Cross-Platform SIP Client (Audio/Video, P2P + Conferencing) — iOS, Android, Windows, macOS

@augurstech

A Warm Hello! We are readily available to start working on this project! Your project aligns exceptionally well with our expertise in real-time communications, SIP/VoIP systems, video conferencing, and cross-platform application development. The combination of registration-less SIP calling, multi-platform support, video conferencing interoperability, BFCP screen sharing, and codec compatibility requires a team that understands both telephony protocols and modern application architecture. We would be excited to partner with you to deliver a production-ready SIP client that meets your July 2026 deadline while maintaining performance, interoperability, and long-term maintainability. We will provide you cross-platform SIP client capable of: - Registration-free peer-to-peer SIP audio/video calls - Optional SIP registration for future deployments - Joining third-party video conferences - Multi-codec audio/video support - BFCP-based screen sharing - Participant list visibility - Shared core architecture across all platforms - Full source code ownership and GitHub access We look forward to discussing your target conferencing environments, interoperability requirements, and deployment strategy in greater detail. Best regards, Ana

@diektech

Hi — Elias here from Miami. I see you're developing a cross-platform SIP client for audio and video communications. The goal is to create a reliable and scalable solution across multiple platforms. What usually matters most here is ensuring seamless performance and low latency during calls, especially in P2P and conferencing scenarios. A common issue in systems like this is managing complex workflows and integrations across devices. The tricky part is ensuring state management and permissions align correctly, which can be challenging in real-time communications. My approach would involve a modular architecture, focusing on robust backend services that can scale as user demands grow. This will facilitate future feature expansions while ensuring maintainability. I have experience with similar VoIP solutions, tackling integration and performance challenges for a smooth user experience. A few questions to better understand the scope: Q1 – What specific user roles and access controls do you envision for the application? Q2 – Are there particular integrations with existing systems that you require? Q3 – How do you plan to handle data privacy and security for user communications? Happy to discuss the details and suggest the best technical approach. Looking forward to hearing from you.

@corpmember29

HELLO, I HAVE CAREFULLY REVIEWED YOUR REQUIREMENTS AND UNDERSTAND THAT YOU NEED A CROSS-PLATFORM SIP CLIENT SUPPORTING P2P AUDIO/VIDEO CALLING, OPTIONAL SIP REGISTRATION, CONFERENCE JOINING, BFCP SCREEN SHARING, AND MULTI-PLATFORM DEPLOYMENT ACROSS IOS, ANDROID, WINDOWS, AND MACOS. I HAVE 10+ YEARS OF EXPERIENCE IN VoIP, SIP, RTC, VIDEO STREAMING, CROSS-PLATFORM DEVELOPMENT, AND TELECOMMUNICATION SYSTEMS, I CAN DELIVER A SCALABLE AND PRODUCTION-READY SOLUTION WITH FULL SOURCE CODE OWNERSHIP. FOR THIS PROJECT, I WOULD RECOMMEND PJSIP AS THE CORE SIP STACK DUE TO ITS MATURITY, CROSS-PLATFORM SUPPORT, STABILITY, CODEC FLEXIBILITY, AND STRONG SUPPORT FOR CUSTOM SIP WORKFLOWS. A SHARED SIP ENGINE CAN BE DEVELOPED AS A COMMON CORE LAYER AND INTEGRATED ACROSS ALL TARGET PLATFORMS TO MAXIMIZE CODE REUSE. THE SOLUTION WILL INCLUDE: • 1:1 SIP AUDIO/VIDEO CALLING • OPTIONAL SIP REGISTRATION • Conference Joining Support • H.264 / H.265 Video Codecs • Opus, G.711, G.722, G.729 Audio Codecs (LICENSING PERMITTING) • BFCP SCREEN SHARING • Participant List Retrieval VIA DIRECT OR PROXY APPROACH • GITHUB-BASED SOURCE CODE MANAGEMENT • CLEAN AND USER-FRIENDLY UI PROPOSED MILESTONES: • Architecture & SIP Core Setup • Calling & Media Features • Conference & BFCP Integration • Cross-Platform UI Development • Testing, Optimization & Deployment I EAGERLY AWAIT YOUR POSITIVE RESPONSE. THANKS

@rahuliitm69

Hi there, I have my own team, and we have worked on video calling, real-time communication, SIP, WebRTC, and conferencing-based applications, so we can build your cross-platform SIP client across iOS, Android, Windows, and macOS and deliver within timeline. As your application requires peer-to-peer SIP calling, optional registration, video conferencing support, BFCP screen sharing, participant management, and multiple codec support, we will first finalize the core communication architecture and select the most suitable stack between PJSIP and baresip based on long-term maintainability and feature compatibility. We will also design the application in a way that the SIP engine can be shared across platforms while keeping the UI native and user-friendly, and ensure all source code is maintained in your GitHub repository throughout development. We would request to connect once so we can discuss and finalize the milestone plan against your July 2026 deadline. Thanks, Rahul A.

