2020-04-20 20:51:28 -04:00
---
title: "Replace Audio in Video"
date: 2020-04-20T20:32:26-04:00
draft: false
2022-01-02 14:24:29 -05:00
tags: ["Audio-Video"]
2023-01-05 14:04:45 -05:00
medium_enabled: true
2020-04-20 20:51:28 -04:00
---
I recorded a video and wanted to touch up my audio in audacity. Here's how I used `ffmpeg` to extract the audio, and then replace it with a modified version.
## Extract Audio
If you know the format of the audio (mp3, ogg, aac) then it's possible to do a byte copy of the audio track into a file:
```bash
ffmpeg -i input_video.mkv -vn -acodec copy output.aac
```
| Argument | Description |
| -------------- | -------------------------- |
| `-i` | Input |
| `-vn` | No Video |
| `-acodec copy` | Copy audio stream directly |
If you don't know the audio codec and have `mediainfo` installed, then run
```bash
mediainfo --Inform="Audio;%Format%" input_video.mkv
```
If you gave up, then you can transcode the audio (will take longer than direct copy)
```bash
ffmpeg -i input_video.mkv -vn output.aac
```
## Replacing Audio
Once you're done touching up the audio (`touchup.mp3`), you'll want to replace the existing audio with it.
```bash
ffmpeg -i input_video.mkv \
-i touchup.mp3 \
-c:v copy \
-map 0:v:0 \
-map 1:a:0 \
output_video.mp4
```
| Argument | Description |
| ---------------------- | ------------------------------------------------------------ |
| `-i` | Inputs |
| `-c:v copy` | Make this a copy operation |
| `-c:v copy -map 0:v:0` | Map the video from the first input to the first video output |
| `-map 1:a:0` | Map the audio from the second input to the first video output |
