Adaptive Bitrate (ABR)

What is Adaptive Bitrate?

Adaptive Bitrate (ABR) is a streaming technique that automatically adjusts the quality of a video stream in real-time to match the user's available bandwidth and CPU capacity. The goal is to provide the best possible experience—minimizing buffering or freezing—even if network conditions fluctuate.

How It Works

The client (video player or WebRTC engine) constantly monitors network performance metrics like throughput, packet loss, and latency. If the connection weakens, ABR lowers the bitrate (and often the resolution), resulting in a fuzzier image but continuous playback. When the connection improves, it scales the quality back up.

ABR vs. Simulcast

While both solve similar problems, they work differently:

• ABR (Sender-side): In a 1-to-1 call, the sender's encoder adjusts its single output stream based on feedback from the receiver.
• Simulcast (Receiver-side/SFU): The sender produces multiple streams (Low, Mid, High). The central server (SFU) decides which stream to forward to each receiver based on their individual bandwidth.

Why It Matters

Without adaptive bitrate, a temporary network dip would cause the video to freeze completely. ABR ensures that the conversation continues seamlessly, prioritizing audio and motion over pure visual sharpness when necessary.