Encoding errors not being raised, just creating empty file.

[hayden-t]

2 different Errors:
x264 [error]: main profile doesn't support 4:4:4
x264 [error]: main profile doesn't support a bit depth of 10

These were corrected with the -vf format=yuv420p option in custom ffmpeg options, but this will override earlier -vf option inserted by the app:
Multiple -filter, -af or -vf options specified for stream 0, only the last option '-filter:v format=yuv420p' will be used.
So you must combine the existing one seen in logs with the new one: (in my case converting to 1080p
-vf scale=1920:trunc(ow/a/2)*2 format=yuv420p

But then on some files I came across another error:

[mp4 @ 000000000332fc00] Could not find tag for codec h264 in stream #0, codec not currently supported in container
[out#0/mp4 @ 00000000001a7800] Could not write header (incorrect codec parameters ?): Invalid argument

Looking further back in the log it seems this is from the incorrect video stream source being selected, in this case some cover art:

Stream mapping:
  Stream #0:6 -> #0:0 (mjpeg (native) -> h264 (libx264))
  Stream #0:1 -> #0:1 (dts (dca) -> aac (native))

This is a little more difficult, as adding -map 0:0 -map 0:1 just adds 2 more streams to the output rather than override the earlier usage.
Ideally the app needs a video stream selector as well as an audio one.
I guess ill have to use a different app for these files.

[hayden-t]

OK, I worked out a work around, I found out you can do negative map commands to remove any earlier ones, only problem is that where TEncoder inserts the custom video options is before where it inserts the map commands.
Luckily if you put the commands in the custom audio section it works, because it puts the audio options after the video ones:
-map -0 -map 0:0 -map 0:1
this removes all existing maps, and then adds stream 0 and 1 in that order.
https://trac.ffmpeg.org/wiki/Map#Modifiers