First, add a "Channel mapper" prior to your encoder. Then set video codec to "mpeg2video" and audio codec to "pcm_s16le". If you want aac instead of pcm then you must add "-strict -2" to you command line, otherwise aac wont work at all.
Other than that, please read this: viewtopic.php?f=5&t=235 because your ffmpeg options would fail regardless. The mantra is: Create a working example using ffmpeg command line before creating a "Custom FFmpeg"-encoder i FFAStrans. A valid FFAStrans "certified" ffmpeg executable can be found in <your FFAStrans folder>\Processors\FFMpeg
-steipal