Add H264 bitstream rewriting to limit frame reordering marker in header

webrtc/common_video/h264/sps_parser.h

+/*
+ *  Copyright (c) 2016 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_COMMON_VIDEO_H264_SPS_PARSER_H_
+#define WEBRTC_COMMON_VIDEO_H264_SPS_PARSER_H_
+
+#include "webrtc/base/common.h"
+#include "webrtc/base/optional.h"
+
+namespace rtc {
+class BitBuffer;
+}
+
+namespace webrtc {
+
+// A class for parsing out sequence parameter set (SPS) data from an H264 NALU.
+class SpsParser {
+ public:
+  // The parsed state of the SPS. Only some select values are stored.
+  // Add more as they are actually needed.
+  struct SpsState {
+    SpsState() = default;
+
+    uint32_t width = 0;
+    uint32_t height = 0;
+    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;
+    uint32_t max_num_ref_frames = 0;
+    uint32_t vui_params_present = 0;
+  };
+
+  // Unpack RBSP and parse SPS state from the supplied buffer.
+  static rtc::Optional<SpsState> ParseSps(const uint8_t* data, size_t length);
+
+ protected:
+  // Parse the SPS state, up till the VUI part, for a bit buffer where RBSP
+  // decoding has already been performed.
+  static rtc::Optional<SpsState> ParseSpsUpToVui(rtc::BitBuffer* buffer);
+};
+
+}  // namespace webrtc
+#endif  // WEBRTC_COMMON_VIDEO_H264_SPS_PARSER_H_