common_video/h265/h265_pps_parser.h

/*
 *  Copyright (c) 2023 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 COMMON_VIDEO_H265_H265_PPS_PARSER_H_
#define COMMON_VIDEO_H265_H265_PPS_PARSER_H_

#include "absl/types/optional.h"
#include "api/array_view.h"
#include "common_video/h265/h265_sps_parser.h"
#include "rtc_base/bitstream_reader.h"
#include "rtc_base/system/rtc_export.h"

namespace webrtc {

// A class for parsing out picture parameter set (PPS) data from a H265 NALU.
class RTC_EXPORT H265PpsParser {
 public:
  // The parsed state of the PPS. Only some select values are stored.
  // Add more as they are actually needed.
  struct PpsState {
    PpsState() = default;

    bool dependent_slice_segments_enabled_flag = false;
    bool cabac_init_present_flag = false;
    bool output_flag_present_flag = false;
    uint32_t num_extra_slice_header_bits = 0;
    uint32_t num_ref_idx_l0_default_active_minus1 = 0;
    uint32_t num_ref_idx_l1_default_active_minus1 = 0;
    int init_qp_minus26 = 0;
    bool weighted_pred_flag = false;
    bool weighted_bipred_flag = false;
    bool lists_modification_present_flag = false;
    uint32_t pps_id = 0;
    uint32_t sps_id = 0;
    int qp_bd_offset_y = 0;
  };

  // Unpack RBSP and parse PPS state from the supplied buffer.
  static absl::optional<PpsState> ParsePps(const uint8_t* data,
                                           size_t length,
                                           const H265SpsParser::SpsState* sps);

  static bool ParsePpsIds(const uint8_t* data,
                          size_t length,
                          uint32_t* pps_id,
                          uint32_t* sps_id);

 protected:
  // Parse the PPS state, for a bit buffer where RBSP decoding has already been
  // performed.
  static absl::optional<PpsState> ParseInternal(
      rtc::ArrayView<const uint8_t> buffer,
      const H265SpsParser::SpsState* sps);
  static bool ParsePpsIdsInternal(BitstreamReader& reader,
                                  uint32_t& pps_id,
                                  uint32_t& sps_id);
};

}  // namespace webrtc

#endif  // COMMON_VIDEO_H265_H265_PPS_PARSER_H_