Struct SDPAudioVideoMediaFormat

Represents a single media format within a media announcement. Often the whole media format can be represented and described by a single character, e.g. "0" without additional info represents standard "PCMU", "8" represents "PCMA" etc. For other media types that have variable parameters additional attributes can be provided.

Inherited Members

System.ValueType.Equals(System.Object)

System.ValueType.GetHashCode()

System.ValueType.ToString()

System.Object.Equals(System.Object, System.Object)

System.Object.GetType()

System.Object.ReferenceEquals(System.Object, System.Object)

Namespace: SIPSorcery.Net

Assembly: SIPSorcery.dll

Syntax

public struct SDPAudioVideoMediaFormat

Remarks

This struct is designed to be immutable. If new information becomes available for a media format, such as when parsing further into an SDP payload, a new media format should be created. TODO: With C#9 the struct could become a "record" type.

Constructors

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SDPAudioVideoMediaFormat(SDPMediaTypesEnum, Int32, String, Int32, Int32, String)

Creates a new SDP media format for a dynamic media type. Dynamic media types are those that use ID's between 96 and 127 inclusive and require an rtpmap attribute and optionally an fmtp attribute.

Declaration

public SDPAudioVideoMediaFormat(SDPMediaTypesEnum kind, int id, string name, int clockRate, int channels = 1, string fmtp = null)

Parameters

Type	Name	Description
SDPMediaTypesEnum	kind
System.Int32	id
System.String	name
System.Int32	clockRate
System.Int32	channels
System.String	fmtp

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SDPAudioVideoMediaFormat(SDPMediaTypesEnum, Int32, String, String)

Creates a new SDP media format for a dynamic media type. Dynamic media types are those that use ID's between 96 and 127 inclusive and require an rtpmap attribute and optionally an fmtp attribute.

Declaration

public SDPAudioVideoMediaFormat(SDPMediaTypesEnum kind, int id, string rtpmap, string fmtp = null)

Parameters

Type	Name	Description
SDPMediaTypesEnum	kind
System.Int32	id
System.String	rtpmap
System.String	fmtp

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SDPAudioVideoMediaFormat(AudioFormat)

Creates a new SDP media format from a Audio Format instance. The Audio Format contains the equivalent information to the SDP format object but has well defined audio properties separate from the SDP serialisation.

Declaration

public SDPAudioVideoMediaFormat(AudioFormat audioFormat)

Parameters

Type	Name	Description
SIPSorceryMedia.Abstractions.AudioFormat	audioFormat	The Audio Format to map to an SDP format.

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SDPAudioVideoMediaFormat(SDPWellKnownMediaFormatsEnum)

Creates a new SDP media format for a well known media type. Well known type are those that use ID's less than 96 and don't require rtpmap or fmtp attributes.

Declaration

public SDPAudioVideoMediaFormat(SDPWellKnownMediaFormatsEnum knownFormat)

Parameters

Type	Name	Description
SIPSorceryMedia.Abstractions.SDPWellKnownMediaFormatsEnum	knownFormat

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SDPAudioVideoMediaFormat(VideoFormat)

Creates a new SDP media format from a Video Format instance. The Video Format contains the equivalent information to the SDP format object but has well defined video properties separate from the SDP serialisation.

Declaration

public SDPAudioVideoMediaFormat(VideoFormat videoFormat)

Parameters

Type	Name	Description
SIPSorceryMedia.Abstractions.VideoFormat	videoFormat	The Video Format to map to an SDP format.

Fields

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DEFAULT_AUDIO_CHANNEL_COUNT

Declaration

public const int DEFAULT_AUDIO_CHANNEL_COUNT = 1

Field Value

Type	Description
System.Int32

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DYNAMIC_ID_MAX

Declaration

public const int DYNAMIC_ID_MAX = 127

Field Value

Type	Description
System.Int32

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DYNAMIC_ID_MIN

Declaration

public const int DYNAMIC_ID_MIN = 96

Field Value

Type	Description
System.Int32

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Empty

Declaration

public static SDPAudioVideoMediaFormat Empty

Field Value

Type	Description
SDPAudioVideoMediaFormat

Properties

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Fmtp

The optional format parameter attribute for the media format. For standard media types this is not necessary.

// Example
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000 
a=fmtp:101 0-16                     ← "101 0-16" is the fmtp attribute.

Declaration

public readonly string Fmtp { get; }

Property Value

Type	Description
System.String

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ID

The mandatory ID for the media format. Warning, even though some ID's are normally used to represent a standard media type, e.g "0" for "PCMU" etc, there is no guarantee that's the case. "0" can be used for any media format if there is a format attribute describing it. In the absence of a format attribute then it is required that it represents a standard media type.

Note (rj2): FormatID MUST be string (not int), in case ID is 't38' and type is 'image' Note to above: The FormatID is always numeric for profile "RTP/AVP" and "RTP/SAVP", see https://tools.ietf.org/html/rfc4566#section-5.14 and section on "fmt": "If the [proto] sub-field is "RTP/AVP" or "RTP/SAVP" the [fmt] sub-fields contain RTP payload type numbers" In the case of T38 the format name is "t38" but the formatID must be set as a dynamic ID.

// Example
// Note in this example "0" is representing a standard format so the format attribute is optional.
m=audio 12228 RTP/AVP 0 101         // "0" and "101" are media format ID's.
a=rtpmap:0 PCMU/8000                // "0" is the media format ID.
a=rtpmap:101 telephone-event/8000   // "101" is the media format ID.
a=fmtp:101 0-16

 
// t38 example from https://tools.ietf.org/html/rfc4612.
m=audio 6800 RTP/AVP 0 98 
a=rtpmap:98 t38/8000 
a=fmtp:98 T38FaxVersion=2;T38FaxRateManagement=transferredTCF

Declaration

public readonly int ID { get; }

Property Value

Type	Description
System.Int32

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Kind

Indicates whether the format is for audio or video.

