Full-Stack Webinar Platform with Live Video Streaming
The Problem
An education technology company needed a webinar platform that could deliver live, accessible learning experiences to large audiences. Their existing tools could not combine reliable video streaming with real-time speech-to-text transcription, screen sharing, and interactive audience engagement in a single, scalable product. They needed accessible-by-default design — live subtitles were not an add-on feature but a core requirement for inclusive education. The platform had to handle hundreds of concurrent viewers per session, maintain stable performance under high traffic, and provide the interactive tooling that keeps online learners engaged.
Why Building an Accessible Webinar Platform Is Hard
Live education webinars combine the reliability demands of broadcast media with the accessibility requirements of inclusive design and the engagement challenges of virtual classrooms:
- Real-time speech-to-text must be accurate and instant — live subtitles need to appear within seconds of the speaker's words with accuracy high enough to be educational. Poor transcription is worse than none — it creates a false sense of accessibility while delivering unusable content
- Video streaming and screen sharing must coexist seamlessly — presenters switch between camera, slides, and screen sharing during a session, and each transition must be smooth with no audio gaps or frozen frames
- Large audience scalability with interactive features — hundreds of concurrent viewers need stable video while participating through chat, Q&A, polls, and reactions, with neither degrading the other
- Accessibility is architectural, not cosmetic — real-time subtitles, keyboard navigation, screen reader support, and inclusive design patterns must be built into the platform's core, not layered on afterward
- High availability for scheduled education events — webinars are scheduled events with enrolled audiences; downtime during a live session means hundreds of learners lose access at once, with no try-again fallback
- Full-stack build from open-source foundations — Jitsi Meet provides the video core, but extending it with speech-to-text, custom engagement tools, and enterprise-grade scalability requires significant custom engineering
What We Did
Architecture & Video Infrastructure
- Designed the full-stack architecture with NestJS backend services on Node.js, leveraging Jitsi Meet as the open-source video conferencing foundation for reliable, self-hosted webinar delivery
- Deployed on AWS with auto-scaling infrastructure optimized for webinar traffic — pre-warmed capacity for scheduled events and elastic scaling for unexpected audience growth
- Established Firebase for real-time data synchronization — chat messages, Q&A submissions, poll responses, and engagement metrics delivered with sub-second latency
Core Webinar Platform
- Built the webinar experience with live video streaming, screen sharing, and presenter controls — optimized for educational content with smooth transitions between camera and presentation modes
- Developed the audience interface with live video playback, real-time subtitles overlay, interactive chat sidebar, Q&A panel, and polling tools — all working simultaneously without degrading video performance
- Implemented the presenter dashboard — session scheduling, audience management, screen sharing controls, recording triggers, and real-time engagement analytics
Accessibility & Speech-to-Text
- Integrated real-time speech-to-text transcription that generates live subtitles during sessions — displaying synchronized captions with speaker identification for multi-presenter events
- Built the subtitle rendering system with customizable display options — font size, position, contrast settings, and language preferences — usable across diverse accessibility needs
- Implemented post-session transcript generation — full searchable transcripts produced from the live speech-to-text data, available for review and download after each webinar
Scalability & Engagement
- Built interactive audience tools — live polls with real-time results, moderated Q&A with upvoting, emoji reactions, and hand-raise functionality — synchronized across hundreds of participants via Firebase
- Load-tested the platform for high-traffic webinar scenarios — hundreds of concurrent viewers with active chat, polling, and subtitle rendering running simultaneously
- Implemented connection quality monitoring and adaptive streaming to maintain stable video delivery across varying audience network conditions
Key Results
In Their Words
The platform transformed how we deliver online education. Live subtitles mean every learner can follow along, and the interactive tools keep audiences engaged in ways pre-recorded content never could.
Their proactive team gets things done as if it were their own project.
What We Learned
Accessibility done right improves the experience for everyone, not just those who need it
We built real-time subtitles as a core feature for hearing-impaired learners. What we discovered is that the majority of attendees turned subtitles on regardless of hearing ability — they helped with comprehension, note-taking, and following along in noisy environments. The subtitle system became the platform's most-used feature. Designing for accessibility did not create a niche feature; it created a universally valued one.
Speech-to-text accuracy is a pipeline problem, not a model problem
The raw transcription model produces reasonable output, but turning that into usable live subtitles requires a complete pipeline: audio pre-processing for varying microphone quality, speaker diarization for multi-presenter events, punctuation restoration, timing alignment with the video stream, and graceful handling of corrections as the model refines predictions. We built each stage as an independent, tunable component.
Interactive features during live education need rate limiting and moderation by design
A webinar with 300 engaged learners generates a volume of chat, Q&A, and poll responses that can overwhelm both the UI and the backend. We built rate limiting, message queuing, and moderation controls into the engagement layer from day one — not as restrictions, but as quality controls that keep the experience useful rather than chaotic. Firebase handled delivery; the NestJS backend handled curation.
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