[Chromecast] Process streams with different post-processing.

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

Index: chromecast/media/cma/backend/alsa/filter_group.cc
diff --git a/chromecast/media/cma/backend/alsa/filter_group.cc b/chromecast/media/cma/backend/alsa/filter_group.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5d1d89d634986d891421185d12d1c3135be559c4
--- /dev/null
+++ b/chromecast/media/cma/backend/alsa/filter_group.cc
@@ -0,0 +1,105 @@
+// Copyright 2017 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/filter_group.h"
+#include "media/base/audio_bus.h"
+
+namespace chromecast {
+namespace media {
+
+namespace {
+
+// How many seconds of silence should be passed to the filters to flush them.
+const float kSilenceSecondsToFilter = 1.0f;
+const int kNumOutputChannels = 2;
+
+}  // namespace
+
+FilterGroup::FilterGroup(const std::unordered_set<std::string>& input_types,
+                         AudioFilterFactory::FilterType filter_type)
+    : input_types_(input_types),
+      audio_filter_(AudioFilterFactory::MakeAudioFilter(filter_type)) {}
+
+void FilterGroup::Initialize(int output_samples_per_second,
+                             ::media::SampleFormat format,
+                             ssize_t bytes_per_output_format_sample) {
+  output_samples_per_second_ = output_samples_per_second;
+  sample_format_ = format;
+  bytes_per_output_format_sample_ = bytes_per_output_format_sample;
+  audio_filter_->SetSampleRateAndFormat(output_samples_per_second_,
+                                        sample_format_);
+}
+
+bool FilterGroup::TryAddActiveInput(StreamMixerAlsa::InputQueue* input) {
+  if (input_types_.find(input->name()) == input_types_.end()) {
+    return false;
+  }
+  active_inputs_.push_back(input);
+  return true;
+}
+
+std::vector<uint8_t>* FilterGroup::GetInterleaved() {
+  return &interleaved_;
+}
+
+bool FilterGroup::MixAndFilter(int chunk_size) {
+  if (active_inputs_.empty()) {
+    int silence_frames_to_filter =
+        output_samples_per_second_ * kSilenceSecondsToFilter;
+    if (silence_frames_filtered_ < silence_frames_to_filter) {
+      silence_frames_filtered_ += chunk_size;
+    } else {
+      return false;  // Output will be silence, no need to mix.
+    }
+  } else {
+    silence_frames_filtered_ = 0;
+  }
+
+  ResizeBuffersIfNecessary(chunk_size);
+
+  mixed_->ZeroFramesPartial(0, chunk_size);
+  for (StreamMixerAlsa::InputQueue* input : active_inputs_) {
+    input->GetResampledData(temp_.get(), chunk_size);
+    for (int c = 0; c < kNumOutputChannels; ++c) {
+      input->VolumeScaleAccumulate(c, temp_->channel(c), chunk_size,
+                                   mixed_->channel(c));
+    }
+  }
+
+  active_inputs_.clear();
+  mixed_->ToInterleaved(chunk_size, bytes_per_output_format_sample_,
+                        interleaved_.data());
+  if (audio_filter_) {
+    audio_filter_->ProcessInterleaved(interleaved_.data(), chunk_size);
+  }
+
+  return true;
+}
+
+void FilterGroup::ClearInterleaved(int chunk_size) {
+  ResizeBuffersIfNecessary(chunk_size);
+  memset(interleaved_.data(), 0, static_cast<size_t>(chunk_size) *
+                                     kNumOutputChannels *
+                                     bytes_per_output_format_sample_);
+}
+
+void FilterGroup::ResizeBuffersIfNecessary(int chunk_size) {
+  if (!mixed_ || mixed_->frames() < chunk_size) {
+    mixed_ = ::media::AudioBus::Create(kNumOutputChannels, chunk_size);
+  }
+  if (!temp_ || temp_->frames() < chunk_size) {
+    temp_ = ::media::AudioBus::Create(kNumOutputChannels, chunk_size);
+  }
+
+  size_t interleaved_size = static_cast<size_t>(chunk_size) *
+                            kNumOutputChannels *
+                            bytes_per_output_format_sample_;
+
+  if (interleaved_.size() < interleaved_size) {
+    interleaved_.resize(interleaved_size);
+  }
+}
+
+}  // namespace media
+}  // namespace chromecast