Class H264Packetiser

Inheritance
System.Object
H264Packetiser
Inherited Members
System.Object.Equals(System.Object)
System.Object.Equals(System.Object, System.Object)
System.Object.GetHashCode()
System.Object.GetType()
System.Object.MemberwiseClone()
System.Object.ReferenceEquals(System.Object, System.Object)
System.Object.ToString()
Namespace: SIPSorcery.Net
Assembly: SIPSorcery.dll
Syntax
public class H264Packetiser

Fields

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H264_RTP_HEADER_LENGTH

Declaration
public const int H264_RTP_HEADER_LENGTH = 2
Field Value
Type Description
System.Int32

Methods

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GetH264RtpHeader(Byte, Boolean, Boolean)

Constructs the RTP header for an H264 NAL. This method does NOT support aggregation packets where multiple NALs are sent as a single RTP payload. The supported H264 header type is Single-Time Aggregation Packet type A (STAP-A) and Fragmentation Unit A (FU-A). The headers produced correspond to H264 packetization-mode=1.

Declaration
public static byte[] GetH264RtpHeader(byte nal0, bool isFirstPacket, bool isFinalPacket)
Parameters
Type Name Description
System.Byte nal0
System.Boolean isFirstPacket
System.Boolean isFinalPacket
Returns
Type Description
System.Byte[]
Remarks

RTP Payload Format for H.264 Video: https://tools.ietf.org/html/rfc6184

FFmpeg H264 RTP packetisation code: https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/rtpenc_h264_hevc.c

When the payload size is less than or equal to max RTP payload, send as Single-Time Aggregation Packet (STAP): https://tools.ietf.org/html/rfc6184#section-5.7.1

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 Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |STAP-A NAL HDR | NALU 1 Size | NALU 1 HDR | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |F|NRI| Type | | +-+-+-+-+-+-+-+-+

Type = 24 for STAP-A (NOTE: this is the type of the H264 RTP header and NOT the NAL type).

When the payload size is greater than max RTP payload, send as Fragmentation Unit A (FU-A): https://tools.ietf.org/html/rfc6184#section-5.8 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FU indicator | FU header | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Fragmentation Unit (FU) Payload | ...

The FU indicator octet has the following format:

+---------------+ |0|1|2|3|4|5|6|7| +-+-+-+-+-+-+-+-+ |F|NRI| Type | +---------------+

F and NRI bits come from the NAL being transmitted. Type = 28 for FU-A (NOTE: this is the type of the H264 RTP header and NOT the NAL type).

The FU header has the following format:

+---------------+ |0|1|2|3|4|5|6|7| +-+-+-+-+-+-+-+-+ |S|E|R| Type | +---------------+

S: Set to 1 for the start of the NAL FU (i.e. first packet in frame). E: Set to 1 for the end of the NAL FU (i.e. the last packet in the frame). R: Reserved bit must be 0. Type: The NAL unit payload type, comes from NAL packet (NOTE: this IS the type of the NAL message).

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ParseNals(Byte[])

Declaration
public static IEnumerable<H264Packetiser.H264Nal> ParseNals(byte[] accessUnit)
Parameters
Type Name Description
System.Byte[] accessUnit
Returns
Type Description
System.Collections.Generic.IEnumerable<H264Packetiser.H264Nal>

Extension Methods