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_header_extension_size.h" 12 13 #include "api/rtp_parameters.h" 14 15 namespace webrtc { 16 RtpHeaderExtensionSize(rtc::ArrayView<const RtpExtensionSize> extensions,const RtpHeaderExtensionMap & registered_extensions)17int RtpHeaderExtensionSize(rtc::ArrayView<const RtpExtensionSize> extensions, 18 const RtpHeaderExtensionMap& registered_extensions) { 19 // RFC3550 Section 5.3.1 20 static constexpr int kExtensionBlockHeaderSize = 4; 21 22 int values_size = 0; 23 int num_extensions = 0; 24 int each_extension_header_size = 1; 25 for (const RtpExtensionSize& extension : extensions) { 26 int id = registered_extensions.GetId(extension.type); 27 if (id == RtpHeaderExtensionMap::kInvalidId) 28 continue; 29 // All extensions should use same size header. Check if the `extension` 30 // forces to switch to two byte header that allows larger id and value size. 31 if (id > RtpExtension::kOneByteHeaderExtensionMaxId || 32 extension.value_size > 33 RtpExtension::kOneByteHeaderExtensionMaxValueSize) { 34 each_extension_header_size = 2; 35 } 36 values_size += extension.value_size; 37 num_extensions++; 38 } 39 if (values_size == 0) 40 return 0; 41 int size = kExtensionBlockHeaderSize + 42 each_extension_header_size * num_extensions + values_size; 43 // Extension size specified in 32bit words, 44 // so result must be multiple of 4 bytes. Round up. 45 return size + 3 - (size + 3) % 4; 46 } 47 48 } // namespace webrtc 49