1 /* 2 * Copyright (c) 2016 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef COMMON_VIDEO_H264_H264_COMMON_H_ 12 #define COMMON_VIDEO_H264_H264_COMMON_H_ 13 14 #include <stddef.h> 15 #include <stdint.h> 16 17 #include <vector> 18 19 #include "rtc_base/buffer.h" 20 21 namespace webrtc { 22 23 namespace H264 { 24 // The size of a full NALU start sequence {0 0 0 1}, used for the first NALU 25 // of an access unit, and for SPS and PPS blocks. 26 const size_t kNaluLongStartSequenceSize = 4; 27 28 // The size of a shortened NALU start sequence {0 0 1}, that may be used if 29 // not the first NALU of an access unit or an SPS or PPS block. 30 const size_t kNaluShortStartSequenceSize = 3; 31 32 // The size of the NALU type byte (1). 33 const size_t kNaluTypeSize = 1; 34 35 enum NaluType : uint8_t { 36 kSlice = 1, 37 kIdr = 5, 38 kSei = 6, 39 kSps = 7, 40 kPps = 8, 41 kAud = 9, 42 kEndOfSequence = 10, 43 kEndOfStream = 11, 44 kFiller = 12, 45 kPrefix = 14, 46 kStapA = 24, 47 kFuA = 28 48 }; 49 50 enum SliceType : uint8_t { kP = 0, kB = 1, kI = 2, kSp = 3, kSi = 4 }; 51 52 struct NaluIndex { 53 // Start index of NALU, including start sequence. 54 size_t start_offset; 55 // Start index of NALU payload, typically type header. 56 size_t payload_start_offset; 57 // Length of NALU payload, in bytes, counting from payload_start_offset. 58 size_t payload_size; 59 }; 60 61 // Returns a vector of the NALU indices in the given buffer. 62 std::vector<NaluIndex> FindNaluIndices(const uint8_t* buffer, 63 size_t buffer_size); 64 65 // Get the NAL type from the header byte immediately following start sequence. 66 NaluType ParseNaluType(uint8_t data); 67 68 // Methods for parsing and writing RBSP. See section 7.4.1 of the H264 spec. 69 // 70 // The following sequences are illegal, and need to be escaped when encoding: 71 // 00 00 00 -> 00 00 03 00 72 // 00 00 01 -> 00 00 03 01 73 // 00 00 02 -> 00 00 03 02 74 // And things in the source that look like the emulation byte pattern (00 00 03) 75 // need to have an extra emulation byte added, so it's removed when decoding: 76 // 00 00 03 -> 00 00 03 03 77 // 78 // Decoding is simply a matter of finding any 00 00 03 sequence and removing 79 // the 03 emulation byte. 80 81 // Parse the given data and remove any emulation byte escaping. 82 std::vector<uint8_t> ParseRbsp(const uint8_t* data, size_t length); 83 84 // Write the given data to the destination buffer, inserting and emulation 85 // bytes in order to escape any data the could be interpreted as a start 86 // sequence. 87 void WriteRbsp(const uint8_t* bytes, size_t length, rtc::Buffer* destination); 88 } // namespace H264 89 } // namespace webrtc 90 91 #endif // COMMON_VIDEO_H264_H264_COMMON_H_ 92