FFmpeg `Guessed Channel Layout for Input Stream`

Question

Consider a simple FFmpeg conversion, such as:

ffmpeg -i dream.wav dream-ffmpeg.mp3 -y

It produces the following warning:

Guessed Channel Layout for Input Stream #0.0 : mono

How can I tell FFmpeg, via command-line arguments, that the input stream will always be mono?

By goal is to be more specific, to avoid unnecessary warnings and keep my code clean. (So I may spot actual issues.)

(I am not trying to get rid of all warnings altogether.)

My understand form the FFmpeg docs was that -ac 1 would do the trick, e.g.:

ffmpeg -i dream.wav -ac 1 dream-ffmpeg.mp3 -y

But the warning's still here.

Answer 1

I'd actually seen the answer but somehow failed to use the argument it seems…

In any case -guess_layout_max 0 will do the trick. e.g.:

ffmpeg -guess_layout_max 0 -i dream.wav dream-ffmpeg.mp3 -y