[Chromecast] Correct libcast_governor behavior.

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

Index: chromecast/media/cma/backend/alsa/slew_volume.cc
diff --git a/chromecast/media/cma/backend/alsa/slew_volume.cc b/chromecast/media/cma/backend/alsa/slew_volume.cc
index 38ce1a72a186e43f64ebc3b301fb627e2013a2e2..eabba92ce3bc5ae2885e1c7785f3fc252dcbc5b5 100644
--- a/chromecast/media/cma/backend/alsa/slew_volume.cc
+++ b/chromecast/media/cma/backend/alsa/slew_volume.cc
@@ -14,7 +14,8 @@ namespace {
 // The time to slew from current volume to target volume.
 const int kMaxSlewTimeMs = 100;
 const int kDefaultSampleRate = 44100;
-}
+
+}  // namespace
 
 namespace chromecast {
 namespace media {
@@ -24,11 +25,11 @@ SlewVolume::SlewVolume() : SlewVolume(kMaxSlewTimeMs) {}
 SlewVolume::SlewVolume(int max_slew_time_ms)
     : sample_rate_(kDefaultSampleRate),
       max_slew_time_ms_(max_slew_time_ms),
-      max_slew_per_sample_(1000.0 / (max_slew_time_ms_ * sample_rate_)) {
-  LOG(INFO) << "Creating a slew volume: " << max_slew_time_ms;
-}
+      max_slew_per_sample_(1000.0 / (max_slew_time_ms_ * sample_rate_)) {}
 
 void SlewVolume::SetSampleRate(int sample_rate) {
+  DCHECK_GT(sample_rate, 0);
+
   sample_rate_ = sample_rate;
   SetVolume(volume_scale_);
 }
@@ -49,6 +50,8 @@ void SlewVolume::SetVolume(double volume_scale) {
 }
 
 void SlewVolume::SetMaxSlewTimeMs(int max_slew_time_ms) {
+  DCHECK_GE(max_slew_time_ms, 0);
+
   max_slew_time_ms_ = max_slew_time_ms;
 }
 
@@ -86,7 +89,9 @@ void SlewVolume::ProcessFMAC(bool repeat_transition,
     }
     ::media::vector_math::FMAC(src, current_volume_, frames, dest);
     return;
-  } else if (current_volume_ < volume_scale_) {
+  }
+
+  if (current_volume_ < volume_scale_) {
     do {
       (*dest) += (*src) * current_volume_;
       ++src;
@@ -105,68 +110,90 @@ void SlewVolume::ProcessFMAC(bool repeat_transition,
     } while (current_volume_ > volume_scale_ && frames);
     current_volume_ = std::max(current_volume_, volume_scale_);
   }
-
-  if (frames) {
-    for (int f = 0; f < frames; ++f) {
-      dest[f] += src[f] * current_volume_;
-    }
+  while (frames && (reinterpret_cast<uintptr_t>(src) &
+                    (::media::vector_math::kRequiredAlignment - 1))) {
+    (*dest) += (*src) * current_volume_;
+    ++src;
+    ++dest;
+    --frames;
+  }
+  if (!frames) {
+    return;
   }
+  ::media::vector_math::FMAC(src, current_volume_, frames, dest);
 }
 
-// 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);
+void SlewVolume::ProcessFMUL(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 true;
+    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_ == 1.0) {
-      return true;
+    if (current_volume_ == 0.0) {
+      memset(dest, 0, frames * sizeof(*dest));
+      return;
     }
-    for (int i = 0; i < 2 * frames; ++i) {
-      data[i] *= current_volume_;
+    if (current_volume_ == 1.0) {
+      if (src == dest) {
+        return;
+      }
+      std::memcpy(dest, src, frames * sizeof(*dest));
+      return;
     }
-    return true;
-  } else if (current_volume_ < volume_scale_) {
+    ::media::vector_math::FMUL(src, current_volume_, frames, dest);
+    return;
+  }
+
+  LOG(INFO) << "max slew per sample " << max_slew_per_sample_;
+  if (current_volume_ < volume_scale_) {
     do {
-      (*data) *= current_volume_;
-      ++data;
-      (*data) *= current_volume_;
-      ++data;
+      (*dest) = (*src) * current_volume_;
+      ++src;
+      ++dest;
       --frames;
       current_volume_ += max_slew_per_sample_;
     } while (current_volume_ < volume_scale_ && frames);
     current_volume_ = std::min(current_volume_, volume_scale_);
-  } else {
+  } else {  // current_volume_ > volume_scale_
     do {
-      (*data) *= current_volume_;
-      ++data;
-      (*data) *= current_volume_;
-      ++data;
+      (*dest) = (*src) * current_volume_;
+      ++src;
+      ++dest;
       --frames;
       current_volume_ -= max_slew_per_sample_;
     } while (current_volume_ > volume_scale_ && frames);
     current_volume_ = std::max(current_volume_, volume_scale_);
   }
 
-  if (current_volume_ == 1.0) {
-    return true;
-  }
-
-  if (current_volume_ == 0.0) {
-    std::fill_n(data, frames * 2, 0);
-    return true;
+  while (frames && (reinterpret_cast<uintptr_t>(src) &
+                    (::media::vector_math::kRequiredAlignment - 1))) {
+    (*dest) = (*src) * current_volume_;
+    ++src;
+    ++dest;
+    --frames;
   }
-
-  for (int i = 0; i < 2 * frames; ++i) {
-    data[i] *= current_volume_;
+  if (!frames) {
+    return;
   }
-  return true;
+  ::media::vector_math::FMUL(src, current_volume_, frames, dest);
 }
 
 }  // namespace media