sdp library android with code examples

Introduction:

SIP or Session Initiation Protocol is one of the most popular signaling protocols used for setting up and managing voice and video communication sessions over IP networks. SDP or Session Description Protocol, on the other hand, is used for describing the parameters of communication sessions, including codecs, media types, and network information.

SDP Library Android is a library that allows developers to build SIP-based communication applications for Android. This library provides a comprehensive set of APIs that makes it easy to handle SIP transactions and session management tasks. In this article, we will explore the features of the SDP Library Android and also provide sample code examples for some of the most common use cases.

Features of SDP Library Android:

  1. SIP Session Management

SDP Library Android provides APIs for establishing and managing SIP sessions. These APIs allow you to set up a session, invite a user to join the session, and handle call states like ringing, answering, and ending the call.

  1. SIP Signaling

The library also provides APIs for signaling transaction management, including handling SIP requests and responses. These APIs allow you to send and receive invitations, call offers, acknowledgments, and other signaling messages.

  1. SDP Parsing

SDP Library Android supports parsing of SDP messages that describe session parameters. These APIs allow you to extract information from an SDP message, such as the codec used, network information, and media types.

  1. NAT Traversal

SDP Library Android also supports NAT traversal mechanisms, which enables two SIP endpoints to communicate even if they are behind NAT devices. This is accomplished by manipulating the SDP message in a way that allows the network to route the media traffic correctly.

  1. Media Handling

SDP Library Android provides APIs to handle the media components of a session. These APIs allow you to select codecs, set up RTP/RTCP connections, and manage media streams.

Code Examples:

Example 1: Setting up a Call

The following code example demonstrates how to set up a call between two SIP endpoints using SDP Library Android.

SipSession session = getSipSession();
SipProfile remote = getSipProfile();
SipProfile local = getSipProfile();

//create SipManager instance
SipManager sipManager = new SipManager();

//register with the SIP server
sipManager.register(local);

//invite the remote user to join the session
session = sipManager.createSession(local, remote);
session.invite(remote.getUri());

//handle the incoming call on the remote end
session.setListener(new SipSession.Listener() {
	public void onCallEstablished(SipSession session) {
		//handle call state for remote endpoint
	}
});

//handle the outgoing call on the local end
session.setListener(new SipSession.Listener() {
	public void onCalling(SipSession session) {
		//handle call state for local endpoint
	}
});

Example 2: Parsing SDP Parameters

The following code example demonstrates how to parse an SDP message and extract certain session parameters.

String sdpMessage = "v=0\r
" +
	"o=- 54877581 1 IN IP4 192.168.1.1\r
" +
	"s=Mozilla Firefox\r
" +
	"t=0 0\r
" +
	"a=sendrecv\r
" +
	"m=audio 48000 RTP/AVP 0 8 101\r
" +
	"c=IN IP4 192.168.1.1\r
" +
	"a=rtpmap:0 PCMU/8000\r
" +
	"a=rtpmap:8 PCMA/8000\r
" +
	"a=rtpmap:101 telephone-event/8000\r
" +
	"a=fmtp:101 0-16\r
";

//create an SDP object
SessionDescription sdp = new SessionDescription();
sdp.fromSDP(sdpMessage);

//get the media components of the session
List<MediaDescription> mediaDescriptions = sdp.getMediaDescriptions(true);

//iterate through the media components to find the codecs used
for (MediaDescription mediaDescription : mediaDescriptions) {
	//get the media type
	String mediaType = mediaDescription.getMedia().getMediaType();

	//get the codec used
	String codec = mediaDescription.getMedia().getProtocol().charAt(0) + "/" + mediaDescription.getMedia().getProtocol().substring(1);

	//display the codec used for each media type
	System.out.println(mediaType + ": " + codec);
}

Example 3: Handling Media Streams

The following code example demonstrates how to handle media streams in a session using SDP Library Android.

