Add H264 bitstream rewriting to limit frame reordering marker in header

webrtc/common_video/h264/h264_common.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_H264_COMMON_H_
+#define WEBRTC_COMMON_VIDEO_H264_H264_COMMON_H_
+
+#include <memory>
+#include <vector>
+
+#include "webrtc/base/common.h"
+#include "webrtc/base/buffer.h"
+
+namespace webrtc {
+
+namespace H264 {
+// The size of a full NALU start sequence {0 0 0 1}, used for the first NALU
+// of an access unit, and for SPS and PPS blocks.
+const size_t kNaluLongStartSequenceSize = 4;
+
+// The size of a shortened NALU start sequence {0 0 1}, that may be used if
+// not the first NALU of an access unit or an SPS or PPS block.
+const size_t kNaluShortStartSequenceSize = 3;
+
+// The size of the NALU type byte (1).
+const size_t kNaluTypeSize = 1;
+
+enum NaluType : uint8_t {
+  kSlice = 1,
+  kIdr = 5,
+  kSei = 6,
+  kSps = 7,
+  kPps = 8,
+  kAud = 9,
+  kEndOfSequence = 10,
+  kEndOfStream = 11,
+  kFiller = 12,
+  kStapA = 24,
+  kFuA = 28
+};
+
+enum SliceType : uint8_t { kP = 0, kB = 1, kI = 2, kSp = 3, kSi = 4 };
+
+struct NaluIndex {
+  // Start index of NALU, including start sequence.
+  size_t start_offset;
+  // Start index of NALU payload, typically type header.
+  size_t payload_start_offset;
+  // Length of NALU payload, in bytes, counting from payload_start_offset.
+  size_t payload_size;
+};
+
+// Returns a vector of the NALU indices in the given buffer.
+std::vector<NaluIndex> FindNaluIndices(const uint8_t* buffer,
+                                       size_t buffer_size);
+
+// Get the NAL type from the header byte immediately following start sequence.
+NaluType ParseNaluType(uint8_t data);
+
+// Methods for parsing and writing RBSP. See section 7.4.1 of the H264 spec.
+//
+// The following sequences are illegal, and need to be escaped when encoding:
+// 00 00 00 -> 00 00 03 00
+// 00 00 01 -> 00 00 03 01
+// 00 00 02 -> 00 00 03 02
+// And things in the source that look like the emulation byte pattern (00 00 03)
+// need to have an extra emulation byte added, so it's removed when decoding:
+// 00 00 03 -> 00 00 03 03
+//
+// Decoding is simply a matter of finding any 00 00 03 sequence and removing
+// the 03 emulation byte.
+
+// Parse the given data and remove any emulation byte escaping.
+std::unique_ptr<rtc::Buffer> ParseRbsp(const uint8_t* data, size_t length);
+
+// Write the given data to the destination buffer, inserting and emulation
+// bytes in order to escape any data the could be interpreted as a start
+// sequence.
+void WriteRbsp(const uint8_t* bytes, size_t length, rtc::Buffer* destination);
+}  // namespace H264
+}  // namespace webrtc
+
+#endif  // WEBRTC_COMMON_VIDEO_H264_H264_COMMON_H_