frame_buffer.h - mozsearch

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/*

 *  Copyright (c) 2021 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 API_VIDEO_FRAME_BUFFER_H_

#define API_VIDEO_FRAME_BUFFER_H_

#include <cstddef>

#include <cstdint>

#include <map>

#include <memory>

#include "absl/container/inlined_vector.h"

#include "absl/types/optional.h"

#include "api/field_trials_view.h"

#include "api/video/encoded_frame.h"

#include "modules/video_coding/utility/decoded_frames_history.h"

namespace webrtc {

// The high level idea of the FrameBuffer is to order frames received from the

// network into a decodable stream. Frames are order by frame ID, and grouped

// into temporal units by timestamp. A temporal unit is decodable after all

// referenced frames outside the unit has been decoded, and a temporal unit is

// continuous if all referenced frames are directly or indirectly decodable.

// The FrameBuffer is thread-unsafe.

class FrameBuffer {

 public:

  struct DecodabilityInfo {

    uint32_t next_rtp_timestamp;

    uint32_t last_rtp_timestamp;

};

  // The `max_size` determines the maximum number of frames the buffer will

  // store, and max_decode_history determines how far back (by frame ID) the

  // buffer will store if a frame was decoded or not.

  FrameBuffer(int max_size,

              int max_decode_history,

              // TODO(hta): remove field trials!

              const FieldTrialsView& field_trials);

  FrameBuffer(const FrameBuffer&) = delete;

  FrameBuffer& operator=(const FrameBuffer&) = delete;

  ~FrameBuffer() = default;

  // Inserted frames may only reference backwards, and must have no duplicate

  // references. Frame insertion will fail if `frame` is a duplicate, has

  // already been decoded, invalid, or if the buffer is full and the frame is

  // not a keyframe. Returns true if the frame was successfully inserted.

  bool InsertFrame(std::unique_ptr<EncodedFrame> frame);

  // Mark all frames belonging to the next decodable temporal unit as decoded

  // and returns them.

  absl::InlinedVector<std::unique_ptr<EncodedFrame>, 4>

  ExtractNextDecodableTemporalUnit();

  // Drop all frames in the next decodable unit.

  void DropNextDecodableTemporalUnit();

  absl::optional<int64_t> LastContinuousFrameId() const;

  absl::optional<int64_t> LastContinuousTemporalUnitFrameId() const;

  absl::optional<DecodabilityInfo> DecodableTemporalUnitsInfo() const;

  int GetTotalNumberOfContinuousTemporalUnits() const;

  int GetTotalNumberOfDroppedFrames() const;

  int GetTotalNumberOfDiscardedPackets() const;

  size_t CurrentSize() const;

 private:

  struct FrameInfo {

    std::unique_ptr<EncodedFrame> encoded_frame;

    bool continuous = false;

};

  using FrameMap = std::map<int64_t, FrameInfo>;

  using FrameIterator = FrameMap::iterator;

  struct TemporalUnit {

    // Both first and last are inclusive.

    FrameIterator first_frame;

    FrameIterator last_frame;

};

  bool IsContinuous(const FrameIterator& it) const;

  void PropagateContinuity(const FrameIterator& frame_it);

  void FindNextAndLastDecodableTemporalUnit();

  void Clear();

  void UpdateDroppedFramesAndDiscardedPackets(FrameIterator begin_it,

                                              FrameIterator end_it);

  const bool legacy_frame_id_jump_behavior_;

  const size_t max_size_;

  FrameMap frames_;

  absl::optional<TemporalUnit> next_decodable_temporal_unit_;

  absl::optional<DecodabilityInfo> decodable_temporal_units_info_;

  absl::optional<int64_t> last_continuous_frame_id_;

  absl::optional<int64_t> last_continuous_temporal_unit_frame_id_;

  video_coding::DecodedFramesHistory decoded_frame_history_;

  int num_continuous_temporal_units_ = 0;

  int num_dropped_frames_ = 0;

  int num_discarded_packets_ = 0;

};

}  // namespace webrtc

#endif  // API_VIDEO_FRAME_BUFFER_H_