[Chromecast] Correct libcast_governor behavior.

chromecast/media/cma/backend/alsa/post_processors/governor_shlib.cc

-// 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 <memory>
-#include <string>
-
-#include "base/logging.h"
-#include "base/macros.h"
-#include "base/values.h"
-#include "chromecast/base/serializers.h"
-#include "chromecast/media/cma/backend/alsa/slew_volume.h"
-#include "chromecast/public/media/audio_post_processor_shlib.h"
-
-namespace chromecast {
-namespace media {
-
-namespace {
-const int kNoSampleRate = -1;
-
-// Configuration strings:
-const char kOnsetVolumeKey[] = "onset_volume";
-const char kClampMultiplierKey[] = "clamp_multiplier";
-
-}  // namespace
-
-// Provides a flat reduction in output volume if the input volume is above a
-// given threshold.
-// Used to protect speakers at high output levels
-// while providing dyanmic range at low output level.
-// The configuration string for this plugin is:
-//  {"onset_volume": |VOLUME_TO_CLAMP|, "clamp_multiplier": |CLAMP_MULTIPLIER|}
-// Input volumes > |VOLUME_TO_CLAMP| will be attenuated by |CLAMP_MULTIPLIER|.
-class Governor : public AudioPostProcessor {
- public:
-  Governor(const std::string& config, int channels);
-  ~Governor() override;
-
-  bool SetSampleRate(int sample_rate) override;
-  int ProcessFrames(const std::vector<float*>& data,
-                    int frames,
-                    float volume) override;
-  int GetRingingTimeInFrames() override;
-
- private:
-  float GetGovernorMultiplier();
-
-  int channels_;
-  int sample_rate_;
-  float volume_;
-  double onset_volume_;
-  double clamp_multiplier_;
-  SlewVolume governor_;
-  DISALLOW_COPY_AND_ASSIGN(Governor);
-};
-
-Governor::Governor(const std::string& config, int channels)
-    : channels_(channels), sample_rate_(kNoSampleRate), volume_(1.0) {
-  auto config_dict = base::DictionaryValue::From(DeserializeFromJson(config));
-  CHECK(config_dict) << "Governor config is not valid json: " << config;
-  CHECK(config_dict->GetDouble(kOnsetVolumeKey, &onset_volume_));
-  CHECK(config_dict->GetDouble(kClampMultiplierKey, &clamp_multiplier_));
-  DCHECK_EQ(channels_, 2);
-  governor_.SetVolume(1.0);
-  LOG(INFO) << "Created a governor: onset_volume = " << onset_volume_
-            << ", clamp_multiplier = " << clamp_multiplier_;
-}
-
-Governor::~Governor() = default;
-
-bool Governor::SetSampleRate(int sample_rate) {
-  sample_rate_ = sample_rate;
-  governor_.SetSampleRate(sample_rate);
-  return true;
-}
-
-int Governor::ProcessFrames(const std::vector<float*>& data,
-                            int frames,
-                            float volume) {
-  DCHECK_EQ(data.size(), static_cast<size_t>(channels_));
-
-  if (volume != volume_) {
-    volume_ = volume;
-    governor_.SetVolume(GetGovernorMultiplier());
-  }
-
-  for (int c = 0; c < channels_; ++c) {
-    DCHECK(data[c]);
-    governor_.ProcessFMAC(c != 0 /* repeat_transition */, data[c], frames,
-                          data[c]);
-  }
-
-  return 0;  // No delay in this pipeline.
-}
-
-int Governor::GetRingingTimeInFrames() {
-  return 0;
-}
-
-float Governor::GetGovernorMultiplier() {
-  if (volume_ >= onset_volume_) {
-    return clamp_multiplier_;
-  }
-  return 1.0;
-}
-
-}  // namespace media
-}  // namespace chromecast
-
-chromecast::media::AudioPostProcessor* AudioPostProcessorShlib_Create(
-    const std::string& config,
-    int channels) {
-  return static_cast<chromecast::media::AudioPostProcessor*>(
-      new chromecast::media::Governor(config, channels));
-}