There's no voice in output

[Utka]

Hello everyone.

I recently tried to change the audio format of the video to AC3 (lav), however I can't hear actual voices of actors in the video, just some background noises.

Does anyone have clue what is going on there?

Original video is mp4 and its audio works just fine.

[eumagga0x2a]

"mp4" gives pretty much zero information about audio track properties. How many channels did the source have? How many does the output have? If you try to play multichannel audio on stereo-only equipment without proper downmixing, you might experience exactly what you describe.