[Chromecast] Encapsulate path to cast_audio.json

CastAudioJson encapsulates the path to tuning config and system config.

The commit also makes CastAudioJson as its own build target so that it
can be used by other components.

Bug: internal b/109845931
Test: Tested on Joplin
Change-Id: I6aef283b94f9ff48c9cadb15db6fbdb73756fbf1
Reviewed-on: https://chromium-review.googlesource.com/1095117
Commit-Queue: Chinyue Chen <chinyue@chromium.org>
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567585}

chromecast/media/cma/backend/BUILD.gn

@@ -156,14 +156,23 @@ cast_source_set("audio_codec_support") {
   ]
 }
 
+cast_source_set("cast_audio_json") {
+  sources = [
+    "cast_audio_json.cc",
+    "cast_audio_json.h",
+  ]
+
+  deps = [
+    "//base",
+  ]
+}
+
 cast_source_set("for_mixer_audio") {
   sources = [
     "audio_decoder_for_mixer.cc",
     "audio_decoder_for_mixer.h",
     "buffering_mixer_source.cc",
     "buffering_mixer_source.h",
-    "cast_audio_json.cc",
-    "cast_audio_json.h",
     "direct_mixer_source.cc",
     "direct_mixer_source.h",
     "filter_group.cc",
@@ -189,6 +198,7 @@ cast_source_set("for_mixer_audio") {
   deps = [
     ":audio_buildflags",
     ":audio_helpers",
+    ":cast_audio_json",
     ":public",
     "//base",
     "//chromecast/base",

chromecast/media/cma/backend/cast_audio_json.cc

@@ -4,6 +4,7 @@
 
 #include "chromecast/media/cma/backend/cast_audio_json.h"
 
+#include "base/files/file_util.h"
 #include "build/build_config.h"
 
 namespace chromecast {
@@ -14,6 +15,22 @@ const char kCastAudioJsonFilePath[] = "/system/data/cast_audio.json";
 #else
 const char kCastAudioJsonFilePath[] = "/etc/cast_audio.json";
 #endif
+const char kCastAudioJsonFileName[] = "cast_audio.json";
+
+// static
+base::FilePath CastAudioJson::GetFilePath() {
+  base::FilePath tuning_path = CastAudioJson::GetFilePathForTuning();
+  if (base::PathExists(tuning_path)) {
+    return tuning_path;
+  }
+
+  return base::FilePath(kCastAudioJsonFilePath);
+}
+
+// static
+base::FilePath CastAudioJson::GetFilePathForTuning() {
+  return base::GetHomeDir().Append(kCastAudioJsonFileName);
+}
 
 }  // namespace media
 }  // namespace chromecast

chromecast/media/cma/backend/cast_audio_json.h

@@ -5,10 +5,16 @@
 #ifndef CHROMECAST_MEDIA_CMA_BACKEND_CAST_AUDIO_JSON_H_
 #define CHROMECAST_MEDIA_CMA_BACKEND_CAST_AUDIO_JSON_H_
 
+#include "base/files/file_path.h"
+
 namespace chromecast {
 namespace media {
 
-extern const char kCastAudioJsonFilePath[];
+class CastAudioJson {
+ public:
+  static base::FilePath GetFilePath();
+  static base::FilePath GetFilePathForTuning();
+};
 
 }  // namespace media
 }  // namespace chromecast

chromecast/media/cma/backend/post_processing_pipeline_parser.cc

@@ -41,21 +41,19 @@ StreamPipelineDescriptor::StreamPipelineDescriptor(
 PostProcessingPipelineParser::PostProcessingPipelineParser(
     const std::string& json)
     : postprocessor_config_(nullptr) {
-  if (json.empty() &&
-      !base::PathExists(base::FilePath(kCastAudioJsonFilePath))) {
-    LOG(WARNING) << "Could not open post-processing config in "
-                 << kCastAudioJsonFilePath << ".";
+  base::FilePath path = CastAudioJson::GetFilePath();
+  if (json.empty() && !base::PathExists(path)) {
+    LOG(WARNING) << "Could not open post-processing config in " << path << ".";
     return;
   }
 
   if (json.empty()) {
-    config_dict_ = base::DictionaryValue::From(
-        DeserializeJsonFromFile(base::FilePath(kCastAudioJsonFilePath)));
+    config_dict_ = base::DictionaryValue::From(DeserializeJsonFromFile(path));
   } else {
     config_dict_ = base::DictionaryValue::From(DeserializeFromJson(json));
   }
 
-  CHECK(config_dict_) << "Invalid JSON in " << kCastAudioJsonFilePath;
+  CHECK(config_dict_) << "Invalid JSON in " << path;
   if (!config_dict_->GetDictionary(kPostProcessorsKey,
                                    &postprocessor_config_)) {
     LOG(WARNING) << "No post-processor config found.";
@@ -111,7 +109,7 @@ const base::ListValue* PostProcessingPipelineParser::GetPipelineByKey(
   if (!postprocessor_config_ ||
       !postprocessor_config_->GetDictionary(key, &stream_dict)) {
     LOG(WARNING) << "No post-processor description found for \"" << key
-                 << "\" in " << kCastAudioJsonFilePath
+                 << "\" in " << CastAudioJson::GetFilePath()
                  << ". Using passthrough.";
     return nullptr;
   }

chromecast/media/cma/backend/stream_mixer.cc

@@ -297,7 +297,7 @@ void StreamMixer::CreatePostProcessors(
           << "media/audio/audio_device_description.cc";
       CHECK(used_streams.insert(stream_type).second)
           << "Multiple instances of stream type '" << stream_type << "' in "
-          << kCastAudioJsonFilePath << ".";
+          << CastAudioJson::GetFilePath() << ".";
     }
     filter_groups_.push_back(CreateFilterGroup(
         FilterGroup::GroupType::kStream, kNumInputChannels,

chromecast/media/cma/backend/volume_control.cc

@@ -104,7 +104,7 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
     } else {
       // If saved_volumes does not exist, use per device default if it exists.
       auto cast_audio_config =
-          DeserializeJsonFromFile(base::FilePath(kCastAudioJsonFilePath));
+          DeserializeJsonFromFile(CastAudioJson::GetFilePath());
       const base::DictionaryValue* cast_audio_dict;
       if (cast_audio_config &&
           cast_audio_config->GetAsDictionary(&cast_audio_dict)) {

chromecast/media/cma/backend/volume_map.cc

@@ -24,7 +24,7 @@ constexpr float kMinDbFS = -120.0f;
 
 VolumeMap::VolumeMap() {
   auto cast_audio_config =
-      DeserializeJsonFromFile(base::FilePath(kCastAudioJsonFilePath));
+      DeserializeJsonFromFile(CastAudioJson::GetFilePath());
   const base::DictionaryValue* cast_audio_dict;
   if (!cast_audio_config ||
       !cast_audio_config->GetAsDictionary(&cast_audio_dict)) {