[Chromecast] Process streams with different post-processing.

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

Index: chromecast/media/cma/backend/alsa/filter_group.h
diff --git a/chromecast/media/cma/backend/alsa/filter_group.h b/chromecast/media/cma/backend/alsa/filter_group.h
new file mode 100644
index 0000000000000000000000000000000000000000..dddbf83e418b0db4468b87a7d6aebf45f24bbca6
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+++ b/chromecast/media/cma/backend/alsa/filter_group.h
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+// 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.
+
+#ifndef CHROMECAST_MEDIA_CMA_BACKEND_ALSA_FILTER_GROUP_H_
+#define CHROMECAST_MEDIA_CMA_BACKEND_ALSA_FILTER_GROUP_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+#include <unordered_set>
+#include <vector>
+
+#include "base/macros.h"
+#include "chromecast/media/cma/backend/alsa/audio_filter_factory.h"
+#include "chromecast/media/cma/backend/alsa/stream_mixer_alsa.h"
+
+namespace chromecast {
+namespace media {
+class AudioBus;
+
+// FilterGroup contains state for an AudioFilter.
+// It takes multiple StreamMixerAlsa::InputQueues,
+// mixes them, and processes them.
+
+// ActiveInputs are added with AddActiveInput(), then cleared when
+// MixAndFilter() is called (they must be added each time data is queried).
+class FilterGroup {
+ public:
+  // |input_types| is a set of strings that is used as a filter to determine
+  // if an input belongs to this group (InputQueue->name() must exactly match an
+  // entry in |input_types| to be processed by this group.
+  // |filter_type| is passed to AudioFilterFactory to create an AudioFilter.
+  FilterGroup(const std::unordered_set<std::string>& input_types,
+              AudioFilterFactory::FilterType filter_type);
+  ~FilterGroup();
+
+  // Sets the sample rate and format in the AudioFilter.
+  void Initialize(int output_samples_per_second, ::media::SampleFormat format);
+
+  // Returns |true| if this FilterGroup is appropriate to process |input|.
+  bool CanProcessInput(StreamMixerAlsa::InputQueue* input);
+
+  // Adds |input| to |active_inputs_|.
+  void AddActiveInput(StreamMixerAlsa::InputQueue* input);
+
+  // Retrieves a pointer to the output buffer |interleaved_|.
+  std::vector<uint8_t>* GetInterleaved();
+
+  // Mixes all active inputs and passes them through the audio filter.
+  bool MixAndFilter(int chunk_size);
+
+  // Overwrites |interleaved_| with 0's, ensuring at least
+  // |chunk_size| bytes.
+  void ClearInterleaved(int chunk_size);
+
+  // Clear all |active_inputs_|. This should be called before AddActiveInputs
+  // on each mixing iteration.
+  void ClearActiveInputs();
+
+ private:
+  void ResizeBuffersIfNecessary(int chunk_size);
+  int BytesPerOutputFormatSample();
+
+  const std::unordered_set<std::string> input_types_;
+  std::vector<StreamMixerAlsa::InputQueue*> active_inputs_;
+
+  int output_samples_per_second_;
+  ::media::SampleFormat sample_format_;
+
+  // Buffers that hold audio data while it is mixed.
+  // These are kept as members of this class to minimize copies and
+  // allocations.
+  std::unique_ptr<::media::AudioBus> temp_;
+  std::unique_ptr<::media::AudioBus> mixed_;
+  std::vector<uint8_t> interleaved_;
+
+  std::unique_ptr<AudioFilterInterface> audio_filter_;
+  int silence_frames_filtered_;
+
+  DISALLOW_COPY_AND_ASSIGN(FilterGroup);
+};
+
+}  // namespace media
+}  // namespace chromecast
+#endif  // CHROMECAST_MEDIA_CMA_BACKEND_ALSA_FILTER_GROUP_H_