| /* |
| * 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 "webrtc/common_video/h264/h264_common.h" |
| |
| 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. |
| RTC_CHECK_GE(buffer_size, kNaluShortStartSequenceSize); |
| std::vector<NaluIndex> sequences; |
| 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 && 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::unique_ptr<rtc::Buffer> ParseRbsp(const uint8_t* data, size_t length) { |
| std::unique_ptr<rtc::Buffer> rbsp_buffer(new rtc::Buffer(0, length)); |
| const char* sps_bytes = reinterpret_cast<const char*>(data); |
| 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] == 0 && data[i + 1] == 0 && |
| data[i + 2] == 3) { |
| // Two rbsp bytes + the emulation byte. |
| rbsp_buffer->AppendData(sps_bytes + i, 2); |
| i += 3; |
| } else { |
| // Single rbsp byte. |
| rbsp_buffer->AppendData(sps_bytes[i]); |
| ++i; |
| } |
| } |
| return rbsp_buffer; |
| } |
| |
| 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 |