Working on a project... adding some notes here.
Following http://wiki.webmproject.org/ffmpeg/vp9-encoding-guide
Encoding bm layer (soundtrack with beats)
Beat Meter 1
First pass
ffmpeg -i bm.mov -passlogfile bm -c:v libvpx-vp9 -pix_fmt yuva420p -auto-alt-ref 0 -pass 1 -b:v 10M -threads 8 -speed 4 -tile-columns 4 -row-mt 1 -tile-rows 2 -g 4 -aq-mode 0 -c:a libvorbis -b:a 64k -f webm /dev/null
Second pass
ffmpeg -i bm.mov -passlogfile bm -c:v libvpx-vp9 -pix_fmt yuva420p -auto-alt-ref 0 -pass 2 -b:v 10M -threads 8 -speed 0 -tile-columns 4 -row-mt 1 -tile-rows 2 -lag-in-frames 25 -g 4 -aq-mode 0 -c:a libvorbis -b:a 64k -f webm dfy-1.webm