Notes on encoding settings

GOP

ffmpeg -c:v libvpx-vp9 would use kf_mode=audo and kf_max_dist=9999 (infinite) by default which means if you source is mostly static, you will have only one keyframe for the entire video.

• use ffmpeg -loglevel debug in encoding command to check the actual settings
• passing gop_size (-g) from ffmpeg: libvpxenc.c
• default values of kf_max_dist and kf_mode: vp9_cx_iface.c
• docs on vpxenc CLI tool
• slices on VP9, page 36

Defaults

These are the defaults when using ffmpeg with libvpx 1.4.0:

• g_threads=0
• quality=good (deadline=1000000)
• cpu-used=1 (-cpu-used = -speed)
• frame-parallel=1
• tile-columns=6
• auto-alt-ref=1
• lag-in-frames=15
• aq-mode=0
• kf_max_dist=9999 (-g)