SipSession session = getSipSession();

//select the codecs to use for the session
List<RtpCodec> codecs = new ArrayList<>();
codecs.add(RtpCodec.AUDIO_PCMU);
codecs.add(RtpCodec.AUDIO_PCMA);

//set up the RTP/RTCP connections for the media streams
RtpStream rtpStream = new RtpStream();
rtpStream.setLocalAddress(getLocalAddress());
rtpStream.setRemoteAddress(getRemoteAddress());
rtpStream.setLocalPort(5004);
rtpStream.setRemotePort(5004);
RtcpStream rtcpStream = new RtcpStream();
rtcpStream.setLocalAddress(getLocalAddress());
rtcpStream.setRemoteAddress(getRemoteAddress());
rtcpStream.setLocalPort(5005);
rtcpStream.setRemotePort(5005);

//start the media streams
rtpStream.start();
rtcpStream.start();

//create a media stream object
MediaStream mediaStream = session.createMediaStream();
mediaStream.setMediaType("audio");
mediaStream.setCodecList(codecs);
mediaStream.setLocalRtpStream(rtpStream);
mediaStream.setLocalRtcpStream(rtcpStream);

//set the media stream for the session
session.setMediaStream(mediaStream);

Conclusion:

SDP Library Android is a powerful tool for developing SIP-based communication applications for Android. With its comprehensive set of APIs, developers can easily handle SIP transactions and session management tasks. Additionally, the library provides support for SDP parsing, NAT traversal mechanisms, and media handling, making it a complete solution for building robust SIP applications. The sample code examples provided in this article can be used as a guide for integrating SDP Library Android into your Android applications.

let's dive a bit deeper into some of the topics covered in the previous article.

SDP Parsing:

Session Description Protocol (SDP) messages describe the parameters of communication sessions, including codecs, media types, and network information. In SIP-based communication, SDP messages are used to negotiate media parameters between endpoints. SDP Library Android provides APIs for parsing SDP messages and extracting the relevant session parameters.

The SessionDescription class in the SDP Library Android provides an easy-to-use API for parsing SDP messages. The fromSDP() method of the SessionDescription class can be used to parse an SDP message and create a SessionDescription object. Once the SessionDescription object is created, you can retrieve various session parameters such as media types, codecs, network information, and so on.

For example, let's say you received an SDP message from a remote endpoint and you want to extract the codec used. The following code example demonstrates how to extract the codec information from the SDP message:

String sdpMessage = "v=0\r
" +
	"o=- 54877581 1 IN IP4 192.168.1.1\r
" +
	"s=Mozilla Firefox\r
" +
	"t=0 0\r
" +
	"a=sendrecv\r
" +
	"m=audio 48000 RTP/AVP 0 8 101\r
" +
	"c=IN IP4 192.168.1.1\r
" +
	"a=rtpmap:0 PCMU/8000\r
" +
	"a=rtpmap:8 PCMA/8000\r
" +
	"a=rtpmap:101 telephone-event/8000\r
" +
	"a=fmtp:101 0-16\r
";

//create a SessionDescription object
SessionDescription sdp = new SessionDescription();
sdp.fromSDP(sdpMessage);

//get the media components of the session
List<MediaDescription> mediaDescriptions = sdp.getMediaDescriptions(true);

//iterate through the media components to find the codecs used
for (MediaDescription mediaDescription : mediaDescriptions) {
	//get the media type
	String mediaType = mediaDescription.getMedia().getMediaType();

	//get the codec used
	String codec = mediaDescription.getMedia().getProtocol().charAt(0) + "/" + mediaDescription.getMedia().getProtocol().substring(1);

	//display the codec used for each media type
	System.out.println(mediaType + ": " + codec);
}

In the code example above, we first create an SDP message as a string. We then create a SessionDescription object using the fromSDP() method of the SessionDescription class. We then use the getMediaDescriptions(true) method of the SessionDescription class to retrieve the media components of the session. Finally, we iterate through the media components to extract the codec information for each media type.

Media Handling:

SDP Library Android provides APIs for handling the media components of a session. The MediaStream class in the library provides an easy-to-use API for managing media streams. A MediaStream object represents a media stream for a session and encapsulates the necessary information to transmit media data, such as codecs and RTP/RTCP connections.

