$ ffmpeg -hwaccel vaapi -vaapi_device /dev/dri/renderD128 -i 2017-05-05\ 20-45-04.mkv -vf format='nv12,hwupload' -an -threads 1 -f matroska -crf 44 -profile:v 66 -vcodec h264_vaapi test.mp4
ffmpeg version N-85887-g523205ce1e Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.3.1 (GCC) 20170306
  configuration: --prefix=/usr --disable-debug --disable-static --enable-avisynth --enable-avresample --enable-fontconfig --enable-gnutls --enable-gpl --enable-ladspa --enable-libass --enable-libbluray --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libfdk-aac --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-nonfree --enable-shared --enable-version3 --enable-vaapi
  libavutil      55. 61.100 / 55. 61.100
  libavcodec     57. 94.101 / 57. 94.101
  libavformat    57. 72.101 / 57. 72.101
  libavdevice    57.  7.100 / 57.  7.100
  libavfilter     6. 88.100 /  6. 88.100
  libavresample   3.  6.  0 /  3.  6.  0
  libswscale      4.  7.101 /  4.  7.101
  libswresample   2.  8.100 /  2.  8.100
  libpostproc    54.  6.100 / 54.  6.100
libva info: VA-API version 0.40.0
libva info: va_getDriverName() returns 0
libva info: Trying to open /usr/lib/dri/radeonsi_drv_video.so
libva info: Found init function __vaDriverInit_0_40
libva info: va_openDriver() returns 0
Input #0, matroska,webm, from '2017-05-05 20-45-04.mkv':
  Metadata:
    ENCODER         : Lavf57.72.101
  Duration: 00:00:01.53, start: 0.000000, bitrate: 426 kb/s
    Stream #0:0: Video: h264 (High), yuv420p(tv, bt470bg/unknown/unknown, progressive), 1280x720, 1k fps, 120 tbr, 1k tbn, 47.95 tbc (default)
    Metadata:
      DURATION        : 00:00:00.774000000
    Stream #0:1: Audio: aac (LC), 44100 Hz, stereo, fltp (default)
    Metadata:
      DURATION        : 00:00:01.532000000
Codec AVOption crf (Select the quality for constant quality mode) specified for output file #0 (test.mp4) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
File 'test.mp4' already exists. Overwrite ? [y/N] y
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (h264_vaapi))
Press [q] to stop, [?] for help
[h264_vaapi @ 0x1e93d40] H.264 baseline profile doesn't support encoding with B frames, disabling them.
[h264_vaapi @ 0x1e94220] Encoding profile not found (5).
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
Conversion failed!