@Herculesz

Hi I can build the cross-platform SIP client with 1:1 P2P calling, optional SIP registration, audio/video support, and conference-join capability across iOS, Android, Windows, and macOS. I have experience with PJSIP/baresip, SIP signaling, RTP/SRTP, H.264/H.265, Opus, G.711, G.722, G.729 licensing considerations, BFCP, WebRTC-style media flows, and cross-platform VoIP app architecture. For this scope, I would lean toward PJSIP because it is mature, portable, and better suited for sharing a common SIP/media core across all four target platforms. The main technical challenge is supporting no-registration P2P SIP calls while also joining varied video conference systems that may expose participants and screen sharing differently. I will solve this with a shared SIP engine, platform-specific UI wrappers, configurable account/registration logic, codec negotiation, BFCP handling where supported, and fallback backend proxy logic for participant-list retrieval. For conference compatibility, I would first define supported SIP/H.323/WebRTC gateway paths rather than assuming every proprietary platform can be joined directly. I can provide clean source code in your GitHub repo, documented build steps, and a practical milestone breakdown after reviewing the exact conference targets. Thanks, Hercules

@DrSyafiq

The SIP client scope is serious because the risk is not only UI; it is codec support, BFCP, optional registration, conference joining, participant discovery, and sharing one reliable SIP core across mobile and desktop before the July deadline. I would propose validating PJSIP first unless licensing or platform constraints make baresip more suitable, then building a small proof milestone that covers 1:1 audio/video, optional registration, and conference join behavior before expanding to all platforms. BFCP and participant-list retrieval should be designed early, including the backend/proxy path for platforms that do not expose participants cleanly. For this project, I would focus especially on: - PJSIP/baresip stack decision, codec feasibility, and G.729 licensing reality - Shared SIP engine strategy across iOS, Android, Windows, and macOS - BFCP screen sharing, participant-list proxy, and conference interoperability tests - Milestone plan from proof of call to UI polish, repo handover, and release builds If helpful, I can start with a milestone breakdown that identifies what is realistic before the end-of-July deadline. Best, Dr. Syafiq

@vladang

Building a cross-platform SIP client without mandatory registration is mostly about getting the media core and signaling boundaries right from day one. I’d go with PJSIP because it gives consistent SIP + media stack across mobile and desktop and wrap a shared C/C++ core so iOS Android Windows and macOS in sync. First step is stabilizing P2P call flows (SDP negotiation, NAT traversal via STUN/TURN, codec fallback for Opus/G.711/G.722, and graceful handling when H.265 isn’t available). I’d layer optional registration without coupling it to call initiation. For BFCP I’d treat as a parallel control channel with fallback to RTP-based screen share when unsupported. Participant lists proxied through a lightweight backend that maps conference sessions to SIP dialogs. At Bubbl I worked on real-time calling flows with Vue/Nuxt and Express, keeping latency and state consistency tight. Timeline feels if milestones are split per platform wrapper, media core, and conferencing layer. When’s your expected conferencing provider scope finalized?

@opencollar

Hi, I see you need a smooth way for users to make direct calls without registration and join conference calls easily. I will focus on building a reliable SIP engine that works on all platforms using PJSIP, which I believe is a great fit because of its flexibility and support for the codecs you need. For screen sharing with BFCP and participant lists, I will implement a simple but effective method to pull info from your server, keeping everything clear and up-to-date. The optional registration will be built in so you can enable it later without fuss. I believe good communication, high quality, and timely delivery are key to helping your business grow; I will also support you after the project wraps up. Let's chat about your plan and create something bigger together. Regards, Nick

@Srashtasoft

Hi there, I have read your project requirements. You need a cross-platform SIP/VoIP client supporting P2P calls, optional SIP registration, and multi-platform video conferencing (iOS, Android, Windows, macOS) with full codec support, BFCP screen sharing, and scalable architecture using PJSIP or Baresip with a clean UI and shared core engine. We can design a modular VoIP architecture using PJSIP (preferred for full SIP stack control and multi-platform stability) with a shared core engine handling SIP signalling, media negotiation, codec management, and conferencing integration, while platform-specific UI layers will be built separately for iOS, Android, and desktop apps. To proceed further, I need a few clarifications: ===================================== Do you want native UI for each platform or a unified framework like Flutter/Electron with a native SIP core? Should conferencing support third-party systems (Zoom/Teams/WebRTC rooms), or only SIP-based rooms? Do you already have a signalling server, or should we design backend infrastructure as well? Is G.729 strictly required (licensing implications), or can we prioritise Opus for all audio scenarios? Best Regards, SrashtaSoft Team

@tangramua

Dear ,   We carefully studied the description of your project and we can confirm that we understand your needs and are also interested in your project. Our team has the necessary resources to start your project as soon as possible and complete it in a very short time.   We are 25 years in this business and our technical specialists have strong experience in Java, Mobile App Development, Android, VoIP, Software Development, iOS Development, Audio Processing, SIP, WebRTC, Video Conferencing and other technologies relevant to your project.   Please, review our profile https://www.freelancer.com/u/tangramua where you can find detailed information about our company, our portfolio, and the client's recent reviews.   Please contact us via Freelancer Chat to discuss your project in details.   Best regards, Sales department Tangram Canada Inc.     

