Posts

Showing posts from October, 2018

Measuring WebRTC video quality for different bitrates - Playing with VMAF

Image
I've been wanting to play with Netflix Video Multi-Method Assessment Fusion (VMAF) for a while and yesterday I found the time and the motivation to give it a try.

Netflix VMAF is an algorithm to generate a video quality score by comparing a reference image/video with a distorted image/video.   To do that VMAF calculates scores using tradicional image quality metrics like VIF or DLM and then aggregate them using a Machine Learning model (SVM) trained with the videos and scores coming from real users.  Smart, isn't it?  (You can see a high level description of those metrics that are aggregated in this Netflix post or the Wikipedia page)

It is important to notice that VMAF works in a per-frame base so it is NOT a good tool to measure the quality impact of many artefacts happening in Real Time Communications (delays, reduced/frozen framerate, audio/video desync).   However we can use it to measure the impact of different encoding settings like the average bitrate of the encoding.