// Copyright 2019 The Chromium Authors // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef CAST_STREAMING_IMPL_RTP_DEFINES_H_ #define CAST_STREAMING_IMPL_RTP_DEFINES_H_ #include <stdint.h> #include "cast/streaming/public/constants.h" namespace openscreen::cast { // Note: Cast Streaming uses a subset of the messages in the RTP/RTCP // specification, but also adds some of its own extensions. See: // https://tools.ietf.org/html/rfc3550 // Uniquely identifies one packet within a frame. These are sequence numbers, // starting at 0. Each Cast RTP packet also includes the "last ID" so that a // receiver always knows the range of valid FramePacketIds for a given frame. FramePacketId; // A special FramePacketId value meant to represent "all packets lost" in Cast // RTCP Feedback messages. constexpr FramePacketId kAllPacketsLost = …; constexpr FramePacketId kMaxAllowedFramePacketId = …; // The maximum size of any RTP or RTCP packet, in bytes. The calculation below // is: Standard Ethernet MTU bytes minus IP header bytes minus UDP header bytes. // The remainder is available for RTP/RTCP packet data (header + payload). // // A nice explanation of this: https://jvns.ca/blog/2017/02/07/mtu/ // // Constants are provided here for UDP over IPv4 and IPv6 on Ethernet. Other // transports and network mediums will need additional consideration, alternate // calculations. Note that MTU is dynamic, depending on the path the packets // take between two endpoints (the 1500 here is just a commonly-used value for // LAN Ethernet). constexpr int kMaxRtpPacketSizeForIpv4UdpOnEthernet = …; constexpr int kMaxRtpPacketSizeForIpv6UdpOnEthernet = …; // The Cast RTP packet header: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ^ // |V=2|P|X| CC=0 |M| PT | sequence number | | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+RTP // + RTP timestamp |Spec // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | // + synchronization source (SSRC) identifier | v // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // |K|R| EXT count | FID | PID | ^ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Cast // | Max PID | optional fields, extensions, Spec // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ then payload... v // // Byte 0: Version 2, no padding, no RTP extensions, no CSRCs. // Byte 1: Marker bit indicates whether this is the last packet, followed by a // 7-bit payload type. // Byte 12: Key Frame bit, followed by "RFID will be provided" bit, followed by // 6 bits specifying the number of extensions that will be provided. // The minimum-possible valid size of a Cast RTP packet (i.e., no optional // fields, extensions, nor payload). constexpr int kRtpPacketMinValidSize = …; // All Cast RTP packets must carry the version 2 flag, not use padding, not use // RTP extensions, and have zero CSRCs. constexpr uint8_t kRtpRequiredFirstByte = …; // Bitmasks to isolate fields within byte 2 of the Cast RTP header. constexpr uint8_t kRtpMarkerBitMask = …; constexpr uint8_t kRtpPayloadTypeMask = …; // Describes the content being transported over RTP streams. These are Cast // Streaming specific assignments, within the "dynamic" range provided by // IANA. Note that this Cast Streaming implementation does not manipulate // already-encoded data, and so these payload types are only "informative" in // purpose and can be used to check for corruption while parsing packets. enum class RtpPayloadType : uint8_t { … }; // Returns the stream type associated with the RTP payload type. StreamType ToStreamType(RtpPayloadType type, bool use_android_rtp_hack); // Setting |use_android_rtp_hack| to true means that we match the legacy Chrome // sender's behavior of always sending the audio and video hacks for AndroidTV, // as some legacy android receivers require these. // TODO(issuetracker.google.com/184438154): we need to figure out what receivers // need this still, if any. The hack should be removed when possible. RtpPayloadType GetPayloadType(AudioCodec codec, bool use_android_rtp_hack); RtpPayloadType GetPayloadType(VideoCodec codec, bool use_android_rtp_hack); // Returns true if the |raw_byte| can be type-casted to a RtpPayloadType, and is // also not RtpPayloadType::kNull. The caller should mask the byte, to select // the lower 7 bits, if applicable. bool IsRtpPayloadType(uint8_t raw_byte); // Bitmasks to isolate fields within byte 12 of the Cast RTP header. constexpr uint8_t kRtpKeyFrameBitMask = …; constexpr uint8_t kRtpHasReferenceFrameIdBitMask = …; constexpr uint8_t kRtpExtensionCountMask = …; // Cast extensions. This implementation supports only the Adaptive Latency // extension, and ignores all others: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | TYPE = 1 | Ext data SIZE = 2 |Playout Delay (unsigned millis)| // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // // The Adaptive Latency extension permits changing the fixed end-to-end playout // delay of a single RTP stream. constexpr uint8_t kAdaptiveLatencyRtpExtensionType = …; constexpr int kNumExtensionDataSizeFieldBits = …; // RTCP Common Header: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // |V=2|P|RC/Subtyp| Packet Type | Length | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ constexpr int kRtcpCommonHeaderSize = …; // All RTCP packets must carry the version 2 flag and not use padding. constexpr uint8_t kRtcpRequiredVersionAndPaddingBits = …; constexpr int kRtcpReportCountFieldNumBits = …; // https://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml enum class RtcpPacketType : uint8_t { … }; // Returns true if the |raw_byte| can be type-casted to a RtcpPacketType, and is // also not RtcpPacketType::kNull. bool IsRtcpPacketType(uint8_t raw_byte); // Supported subtype values in the RTCP Common Header when the packet type is // kApplicationDefined or kPayloadSpecific. enum class RtcpSubtype : uint8_t { … }; // RTCP Sender Report: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | SSRC of Sender | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | | // | NTP Timestamp | // | | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | RTP Timestamp | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Sender's Packet Count | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Sender's Octet Count | // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // ...Followed by zero or more "Report Blocks"... constexpr int kRtcpSenderReportSize = …; // RTCP Receiver Report: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | SSRC of Receiver | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // ...Followed by zero or more "Report Blocks"... constexpr int