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