Combining Audio & Video with FFmpeg

Описание: Learn how to replace the audio of a movie file without any loss in quality, and also how to add a new audio track to a movie file. We show how to do all this using FFmpeg, a free cross-platform tool.
Links and full commands are provided after the chapter list below:
00:00 Intro
00:58 Recap of last session
01:29 Replacing an Audio Track
02:38 The FFmpeg command to replace a track
08:05 Adding an Audio Track
10:00 The FFmpeg command to add tracks
12:35 Closing words

Installing FFmpeg was covered in this video:    • Extracting Audio Tracks with FFmpeg  
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Listing of Commands executed within this video::
A short description precedes each command as a "#" comment

Command to list info about a movie file. (Note: the "-i" is optional for ffprobe)
ffprobe -i moviefile.ext

Create a new movie file "out.mkv" by combining the video within "video.mp4" and the audio within "audio.mp4"
ffmpeg -i video.mp4 -i audio.mp4 -c copy -map 0:v:0 -map 1:a:0 out.mkv

Create a new movie file "out.mkv" by adding the audio track within "audio.mp4" to everything within "base.mp4"
ffmpeg -i base.mp4 -i audio.mp4 -c copy -map 0 -map 1:a:0 out.mkv