How To Merge Video .MP4 With Audio .MP3 With FFMPEG
ffmpeg -i lastA.mp4 -i voice1.mp3 -filter_complex "[0]volume=3.0[00];[1]volume=200.0[11];[00][11]amix=2[o]" -map 0:v -map [o] finished.mp4
ffmpeg -i lastA.mp4 -i voice1.mp3 -filter_complex "[0]volume=3.0[00];[1]volume=200.0[11];[00][11]amix=2[o]" -map 0:v -map [o] finished.mp4