H264 bitstream parser.

webrtc/modules/rtp_rtcp/source/h264_bitstream_parser.h

Index: webrtc/modules/rtp_rtcp/source/h264_bitstream_parser.h
diff --git a/webrtc/modules/rtp_rtcp/source/h264_bitstream_parser.h b/webrtc/modules/rtp_rtcp/source/h264_bitstream_parser.h
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+/*
+ *  Copyright (c) 2015 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 WEBRTC_MODULES_RTP_RTCP_SOURCE_H264_BITSTREAM_PARSER_H_
+#define WEBRTC_MODULES_RTP_RTCP_SOURCE_H264_BITSTREAM_PARSER_H_
+
+#include <stdint.h>
+#include <stddef.h>
+
+namespace rtc {
+class BitBuffer;
+}
+
+namespace webrtc {
+
+// Stateful H264 bitstream parser (due to SPS/PPS). Used to parse out QP values
+// from the bitstream.
+// TODO(pbos): Unify with RTP SPS parsing and only use one H264 parser.
+// TODO(pbos): If/when this gets used on the receiver side CHECKs must be
+// removed and gracefully abort as we have no control over receive-side
+// bitstreams.
+class H264BitstreamParser {
+ public:
+  // Parse an additional chunk of H264 bitstream.
+  void ParseBitstream(const uint8_t* bitstream, size_t length);
+
+  // Get the last extracted QP value from the parsed bitstream.
+  bool GetLastSliceQp(int* qp) const;
+
+ private:
+  // Captured in SPS and used when parsing slice NALUs.
+  struct SpsState {
+    SpsState();
+
+    uint32_t delta_pic_order_always_zero_flag = 0;
+    uint32_t separate_colour_plane_flag = 0;
+    uint32_t frame_mbs_only_flag = 0;
+    uint32_t log2_max_frame_num_minus4 = 0;
+    uint32_t log2_max_pic_order_cnt_lsb_minus4 = 0;
+    uint32_t pic_order_cnt_type = 0;
+  };
+
+  struct PpsState {
+    PpsState();
+
+    bool bottom_field_pic_order_in_frame_present_flag = false;
+    bool weighted_pred_flag = false;
+    uint32_t weighted_bipred_idc = false;
+    uint32_t redundant_pic_cnt_present_flag = 0;
+    int pic_init_qp_minus26 = 0;
+  };
+
+  void ParseSlice(const uint8_t* slice, size_t length);
+  bool ParseSpsNalu(const uint8_t* sps_nalu, size_t length);
+  bool ParsePpsNalu(const uint8_t* pps_nalu, size_t length);
+  bool ParseNonParameterSetNalu(const uint8_t* source,
+                                size_t source_length,
+                                uint8_t nalu_type);
+
+  // SPS/PPS state, updated when parsing new SPS/PPS, used to parse slices.
+  bool sps_parsed_ = false;
+  SpsState sps_;
+  bool pps_parsed_ = false;
+  PpsState pps_;
+
+  // Last parsed slice QP.
+  bool last_slice_qp_delta_parsed_ = false;
+  int32_t last_slice_qp_delta_ = 0;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_H264_BITSTREAM_PARSER_H_