Implement runtime audio post-processing pipeline. See go/cast_audio.json

chromecast/media/cma/backend/alsa/post_processing_pipeline.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 "chromecast/media/cma/backend/alsa/post_processing_pipeline.h"
+
+#include <dlfcn.h>
+
+#include <string>
+
+#include "base/files/file_path.h"
+#include "base/memory/ptr_util.h"
+#include "base/scoped_native_library.h"
+#include "base/values.h"
+#include "chromecast/base/serializers.h"
+#include "chromecast/public/media/audio_post_processor_shlib.h"
+
+namespace chromecast {
+namespace media {
+
+namespace {
+
+const int kNoSampleRate = -1;
+const char kSoCreateFunction[] = "AudioPostProcessorShlib_Create";
+
+}  // namespace
+
+using CreatePostProcessor =
+    std::unique_ptr<AudioPostProcessor> (*)(const std::string&, int);
+
+PostProcessingPipeline::PostProcessingPipeline(
+    const base::ListValue* filter_description_list,
+    int channels)
+    : sample_rate_(kNoSampleRate) {
+  if (!filter_description_list) {
+    return;  // Warning logged.
+  }
+  for (size_t i = 0; i < filter_description_list->GetSize(); ++i) {
+    const base::DictionaryValue* processor_description_dict;
+    CHECK(
+        filter_description_list->GetDictionary(i, &processor_description_dict));
+    std::string library_path;
+    CHECK(processor_description_dict->GetString("processor", &library_path));
+    if (library_path == "null" || library_path == "none") {
+      continue;
+    }
+    const base::Value* processor_config_val;
+    CHECK(processor_description_dict->Get("config", &processor_config_val));
+    CHECK(processor_config_val->is_dict() || processor_config_val->is_string());
+    auto processor_config_string = SerializeToJson(*processor_config_val);
+
+    LOG(INFO) << "Creating an instance of " << library_path << "("
+              << *processor_config_string << ")";
+    if (libraries_.find(library_path) == libraries_.end()) {
+      libraries_[library_path] = base::MakeUnique<base::ScopedNativeLibrary>(
+          base::FilePath(library_path));
+    }
+    auto& library = libraries_[library_path];
+    CHECK(library->is_valid()) << "Could not open post processing library "
+                               << library_path << ": " << dlerror();
+    CreatePostProcessor create = reinterpret_cast<CreatePostProcessor>(
+        library->GetFunctionPointer(kSoCreateFunction));
+
+    char* error;
+    CHECK(!(error = dlerror())) << "Could not find " << kSoCreateFunction

[kmackay, 2017/03/24 04:47:57]

Seems a bit odd to call dlerror() here since we don't explicitly call any other
dl functions. You could just check (create)  instead (although you wouldn't get
the error message)

[bshaya, 2017/03/24 18:55:10]

Done.

+                                << "() in " << library_path << ": " << error;
+    processors_.push_back(create(*processor_config_string, channels));
+  }
+}
+
+PostProcessingPipeline::~PostProcessingPipeline() = default;
+
+int PostProcessingPipeline::ProcessFrames(uint8_t* data,
+                                          int num_frames,
+                                          float current_volume) {
+  DCHECK_NE(sample_rate_, kNoSampleRate);
+  int total_delay = 0;
+  for (auto& processor : processors_) {
+    total_delay += processor->ProcessFrames(data, num_frames, current_volume);
+  }
+  return total_delay;
+}
+
+bool PostProcessingPipeline::SetSampleRate(int sample_rate) {
+  sample_rate_ = sample_rate;
+  bool result = true;
+  for (auto& processor : processors_) {
+    result &= processor->SetSampleRate(sample_rate_);
+  }
+  return result;
+}
+
+int PostProcessingPipeline::GetRingingTimeInFrames() {
+  int memory_frames = 0;
+  for (auto& processor : processors_) {
+    memory_frames += processor->GetRingingTimeInFrames();
+  }
+  return memory_frames;
+}
+
+}  // namespace media
+}  // namespace chromecast