| // Copyright 2019 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef CAST_STREAMING_RTP_DEFINES_H_ |
| #define CAST_STREAMING_RTP_DEFINES_H_ |
| |
| #include <stdint.h> |
| |
| #include "cast/streaming/constants.h" |
| |
| namespace openscreen { |
| namespace 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. |
| using FramePacketId = uint16_t; |
| |
| // A special FramePacketId value meant to represent "all packets lost" in Cast |
| // RTCP Feedback messages. |
| constexpr FramePacketId kAllPacketsLost = 0xffff; |
| constexpr FramePacketId kMaxAllowedFramePacketId = kAllPacketsLost - 1; |
| |
| // 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 = 1500 - 20 - 8; |
| constexpr int kMaxRtpPacketSizeForIpv6UdpOnEthernet = 1500 - 40 - 8; |
| |
| // 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 = 18; |
| |
| // 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 = 0b10000000; |
| |
| // Bitmasks to isolate fields within byte 2 of the Cast RTP header. |
| constexpr uint8_t kRtpMarkerBitMask = 0b10000000; |
| constexpr uint8_t kRtpPayloadTypeMask = 0b01111111; |
| |
| // 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 { |
| kNull = 0, |
| |
| kAudioFirst = 96, |
| kAudioOpus = 96, |
| kAudioAac = 97, |
| kAudioPcm16 = 98, |
| kAudioVarious = 99, // Codec being used is not fixed. |
| |
| kVideoFirst = 100, |
| kVideoVp8 = 100, |
| kVideoH264 = 101, |
| kVideoVarious = 102, // Codec being used is not fixed. |
| kVideoLast = 102, |
| |
| // Some AndroidTV receivers require the payload type for audio to be 127, and |
| // video to be 96; regardless of the codecs actually being used. This is |
| // definitely out-of-spec, and inconsistent with the audio versus video range |
| // of values, but must be taken into account for backwards-compatibility. |
| // TODO(crbug.com/1127978): RTP payload types need to represent actual type, |
| // as well as have options for new codecs like VP9. |
| kAudioHackForAndroidTV = 127, |
| kVideoHackForAndroidTV = 96, |
| }; |
| |
| // NOTE: currently we match the legacy Chrome sender's behavior of always |
| // sending the audio and video hacks for AndroidTV, however we should migrate |
| // to using proper rtp payload types. New payload types for new codecs, such |
| // as VP9, should also be defined. |
| // TODO(crbug.com/1127978): RTP payload types need to represent actual type, |
| // as well as have options for new codecs like VP9. |
| RtpPayloadType GetPayloadType(AudioCodec codec); |
| RtpPayloadType GetPayloadType(VideoCodec codec); |
| |
| // 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 = 0b10000000; |
| constexpr uint8_t kRtpHasReferenceFrameIdBitMask = 0b01000000; |
| constexpr uint8_t kRtpExtensionCountMask = 0b00111111; |
| |
| // 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 = 1; |
| constexpr int kNumExtensionDataSizeFieldBits = 10; |
| |
| // 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 = 4; |
| // All RTCP packets must carry the version 2 flag and not use padding. |
| constexpr uint8_t kRtcpRequiredVersionAndPaddingBits = 0b100; |
| constexpr int kRtcpReportCountFieldNumBits = 5; |
| |
| // https://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml |
| enum class RtcpPacketType : uint8_t { |
| kNull = 0, |
| |
| kSenderReport = 200, |
| kReceiverReport = 201, |
| kSourceDescription = 202, |
| kApplicationDefined = 204, |
| kPayloadSpecific = 206, |
| kExtendedReports = 207, |
| }; |
| |
| // 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 { |
| kNull = 0, |
| |
| kPictureLossIndicator = 1, |
| kReceiverLog = 2, |
| kFeedback = 15, |
| }; |
| |
| // 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 = 24; |
| |
| // 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 = 4; |
| |
| // 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 = 24; |
| constexpr int kRtcpCumulativePacketsFieldNumBits = 24; |
| |
| // 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 = 16; |
| constexpr uint32_t kRtcpCastIdentifierWord = |
| (uint32_t{'C'} << 24) | (uint32_t{'A'} << 16) | (uint32_t{'S'} << 8) | |
| uint32_t{'T'}; |
| // |
| // "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 = 4; |
| // |
| // "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 = 6; |
| constexpr uint32_t kRtcpCst2IdentifierWord = |
| (uint32_t{'C'} << 24) | (uint32_t{'S'} << 16) | (uint32_t{'T'} << 8) | |
| uint32_t{'2'}; |
| constexpr int kRtcpMinAckBitVectorOctets = 2; |
| constexpr int kRtcpMaxAckBitVectorOctets = 254; |
| // |
| // "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 = 4; |
| // |
| // ...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 = 4; |
| // |
| // 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 = 4; |
| constexpr int kRtcpReceiverReferenceTimeReportBlockSize = 8; |
| |
| // 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 = 8; |
| |
| } // namespace cast |
| } // namespace openscreen |
| |
| #endif // CAST_STREAMING_RTP_DEFINES_H_ |