Declaration

public readonly SDPMediaTypesEnum Kind { get; }

Property Value

Type	Description
SDPMediaTypesEnum

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Rtpmap

The optional rtpmap attribute properties for the media format. For standard media types this is not necessary.

// Example
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000 ← "101 telephone-event/8000" is the rtpmap properties.
a=fmtp:101 0-16

Declaration

public readonly string Rtpmap { get; }

Property Value

Type	Description
System.String

Methods

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AreMatch(SDPAudioVideoMediaFormat, SDPAudioVideoMediaFormat)

For two formats to be a match only the codec and rtpmap parameters need to match. The fmtp parameter does not matter.

Declaration

public static bool AreMatch(SDPAudioVideoMediaFormat format1, SDPAudioVideoMediaFormat format2)

Parameters

Type	Name	Description
SDPAudioVideoMediaFormat	format1
SDPAudioVideoMediaFormat	format2

Returns

Type	Description
System.Boolean

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Channels()

Declaration

public int Channels()

Returns

Type	Description
System.Int32

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ClockRate()

Declaration

public int ClockRate()

Returns

Type	Description
System.Int32

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GetCommonRtpEventFormat(List<SDPAudioVideoMediaFormat>, List<SDPAudioVideoMediaFormat>)

Attempts to get a common SDP media format that supports telephone events. If compatible an RTP event format will be returned that matches the local format with the remote format.

Declaration

public static SDPAudioVideoMediaFormat GetCommonRtpEventFormat(List<SDPAudioVideoMediaFormat> a, List<SDPAudioVideoMediaFormat> b)

Parameters

Type	Name	Description
System.Collections.Generic.List<SDPAudioVideoMediaFormat>	a	The first of supported media formats.
System.Collections.Generic.List<SDPAudioVideoMediaFormat>	b	The second of supported media formats.

Returns

Type	Description
SDPAudioVideoMediaFormat	An SDP media format with a compatible RTP event format.

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GetCompatibleFormats(List<SDPAudioVideoMediaFormat>, List<SDPAudioVideoMediaFormat>)

Attempts to get the compatible formats between two lists. Formats for "RTP Events" are not included.

Declaration

public static List<SDPAudioVideoMediaFormat> GetCompatibleFormats(List<SDPAudioVideoMediaFormat> a, List<SDPAudioVideoMediaFormat> b)

Parameters

Type	Name	Description
System.Collections.Generic.List<SDPAudioVideoMediaFormat>	a	The first list to match the media formats for.
System.Collections.Generic.List<SDPAudioVideoMediaFormat>	b	The second list to match the media formats for.

Returns

Type	Description
System.Collections.Generic.List<SDPAudioVideoMediaFormat>	A list of media formats that are compatible for BOTH lists.

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IsEmpty()

Declaration

public bool IsEmpty()

Returns

Type	Description
System.Boolean

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Name()

Declaration

public string Name()

Returns

Type	Description
System.String

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SortMediaCapability(List<SDPAudioVideoMediaFormat>, List<SDPAudioVideoMediaFormat>)

Sort capabilities array based on another capability array

Declaration

public static void SortMediaCapability(List<SDPAudioVideoMediaFormat> capabilities, List<SDPAudioVideoMediaFormat> priorityOrder)

Parameters

Type	Name	Description
System.Collections.Generic.List<SDPAudioVideoMediaFormat>	capabilities
System.Collections.Generic.List<SDPAudioVideoMediaFormat>	priorityOrder

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ToAudioFormat()

Maps an audio SDP media type to a media abstraction layer audio format.

Declaration

public AudioFormat ToAudioFormat()

Returns

Type	Description
SIPSorceryMedia.Abstractions.AudioFormat	An audio format value.

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ToVideoFormat()

Maps a video SDP media type to a media abstraction layer video format.

Declaration

public VideoFormat ToVideoFormat()

Returns

Type	Description
SIPSorceryMedia.Abstractions.VideoFormat	A video format value.

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TryParseRtpmap(String, out String, out Int32, out Int32)

Parses an rtpmap attribute in the form "name/clock" or "name/clock/channels".

Declaration

public static bool TryParseRtpmap(string rtpmap, out string name, out int clockRate, out int channels)

Parameters

Type	Name	Description
System.String	rtpmap
System.String	name
System.Int32	clockRate
System.Int32	channels

Returns

Type	Description
System.Boolean

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WithUpdatedFmtp(String)

Declaration

public SDPAudioVideoMediaFormat WithUpdatedFmtp(string fmtp)

Parameters

Type	Name	Description
System.String	fmtp

Returns

Type	Description
SDPAudioVideoMediaFormat

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WithUpdatedID(Int32)

Creates a new media format based on an existing format but with a different ID. The typical case for this is during the SDP offer/answer exchange the dynamic format ID's for the equivalent type need to be adjusted by one party.

Declaration

public SDPAudioVideoMediaFormat WithUpdatedID(int id)

Parameters

Type	Name	Description
System.Int32	id	The ID to set on the new format.

Returns

Type	Description
SDPAudioVideoMediaFormat	A new format.

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WithUpdatedRtpmap(String)

Declaration

public SDPAudioVideoMediaFormat WithUpdatedRtpmap(string rtpmap)

Parameters

Type	Name	Description
System.String	rtpmap

Returns

Type	Description
SDPAudioVideoMediaFormat

Extension Methods

JSONWriter.ToJson(Object)