Class Nalu

An H264 Network Abstraction Layer Unit.

Inheritance

System.Object

Nalu

Namespace: FM.LiveSwitch.H264

Assembly: FM.LiveSwitch.dll

Syntax

public class Nalu : object

Constructors

Nalu()

Creates an empty NAL Unit.

Declaration

public Nalu()

Nalu(DataBuffer)

Creates a NAL Unit from a byte array.

Declaration

public Nalu(DataBuffer naluBytes)

Parameters

Type	Name	Description
DataBuffer	naluBytes	The NALU bytes.

Properties

BottomFieldFlag

Gets the bottom_field_flag.

Declaration

protected int BottomFieldFlag { get; }

Property Value

Type	Description
System.Int32

Buffer

Gets the backing DataBuffer.

Declaration

public DataBuffer Buffer { get; }

Property Value

Type	Description
DataBuffer

DeltaPicOrderCnt

Gets the pic_order_cnt_lsb

Declaration

protected int[] DeltaPicOrderCnt { get; }

Property Value

Type	Description
System.Int32[]

FBit

Gets the forbidden Zero Bit. The H.264 specification declares a value of 1 as a syntax violation.

Declaration

public bool FBit { get; }

Property Value

Type	Description
System.Boolean

FBitMask

Gets the forbidden zero bit mask.

Declaration

public static int FBitMask { get; }

Property Value

Type	Description
System.Int32

FieldPicFlag

Gets the field_pic_flag.

Declaration

protected int FieldPicFlag { get; }

Property Value

Type	Description
System.Int32

FirstMbInSlice

Gets the first_mb_in_slice specifies the address of the first macroblock in the slice. When arbitrary slice order is not allowed as specified in Annex A, the value of first_mb_in_slice is constrained as follows: – If separate_colour_plane_flag is equal to 0, the value of first_mb_in_slice shall not be less than the value of first_mb_in_slice for any other slice of the current picture that precedes the current slice in decoding order. – Otherwise (separate_colour_plane_flag is equal to 1), the value of first_mb_in_slice shall not be less than the value of first_mb_in_slice for any other slice of the current picture that precedes the current slice in decoding order and has the same value of colour_plane_id.

Declaration

protected int FirstMbInSlice { get; }

Property Value

Type	Description
System.Int32

FrameNum

Gets the frame_num: The Frame Number is used as an identifier for pictures and shall be represented by log2_max_frame_num_minus4 + 4 bits in the bitstream.

Declaration

protected int FrameNum { get; }

Property Value

Type	Description
System.Int32

Header

Gets the NAL header.

Declaration

public int Header { get; }

Property Value

Type	Description
System.Int32

IdrPicFlag

Gets the idr_pic_flag.

Declaration

protected int IdrPicFlag { get; }

Property Value

Type	Description
System.Int32

IdrPicId

Gets the idr_pic_id: The values of idr_pic_id in all the slices of an IDR picture shall remain unchanged. When two consecutive access units in decoding order are both IDR access units, the value of idr_pic_id in the slices of the first such IDR access unit shall differ from the idr_pic_id in the second such IDR access unit. The value of idr_pic_id shall be in the range of 0 to 65535, inclusive.

Declaration

protected int IdrPicId { get; }

Property Value

Type	Description
System.Int32

NalRefIdc

Gets the NRI: 2bits otherwise known as nal_ref_idc.

Declaration

public int NalRefIdc { get; }

Property Value

Type	Description
System.Int32

NriMask

Gets the nal_ref_idc mask.

Declaration

public static int NriMask { get; }

Property Value

Type	Description
System.Int32

Payload

Gets or sets the NAL payload.

Declaration

public DataBuffer Payload { get; }

Property Value

Type	Description
DataBuffer

PicOrderCntLsb

Gets the pic_order_cnt_lsb.

Declaration

protected int PicOrderCntLsb { get; }

Property Value

Type	Description
System.Int32

PicOrderCntType

Gets the pic_order_cnt_type.

Declaration

protected int PicOrderCntType { get; }

Property Value

Type	Description
System.Int32

PpsId

Gets the Picture Parameter Set specifies the picture parameter set in use. The value of pic_parameter_set_id shall be in the range of 0 to 255, inclusive.

Declaration

protected int PpsId { get; }

Property Value

Type	Description
System.Int32

ShortLength

Gets the size of the NAL Unit (including NAL header) in two octets stored in the returned byte array. Useful for creating certain types of H264 such as STAP.

Declaration

public DataBuffer ShortLength { get; }

Property Value

Type	Description
DataBuffer

SliceType

Gets the type of Slice contained in this NAL.

Declaration

protected int SliceType { get; }

Property Value

Type	Description
System.Int32

SpsId

Gets the Sequence Parameter Set this NAL references.

Declaration

protected int SpsId { get; }

Property Value

Type	Description
System.Int32

StartCode

Gets the 4-byte NALU start code.

Declaration

public static DataBuffer StartCode { get; }

Property Value

Type	Description
DataBuffer

Type

Gets the NAL Unit Type.

Declaration

public int Type { get; }

Property Value

Type	Description
System.Int32

TypeMask

Gets the NAL Unit Type mask.

Declaration

public static int TypeMask { get; }

Property Value

Type	Description
System.Int32

Methods

FindNalu(DataBuffer)

Scans for the index of the first NAL Unit after start.

Declaration

public static int FindNalu(DataBuffer encodedData)

Parameters

Type	Name	Description
DataBuffer	encodedData	The stream to search.

Returns

Type	Description
System.Int32

FindNextNalu(DataBuffer, Int32)

Scans for the index of the first NAL Unit after start.

Declaration

public static int FindNextNalu(DataBuffer encodedData, int start)

Parameters

Type	Name	Description
DataBuffer	encodedData	The stream to search.
System.Int32	start	The index to start searching from.

Returns

Type	Description
System.Int32

GetBytes()

Gets the NAL Unit as a byte array that can be passed to an encoder (includes Start Code).

Declaration

public DataBuffer GetBytes()

Returns

Type	Description
DataBuffer

GetNalu(DataBuffer)

Returns the first NAL unit after nalStart.

Declaration

public static Nalu GetNalu(DataBuffer encodedData)

Parameters

Type	Name	Description
DataBuffer	encodedData	The byte array to search.

Returns

Type	Description
Nalu

GetNalu(DataBuffer, Int32, out Int32)

Returns the first NAL unit after nalStart.

Declaration

public static Nalu GetNalu(DataBuffer encodedData, int nalStart, out int nextStartCodeLength)

Parameters

Type	Name	Description
DataBuffer	encodedData	The byte array to search.
System.Int32	nalStart	The start index of the NAL.
System.Int32	nextStartCodeLength	OUT The length of the next the NAL startcode.

Returns

Type	Description
Nalu