Call1.Content.MediaDescription — Telepathy D-Bus Interface Specification

# Interface Call1.Content.MediaDescription

Interface Index (Compact) | Summary | Description | Methods | Properties | Types

### Methods

Accept | (a{sv}: Local_Media_Description) | → | nothing |
Reject | () | → | (uuss): Reason |

### Properties

Interfaces | as (DBus_Interface_List) | Read only | Immutable |
FurtherNegotiationRequired | b | Read only | Immutable |
HasRemoteInformation | b | Read only | Immutable |
Codecs | a(usuuba{ss}) (Codec_List) | Read only | Immutable |
RemoteContact | u (Contact_Handle) | Read only | Immutable |
SSRCs | a{uau} (Contact_SSRCs_Map) | Read only | Immutable |

### Types

Contact_SSRCs_Map | Mapping | a{uau} |
Media_Description_Properties | Mapping | a{sv} |

WARNING: This interface is experimental and is likely to cause havoc to your API/ABI if bindings are generated. Do not include this interface in libraries that care about compatibility.
Added in 0.23.4. (draft 1)

### Description

This object represents a remote Description Offer to which the local streaming implementation should reply with its local Description. This is intended as a temporary transactional object for use with Content.Interface.Media. There will always be 0 or 1 MediaDescription object per Content. In most cases, this object will stay alive until you call either Accept or Reject, and then disappear. There are some cases (e.g. an endpoint being removed from the call) where a MediaDescription object will disappear before you have had a chance to either Accept or Reject it.

# Methods

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## Accept (a{sv}: Local_Media_Description) → nothing

### Parameters

- Local_Media_Description — a{sv} (Media_Description_Properties)
The local description to send to the remote contacts and to use in the Content.

Accepts the updated Description and update the corresponding local description. If FurtherNegotiationRequired is True, calling this method will generally cause a network round-trip and a new MediaDescription to be offered (hopefully with FurtherNegotiationRequired set to False).

### Possible Errors

- Invalid Argument
The description given is invalid in some way.

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## Reject () → (uuss): Reason

### Returns

- Reason — (uuss) (Call_State_Reason)
A structured reason for the rejection.

Reject the proposed update to the remote description.

# Properties

Accessed using the org.freedesktop.DBus.Properties interface.
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## Interfaces — as (DBus_Interface_List)

Read only
This property is immutable which means that it can never change.

Extra interfaces provided by this media description. This SHOULD NOT include the Description interface itself.

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## FurtherNegotiationRequired — b

Read only
This property is immutable which means that it can never change.

If this is set to True by the CM in a MediaDescriptionOffer, it means "This is an offer under the SDP Offer/Answer model. Whatever you accept this offer with is what I will send to the other side in my answer." If this is set to False by the CM then it means "This is an Answer under the SDP Offer/Answer model, and if it remains False in the Accept(), no further codec negotiation needs to happen." If this is set to True by the streaming implementation (e.g. in an Accept or UpdateLocalMediaDescription call) then a new SDP Offer/Answer round-trip will be initiated.

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## HasRemoteInformation — b

Read only
This property is immutable which means that it can never change.

True if this offer contains information from the remote side: If False then the Accept response solely depends on the capabilities and preferences of the local side. In most protocols this property will be False for the initial DescriptionOffer on an outgoing call.

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## Codecs — a(usuuba{ss}) (Codec_List)

Read only
This property is immutable which means that it can never change.
A list of codecs the remote contact supports. When used with Accept, it means the locally supported codecs.
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## RemoteContact — u (Contact_Handle)

Read only
This property is immutable which means that it can never change.
The contact handle that this description applies to. This property can be used as an opaque identifier, and searched for in RemoteMembers for each Stream in this Content, to determine which Stream this MediaDescription applies to. If multiple MediaDescriptions apply to the same Stream, the SSRCs property should be used to separate media before decoding. If this property is 0, this MediaDescription applies to all streams, so the above matching method is unneccesary (e.g. in conference calls with a mixer, media from all participants is mixed into one stream). When calling Accept or UpdateLocalMediaDescription, this should always be set to 0, or omitted, because it is assumed that you send the same MediaDescription to everyone (Encoding a stream separately for each contact in a call is inefficient, and should be avoided).
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## SSRCs — a{uau} (Contact_SSRCs_Map)

Read only
This property is immutable which means that it can never change.

A map from Handle to list of Synchronisation Sources, as defined by RFC 3550.

Some protocols require the negotiation of SSRC identifiers for RTP streams. If this is the case, then MediaDescription offers will appear with this property set. The streaming implementation should then call Accept with a map from 0 to a list containing a single SSRC (which does not collide with these, or any previously seen SSRCs). If a new MediaDescription offer appears with an SSRC the same as one in LocalMediaDescriptions, then the streaming implementation should pick a new SSRC to resolve the collision.

It is expected that this list will normally be at most one element long, but it is kept as a list for extensibility. The concatenation of all SSRCs associated with a Stream should contain no duplicate entries. If there are collisions, then it is the responsibility of the protocol implementation to resolve them and generate new offers.

If this property is omitted, then the streaming implementation can assume that there is only one MediaDescription per Stream.

If there is a single multicast Call Stream with multiple Remote Members, and all members are forced to use the same MediaDescription, this map can be used by the streaming implementation to determine which video sources belong to which contacts (e.g. in order to put a name under each face in the call)

# Types

Mapping (Permalink)

## Contact_SSRCs_Map — a{uau}

- Contact — u (Handle)
The remote contact these SSRCs belong to or 0.
- SSRCs — au
The list of Synchronisation Sources.

Mapping (Permalink)

## Media_Description_Properties — a{sv}

A mapping containing all properties that define the information from a MediaDescription and its interfaces.

If HasRemoteInformation is True, then this mapping will always contains at least Codecs

- Media_Description_Property — s (DBus_Qualified_Member)
A D-Bus interface name, followed by a dot and a D-Bus property name.
- Media_Description_Property_Value — v
The value of the property