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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| * Copyright (c) 2018 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. | ||
| */ | ||
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| #include "common_video/h265/h265_common.h" | ||
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| namespace webrtc { | ||
| namespace H265 { | ||
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| const uint8_t kNaluTypeMask = 0x7E; | ||
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| 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; | ||
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| 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; | ||
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| // Update length of previous entry. | ||
| auto it = sequences.rbegin(); | ||
| if (it != sequences.rend()) | ||
| it->payload_size = index.start_offset - it->payload_start_offset; | ||
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| sequences.push_back(index); | ||
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| i += 3; | ||
| } else { | ||
| ++i; | ||
| } | ||
| } | ||
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| // Update length of last entry, if any. | ||
| auto it = sequences.rbegin(); | ||
| if (it != sequences.rend()) | ||
| it->payload_size = buffer_size - it->payload_start_offset; | ||
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| return sequences; | ||
| } | ||
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| NaluType ParseNaluType(uint8_t data) { | ||
| return static_cast<NaluType>((data & kNaluTypeMask) >> 1); | ||
| } | ||
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| std::vector<uint8_t> ParseRbsp(const uint8_t* data, size_t length) { | ||
| std::vector<uint8_t> out; | ||
| out.reserve(length); | ||
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| 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; | ||
| } | ||
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| 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); | ||
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| 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; | ||
| } | ||
| } | ||
| } | ||
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| } // namespace H265 | ||
| } // namespace webrtc |
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