When enabled, the silent option will avoid popping up dialog boxes for
overwrite confirmation or codec selection. The codec selection defaults to
uncompressed RGB.
This is required for FifoCI on Windows which needs to drive Dolphin from the
command line exclusively.
The timing information is set on s_scaled_frame->pts, giving precise
timing information to the encoder. Frames arriving too early (less than
one tick after the previous frame) are droped. The setting of packet's
timestamps and flags is done after the call to avcodec_encode_video2()
as this function resets these fields according to its documentation.
ffmpeg 2.0 changed requirements for the FFV1 encoder and made them more strict,
requiring more fields of the input frame to be initialized. Explicitly setting
pixfmt, width and height solve the EINVAL issues with FFV1 encoding.
Original fix from http://ffmpeg.org/pipermail/libav-user/2013-October/005759.html
