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SIP network deployment made easy thanks to mDNS

Thanks to recent developments performed by our engineering team, Liblinphone and Flexisip are now able to use Multicast DNS in a local area network.

Our Flexisip SIP server has been added with mDNS capabilities so that the SIP service it is running gets advertised through mDNS, and in order to resolve other SIP nodes in the local network.

mDNS is available as a build-time option in Liblinphone mobile SDKs with versions greater than 4.0, and in development branch ("master") of Flexisip and Linphone-desktop projects.



100rel implementation in Liblinphone

The Session Initiation Protocol (SIP - RFC 3261) is a request-response protocol for initiating and managing communications sessions. SIP defines two types of responses, provisional and final. Final responses convey the result of the request processing, and are sent reliably, whereas Provisional responses provide information on the progress of the request processing, but are not sent reliably.

However, reliability proved to be important in several cases, including interoperability scenarios with the PSTN (standard telephony). Therefore, an optional capability was needed to support reliable transmission of provisional responses.

Reliable Provisional Response (100rel) is now supported in Linphone, as Liblinphone library implements the reliability mechanisms described in RFC 3262.


Liblinphone SDK available through GIT Maven repository

Until today, integrating Liblinphone SDK into a third party application required compiling a SDK from the sources or importing SDK binary files from our website. In order to facilitate the integration of this SDK in customers’ projects, we adapted a Gitlab repository as a Maven one.

Maven is a standardized tool to manage and build Java-based projects, which core unit of work is Project Object Model. With Gradle and this Maven repository, we now offer the ability to either host or import Liblinphone SDK remotely, as well as any future library.

More technical information is available on our Wiki.


Group chat now available in Linphone!

For many years, Linphone has been one of the most active communication software in the open source world. Originally focused on voice, additional functionalities were rapidly added, like video, instant messaging (IM) and presence.

Over the past year, most of our internal development resources have been dedicated to the big challenge of developing Linphone’s own implementation of group Instant Messaging.
The whole Linphone team is now delighted to offer the first entirely SIP-based open source solution for multi-participant Instant Messaging.



Linphone enhanced adaptive bitrate control

Linphone has now a brand-new algorithm to adapt the audio and video codec bitrates to the available bandwidth, and hence optimize audio and video quality.

The two objectives of our brand new adaptive bitrate algorithm are then to :

  • Detect network congestion, so that the output bitrate of the encoder can quickly be reduced, which allows to recover an optimal latency and stop video artefacts caused by packet losses
  • Detect the bandwidth capacity available, so that the output bitrate of the encoder can be increased dynamically up to this capacity in order to offer the best possible audio and video experience to the users.

Our algorithm operates by doing at receiver side some statistical analysis of timings of arrivals of audio & video packets, and send target bitrate commands to the remote audio and video encoders.



Linphone 4.0 for desktop platforms is available!

Our engineering team intensively worked in the past few months on the development of our new Linphone 4.0 app for desktop platforms. We are glad to announce that this new version has officially been released on June 14!

We consequently improved the app’s look and feel with a more user-friendly and modern user interface. We also implemented various new features to bring new specific possibilities for a desktop usage and reach the same level of usability as in our mobile versions.



IM Delivery status now available in Linphone for iOS and Android

With our latest Linphone-Android and iOS versions, you can now clearly see the delivery status of your instant messages : delivered, read, error...

Based on parts of RFC 5438, Instant Message Delivery Notifications have been implemented so that Linphone users can see delivery status of each sent message.

Following status have been added :

  • delivered : successfully received by the recipient client, but not read yet
  • read : successfully delivered and read
  • error : not delivered. It is then possible to resend the undelivered message



Creation of a Liblinphone C# wrapper for Xamarin

We are pleased to announce that we have developed a C# wrapper that can be used for the development of Xamarin apps based on LibLinphone, our cross-platform VoIP library.

Developing native apps for several major platforms might be time consuming and expensive as it requires code duplication and coding skills in different languages. Thus, Xamarin has become a very appreciated tool to develop mobile apps, as it allows developers to easily share common app code across iOS, Android and Windows platforms while still delivering fully native experiences for each platform.

With our Xamarin SDK and C# wrapper, developers can now use Xamarin tool to write Liblinphone-based Android and iOS apps with either native user interfaces or Xamarin Forms.



Introduction to our new RTP adaptive jitter buffer algorithm

Recent Linphone releases now incorporate a new RTP jitter buffer algorithm, which is the result of an internal R&D program started two years ago by Belledonne Communications. The benefits of this new algorithm is an improved audio & video quality.

The adaptive nature of the jitter buffer resides in the fact that it has to measure the network transmission characteristics in order to choose the most adequate latency to be applied in order to maximise the audio experience. More latency decreases the number of underruns, preserving audio quality, however unnecessary latency is detrimental for real time conversations.

Our new algorithm, compared to the former one, more finely estimates the clock skew between sender and receiver and the network jitter, thanks to linear regression techniques applied on the timestamp information carried by received RTP packets.



Linphone smart contact list, a major new feature

Linphone’s address book becomes a smart contact list : you can now quickly and clearly see which of your friends have a account.

Linphone imports your contacts’ phone numbers from your phone’s address book and automatically tags with a Linphone icon the contacts who have created an account on free SIP service.You can also filter your contacts to only display such Linphone users.