DP44/docs/ai/Common/DTS.Common.Serialization/IRIGCH10/Packets.md

source_files, generated_at, model, schema_version, sha256

source_files	generated_at	model	schema_version	sha256
Common/DTS.Common.Serialization/IRIGCH10/Packets/ITransportStreamHeader.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/ISecondaryTimeFormatHeader.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/TransportStreamHeader.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/SecondaryTimeFormatHeader.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/TimeDataPacket.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/TMATSPacket.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/RootRecorderIndexPacket.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/RecorderIndexPacket.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/TimePacketFormat2.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/IDataPacket.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/TimePacketFormat1.cs Common/DTS.Common.Serialization/IRIGCH10/Packets/AnalogDataFormat1Packet.cs	2026-04-17T15:30:22.882503+00:00	zai-org/GLM-5-FP8	1	ea68d7597278f2c1

IRIG Chapter 10 Packet Serialization Module Documentation

1. Purpose

This module provides serialization and deserialization support for IRIG 106 Chapter 10 data packets. It implements the packet structures defined in the Chapter 10 standard for recording and playback of telemetry data, including time data packets (Format 1 and Format 2), TMATS configuration packets, analog data packets, and recorder index packets. The module serves as the foundational layer for reading and writing Chapter 10 format files, handling binary encoding, checksums, and time format conversions.

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2. Public Interface

Interfaces

ITransportStreamHeader

public interface ITransportStreamHeader
{
    int MessageFormat { get; }
    int MessageType { get; }
    int SequenceNumber { get; }
}

Defines read-only access to transport stream header fields.

ISecondaryTimeFormatHeader

public interface ISecondaryTimeFormatHeader
{
    int NanoSeconds { get; }
    int Seconds { get; }
    ushort Reserved { get; }
    ushort CheckSum { get; }
    DateTime LocalTime { get; }
}

Defines read-only access to secondary time format header fields.

IDataPacket

public interface IDataPacket
{
    IPacketHeader PacketHeader { get; }
    uint ComputeCheckSum();
    byte[] GetBytes();
    void SetRTC(long rtc);
    void SetDataVersion(DataTypeVersion version);
    void SetChannelID(ushort channelID);
    void SetSequenceNumber(ushort seq);
}

Defines the contract for all Chapter 10 data packets.

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Abstract Base Class

AbstractDataPacket

Base class for all packet types. Provides common functionality:

Member	Signature	Description
ChannelSpecificDataWord	uint property	Gets/sets the Channel Specific Data Word (CSDW).
PacketHeader	IPacketHeader property	Gets the packet header.
ComputeCheckSum	uint ComputeCheckSum()	Computes 32-bit checksum of packet data.
GetRTC	long GetRTC()	Returns the 10MHz Realtime Counter value.
SetRTC	void SetRTC(long rtc)	Sets the RTC value in both the packet and header.
SetSequenceNumber	void SetSequenceNumber(ushort seq)	Sets the packet sequence number.
SetDataVersion	void SetDataVersion(DataTypeVersion version)	Sets the data version in the header.
SetChannelID	void SetChannelID(ushort channelID)	Sets the channel ID in the header.
GetBytes	virtual byte[] GetBytes()	Serializes the packet to a byte array.
BASE_RTC	const long = 141989612500056L	Base RTC value constant.

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Concrete Packet Classes

TransportStreamHeader

public TransportStreamHeader(byte[] input)
public const int TRANSPORT_HEADER_LENGTH = 4;

Parses a 4-byte transport stream header. Extracts MessageFormat (bits 0-3), MessageType (bits 4-7), and SequenceNumber (bits 8-31) from the input bytes.

SecondaryTimeFormatHeader

public SecondaryTimeFormatHeader(byte[] input)
public static byte[] GetBytes(int nanoseconds, int seconds)
public const int SECONDARY_TIME_HEADER_LENGTH = 12;

Parses or constructs a 12-byte secondary time header. LocalTime is computed as Unix epoch (1970-01-01) plus Seconds and NanoSeconds converted to ticks, then converted to local time. Constructor validates checksum and writes to Trace on mismatch.

TimeDataPacket

public TimeDataPacket()
public DateTime GetDateTime()
public void SetTime(DateTime dt)
public void SetTimeSource(byte b)
public void SetTimeSource(TimeSource src)
public void SetTimeFormat(TimeFormats fmt)

Implements Time Data Format 1 packet. SetTime encodes a DateTime into BCD format in a 12-byte payload at positions 4-11.

TimePacketFormat1

public TimePacketFormat1(byte sequenceNumber, DateTime packetTime, long rtc, int nanoseconds, int seconds)

Implements Time Data Format 1 with full IRIG time encoding. Properties include:

• ITS (IRIGTimeSource enum) - IRIG time source (bits 15-12, not serialized per comment)
• TimeFormat (TimeFormats enum) - bits 7-4
• TimeSource (TimeSources enum) - bits 3-0
• DateFormat (DateFormats enum) - bit 9
• IsLeapYear (bool) - bit 8
• TimePacketTime (DateTime) - the time represented by this packet

TimePacketFormat2

public TimePacketFormat2(byte sequenceNumber, bool rtcSyncError, int nanoseconds, int seconds, long rtc, bool includeSecondaryHeader)
public TimePacketFormat2(byte[] bytes)

Implements Time Data Format 2 for network time protocols. Properties include:

• LocalTimeOfFirstSample (DateTime)
• NetworkTimeFormat (NetworkTimeFormats enum) - bits 7-4
• TimeStatus (TimeStatuses enum) - bits 3-0
• UnsignedSeconds (uint)
• UnsignedNanoSeconds (uint)
• PTPTime (string) - formatted PTP timestamp

TMATSPacket

public TMATSPacket(int nanoseconds, int seconds, string tmatsDoc, bool secondaryHeaderPresent)
public TMATSPacket(byte[] bytes)
public string TMATSDocument { get; }
public bool XMLFormat { get; }
public bool SetupRecordConfigurationChange { get; }
public RCCChapter10Versions Chapter10Version { get; }

Implements TMATS (Telemetry Attributes Transfer Standard) packet. TMATSDocument returns ASCII-decoded content. RCCChapter10Versions enum maps values 0x07-0x0B to versions RCC_106_07 through RCC_106_15.

