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diff --git a/third_party/libwebrtc/sdk/objc/components/video_codec/nalu_rewriter.h b/third_party/libwebrtc/sdk/objc/components/video_codec/nalu_rewriter.h
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+++ b/third_party/libwebrtc/sdk/objc/components/video_codec/nalu_rewriter.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 SDK_OBJC_FRAMEWORK_CLASSES_VIDEOTOOLBOX_NALU_REWRITER_H_
+#define SDK_OBJC_FRAMEWORK_CLASSES_VIDEOTOOLBOX_NALU_REWRITER_H_
+
+#include "modules/video_coding/codecs/h264/include/h264.h"
+
+#include <CoreMedia/CoreMedia.h>
+#include <vector>
+
+#include "common_video/h264/h264_common.h"
+#include "rtc_base/buffer.h"
+
+using webrtc::H264::NaluIndex;
+
+namespace webrtc {
+
+// Converts a sample buffer emitted from the VideoToolbox encoder into a buffer
+// suitable for RTP. The sample buffer is in avcc format whereas the rtp buffer
+// needs to be in Annex B format. Data is written directly to `annexb_buffer`.
+bool H264CMSampleBufferToAnnexBBuffer(CMSampleBufferRef avcc_sample_buffer,
+                                      bool is_keyframe,
+                                      rtc::Buffer* annexb_buffer);
+
+// Converts a buffer received from RTP into a sample buffer suitable for the
+// VideoToolbox decoder. The RTP buffer is in annex b format whereas the sample
+// buffer is in avcc format.
+// If `is_keyframe` is true then `video_format` is ignored since the format will
+// be read from the buffer. Otherwise `video_format` must be provided.
+// Caller is responsible for releasing the created sample buffer.
+bool H264AnnexBBufferToCMSampleBuffer(const uint8_t* annexb_buffer,
+                                      size_t annexb_buffer_size,
+                                      CMVideoFormatDescriptionRef video_format,
+                                      CMSampleBufferRef* out_sample_buffer,
+                                      CMMemoryPoolRef memory_pool);
+
+// Returns a video format description created from the sps/pps information in
+// the Annex B buffer. If there is no such information, nullptr is returned.
+// The caller is responsible for releasing the description.
+CMVideoFormatDescriptionRef CreateVideoFormatDescription(
+    const uint8_t* annexb_buffer,
+    size_t annexb_buffer_size);
+
+// Helper class for reading NALUs from an RTP Annex B buffer.
+class AnnexBBufferReader final {
+ public:
+  AnnexBBufferReader(const uint8_t* annexb_buffer, size_t length);
+  ~AnnexBBufferReader();
+  AnnexBBufferReader(const AnnexBBufferReader& other) = delete;
+  void operator=(const AnnexBBufferReader& other) = delete;
+
+  // Returns a pointer to the beginning of the next NALU slice without the
+  // header bytes and its length. Returns false if no more slices remain.
+  bool ReadNalu(const uint8_t** out_nalu, size_t* out_length);
+
+  // Returns the number of unread NALU bytes, including the size of the header.
+  // If the buffer has no remaining NALUs this will return zero.
+  size_t BytesRemaining() const;
+
+  // Reset the reader to start reading from the first NALU
+  void SeekToStart();
+
+  // Seek to the next position that holds a NALU of the desired type,
+  // or the end if no such NALU is found.
+  // Return true if a NALU of the desired type is found, false if we
+  // reached the end instead
+  bool SeekToNextNaluOfType(H264::NaluType type);
+
+ private:
+  // Returns the the next offset that contains NALU data.
+  size_t FindNextNaluHeader(const uint8_t* start,
+                            size_t length,
+                            size_t offset) const;
+
+  const uint8_t* const start_;
+  std::vector<NaluIndex> offsets_;
+  std::vector<NaluIndex>::iterator offset_;
+  const size_t length_;
+};
+
+// Helper class for writing NALUs using avcc format into a buffer.
+class AvccBufferWriter final {
+ public:
+  AvccBufferWriter(uint8_t* const avcc_buffer, size_t length);
+  ~AvccBufferWriter() {}
+  AvccBufferWriter(const AvccBufferWriter& other) = delete;
+  void operator=(const AvccBufferWriter& other) = delete;
+
+  // Writes the data slice into the buffer. Returns false if there isn't
+  // enough space left.
+  bool WriteNalu(const uint8_t* data, size_t data_size);
+
+  // Returns the unused bytes in the buffer.
+  size_t BytesRemaining() const;
+
+ private:
+  uint8_t* const start_;
+  size_t offset_;
+  const size_t length_;
+};
+
+}  // namespace webrtc
+
+#endif  // SDK_OBJC_FRAMEWORK_CLASSES_VIDEOTOOLBOX_NALU_REWRITER_H_