The problem

It's a situation many of us have found ourselves in - you have two separate files, one with the video content you want, and the other containing the corresponding audio. Perhaps you've downloaded a silent film and a separate commentary track, or you've recorded a presentation and the audio separately. Whatever the case may be, you're now faced with the task of merging these two into a single, cohesive file. In this blog post, we'll explore how to do exactly that using the FFmpeg tool.

The analysis

FFmpeg is a free and open-source software that allows you to manipulate multimedia files. It can convert audio and video into almost any format, and it is widely used for video and audio streaming.

The solution

The command we will be using today is as follows:

ffmpeg -i video.mp4 -i audio.mp4 -c:v copy -c:a aac -map 0:v:0 -map 1:a:0 output.mp4

Now, let's do a detailed analysis of this command:

ffmpeg: This is the command that starts the FFmpeg program.
-i video.mp4 -i audio.mp4: These are the input files. The first -i video.mp4 tells FFmpeg that video.mp4 is our input video file, while the second -i audio.mp4 tells FFmpeg that audio.mp4 is our input audio file.
-c:v copy -c:a aac: These options define the codecs we want to use. -c:v copy tells FFmpeg to copy the original video codec. -c:a aac tells FFmpeg to use the AAC audio codec for the output file.
-map 0:v:0 -map 1:a:0: These commands map the input streams to the output file. -map 0:v:0 tells FFmpeg to take the first video stream (v:0) from the first input file (0) and -map 1:a:0 tells FFmpeg to take the first audio stream (a:0) from the second input file (1).
output.mp4: This is the name of the output file. The resulting file will be a .mp4 file with the video from the first input file and the audio from the second input file.

And there you have it! With a single command, you can merge a video with an audio. I hope this post has been helpful. If you have any questions or comments, don't hesitate to leave them below.

Cheers!