AnalogDataFormat1Packet

public AnalogDataFormat1Packet(int nanoseconds, int seconds, Chapter10File.GetNextSampleDelegate getNextSample, int totalChannels, long channelLength, long rtc, long numSamples, long currentSample, byte sequenceNumber, ushort channelId, bool includeSecondaryHeader)
public AnalogDataFormat1Packet(byte[] bytes)
public SampleData[] Samples { get; }

Implements Analog Data Format 1 packet. CSDW properties:

• Same (bit 28)
• Factor (bits 27-24)
• TotChan (bits 23-16)
• Subchan (bits 15-8)
• Length (bits 7-2)
• Mode (Modes enum, bits 1-0)

SampleData inner class holds ChannelData as short[].

RecorderIndexPacket

public RecorderIndexPacket()
public void SetRootPacketAddress(long address)
public void AddRecordingIndex(RecordingIndex index)
public int NumberOfEntries { get; }
public DateTime GetDateTime()
public override byte[] GetBytes()

Implements recorder index packet. Uses hardcoded ChannelSpecificDataWord = {0x8D, 0x02, 0x00, 0xE0}.

RootRecorderIndexPacket

public RootRecorderIndexPacket(DateTime dt)
public void SetRootPacketAddress(long address)
public void AddRecordingIndex(RecordingIndexIndex index)
public override byte[] GetBytes()

Implements root recorder index packet (last packet in file). Uses hardcoded ChannelSpecificDataWord = {0x8D, 0x00, 0x00, 0x60}.

RecordingIndex

public RecordingIndex(long rtc, long offset, DateTime dt)
public const int SIZE = 28;
public byte[] GetBytes()
public DateTime GetDateTime()

Helper structure for recorder index entries. Fixed size of 28 bytes.

RecordingIndexIndex

public RecordingIndexIndex(long rtc, long offset, DateTime dt)
public const int SIZE = 24;
public byte[] GetBytes()

Helper structure for root index entries. Fixed size of 24 bytes.

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3. Invariants

• TransportStreamHeader: Input must be exactly TRANSPORT_HEADER_LENGTH (4) bytes; null input throws NullReferenceException.
• SecondaryTimeFormatHeader: Input must be exactly SECONDARY_TIME_HEADER_LENGTH (12) bytes.
• Packet alignment: PacketHeader.PacketLength is always padded to a multiple of 4 bytes.
• RTC consistency: Setting RTC via SetRTC(long) updates both the internal _rtc field and PacketHeader.
• Sequence numbers: Should be monotonically increasing and wrap to 0 after maximum value (caller responsibility).
• TimeDataPacket: _dataBytes is initialized to 12 bytes; time data is written at positions 4-11.
• TMATSDocument encoding: Always decoded as ASCII.
• AnalogDataFormat1Packet sample data: Samples are byte-swapped and offset by 0x8000 for signed/unsigned conversion.

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4. Dependencies

This module depends on:

• DTS.Serialization.IRIGCH10.Enums - Data type enumerations (DataFileDataTypes, DataTypeVersion)
• DTS.Serialization.IRIGCh10.Attributes - PacketHeaderValueAttribute
• DTS.Serialization.IRIGCH10.Packets - PacketHeader, IPacketHeader
• DTS.Common.Utilities - PTP1588Timestamps (referenced in TimePacketFormat2)
• Utils.Utils (external utility class) - Static methods: BitArrayToInt32, SetBits, GetCheckSum8, GetCheckSum32, GetBCDBytes
• System.IO - MemoryStream, BinaryWriter
• System.Collections - BitArray

What depends on this module:

• Chapter10File (referenced in AnalogDataFormat1Packet constructor delegate type GetNextSampleDelegate)

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5. Gotchas

1. SecondaryTimeFormatHeader checksum validation is non-blocking: When checksum mismatch occurs, the constructor only writes to System.Diagnostics.Trace.WriteLine rather than throwing an exception. Callers must not assume valid checksums.

2. TimePacketFormat1 ITS field not serialized: The ITS property (IRIGTimeSource) is explicitly not serialized to the CSDW due to EMC validation tool compatibility issues (comment dated 2023-10-27).

3. Hardcoded ChannelSpecificDataWord values: RecorderIndexPacket and RootRecorderIndexPacket use hardcoded byte arrays for ChannelSpecificDataWord with comments indicating uncertainty about individual field breakdown.

4. AnalogDataFormat1Packet data version selection: Uses DATA_VERSION_DASSAULT (0x06) when secondary header is present, otherwise DATA_VERSION_V105 (0x01). Comment indicates EMC validation tool only supports CH10 106v5.

5. TimeDataPacket SetTimeSource overloads behave differently: The byte overload sets bits 0-3 directly, while the TimeSource enum overload reverses bit order (bit 0←3, bit 1←2, etc.) per Chapter 10 reference 10-47.

6. LocalTime calculation in SecondaryTimeFormatHeader: Uses AddTicks(NanoSeconds / 100) which truncates nanoseconds to 100-nanosecond tick precision.

7. RecordingIndexIndex added automatically in RootRecorderIndexPacket.GetBytes(): The last index entry pointing back to the current packet is appended internally during GetBytes() call, modifying _indices list state.