Singler line FFMPEG cmd to Merge Video /Audio and retain both audios

Question

I have a project that requires merging of a video file with another audio file. The expected out put is an video file that will have both the audio from actual video and the me

Answer 1

Use case:

• add music to your background
• you rendered a video, but muted some part of it, so you don't want to render it again(coz it's too long), instead you render only audio track(fast) and wanna merge it with original video.

Assuming

• you have your video with you speech (or just audio track, whatever)
• your music_file is not loud. Otherwise, you will not hear yourself D:

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Steps:

1) Extract audio from the video

ffmpeg -i test.mp4 1.mp3

test.mp4 - your file

2) Merge both audio.mp3 and 1.mp3

ffmpeg -i audio.mp3 -i 1.mp3 -filter_complex amerge -c:a libmp3lame -q:a 4 audiofinal.mp3

audiofinal.mp3 - audio with music

3) Delete audio from original

ffmpeg -i example.mkv -c copy -an example-nosound.mkv

example-nosound.mkv - your video without audio

4) Merge with proper audio

ffmpeg -i audiofinal.mp3 -i example-nosound.wmv -c:v copy -vcodec copy final.wmv

final.wmv - your perfect video.