make the output file work on firefox

[iblislin]

add -pix_fmt yuv420p to ffmpeg option

[tawheeler]

Cannot merge until I get back around the 25th. Shashi feel free to take a look.

[tawheeler]

Hmm, the changes don't seem to run for me, and it doesn't pass on Travis either.

[iblislin]

well, my ffmpeg version here,

% ffmpeg -version
ffmpeg version 3.4.1 Copyright (c) 2000-2017 the FFmpeg developers
built with gcc 7.2.1 (GCC) 20171128
configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-avisynth --enable-avresample --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libass --enable-libbluray --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxml2 --enable-libxvid --enable-shared --enable-version3
libavutil      55. 78.100 / 55. 78.100
libavcodec     57.107.100 / 57.107.100
libavformat    57. 83.100 / 57. 83.100
libavdevice    57. 10.100 / 57. 10.100
libavfilter     6.107.100 /  6.107.100
libavresample   3.  7.  0 /  3.  7.  0
libswscale      4.  8.100 /  4.  8.100
libswresample   2.  9.100 /  2.  9.100
libpostproc    54.  7.100 / 54.  7.100

Failure of Traivs is an installation issue.

[tawheeler]

Does ffmpeg 3.4.1 require Ubuntu 16? Travis runs trusty (14)

[iblislin]

hmm, not sure about that. mine is an Arch Linux box.