No sound while using mono channel

im coding webms using the libvpx-vp9 codec, I always used vorbis for the audio codec and everything was fine, but when I change channels from 2 (stereo) to 1 (mono) I dont get any sound.
I also tried to use the audio codec opus, but i dont get any sound at all.
Any suggestions?

You can select the default for format option for the audio codec and you’ll be able to export to mono or stereo.

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When i use WebM and pick the mono channel and make a video, I have audio, but when I use WebM VP9, and pic the same options and make a video, it doesnt have any audio, do you know why?

No I do not. The webmVP9 export with default settings exports both mono and stereo audio here.

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The “WebM” preset uses vorbis audio. The “WebM VP9” preset uses opus audio.

When I try to export using vorbis and one audio channel, I see this error in the export log:

[vorbis @ 0x7f0e301849c0] Current FFmpeg Vorbis encoder only supports 2 channels.

So it looks that only stereo is supported if you use the “WebM” preset - unless you change the audio codec to something that supports mono.