How do you get FFMPEG to encode with vaapi?

Question

I\'ve seen various examples of using libavcodec with vaapi to accelerated decoding, but how do you use it to accelerate encoding?

Answer 1

Update 2020: FFMPEG now fully supports VAAPI encode + decode

you can encode with something like:

ffmpeg -y -vaapi_device /dev/dri/renderD128 -i file_in.avi -vf 'format=nv12,hwupload' -c:v h264_vaapi file_out.mp4