To set up media streaming for a session using SDP Library Android, you need to perform the following tasks:

  1. Select the codecs to use for the session.
  2. Set up the RTP/RTCP connections for the media streams.
  3. Create a MediaStream object and set the codec list and RTP/RTCP connections.
  4. Set the MediaStream object for the session.

The following code example demonstrates how to set up media streaming for a session:

SipSession session = getSipSession();

//select the codecs to use for the session
List<RtpCodec> codecs = new ArrayList<>();
codecs.add(RtpCodec.AUDIO_PCMU);
codecs.add(RtpCodec.AUDIO_PCMA);

//set up the RTP/RTCP connections for the media streams
RtpStream rtpStream = new RtpStream();
rtpStream.setLocalAddress(getLocalAddress());
rtpStream.setRemoteAddress(getRemoteAddress());
rtpStream.setLocalPort(5004);
rtpStream.setRemotePort(5004);
RtcpStream rtcpStream = new RtcpStream();
rtcpStream.setLocalAddress(getLocalAddress());
rtcpStream.setRemoteAddress(getRemoteAddress());
rtcpStream.setLocalPort(5005);
rtcpStream.setRemotePort(5005);

//start the media streams
rtpStream.start();
rtcpStream.start();

//create a media stream object
MediaStream mediaStream = session.createMediaStream();
mediaStream.setMediaType("audio");
mediaStream.setCodecList(codecs);
mediaStream.setLocalRtpStream(rtpStream);
mediaStream.setLocalRtcpStream(rtcpStream);

//set the media stream for the session
session.setMediaStream(mediaStream);

In the code example above, we first get a SipSession object using the getSipSession() method. We then select the codecs to use for the session and set up the RTP/RTCP connections using the RtpStream and RtcpStream classes. We then create a MediaStream object using the createMediaStream() method of the SipSession class. We set the codec list and RTP/RTCP connections for the MediaStream object and set the MediaStream object for the session using the setMediaStream() method of the SipSession class.

Conclusion:

SDP Library Android provides a comprehensive set of APIs for developing SIP-based communication applications for Android. The library provides support for SIP signaling, session management, SDP parsing, NAT traversal mechanisms, and media handling, making it a complete solution for building robust SIP applications. The sample code examples provided in this article can be used as a guide for integrating SDP Library Android into your Android applications.

Popular questions

Sure! Here are five questions and their answers related to SDP Library Android with code examples:

  1. What does SDP stand for and what is its purpose in SIP-based communication?

SDP stands for Session Description Protocol. It is used in SIP-based communication to describe the parameters of communication sessions, including codecs, media types, and network information.

  1. How can the SDP Library Android be used to handle SDP messages?

SDP Library Android provides APIs for parsing SDP messages and extracting the relevant session parameters. The SessionDescription class in the library provides an easy-to-use API for parsing SDP messages. The fromSDP() method of the SessionDescription class can be used to parse an SDP message and create a SessionDescription object. Once the SessionDescription object is created, you can retrieve various session parameters such as media types, codecs, network information, and so on.

  1. What are some features of SDP Library Android related to media handling?

SDP Library Android provides APIs to handle the media components of a session. The MediaStream class in the library provides an easy-to-use API for managing media streams. A MediaStream object represents a media stream for a session and encapsulates the necessary information to transmit media data, such as codecs and RTP/RTCP connections. The library also provides support for selecting codecs, setting up RTP/RTCP connections, and managing media streams.

  1. How can NAT traversal be accomplished using SDP Library Android?

SDP Library Android supports NAT traversal mechanisms, which enables two SIP endpoints to communicate even if they are behind NAT devices. This is accomplished by manipulating the SDP message in a way that allows the network to route the media traffic correctly.

  1. What are some common use cases for SDP Library Android, and how can developers get started with the library?

SDP Library Android can be used to build SIP-based communication applications for Android, such as voice and video calling, messaging, and more. Developers can get started with the library by downloading the library package from a source like Maven or Github and integrating it into their Android projects. They can then use the comprehensive set of APIs provided by the library to handle SIP transactions, manage sessions, parse SDP messages, traverse NAT devices, and handle media streams. Sample code examples (like the ones provided in the article) can be used as guides for building robust SIP applications with SDP Library Android.

Tag

AndroidSDPLib

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