D:\ffmpeg\bin>ffmpeg -i input.mp4 -i mask.png -filter_complex "[0:v]crop=246:60:998:98,alphamerge,boxblur=1[alf];[0:v][alf]overlay[v]" -map "[v]" -map 0:a -c:v libx264 -c:a copy -movflags +faststart output.mp4
ffmpeg version N-85653-gb4330a0 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.3.0 (GCC)
  configuration: --enable-gpl --enable-version3 --enable-cuda --enable-cuvid --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-zlib
  libavutil      55. 61.100 / 55. 61.100
  libavcodec     57. 93.100 / 57. 93.100
  libavformat    57. 72.101 / 57. 72.101
  libavdevice    57.  7.100 / 57.  7.100
  libavfilter     6. 87.100 /  6. 87.100
  libswscale      4.  7.101 /  4.  7.101
  libswresample   2.  8.100 /  2.  8.100
  libpostproc    54.  6.100 / 54.  6.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.72.101
  Duration: 00:00:40.04, start: 0.000000, bitrate: 1183 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 1049 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
Input #1, png_pipe, from 'mask.png':
  Duration: N/A, bitrate: N/A
    Stream #1:0: Video: png, rgb24(pc), 1280x720, 25 tbr, 25 tbn, 25 tbc
Stream mapping:
  Stream #0:0 (h264) -> crop
  Stream #0:0 (h264) -> overlay:main
  Stream #1:0 (png) -> alphamerge:alpha
  overlay -> Stream #0:0 (libx264)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
[Parsed_alphamerge_1 @ 0000000006352e00] Input frame sizes do not match (246x60 vs 1280x720).
[Parsed_alphamerge_1 @ 0000000006352e00] Failed to configure output pad on Parsed_alphamerge_1
Error reinitializing filters!
Failed to inject frame into filter network: Invalid argument
Error while processing the decoded data for stream #1:0
Conversion failed!

D:\ffmpeg\bin>