kRtcpReceiverReportSize = …; // RTCP Report Block. For Cast Streaming, zero or one of these accompanies a // Sender or Receiver Report, which is different than the RTCP spec (which // allows zero or more). // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | "To" SSRC | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Fraction Lost | Cumulative Number of Packets Lost | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | [32-bit extended] Highest Sequence Number Received | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Interarrival Jitter Mean Absolute Deviation (in RTP Timebase) | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Middle 32-bits of NTP Timestamp from last Sender Report | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Delay since last Sender Report (1/65536 sec timebase) | // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ constexpr int kRtcpReportBlockSize = …; constexpr int kRtcpCumulativePacketsFieldNumBits = …; // Cast Feedback Message: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | SSRC of Receiver | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | SSRC of Sender | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Unique identifier 'C' 'A' 'S' 'T' | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | CkPt Frame ID | # Loss Fields | Current Playout Delay (msec) | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ constexpr int kRtcpFeedbackHeaderSize = …; constexpr uint32_t kRtcpCastIdentifierWord = …; // // "Checkpoint Frame ID" indicates that all frames prior to and including this // one have been fully received. Unfortunately, the Frame ID is truncated to its // lower 8 bits in the packet, and 8 bits is not really enough: If a RTCP packet // is received very late (e.g., more than 1.2 seconds late for 100 FPS audio), // the Checkpoint Frame ID here will be mis-interpreted as representing a // higher-numbered frame than what was intended. This could make the sender's // tracking of "completely received" frames inconsistent, and Cast Streaming // would live-lock. However, this design issue has been baked into the spec and // millions of deployments over several years, and so there's no changing it // now. See kMaxUnackedFrames in constants.h. // // "# Loss fields" indicates the number of packet-level NACK words, 0 to 255: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | w/in Frame ID | Lost Frame Packet ID | PID BitVector | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ constexpr int kRtcpFeedbackLossFieldSize = …; // // "Within Frame ID" is a truncated-to-8-bits frame ID field and, when // bit-expanded should always be interpreted to represent a value greater than // the Checkpoint Frame ID. "Lost Frame Packet ID" is either a specific packet // (within the frame) that has not been received, or kAllPacketsLost to indicate // none the packets for the frame have been received yet. In the former case, // "PID Bit Vector" then represents which of the next 8 packets are also // missing. // // Finally, all of the above is optionally followed by a frame-level ACK bit // vector: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Unique identifier 'C' 'S' 'T' '2' | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // |Feedback Count | # BVectOctets | ACK BitVect (2 to 254 bytes)... // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ → zero-padded to word boundary constexpr int kRtcpFeedbackAckHeaderSize = …; constexpr uint32_t kRtcpCst2IdentifierWord = …; constexpr int kRtcpMinAckBitVectorOctets = …; constexpr int kRtcpMaxAckBitVectorOctets = …; // // "Feedback Count" is a wrap-around counter indicating the number of Cast // Feedbacks that have been sent before this one. "# Bit Vector Octets" // indicates the number of bytes of ACK bit vector following. Cast RTCP // alignment/padding requirements (to 4-byte boundaries) dictates the following // rules for generating the ACK bit vector: // // 1. There must be at least 2 bytes of ACK bit vector, if only to pad the 6 // byte header with two more bytes. // 2. If more than 2 bytes are needed, they must be added 4 at a time to // maintain the 4-byte alignment of the overall RTCP packet. // 3. The total number of octets may not exceed 255; but, because of #2, 254 // is effectively the limit. // 4. The first bit in the first octet represents "Checkpoint Frame ID" plus // two. "Plus two" and not "plus one" because otherwise the "Checkpoint // Frame ID" should have been a greater value! // RTCP Extended Report: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | SSRC of Report Author | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ constexpr int kRtcpExtendedReportHeaderSize = …; // // ...followed by zero or more Blocks: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Block Type | Reserved = 0 | Block Length | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | ..."Block Length" words of report data... | // + + // + + constexpr int kRtcpExtendedReportBlockHeaderSize = …; // // Cast Streaming only uses Receiver Reference Time Reports: // https://tools.ietf.org/html/rfc3611#section-4.4. So, the entire block would // be: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Block Type=4 | Reserved = 0 | Block Length = 2 | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | NTP Timestamp | // | | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ constexpr uint8_t kRtcpReceiverReferenceTimeReportBlockType = …; constexpr int kRtcpReceiverReferenceTimeReportBlockSize = …; // Cast Picture Loss Indicator Message: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | SSRC of Receiver | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | SSRC of Sender | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ constexpr int kRtcpPictureLossIndicatorHeaderSize = …; // The Cast Receiver RTCP frame log message is an application specific // extension that contains receiver side statistics about the Receiver Session. // The message format is: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | RTP Timestamp | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Event Count | Event Timestamp | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ constexpr int kRtcpReceiverFrameLogMessageHeaderSize = …; // // Followed by a list of zero or more event blocks: // // 0 1 2 3 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // | Delay Delta or Packet ID | Type | Event Timestamp | // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ constexpr int kRtcpReceiverFrameLogMessageBlockSize = …; } // namespace openscreen::cast #endif // CAST_STREAMING_IMPL_RTP_DEFINES_H_
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