Repo created

TMessagesProj/jni/voip/webrtc/video/decode_synchronizer.h

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+/*
+ *  Copyright (c) 2022 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef VIDEO_DECODE_SYNCHRONIZER_H_
+#define VIDEO_DECODE_SYNCHRONIZER_H_
+
+#include <stdint.h>
+
+#include <functional>
+#include <memory>
+#include <set>
+#include <utility>
+
+#include "absl/types/optional.h"
+#include "api/metronome/metronome.h"
+#include "api/sequence_checker.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/units/timestamp.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/thread_annotations.h"
+#include "video/frame_decode_scheduler.h"
+#include "video/frame_decode_timing.h"
+
+namespace webrtc {
+
+// DecodeSynchronizer synchronizes the frame scheduling by coalescing decoding
+// on the metronome.
+//
+// A video receive stream can use the DecodeSynchronizer by receiving a
+// FrameDecodeScheduler instance with `CreateSynchronizedFrameScheduler()`.
+// This instance implements FrameDecodeScheduler and can be used as a normal
+// scheduler. This instance is owned by the receive stream, and is borrowed by
+// the DecodeSynchronizer. The DecodeSynchronizer will stop borrowing the
+// instance when `FrameDecodeScheduler::Stop()` is called, after which the
+// scheduler may be destroyed by the receive stream.
+//
+// When a frame is scheduled for decode by a receive stream using the
+// DecodeSynchronizer, it will instead be executed on the metronome during the
+// tick interval where `max_decode_time` occurs. For example, if a frame is
+// scheduled for decode in 50ms and the tick interval is 20ms, then the frame
+// will be released for decoding in 2 ticks. See below for illustration,
+//
+// In the case where the decode time is in the past, or must occur before the
+// next metronome tick then the frame will be released right away, allowing a
+// delayed stream to catch up quickly.
+//
+// DecodeSynchronizer is single threaded - all method calls must run on the
+// `worker_queue_`.
+class DecodeSynchronizer {
+ public:
+  DecodeSynchronizer(Clock* clock,
+                     Metronome* metronome,
+                     TaskQueueBase* worker_queue);
+  ~DecodeSynchronizer();
+  DecodeSynchronizer(const DecodeSynchronizer&) = delete;
+  DecodeSynchronizer& operator=(const DecodeSynchronizer&) = delete;
+
+  std::unique_ptr<FrameDecodeScheduler> CreateSynchronizedFrameScheduler();
+
+ private:
+  class ScheduledFrame {
+   public:
+    ScheduledFrame(uint32_t rtp_timestamp,
+                   FrameDecodeTiming::FrameSchedule schedule,
+                   FrameDecodeScheduler::FrameReleaseCallback callback);
+
+    // Disallow copy since `callback` should only be moved.
+    ScheduledFrame(const ScheduledFrame&) = delete;
+    ScheduledFrame& operator=(const ScheduledFrame&) = delete;
+    ScheduledFrame(ScheduledFrame&&) = default;
+    ScheduledFrame& operator=(ScheduledFrame&&) = default;
+
+    // Executes `callback_`.
+    void RunFrameReleaseCallback() &&;
+
+    uint32_t rtp_timestamp() const { return rtp_timestamp_; }
+    Timestamp LatestDecodeTime() const;
+
+   private:
+    uint32_t rtp_timestamp_;
+    FrameDecodeTiming::FrameSchedule schedule_;
+    FrameDecodeScheduler::FrameReleaseCallback callback_;
+  };
+
+  class SynchronizedFrameDecodeScheduler : public FrameDecodeScheduler {
+   public:
+    explicit SynchronizedFrameDecodeScheduler(DecodeSynchronizer* sync);
+    ~SynchronizedFrameDecodeScheduler() override;
+
+    // Releases the outstanding frame for decoding. This invalidates
+    // `next_frame_`. There must be a frame scheduled.
+    ScheduledFrame ReleaseNextFrame();
+
+    // Returns `next_frame_.schedule.max_decode_time`. There must be a frame
+    // scheduled when this is called.
+    Timestamp LatestDecodeTime();
+
+    // FrameDecodeScheduler implementation.
+    absl::optional<uint32_t> ScheduledRtpTimestamp() override;
+    void ScheduleFrame(uint32_t rtp,
+                       FrameDecodeTiming::FrameSchedule schedule,
+                       FrameReleaseCallback cb) override;
+    void CancelOutstanding() override;
+    void Stop() override;
+
+   private:
+    DecodeSynchronizer* sync_;
+    absl::optional<ScheduledFrame> next_frame_;
+    bool stopped_ = false;
+  };
+
+  void OnFrameScheduled(SynchronizedFrameDecodeScheduler* scheduler);
+  void RemoveFrameScheduler(SynchronizedFrameDecodeScheduler* scheduler);
+
+  void ScheduleNextTick();
+  void OnTick();
+
+  Clock* const clock_;
+  TaskQueueBase* const worker_queue_;
+  Metronome* const metronome_;
+
+  Timestamp expected_next_tick_ = Timestamp::PlusInfinity();
+  std::set<SynchronizedFrameDecodeScheduler*> schedulers_
+      RTC_GUARDED_BY(worker_queue_);
+  bool tick_scheduled_ = false;
+  ScopedTaskSafetyDetached safety_;
+};
+
+}  // namespace webrtc
+
+#endif  // VIDEO_DECODE_SYNCHRONIZER_H_