@mrresearcher99

Hi there, I’ve reviewed your Flutter app requirements and would love to help. With 5+ years of experience in cross-platform development, I specialise in clean UI, smooth performance, and robust API integration. I’ll begin with clear planning, share regular progress updates, and ensure the app is fully tested before launch. Let’s connect to discuss your vision — I’m ready to get started! Best, Bhargav Flutter Developer | Android & iOS Expert

@Ekarthaan

Hi huahmad84, Last week I shipped a cross‑platform SIP client with P2P, H.264/Opus, and BFCP; this is very close, so I’m confident to handle yours really well. Stack choice: I’d use baresip (+re/rem). It has solid BFCP, clean C core I can share across iOS/Android/Windows/macOS, good hooks to hardware H.264/H.265, and stable audio codec modules. Simple, reliable, and easy to maintain. BFCP + participants: Screen share via baresip’s BFCP module. For participant list, I’ll add a tiny proxy service that maps Call‑ID/dial‑in to Zoom/Teams/Webex (or SIP trunk) APIs and pushes a clean list to the app via WebSocket. Works even when SIP doesn’t expose names. UI: Clean, minimal dial/join and share flow, clear device and codec controls. Milestones (no dates): - M1 P2P A/V + ICE/STUN/TURN - M2 Video (H.264/H.265) + full audio set - M3 BFCP + conference join flow - M4 Participant proxy, interop + soak tests i would like to know the below. - Which conferencing platforms/trunks must we interop with for join + participants? - Do you already hold H.265/G.729 licenses, or should I ship them as opitonal toggles? I think we should. - Use geo‑redundant TURN and strict codec fallbacks to reduce call setup failures. - Add automated call‑quality checks and crash log autosubmit to cut rework. Lets follow a plan like this. 1) I confirm requirements and finalize codecs/NAT/UI. 2) I build the shared SIP core and wire simple UIs; deliver P2P A/V

@Mahihassi

As a highly experienced and versatile AI & Embedded Systems Engineer, specializing in complete intelligent product development, I bring a unique blend of skills that makes me the ideal candidate for your SIP Client project. My background in developing end-to-end solutions, combining hardware, firmware, cloud, and mobile applications will be invaluable for creating a high-quality VoIP/SIP client for iOS, Android, Windows, and macOS platforms. With regards to stack selection, I would propose leveraging the power of PJSIP for this project. Being an open-source multimedia communication library, PJSIP is mature and robust with excellent codec support - including the codecs mentioned in your requirements (H.264, H.265, Opus, G.711, G.722, G.729). BFCP and participant-list proxy are critical components for any modern SIP client application and I assure you of my knowledge in effectively implementing these components for optimal performance and seamless experience. Best, sardar (ceo MHTechFusion)

@skalogir

Hi there, I understand you need a cross-platform SIP client for iOS, Android, Windows, and macOS supporting registration-free 1:1 SIP calls, optional SIP registration, audio/video codecs, conference joining, BFCP screen sharing, participant retrieval, source delivery to your GitHub repo, and a clean user-friendly UI by July 2026. I have experience with VoIP/SIP architecture, PJSIP/baresip-based clients, WebRTC-style media flows, codec handling, cross-platform native builds, and real-time communication apps with maintainable shared core logic. I would recommend PJSIP for broader platform maturity, native media support, and extensibility, then implement a shared SIP/media core with platform-specific UI wrappers, evaluate BFCP support carefully, design a backend participant-list proxy where direct conference access is limited, and deliver in milestones covering engine, calling, conferencing, screen sharing, QA, and deployment. Q1: Which conferencing platforms must be supported first? Q2: Do you already have SIP servers, TURN/STUN infrastructure, or test conference endpoints? Q3: Should the first release prioritize call reliability over advanced UI polish? Best regards.

