Is it possible to use 2-pass encoding to create vp9 / webm videos from an image sequence? I'm currently creating webm videos using ffmpeg to encode an image sequence. My command is:
ffmpeg -framerate 30 -f image2 -i frames/%04d.png -i my_audio.flac -c:v libvpx-vp9 -pix_fmt yuva420p -b:v 0 -tile-columns 2 -crf 18 -c:a libopus -b:a 128k -r 30 -g 300 -y my_video.webm

The webm VP9 encoding guide only seems to list examples of 2-pass encoding with ffmpeg. And for image sequences, their example doesn't even seem to use ffmpeg.

So I wonder, is it possible to do 2-pass encoding of image sequences using ffmpeg and libvp9? If so, what would be the equivalent to my single-pass command? Is there any advantage in using the 2-pass approach instead of a single pass in this scenario?

References:

webm wiki > FFmpeg > VP9 Encoding Guide: http://wiki.webmproject.org/ffmpeg/vp9-encoding-guide
webm wiki > HOWTOs‎ > ‎Convert PNG frames to WebM video: http://wiki.webmproject.org/howtos/convert-png-frames-to-webm-video
You would use

ffmpeg -framerate 30 -f image2 -i frames/%04d.png -pass 1 -c:v libvpx-vp9 -pix_fmt yuva420p -b:v 0 -tile-columns 2 -crf 18 -r 30 -g 300 -y -f null -


and then

ffmpeg -framerate 30 -f image2 -i frames/%04d.png -i my_audio.flac -pass 2 -c:v libvpx-vp9 -pix_fmt yuva420p -b:v 0 -tile-columns 2 -crf 18 -c:a libopus -b:a 128k -r 30 -g 300 -y my_video.webm


In FFmpeg the container format or encoding of the input is, in itself, irrelevant in terms of using encoder features like two-pass.