Last Modified: 2016-05-18
Examples given are for 2-pass VP9 encoding with FFMpeg. Ensure that your
FFMpeg has been built with libvpx support.
VOD Recommended Settings
ffmpeg -i <source> -c:v libvpx-vp9 -pass 1 -b:v 1000K -threads 8 -speed 4 \
-tile-columns 6 -frame-parallel 1 \
-an -f webm /dev/null
ffmpeg -i <source> -c:v libvpx-vp9 -pass 2 -b:v 1000K -threads 8 -speed 1 \
-tile-columns 6 -frame-parallel 1 -auto-alt-ref 1 -lag-in-frames 25 \
-c:a libopus -b:a 64k -f webm out.webm
c:v libvpx-vp9 tells FFmpeg to encode the video in VP9.
c:a libopus tells FFmpeg to encode the audio in Opus.
b:v 1000K tells FFmpeg to encode the video with a target of 1000 kilobits.
b:a 64k tells FFmpeg to encode the audio with a target of 64 kilobits.
Most of the current VP9 decoders use tile-based, multi-threaded decoding. In
order for the decoders to take advantage of multiple cores, the encoder must
set tile-columns and frame-parallel.
Setting auto-alt-ref and lag-in-frames >= 12 will turn on VP9's alt-ref
frames, a VP9 feature that enhances quality.
speed 4 tells VP9 to encode really fast, sacrificing quality. Useful to
speed up the first pass.
speed 1 is a good speed vs. quality compromise. Produces output quality
typically very close to speed 0, but usually encodes much faster.
Multi-threaded encoding may be used if -threads > 1 and -tile-columns > 0.
DASH Recommended Settings
Best Quality (Slowest) Recommended Settings
ffmpeg -i <source> -c:v libvpx-vp9 -pass 1 -b:v 1000K -threads 1 -speed 4 \
-tile-columns 0 -frame-parallel 0 \
-g 9999 -aq-mode 0 -an -f webm /dev/null
ffmpeg -i <source> -c:v libvpx-vp9 -pass 2 -b:v 1000K -threads 1 -speed 0 \
-tile-columns 0 -frame-parallel 0 -auto-alt-ref 1 -lag-in-frames 25 \
-g 9999 -aq-mode 0 -c:a libopus -b:a 64k -f webm out.webm
tile-columns 0,
frame-parallel 0: Turning off
tile-columns and
frame-parallel should give a small bump in quality, but will most likely
hamper decode performance severely.
Constant Quality Recommended Settings
Objective is to achieve a constant (perceptual) quality level without regard
to bitrate.
(Note that Constant Quality differs from Constrained Quality, described
below.)
ffmpeg -i <source> -c:v libvpx-vp9 -pass 1 -b:v 0 -crf 33 -threads 8 -speed 4 \
-tile-columns 6 -frame-parallel 1 \
-an -f webm /dev/null
ffmpeg -i <source> -c:v libvpx-vp9 -pass 2 -b:v 0 -crf 33 -threads 8 -speed 2 \
-tile-columns 6 -frame-parallel 1 -auto-alt-ref 1 -lag-in-frames 25 \
-c:a libopus -b:a 64k -f webm out.webm
crf is the quality value (
0-63 for VP9). To trigger this mode, you must
use a combination of
crf <q-value> and
b:v 0.
bv MUST be
0.
Constrained Quality Recommended Settings
Objective is to achieve a constant (perceptual) quality level as long as the
bitrate achieved is below a specified upper bound. Constrained Quality is
useful for bulk encoding large sets of videos in a generally consistent
fashion.
ffmpeg -i <source> -c:v libvpx-vp9 -pass 1 -b:v 1400K -crf 23 -threads 8 -speed 4 \
-tile-columns 6 -frame-parallel 1 \
-an -f webm /dev/null
ffmpeg -i <source> -c:v libvpx-vp9 -pass 2 -b:v 1400K -crf 23 -threads 8 -speed 2 \
-tile-columns 6 -frame-parallel 1 -auto-alt-ref 1 -lag-in-frames 25 \
-c:a libopus -b:a 64k -f webm out.webm
The quality desired is provided as the
crf <q-value> parameter and the
bitrate upper bound is provided as the
b:v <bitrate> parameter, where
bitrate MUST be non-zero.
Both crf <q-value> and b:v <bitrate> MUST be provided. In this mode,
bitrate control will kick in for difficult videos, where the quality specified
cannot be achieved within the given bitrate.
For easy videos, this mode behaves exactly like the constant quality mode, and
the actual bitrate achieved can be much lower than the specified bitrate in
the b:v parameter.
One caveat in FFMpeg is that if you do not provide the b:v parameter, FFMpeg
will assume a default target bitrate of 256K -- so the constrained quality
mode will be triggered with a potentially very low target bitrate.