@Guptapuru304

Hello, We've thoroughly reviewed your project details for developing a cross-platform SIP client, supporting both P2P calls and conference video joining across iOS, Android, Windows, and macOS. This project aligns perfectly with our expertise in building intelligent, scalable applications with a focus on robust audio and video capabilities. Previously, we've successfully delivered a similar project using PJSIP for a VoIP solution that integrated seamlessly across multiple platforms, ensuring smooth audio/video communication with minimal latency. Our experience guarantees we can meet your codec requirements, including H.264, H.265, Opus, and G.711, and implement BFCP for screen sharing. With our top 1% standing on Freelancer.com and a track record of 200+ satisfied clients over the past 8 years, we bring unparalleled expertise in VoIP, mobile app development, and SIP protocol implementation. Our proficiency in Java, Android, iOS development, and audio processing makes us highly suitable for this project. Our AI-first approach and commitment to uncompromised quality ensure that the solution will be both intelligent and user-friendly. We invite you to message us with further details so we can provide a tailored proposal within 24 hours, outlining the stack we recommend and how we'll tackle the BFCP and participant-list proxy requirements. Looking forward to collaborating with you on this impactful project. Best regards, Puru Gupta

@ZohaibRoy

⭐⭐⭐⭐⭐ Build a Cross-Platform SIP Client for P2P Calls and Video Conferencing ❇️ Hi My Friend, I hope you're doing well. I've reviewed your project details and see you are looking for an experienced VoIP/SIP developer. You don’t need to look any further; Zohaib is here to help you! My team has successfully completed 50+ similar projects for VoIP applications. I will create a user-friendly SIP client supporting P2P calls and video conferences, ensuring it meets all your requirements. ➡️ Why Me? I can easily build your cross-platform SIP client as I have over 5 years of experience in VoIP development, specializing in SIP protocols, audio/video codecs, and user interface design. My expertise includes PJSIP, WebRTC, and backend integration. I also have a strong grip on cross-platform development, ensuring a seamless experience across iOS, Android, Windows, and macOS. ➡️ Let's have a quick chat to discuss your project in detail and let me show you samples of my previous work. Looking forward to discussing this with you in our chat. ➡️ Skills & Experience: ✅ VoIP Development ✅ SIP Protocol ✅ PJSIP & baresip ✅ WebRTC ✅ Audio/Video Codecs (H.264, Opus) ✅ User Interface Design ✅ Cross-Platform Development ✅ BFCP Implementation ✅ Backend Integration ✅ GitHub Management ✅ Code Optimization ✅ Problem Solving Waiting for your response! Best Regards, Zohaib

@melikatfz

Hi there, Developing a cross-platform SIP client with robust features like yours can be complex, often leading to compatibility and performance issues across devices and platforms. With my extensive experience in VoIP and SIP development, I can ensure seamless P2P calls and video conferencing through a carefully chosen stack like PJSIP or baresip. My approach will prioritize efficient codec integration and a clean UI, meeting all your core requirements within the hard deadline. Here are my questions: What level of customization do you need on the user interface? Can you share more about your preferred backend for participant list retrieval? Drop me a message so we can get started right away!

@codefusion53

Hi, I can help build a cross-platform SIP client with audio/video calling, optional SIP registration, and a shared core architecture across iOS, Android, Windows, and macOS. For this project, I would recommend starting with PJSIP because it has strong SIP/RTP support, mature cross-platform capabilities, good codec extensibility, and a practical path for maintaining one core VoIP layer with platform-specific UI wrappers. I would validate H.264, Opus, G.711, and G.722 first, then assess H.265 and G.729 based on platform support and licensing constraints. For BFCP and participant list handling, I would treat them as dedicated technical milestones. BFCP support should be tested against target conference systems early, since interoperability can vary. For participant lists, I would implement direct retrieval where supported, and design a backend proxy approach for platforms where participant data must be normalized from APIs or conference bridge metadata. I can work with your owned GitHub repository, provide clean source code, and maintain clear technical documentation throughout development. Best, Justin

@mahig47

Hello! As per your project post, you’re looking to develop a cross platform SIP client that supports both direct peer to peer communication and enterprise grade video conferencing workflows across iOS, Android, Windows, and macOS. The goal is to create a modern, reliable VoIP application capable of handling audio, video, screen sharing, conference participation, and optional SIP registration while maintaining flexibility to integrate with various conferencing environments. My focus will be on delivering a complete SIP communication platform featuring: registration free SIP calling, optional SIP account registration, high quality audio and video calling, support for H.264 and H.265 video codecs, Opus, G.711, G.722, and G.729 audio codecs where licensing permits, BFCP based screen sharing, participant list retrieval mechanisms, conference interoperability, secure media transport. I specialize in real time communication systems, VoIP platforms, SIP protocol development, WebRTC integrations, multimedia streaming, and cross platform application development. My focus will be on building a stable and production ready solution with strong media performance, interoperability, and maintainable code architecture. Let’s connect to discuss the SIP architecture, media stack selection between PJSIP and Baresip, interoperability requirements, and the roadmap for delivering a robust cross platform communication client. Best regards, Nikita Gupta.