Low Latency Video Digital Encoding Introduction

Written 2021-08-16

Tags:H264 Video OpenHD NTSC 


This is the introduction to a series of posts about digital video encoding, focused on low latency optimization. It's well-known that NTSC's framerate is 29.97Hz(~33.4ms) and fieldrate(half frame to be interleaved) is 59.954(~16.7ms), but the actual latency is much less, just the time required to acquire, filter, modulate, transfer, demodulate, and display. This means that while the whole display may only update 30 times per second, the average age of each pixel value can be almost as low as half that. Assuming no additional delays which are common on LCDs.

But, for many digital streaming systems, frames may buffered several times along the way, which is appropriate for certain tasks, but usually not for low-latency video. I'll discuss where and why that happens, and potential ways around it. Sometimes, I'll use OpenHD as an example.