Repo created

TMessagesProj/jni/voip/webrtc/common_video/h264/h264_common.cc

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+/*
+ *  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.
+ */
+
+#include "common_video/h264/h264_common.h"
+
+#include <cstdint>
+
+namespace webrtc {
+namespace H264 {
+
+const uint8_t kNaluTypeMask = 0x1F;
+
+std::vector<NaluIndex> FindNaluIndices(const uint8_t* buffer,
+                                       size_t buffer_size) {
+  // This is sorta like Boyer-Moore, but with only the first optimization step:
+  // given a 3-byte sequence we're looking at, if the 3rd byte isn't 1 or 0,
+  // skip ahead to the next 3-byte sequence. 0s and 1s are relatively rare, so
+  // this will skip the majority of reads/checks.
+  std::vector<NaluIndex> sequences;
+  if (buffer_size < kNaluShortStartSequenceSize)
+    return sequences;
+
+  static_assert(kNaluShortStartSequenceSize >= 2,
+                "kNaluShortStartSequenceSize must be larger or equals to 2");
+  const size_t end = buffer_size - kNaluShortStartSequenceSize;
+  for (size_t i = 0; i < end;) {
+    if (buffer[i + 2] > 1) {
+      i += 3;
+    } else if (buffer[i + 2] == 1) {
+      if (buffer[i + 1] == 0 && buffer[i] == 0) {
+        // We found a start sequence, now check if it was a 3 of 4 byte one.
+        NaluIndex index = {i, i + 3, 0};
+        if (index.start_offset > 0 && buffer[index.start_offset - 1] == 0)
+          --index.start_offset;
+
+        // Update length of previous entry.
+        auto it = sequences.rbegin();
+        if (it != sequences.rend())
+          it->payload_size = index.start_offset - it->payload_start_offset;
+
+        sequences.push_back(index);
+      }
+
+      i += 3;
+    } else {
+      ++i;
+    }
+  }
+
+  // Update length of last entry, if any.
+  auto it = sequences.rbegin();
+  if (it != sequences.rend())
+    it->payload_size = buffer_size - it->payload_start_offset;
+
+  return sequences;
+}
+
+NaluType ParseNaluType(uint8_t data) {
+  return static_cast<NaluType>(data & kNaluTypeMask);
+}
+
+std::vector<uint8_t> ParseRbsp(const uint8_t* data, size_t length) {
+  std::vector<uint8_t> out;
+  out.reserve(length);
+
+  for (size_t i = 0; i < length;) {
+    // Be careful about over/underflow here. byte_length_ - 3 can underflow, and
+    // i + 3 can overflow, but byte_length_ - i can't, because i < byte_length_
+    // above, and that expression will produce the number of bytes left in
+    // the stream including the byte at i.
+    if (length - i >= 3 && !data[i] && !data[i + 1] && data[i + 2] == 3) {
+      // Two rbsp bytes.
+      out.push_back(data[i++]);
+      out.push_back(data[i++]);
+      // Skip the emulation byte.
+      i++;
+    } else {
+      // Single rbsp byte.
+      out.push_back(data[i++]);
+    }
+  }
+  return out;
+}
+
+void WriteRbsp(const uint8_t* bytes, size_t length, rtc::Buffer* destination) {
+  static const uint8_t kZerosInStartSequence = 2;
+  static const uint8_t kEmulationByte = 0x03u;
+  size_t num_consecutive_zeros = 0;
+  destination->EnsureCapacity(destination->size() + length);
+
+  for (size_t i = 0; i < length; ++i) {
+    uint8_t byte = bytes[i];
+    if (byte <= kEmulationByte &&
+        num_consecutive_zeros >= kZerosInStartSequence) {
+      // Need to escape.
+      destination->AppendData(kEmulationByte);
+      num_consecutive_zeros = 0;
+    }
+    destination->AppendData(byte);
+    if (byte == 0) {
+      ++num_consecutive_zeros;
+    } else {
+      num_consecutive_zeros = 0;
+    }
+  }
+}
+
+}  // namespace H264
+}  // namespace webrtc