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