How to Encode VP9 Video with FFmpeg: libvpx-vp9 CRF, Bitrate, and Quality Guide

#ffmpeg #webdev #video #programming

Originally published at ffmpeg-micro.com

VP9 is Google's open, royalty-free video codec. It powers most of YouTube's streaming library, and every modern browser supports it through the WebM container. If you need high-quality web video without licensing headaches, VP9 with FFmpeg's libvpx-vp9 encoder is the standard choice.

This guide covers the practical settings: CRF mode, 2-pass encoding, speed tuning, and multithreading.

TL;DR: The Default VP9 Command

ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 31 -b:v 0 -c:a libopus -b:a 128k output.webm

CRF 31 with -b:v 0 gives you true constant-quality mode. Opus audio at 128k is the natural pairing for WebM.

What CRF Does in VP9

VP9's CRF scale runs from 0 to 63. Lower means better quality and bigger files. This is different from H.264's libx264, which uses a 0-51 range.

You must set -b:v 0 for true CRF mode. If you leave out -b:v 0, FFmpeg treats the CRF value as a constrained quality floor. This is the single most common VP9 encoding mistake.

VP9 CRF Values by Use Case

CRF	Use Case	Notes
15-20	Archival / master copies	Near-lossless. Large files.
24-28	High-quality streaming	Visually transparent for most content
30-33	General web video	Good quality at reasonable file sizes
36-42	Low-bandwidth delivery	Noticeable softness, but watchable
45+	Previews / thumbnails	Significant quality loss

Speed Settings

-cpu-used is a number from 0 to 8. Zero is the slowest and highest quality. For most encodes, -deadline good -cpu-used 2 is the sweet spot.

2-Pass Encoding

ffmpeg -i input.mp4 -c:v libvpx-vp9 -b:v 2M -deadline good -cpu-used 2 -row-mt 1 -pass 1 -an -f null /dev/null
ffmpeg -i input.mp4 -c:v libvpx-vp9 -b:v 2M -deadline good -cpu-used 2 -row-mt 1 -pass 2 -c:a libopus -b:a 128k output.webm