Optionally disable APM limiter in AudioMixer.

webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc

 /*
  *  Copyright (c) 2016 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.
  */
 
@@ skipping 438 matching lines @@
   std::fill(frames[0].data_, frames[0].data_ + kDefaultSampleRateHz / 100,
             std::numeric_limits<int16_t>::max());
   std::vector<bool> expected_status(kAudioSources, true);
   expected_status[0] = false;
 
   MixAndCompare(frames, frame_info, expected_status);
 }
 
 TEST(AudioMixer, MixingRateShouldBeDecidedByRateCalculator) {
   constexpr int kOutputRate = 22000;
-  const auto mixer = AudioMixerImpl::CreateWithOutputRateCalculator(
+  const auto mixer = AudioMixerImpl::CreateWithOutputRateCalculatorAndLimiter(
       std::unique_ptr<OutputRateCalculator>(
-          new CustomRateCalculator(kOutputRate)));
+          new CustomRateCalculator(kOutputRate)),
+      true);
   MockMixerAudioSource audio_source;
   mixer->AddSource(&audio_source);
   ResetFrame(audio_source.fake_frame());
 
   EXPECT_CALL(audio_source, GetAudioFrameWithInfo(kOutputRate, _))
       .Times(Exactly(1));
 
   mixer->Mix(1, &frame_for_mixing);
 }
 
 TEST(AudioMixer, ZeroSourceRateShouldBeDecidedByRateCalculator) {

[ivoc, 2017/02/15 16:58:46]

Can you add a unit test that doesn't use a limiter? You can either test that it
actually doesn't limit, or alternatively just test that it works and doesn't
crash.

[aleloi, 2017/02/16 14:01:35]

Testing that it doesn't limit is pretty hard, I think. The test would have to
detect clipping in the mixed signal.

   constexpr int kOutputRate = 8000;
-  const auto mixer = AudioMixerImpl::CreateWithOutputRateCalculator(
+  const auto mixer = AudioMixerImpl::CreateWithOutputRateCalculatorAndLimiter(
       std::unique_ptr<OutputRateCalculator>(
-          new CustomRateCalculator(kOutputRate)));
+          new CustomRateCalculator(kOutputRate)),
+      true);
 
   mixer->Mix(1, &frame_for_mixing);
 
   EXPECT_EQ(kOutputRate, frame_for_mixing.sample_rate_hz_);
 }
 }  // namespace webrtc