Transcode Audio to AC3 instead of AAC

[kraM1t]

Hi, I have a Sony HTIAB, it only supports PCM, Dolby Digital (AC3) and Dolby Digital Plus (EAC3). I sometimes have files with only DTS or TrueHD audio, the problem is Jellyfin FFMPEG only transcodes the audio to AAC which is unsupported and causes VERY low audio volume playback vs if I pre-transcode it to AC3 myself. Of course that's very time consuming, transcoding then remuxing. Is there any way I can tell JF-FFMPEG to transcode to AAC instead? I dug around all of the Jellyfin installation directory/%appdata% but can't find any FFMPEG folder or config files to set the default transcode formats.

Thanks

::Edit::

ffmpeg -i input.mkv -vcodec copy -acodec ac3 out.mkv

I'm looking to alter the part of JF that instructs FFMPEG like this ^