Low-Latency Video: Building a Real-Time AV Pipeline with WebRTC, SRT, and FPGA

In today’s broadcasting and ProAV ecosystems, latency is everything. A delay of just a few hundred milliseconds can ruin a live concert stream, break interactivity in remote collaboration, or misalign sound and video in synchronized installations. With demand growing for real-time AV solutions in education, medical, and industrial scenarios, the pressure is on vendors and developers to minimize latency at every stage of the signal path.

In this article, we explore how to build a truly low-latency video pipeline using WebRTC, SRT, and FPGA technologies. We'll cover why these technologies matter, how they fit together, and what architectural decisions impact performance.

Understanding the Low-Latency Challenge

Low latency isn't just a nice-to-have feature—it's mission-critical in many deployments. Latency affects:

• Real-time remote control (e.g., surgical robots, UAVs)
• Live broadcasting and sports
• Interactive classrooms and telepresence
• Industrial inspection and automation
• ProAV installations with multi-screen and audio-video sync

The total delay is often a sum of multiple stages: sensor capture, encoding, transport, decoding, buffering, and rendering. Each millisecond counts.

Key Technologies: WebRTC, SRT, and FPGA

Let’s take a closer look at the three core technologies and their role in reducing latency.

WebRTC: Peer-to-Peer Real-Time Communication

Originally developed for web browsers, WebRTC has grown into a robust protocol suite for low-latency audio/video transmission over UDP. It includes:

• Secure transport (DTLS, SRTP)
• Adaptive bitrate and congestion control
• NAT traversal (ICE/STUN/TURN)
• Built-in echo cancellation and jitter buffering

It’s now used far beyond browsers, in STBs, conferencing solutions, and AV-over-IP devices. WebRTC excels in <200 ms roundtrip time scenarios, especially in LAN or CDN-edge deployments.

SRT: Secure Reliable Transport

SRT is a UDP-based open-source protocol created to transport high-quality video across unpredictable networks. It introduces forward error correction, encryption, and adaptive retransmission.

SRT is often used when point-to-point contribution feeds must deliver high bitrate content reliably, such as:

• Camera-to-studio links
• Studio-to-cloud workflows
• Multisite distribution

Its latency is tunable (as low as 50 ms), depending on buffer size and packet loss conditions.

FPGA: Hardware Acceleration for AV Processing

Even with efficient transport protocols, encoding and decoding remain bottlenecks. Software-based codecs introduce unavoidable delay due to CPU scheduling and memory latency.

FPGAs offer:

• Deterministic latency for video pipelines
• Hardware-accelerated H.264/H.265 codecs
• Real-time scaling, filtering, and color space conversion
• Integrated TSN or custom AV bridges

Integrating FPGAs on edge devices (e.g., cameras, encoders) helps eliminate the "software tax" from critical stages.

Building a Real-Time Pipeline: Key Architectural Considerations

A low-latency AV system is more than just dropping in the right protocols. Here’s what to plan:

1. Minimize Buffers

Each stage in the pipeline—from camera sensor to display—should use minimal buffering. This includes encoder delay, protocol jitter buffers, and player queues. FPGA-based designs can remove software queues altogether.

2. Synchronize Audio and Video

Out-of-sync streams are a common issue. Using hardware timestamping (e.g., PTP over Ethernet or FPGA-timed I/Os) helps keep A/V aligned across distributed systems.

3. Optimize for Network Type

• LAN or private 5G: Use WebRTC with aggressive bandwidth estimation and fast ICE restarts
• WAN or internet-based contribution: Use SRT with constrained latency and encryption
• Hybrid environments: Combine WebRTC at the edge with SRT for upstream ingest

4. Use Smart Encoders

Hardware codecs on FPGA can be optimized for real-time use cases, e.g., intra-only frames, low GOP size, CABAC bypass, etc. Promwad has experience building such IP cores and integrating them into camera or encoder products.

Use Cases and Industry Applications

Live Broadcasting

Broadcasters are moving to IP contribution workflows, where remote cameras send content over SRT or WebRTC. FPGA accelerators allow sub-frame latency from lens to studio.

Telepresence and Conferencing

Corporate and educational AV systems increasingly rely on WebRTC and AV-over-IP protocols. Paired with edge AI (e.g., speaker tracking), these systems demand low jitter and ultra-low delay.

ProAV Installations

LED walls, projection mapping, and immersive theaters require strict frame alignment. FPGA-based AV routers and sync bridges keep displays in lockstep.

Industrial Automation

In machine vision or robotics, AV is just one signal among many. Promwad has built FPGA platforms where video, sensor data, and control loops run in parallel with shared time base.

How Promwad Can Help

We support clients in developing end-to-end low-latency video pipelines. Our services include:

• FPGA firmware for H.264/H.265 with ultra-low-latency profiles
• Embedded software with SRT and WebRTC stack integration
• AV system architecture and multi-protocol routing
• Compliance with SMPTE ST 2110, IPMX, and proprietary ProAV formats

We also offer custom hardware design for AV encoders, decoders, and matrix switches with integrated low-latency paths.

Conclusion

Achieving low latency is not about one technology—it’s about the synergy of WebRTC, SRT, and FPGA in a carefully designed system. From protocol tuning to hardware acceleration, every layer counts.

As the demand for real-time AV continues to grow, vendors who prioritize architectural coherence and deterministic performance will set the standard.

At Promwad, we bring this vision to life with engineering expertise that spans hardware, firmware, and protocol-level development.

Let us help you build the AV systems of tomorrow, today.