[Chromecast] Implement new volume control API

chromecast/media/cma/backend/alsa/slew_volume.cc

 // Copyright 2016 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 "chromecast/media/cma/backend/alsa/slew_volume.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "media/base/vector_math.h"
@@ skipping 20 matching lines @@
 }
 
 void SlewVolume::SetSampleRate(int sample_rate) {
   sample_rate_ = sample_rate;
   SetVolume(volume_scale_);
 }
 
 // Slew rate should be volume_to_slew / slew_time / sample_rate
 void SlewVolume::SetVolume(double volume_scale) {
   volume_scale_ = volume_scale;
+  if (interrupted_) {
+    current_volume_ = volume_scale_;
+  }
   if (volume_scale_ > current_volume_) {
     max_slew_up_ = (volume_scale_ - current_volume_) * 1000.0 /
                    (max_slew_time_up_ms_ * sample_rate_);
   } else {
     max_slew_down_ = (current_volume_ - volume_scale_) * 1000.0 /
                      (max_slew_time_down_ms_ * sample_rate_);
   }
 }
 
+void SlewVolume::Interrupted() {
+  interrupted_ = true;
+  current_volume_ = volume_scale_;
+}
+
 void SlewVolume::ProcessFMAC(bool repeat_transition,
                              const float* src,
                              int frames,
                              float* dest) {
   DCHECK(src);
   DCHECK(dest);
   // Ensure |src| and |dest| are 16-byte aligned.
   DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(src) &
                     (::media::vector_math::kRequiredAlignment - 1));
   DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(dest) &
                     (::media::vector_math::kRequiredAlignment - 1));
 
   if (!frames) {
     return;
   }
 
+  interrupted_ = false;
   if (repeat_transition) {
     current_volume_ = last_starting_volume_;
   } else {
     last_starting_volume_ = current_volume_;
   }
 
   if (current_volume_ == volume_scale_) {
     if (current_volume_ == 0.0) {
       return;
     }
@@ skipping 29 matching lines @@
 // Scaling samples naively like this takes 0.2% of the CPU's time @ 44100hz
 // on pineapple.
 // Assumes 2 channel audio.
 bool SlewVolume::ProcessInterleaved(int32_t* data, int frames) {
   DCHECK(data);
 
   if (!frames) {
     return true;
   }
 
+  interrupted_ = false;
   if (current_volume_ == volume_scale_) {
     if (current_volume_ == 1.0) {
       return true;
     }
     for (int i = 0; i < 2 * frames; ++i) {
       data[i] *= current_volume_;
     }
     return true;
   } else if (current_volume_ < volume_scale_) {
     do {
@@ skipping 27 matching lines @@
   }
 
   for (int i = 0; i < 2 * frames; ++i) {
     data[i] *= current_volume_;
   }
   return true;
 }
 
 }  // namespace media
 }  // namespace chromecast