C:\ffmpeg\bin>ffmpeg.exe -i mst3k.mkv -c:v hevc_amf -s 720x480 -r 29.97 -b:v 1000k -c:a copy mst3k1.mkv
ffmpeg version git-2017-12-22-e3b2c85 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 7.2.0 (GCC)
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-bzlib --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-amf --enable-cuda --enable-cuvid --enable-d3d11va --enable-nvenc --enable-dxva2 --enable-avisynth --enable-libmfx
  libavutil      56.  6.100 / 56.  6.100
  libavcodec     58.  8.100 / 58.  8.100
  libavformat    58.  3.100 / 58.  3.100
  libavdevice    58.  0.100 / 58.  0.100
  libavfilter     7.  7.100 /  7.  7.100
  libswscale      5.  0.101 /  5.  0.101
  libswresample   3.  0.101 /  3.  0.101
  libpostproc    55.  0.100 / 55.  0.100
Input #0, matroska,webm, from 'mst3k.mkv':
  Metadata:
    ENCODER         : Lavf58.3.100
  Duration: 01:31:58.67, start: 0.000000, bitrate: 2129 kb/s
    Stream #0:0: Video: h264 (Main), yuv420p(tv, progressive), 720x480 [SAR 1:1 DAR 3:2], 29.97 fps, 29.97 tbr, 1k tbn, 59.94 tbc (default)
    Metadata:
      ENCODER         : Lavc58.8.100 h264_amf
      DURATION        : 01:31:58.667000000
    Stream #0:1: Audio: aac (LC), 48000 Hz, stereo, fltp (default)
    Metadata:
      ENCODER         : Lavc58.8.100 aac
      DURATION        : 01:31:57.597000000
File 'mst3k1.mkv' already exists. Overwrite ? [y/N] y
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> hevc (hevc_amf))
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
[hevc_amf @ 000001d4c026fa20] CreateComponent(AMFVideoEncoderHW_HEVC) failed with error 36
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!