Add a simple, safe gain PostProcessor.

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

Index: chromecast/media/cma/backend/alsa/volume_control.cc
diff --git a/chromecast/media/cma/backend/alsa/volume_control.cc b/chromecast/media/cma/backend/alsa/volume_control.cc
index 7ab987577020a86cc5875d5d60b2069a08bb468a..41468474667704f221984952d43f43cd1f1b8c5c 100644
--- a/chromecast/media/cma/backend/alsa/volume_control.cc
+++ b/chromecast/media/cma/backend/alsa/volume_control.cc
@@ -30,8 +30,10 @@
 #include "chromecast/base/serializers.h"
 #include "chromecast/media/cma/backend/alsa/alsa_features.h"
 #include "chromecast/media/cma/backend/alsa/alsa_volume_control.h"
+#include "chromecast/media/cma/backend/alsa/cast_audio_json.h"
 #include "chromecast/media/cma/backend/alsa/post_processing_pipeline_parser.h"
 #include "chromecast/media/cma/backend/alsa/stream_mixer_alsa.h"
+#include "chromecast/media/cma/backend/alsa/volume_map.h"
 
 namespace chromecast {
 namespace media {
@@ -47,22 +49,8 @@ constexpr float kMinDbFS = -120.0f;
 constexpr char kKeyMediaDbFS[] = "dbfs.media";
 constexpr char kKeyAlarmDbFS[] = "dbfs.alarm";
 constexpr char kKeyCommunicationDbFS[] = "dbfs.communication";
-constexpr char kKeyVolumeMap[] = "volume_map";
-constexpr char kKeyLevel[] = "level";
-constexpr char kKeyDb[] = "db";
 constexpr char kKeyDefaultVolume[] = "default_volume";
 
-struct LevelToDb {
-  float level;
-  float db;
-};
-
-const LevelToDb kDefaultVolumeMap[] = {{0.0f, kMinDbFS},
-                                       {0.01f, -58.0f},
-                                       {0.090909f, -48.0f},
-                                       {0.818182f, -8.0f},
-                                       {1.0f, 0.0f}};
-
 float DbFsToScale(float db) {
   if (db <= kMinDbFS) {
     return 0.0f;
@@ -81,103 +69,6 @@ std::string ContentTypeToDbFSKey(AudioContentType type) {
   }
 }
 
-class VolumeMap {
- public:
-  VolumeMap() {
-    auto cast_audio_config = DeserializeJsonFromFile(
-        base::FilePath(PostProcessingPipelineParser::GetFilePath()));
-    const base::DictionaryValue* cast_audio_dict;
-    if (!cast_audio_config ||
-        !cast_audio_config->GetAsDictionary(&cast_audio_dict)) {
-      LOG(WARNING) << "No cast audio config found; using default volume map.";
-      volume_map_.insert(volume_map_.end(), kDefaultVolumeMap,
-                         kDefaultVolumeMap + arraysize(kDefaultVolumeMap));
-      return;
-    }
-
-    const base::ListValue* volume_map_list;
-    if (!cast_audio_dict->GetList(kKeyVolumeMap, &volume_map_list)) {
-      LOG(WARNING) << "No volume map found; using default volume map.";
-      volume_map_.insert(volume_map_.end(), kDefaultVolumeMap,
-                         kDefaultVolumeMap + arraysize(kDefaultVolumeMap));
-      return;
-    }
-
-    double prev_level = -1.0;
-    for (size_t i = 0; i < volume_map_list->GetSize(); ++i) {
-      const base::DictionaryValue* volume_map_entry;
-      CHECK(volume_map_list->GetDictionary(i, &volume_map_entry));
-
-      double level;
-      CHECK(volume_map_entry->GetDouble(kKeyLevel, &level));
-      CHECK_GE(level, 0.0);
-      CHECK_LE(level, 1.0);
-      CHECK_GT(level, prev_level);
-      prev_level = level;
-
-      double db;
-      CHECK(volume_map_entry->GetDouble(kKeyDb, &db));
-      CHECK_LE(db, 0.0);
-      if (level == 1.0) {
-        CHECK_EQ(db, 0.0);
-      }
-
-      volume_map_.push_back({level, db});
-    }
-
-    if (volume_map_.empty()) {
-      LOG(FATAL) << "No entries in volume map.";
-      return;
-    }
-
-    if (volume_map_[0].level > 0.0) {
-      volume_map_.insert(volume_map_.begin(), {0.0, kMinDbFS});
-    }
-
-    if (volume_map_.rbegin()->level < 1.0) {
-      volume_map_.push_back({1.0, 0.0});
-    }
-  }
-
-  float VolumeToDbFS(float volume) {
-    if (volume <= volume_map_[0].level) {
-      return volume_map_[0].db;
-    }
-    for (size_t i = 1; i < volume_map_.size(); ++i) {
-      if (volume < volume_map_[i].level) {
-        const float x_range = volume_map_[i].level - volume_map_[i - 1].level;
-        const float y_range = volume_map_[i].db - volume_map_[i - 1].db;
-        const float x_pos = volume - volume_map_[i - 1].level;
-
-        return volume_map_[i - 1].db + x_pos * y_range / x_range;
-      }
-    }
-    return volume_map_[volume_map_.size() - 1].db;
-  }
-
-  // static
-  float DbFSToVolume(float db) {
-    if (db <= volume_map_[0].db) {
-      return volume_map_[0].level;
-    }
-    for (size_t i = 1; i < volume_map_.size(); ++i) {
-      if (db < volume_map_[i].db) {
-        const float x_range = volume_map_[i].db - volume_map_[i - 1].db;
-        const float y_range = volume_map_[i].level - volume_map_[i - 1].level;
-        const float x_pos = db - volume_map_[i - 1].db;
-
-        return volume_map_[i - 1].level + x_pos * y_range / x_range;
-      }
-    }
-    return volume_map_[volume_map_.size() - 1].level;
-  }
-
- private:
-  std::vector<LevelToDb> volume_map_;
-
-  DISALLOW_COPY_AND_ASSIGN(VolumeMap);
-};
-
 base::LazyInstance<VolumeMap>::Leaky g_volume_map = LAZY_INSTANCE_INITIALIZER;
 
 class VolumeControlInternal : public AlsaVolumeControl::Delegate {
@@ -209,8 +100,8 @@ class VolumeControlInternal : public AlsaVolumeControl::Delegate {
       }
     } else {
       // If saved_volumes does not exist, use per device default if it exists.
-      auto cast_audio_config = DeserializeJsonFromFile(
-          base::FilePath(PostProcessingPipelineParser::GetFilePath()));
+      auto cast_audio_config =
+          DeserializeJsonFromFile(base::FilePath(kCastAudioJsonFilePath));
       const base::DictionaryValue* cast_audio_dict;
       if (cast_audio_config &&
           cast_audio_config->GetAsDictionary(&cast_audio_dict)) {