Add vector_math::FMUL. Replace audio_util::AdjustVolume.

media/base/audio_converter.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/base/audio_converter.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 160 matching lines @@
        it != transform_inputs_.end(); ++it) {
     InputCallback* input = *it;
 
     float volume = input->ProvideInput(
         mixer_input_audio_bus_.get(), buffer_delay);
 
     // Optimize the most common single input, full volume case.
     if (it == transform_inputs_.begin()) {
       if (volume == 1.0f) {
         mixer_input_audio_bus_->CopyTo(temp_dest);
-        continue;
+      } else if (volume > 0) {
+        for (int i = 0; i < mixer_input_audio_bus_->channels(); ++i) {
+          vector_math::FMUL(
+              mixer_input_audio_bus_->channel(i), volume,
+              mixer_input_audio_bus_->frames(), temp_dest->channel(i));
+        }
+      } else {
+        // Zero |temp_dest| otherwise, so we're mixing into a clean buffer.
+        temp_dest->Zero();
       }
 
-      // Zero |temp_dest| otherwise, so we're mixing into a clean buffer.
-      temp_dest->Zero();
+      continue;
     }
 
     // Volume adjust and mix each mixer input into |temp_dest| after rendering.
     if (volume > 0) {
       for (int i = 0; i < mixer_input_audio_bus_->channels(); ++i) {
         vector_math::FMAC(
             mixer_input_audio_bus_->channel(i), volume,
             mixer_input_audio_bus_->frames(), temp_dest->channel(i));
       }
     }
   }
 
   if (needs_downmix) {
     DCHECK_EQ(temp_dest->frames(), dest->frames());
     channel_mixer_->Transform(temp_dest, dest);
   }
 }
 
 void AudioConverter::ProvideInput(int resampler_frame_delay, AudioBus* dest) {
   resampler_frame_delay_ = resampler_frame_delay;
   if (audio_fifo_)
     audio_fifo_->Consume(dest, dest->frames());
   else
     SourceCallback(0, dest);
 }
 
 }  // namespace media