[chromecast] Slew stream volume changes in StreamMixerAlsa.

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

Index: chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.cc
diff --git a/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.cc b/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.cc
index 1e7cc895cc43fcefb9ff7106d9cf1178d2614106..fd0172c06384b4449eac6aa7b7efffc22e5ec44d 100644
--- a/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.cc
+++ b/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.cc
@@ -56,6 +56,9 @@ const int kPausedReadSamples = 512;
 const int kDefaultReadSize = ::media::SincResampler::kDefaultRequestSize;
 const int64_t kNoTimestamp = std::numeric_limits<int64_t>::min();
 
+const int kMaxSlewTimeUpMs = 100;
+const int kMaxSlewTimeDownMs = 100;
+
 }  // namespace
 
 StreamMixerAlsaInputImpl::StreamMixerAlsaInputImpl(
@@ -71,6 +74,7 @@ StreamMixerAlsaInputImpl::StreamMixerAlsaInputImpl(
       caller_task_runner_(base::ThreadTaskRunnerHandle::Get()),
       resample_ratio_(1.0),
       state_(kStateUninitialized),
+      slew_volume_(kMaxSlewTimeUpMs, kMaxSlewTimeDownMs),
       volume_multiplier_(1.0f),
       queued_frames_(0),
       queued_frames_including_resampler_(0),
@@ -85,6 +89,7 @@ StreamMixerAlsaInputImpl::StreamMixerAlsaInputImpl(
   DCHECK(delegate_);
   DCHECK(mixer_);
   weak_this_ = weak_factory_.GetWeakPtr();
+  slew_volume_.SetSampleRate(input_samples_per_second_);

[kmackay, 2016/09/14 20:48:15]

this doesn't seem right. It is initialized correctly in Initialize()

[jyw, 2016/09/15 01:12:15]

Done.

 }
 
 StreamMixerAlsaInputImpl::~StreamMixerAlsaInputImpl() {
@@ -120,6 +125,7 @@ void StreamMixerAlsaInputImpl::Initialize(
         kNumOutputChannels, resample_ratio_, kDefaultReadSize,
         base::Bind(&StreamMixerAlsaInputImpl::ReadCB, base::Unretained(this))));
     resampler_->PrimeWithSilence();
+    slew_volume_.SetSampleRate(mixer_->output_samples_per_second());
   }
   mixer_rendering_delay_ = mixer_rendering_delay;
   fade_out_frames_total_ = NormalFadeFrames();
@@ -504,6 +510,13 @@ void StreamMixerAlsaInputImpl::SetVolumeMultiplier(float multiplier) {
   if (multiplier < 0.0f)
     multiplier = 0.0f;
   volume_multiplier_ = multiplier;
+  slew_volume_.SetVolume(volume_multiplier_);
+}
+
+bool StreamMixerAlsaInputImpl::VolumeScaleAccumulate(const float* src,
+                                                     int frames,
+                                                     float* dest) {
+  return slew_volume_.ProcessFMAC(src, frames, dest);
 }
 
 }  // namespace media