Add an initial revision of an audio server.

services/media/audio/platform/generic/standard_output_base.h

Index: services/media/audio/platform/generic/standard_output_base.h
diff --git a/services/media/audio/platform/generic/standard_output_base.h b/services/media/audio/platform/generic/standard_output_base.h
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+// Copyright 2015 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 SERVICES_MEDIA_AUDIO_PLATFORM_GENERIC_STANDARD_OUTPUT_BASE_H_
+#define SERVICES_MEDIA_AUDIO_PLATFORM_GENERIC_STANDARD_OUTPUT_BASE_H_
+
+#include "base/callback.h"
+#include "mojo/services/media/common/cpp/linear_transform.h"
+#include "mojo/services/media/common/cpp/local_time.h"
+#include "mojo/services/media/common/interfaces/media_common.mojom.h"
+#include "mojo/services/media/common/interfaces/media_types.mojom.h"
+#include "services/media/audio/audio_output.h"
+#include "services/media/audio/audio_track_to_output_link.h"
+#include "services/media/audio/platform/generic/mixer.h"
+
+namespace mojo {
+namespace media {
+namespace audio {
+
+class StandardOutputBase : public AudioOutput {
+ public:
+  ~StandardOutputBase() override;
+
+ protected:
+  struct MixJob {
+    static constexpr uint32_t INVALID_GENERATION = 0;
+
+    // State for the job set up once by the output implementation and then used
+    // by all tracks.
+    void*    buf;
+    uint32_t buf_frames;
+    int64_t  start_pts_of;  // start PTS, expressed in output frames.
+    uint32_t local_to_output_gen;
+    bool     accumulate;
+    const LinearTransform* local_to_output;
+
+    // State for the job which is set up for each track during SetupMix
+    uint32_t frames_produced;
+  };
+
+  struct TrackBookkeeping : public AudioTrackToOutputLink::Bookkeeping {
+    TrackBookkeeping();
+    ~TrackBookkeeping() override;
+
+    LinearTransform lt_to_track_frames;
+    LinearTransform out_frames_to_track_frames;
+    uint32_t lt_to_track_frames_gen = 0;
+    uint32_t out_frames_to_track_frames_gen = MixJob::INVALID_GENERATION;
+    uint32_t step_size;
+    MixerPtr mixer;
+
+    void UpdateTrackTrans(const AudioTrackImplPtr& track);
+    void UpdateOutputTrans(const MixJob& job);
+  };
+
+  explicit StandardOutputBase(AudioOutputManager* manager);
+
+  void Process() final;
+  MediaResult InitializeLink(const AudioTrackToOutputLinkPtr& link) final;
+
+  void SetNextSchedTime(const LocalTime& next_sched_time) {
+    next_sched_time_ = next_sched_time;
+    next_sched_time_known_ = true;
+  }
+
+  void SetNextSchedDelay(const LocalDuration& next_sched_delay) {
+    SetNextSchedTime(LocalClock::now() + next_sched_delay);
+  }
+
+  virtual bool StartMixJob(MixJob* job, const LocalTime& process_start) = 0;
+  virtual bool FinishMixJob(const MixJob& job) = 0;
+  virtual TrackBookkeeping* AllocBookkeeping();
+
+  LpcmMediaTypeDetailsPtr output_format_;
+  uint32_t output_bytes_per_frame_;
+
+ private:
+  using TrackSetupTask = std::function<bool(const AudioTrackImplPtr& track,
+                                            TrackBookkeeping* info)>;
+  using TrackProcessTask =
+    std::function<bool(const AudioTrackImplPtr& track,
+                       TrackBookkeeping* info,
+                       const AudioPipe::AudioPacketRefPtr& pkt_ref)>;
+
+  void ForeachTrack(const TrackSetupTask& setup,
+                    const TrackProcessTask& process);
+
+  bool SetupMix(const AudioTrackImplPtr& track, TrackBookkeeping* info);
+  bool ProcessMix(const AudioTrackImplPtr& track,
+                  TrackBookkeeping* info,
+                  const AudioPipe::AudioPacketRefPtr& pkt_ref);
+
+  bool SetupTrim(const AudioTrackImplPtr& track, TrackBookkeeping* info);
+  bool ProcessTrim(const AudioTrackImplPtr& track,
+                   TrackBookkeeping* info,
+                   const AudioPipe::AudioPacketRefPtr& pkt_ref);
+
+  LocalTime next_sched_time_;
+  bool next_sched_time_known_;
+
+  // State used by the mix task.
+  TrackSetupTask setup_mix_;
+  TrackProcessTask process_mix_;
+  MixJob cur_mix_job_;
+
+  // State used by the trim task.
+  TrackSetupTask setup_trim_;
+  TrackProcessTask process_trim_;
+  int64_t trim_threshold_;
+};
+
+}  // namespace audio
+}  // namespace media
+}  // namespace mojo
+
+#endif  // SERVICES_MEDIA_AUDIO_PLATFORM_GENERIC_STANDARD_OUTPUT_BASE_H_