_path):
+        return None
+
+
+@EchoPathSimulator.RegisterClass
+class LinearEchoPathSimulator(EchoPathSimulator):
+    """Simulates linear echo path.
+
+  This class applies a given impulse response to the render input and then it
+  sums the signal to the capture input signal.
+  """
+
+    NAME = 'linear'
+
+    def __init__(self, render_input_filepath, impulse_response):
+        """
+    Args:
+      render_input_filepath: Render audio track file.
+      impulse_response: list or numpy vector of float values.
+    """
+        EchoPathSimulator.__init__(self)
+        self._render_input_filepath = render_input_filepath
+        self._impulse_response = impulse_response
+
+    def Simulate(self, output_path):
+        """Simulates linear echo path."""
+        # Form the file name with a hash of the impulse response.
+        impulse_response_hash = hashlib.sha256(
+            str(self._impulse_response).encode('utf-8', 'ignore')).hexdigest()
+        echo_filepath = os.path.join(
+            output_path, 'linear_echo_{}.wav'.format(impulse_response_hash))
+
+        # If the simulated echo audio track file does not exists, create it.
+        if not os.path.exists(echo_filepath):
+            render = signal_processing.SignalProcessingUtils.LoadWav(
+                self._render_input_filepath)
+            echo = signal_processing.SignalProcessingUtils.ApplyImpulseResponse(
+                render, self._impulse_response)
+            signal_processing.SignalProcessingUtils.SaveWav(
+                echo_filepath, echo)
+
+        return echo_filepath
+
+
+@EchoPathSimulator.RegisterClass
+class RecordedEchoPathSimulator(EchoPathSimulator):
+    """Uses recorded echo.
+
+  This class uses the clean capture input file name to build the file name of
+  the corresponding recording containing echo (a predefined suffix is used).
+  Such a file is expected to be already existing.
+  """
+
+    NAME = 'recorded'
+
+    _FILE_NAME_SUFFIX = '_echo'
+
+    def __init__(self, render_input_filepath):
+        EchoPathSimulator.__init__(self)
+        self._render_input_filepath = render_input_filepath
+
+    def Simulate(self, output_path):
+        """Uses recorded echo path."""
+        path, file_name_ext = os.path.split(self._render_input_filepath)
+        file_name, file_ext = os.path.splitext(file_name_ext)
+        echo_filepath = os.path.join(
+            path, '{}{}{}'.format(file_name, self._FILE_NAME_SUFFIX, file_ext))
+        assert os.path.exists(echo_filepath), (
+            'cannot find the echo audio track file {}'.format(echo_filepath))
+        return echo_filepath