Solving issues on 2 Applications - PC (Mjsip) and Android (Sipdroid) for sending-receiving Voip.

INTRODUCTION I'm developping a software that needs, among various other functionalities, to perform Voip communications. I have one applications on PC side and another on Android side. I'm using as Voip library: on Android clients the libraries "Sipdroid"; on Pc clients the library "Mjsip". I have some issues to be solved. I'll provide to the Freelancer 2 simple apps (the source code), one for PC (in Java, developped on Netbeans) and one for Android (on Android Studio). Each app simply send and receive voip packets: the 2 applications perform only the pure Voip job: no GUI is required; no signalling is needed for call setup, it is already done by my main application. The voip comunication is pure peer-to-peer, so it works without any server. Being the 2 applications already done, the developper doesn't have to write those, it has only to solve some issues. TARGET - To get perfectly working the 2 applications, in order to have voip calls between: a) 1 android and 1 PC (that is for me the most important case) b) 2 androids c) 2 PCs - The job is done and specs are 100% satisfied when the 2 applications allow to have a voip call with very good quality, without any speech lost or delay, in the mentioned cases a), b) and c). - The codecs to be used/implemented must be at least: OPUS, GSM, PCMA, PCMU. It means that the 2 appplication must be able to work at least with all the 4 codecs. Inside the code here provided, the selection is done by setting a parameter. - The application for PC must work with whatever PC, Windows or Linux, so not depending from audio board for example. - The application for Android must work with whatever Android device, with Android 4.0 version or later. - On transmitting, the voice trasmission (then the Voip packet sending) must start immediately after the method is invoked, without any delay. - On receiving, the voice playing on speaker must start immediately after the method is invoked and packet are received, without any delay. - The developper will have to get available some static methods (to be invoked from classes of my main application) to activate/disactivate: - SpeakerPhone (only on Android side); already developped - Bluetooth (only on Android side) ; already developped - Mute of microphone (both PC and Android side) KNOWN ISSUES - On PC side, it works with only some PC, depending from audio board; the freelancer will have to sove this problem so to work properly indipendently from PC used. - On PC side, GSM codec doesn't work properly. - On both PC and Android side, Opus codec is missing, so the freelance has to provide (it is available on the web) and get it working. - On Android side I have different behaviours depending from Android device; for example with some devices I loose the first 2-3 seconds of speech. - Other issues can be present, but not discovered by me. GENERAL - The source code must be delivered to the buyer. - The developper will have to support me (replying to my questions for clarification), when I'll have to integrate his job inside my main application. - The developper will have to support me (replying to my questions for clarification), about parameters to be used for optimization of voip. - The application for PC must be opened in Netbeans IDE, without any adaptation. - The application for Android must be opened in Android Studio IDE (ver 1.3.2), without any adaptation. MILESTONE Due to one freelancer that tryied to do a fraud, and also according to Freelancer site best practize, I'll NOT pay any milestone in advance. Any milestone will be realised when I'll get the source code with some targets reached.