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      1 /*
      2  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 #ifndef WEBRTC_MODULES_RTP_RTCP_SOURCE_H264_BITSTREAM_PARSER_H_
     12 #define WEBRTC_MODULES_RTP_RTCP_SOURCE_H264_BITSTREAM_PARSER_H_
     13 
     14 #include <stddef.h>
     15 #include <stdint.h>
     16 
     17 namespace rtc {
     18 class BitBuffer;
     19 }
     20 
     21 namespace webrtc {
     22 
     23 // Stateful H264 bitstream parser (due to SPS/PPS). Used to parse out QP values
     24 // from the bitstream.
     25 // TODO(pbos): Unify with RTP SPS parsing and only use one H264 parser.
     26 // TODO(pbos): If/when this gets used on the receiver side CHECKs must be
     27 // removed and gracefully abort as we have no control over receive-side
     28 // bitstreams.
     29 class H264BitstreamParser {
     30  public:
     31   // Parse an additional chunk of H264 bitstream.
     32   void ParseBitstream(const uint8_t* bitstream, size_t length);
     33 
     34   // Get the last extracted QP value from the parsed bitstream.
     35   bool GetLastSliceQp(int* qp) const;
     36 
     37  private:
     38   // Captured in SPS and used when parsing slice NALUs.
     39   struct SpsState {
     40     SpsState();
     41 
     42     uint32_t delta_pic_order_always_zero_flag = 0;
     43     uint32_t separate_colour_plane_flag = 0;
     44     uint32_t frame_mbs_only_flag = 0;
     45     uint32_t log2_max_frame_num_minus4 = 0;
     46     uint32_t log2_max_pic_order_cnt_lsb_minus4 = 0;
     47     uint32_t pic_order_cnt_type = 0;
     48   };
     49 
     50   struct PpsState {
     51     PpsState();
     52 
     53     bool bottom_field_pic_order_in_frame_present_flag = false;
     54     bool weighted_pred_flag = false;
     55     uint32_t weighted_bipred_idc = false;
     56     uint32_t redundant_pic_cnt_present_flag = 0;
     57     int pic_init_qp_minus26 = 0;
     58   };
     59 
     60   void ParseSlice(const uint8_t* slice, size_t length);
     61   bool ParseSpsNalu(const uint8_t* sps_nalu, size_t length);
     62   bool ParsePpsNalu(const uint8_t* pps_nalu, size_t length);
     63   bool ParseNonParameterSetNalu(const uint8_t* source,
     64                                 size_t source_length,
     65                                 uint8_t nalu_type);
     66 
     67   // SPS/PPS state, updated when parsing new SPS/PPS, used to parse slices.
     68   bool sps_parsed_ = false;
     69   SpsState sps_;
     70   bool pps_parsed_ = false;
     71   PpsState pps_;
     72 
     73   // Last parsed slice QP.
     74   bool last_slice_qp_delta_parsed_ = false;
     75   int32_t last_slice_qp_delta_ = 0;
     76 };
     77 
     78 }  // namespace webrtc
     79 
     80 #endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_H264_BITSTREAM_PARSER_H_
     81