1 /* 2 * Copyright (c) 2018 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 #include "modules/rtp_rtcp/source/rtp_generic_frame_descriptor_extension.h" 12 13 #include "rtc_base/checks.h" 14 15 namespace webrtc { 16 namespace { 17 18 constexpr uint8_t kFlagBeginOfSubframe = 0x80; 19 constexpr uint8_t kFlagEndOfSubframe = 0x40; 20 21 // In version 00, the flags F and L in the first byte correspond to 22 // kFlagFirstSubframeV00 and kFlagLastSubframeV00. In practice, they were 23 // always set to `true`. 24 constexpr uint8_t kFlagFirstSubframeV00 = 0x20; 25 constexpr uint8_t kFlagLastSubframeV00 = 0x10; 26 27 constexpr uint8_t kFlagDependencies = 0x08; 28 constexpr uint8_t kMaskTemporalLayer = 0x07; 29 30 constexpr uint8_t kFlagMoreDependencies = 0x01; 31 constexpr uint8_t kFlageXtendedOffset = 0x02; 32 } // namespace 33 // 0 1 2 3 4 5 6 7 34 // +-+-+-+-+-+-+-+-+ 35 // |B|E|F|L|D| T | 36 // +-+-+-+-+-+-+-+-+ 37 // B: | S | 38 // +-+-+-+-+-+-+-+-+ 39 // | | 40 // B: + FID + 41 // | | 42 // +-+-+-+-+-+-+-+-+ 43 // | | 44 // + Width + 45 // B=1 | | 46 // and +-+-+-+-+-+-+-+-+ 47 // D=0 | | 48 // + Height + 49 // | | 50 // +-+-+-+-+-+-+-+-+ 51 // D: | FDIFF |X|M| 52 // +---------------+ 53 // X: | ... | 54 // +-+-+-+-+-+-+-+-+ 55 // M: | FDIFF |X|M| 56 // +---------------+ 57 // | ... | 58 // +-+-+-+-+-+-+-+-+ 59 constexpr RTPExtensionType RtpGenericFrameDescriptorExtension00::kId; 60 Parse(rtc::ArrayView<const uint8_t> data,RtpGenericFrameDescriptor * descriptor)61bool RtpGenericFrameDescriptorExtension00::Parse( 62 rtc::ArrayView<const uint8_t> data, 63 RtpGenericFrameDescriptor* descriptor) { 64 if (data.empty()) { 65 return false; 66 } 67 68 bool begins_subframe = (data[0] & kFlagBeginOfSubframe) != 0; 69 descriptor->SetFirstPacketInSubFrame(begins_subframe); 70 descriptor->SetLastPacketInSubFrame((data[0] & kFlagEndOfSubframe) != 0); 71 72 // Parse Subframe details provided in 1st packet of subframe. 73 if (!begins_subframe) { 74 return data.size() == 1; 75 } 76 if (data.size() < 4) { 77 return false; 78 } 79 descriptor->SetTemporalLayer(data[0] & kMaskTemporalLayer); 80 descriptor->SetSpatialLayersBitmask(data[1]); 81 descriptor->SetFrameId(data[2] | (data[3] << 8)); 82 83 // Parse dependencies. 84 descriptor->ClearFrameDependencies(); 85 size_t offset = 4; 86 bool has_more_dependencies = (data[0] & kFlagDependencies) != 0; 87 if (!has_more_dependencies && data.size() >= offset + 4) { 88 uint16_t width = (data[offset] << 8) | data[offset + 1]; 89 uint16_t height = (data[offset + 2] << 8) | data[offset + 3]; 90 descriptor->SetResolution(width, height); 91 offset += 4; 92 } 93 while (has_more_dependencies) { 94 if (data.size() == offset) 95 return false; 96 has_more_dependencies = (data[offset] & kFlagMoreDependencies) != 0; 97 bool extended = (data[offset] & kFlageXtendedOffset) != 0; 98 uint16_t fdiff = data[offset] >> 2; 99 offset++; 100 if (extended) { 101 if (data.size() == offset) 102 return false; 103 fdiff |= (data[offset] << 6); 104 offset++; 105 } 106 if (!descriptor->AddFrameDependencyDiff(fdiff)) 107 return false; 108 } 109 return true; 110 } 111 ValueSize(const RtpGenericFrameDescriptor & descriptor)112size_t RtpGenericFrameDescriptorExtension00::ValueSize( 113 const RtpGenericFrameDescriptor& descriptor) { 114 if (!descriptor.FirstPacketInSubFrame()) 115 return 1; 116 117 size_t size = 4; 118 for (uint16_t fdiff : descriptor.FrameDependenciesDiffs()) { 119 size += (fdiff >= (1 << 6)) ? 2 : 1; 120 } 121 if (descriptor.FirstPacketInSubFrame() && 122 descriptor.FrameDependenciesDiffs().empty() && descriptor.Width() > 0 && 123 descriptor.Height() > 0) { 124 size += 4; 125 } 126 return size; 127 } 128 Write(rtc::ArrayView<uint8_t> data,const RtpGenericFrameDescriptor & descriptor)129bool RtpGenericFrameDescriptorExtension00::Write( 130 rtc::ArrayView<uint8_t> data, 131 const RtpGenericFrameDescriptor& descriptor) { 132 RTC_CHECK_EQ(data.size(), ValueSize(descriptor)); 133 uint8_t base_header = 134 (descriptor.FirstPacketInSubFrame() ? kFlagBeginOfSubframe : 0) | 135 (descriptor.LastPacketInSubFrame() ? kFlagEndOfSubframe : 0); 136 base_header |= kFlagFirstSubframeV00; 137 base_header |= kFlagLastSubframeV00; 138 139 if (!descriptor.FirstPacketInSubFrame()) { 140 data[0] = base_header; 141 return true; 142 } 143 data[0] = 144 base_header | 145 (descriptor.FrameDependenciesDiffs().empty() ? 0 : kFlagDependencies) | 146 descriptor.TemporalLayer(); 147 data[1] = descriptor.SpatialLayersBitmask(); 148 uint16_t frame_id = descriptor.FrameId(); 149 data[2] = frame_id & 0xff; 150 data[3] = frame_id >> 8; 151 rtc::ArrayView<const uint16_t> fdiffs = descriptor.FrameDependenciesDiffs(); 152 size_t offset = 4; 153 if (descriptor.FirstPacketInSubFrame() && fdiffs.empty() && 154 descriptor.Width() > 0 && descriptor.Height() > 0) { 155 data[offset++] = (descriptor.Width() >> 8); 156 data[offset++] = (descriptor.Width() & 0xFF); 157 data[offset++] = (descriptor.Height() >> 8); 158 data[offset++] = (descriptor.Height() & 0xFF); 159 } 160 for (size_t i = 0; i < fdiffs.size(); i++) { 161 bool extended = fdiffs[i] >= (1 << 6); 162 bool more = i < fdiffs.size() - 1; 163 data[offset++] = ((fdiffs[i] & 0x3f) << 2) | 164 (extended ? kFlageXtendedOffset : 0) | 165 (more ? kFlagMoreDependencies : 0); 166 if (extended) { 167 data[offset++] = fdiffs[i] >> 6; 168 } 169 } 170 return true; 171 } 172 173 } // namespace webrtc 174