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55 lines
1.8 KiB
Markdown
55 lines
1.8 KiB
Markdown
---
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title: "Replace Audio in Video"
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date: 2020-04-20T20:32:26-04:00
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draft: false
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tags: []
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---
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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.
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## Extract Audio
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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:
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```bash
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ffmpeg -i input_video.mkv -vn -acodec copy output.aac
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```
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| Argument | Description |
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| -------------- | -------------------------- |
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| `-i` | Input |
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| `-vn` | No Video |
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| `-acodec copy` | Copy audio stream directly |
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If you don't know the audio codec and have `mediainfo` installed, then run
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```bash
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mediainfo --Inform="Audio;%Format%" input_video.mkv
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```
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If you gave up, then you can transcode the audio (will take longer than direct copy)
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```bash
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ffmpeg -i input_video.mkv -vn output.aac
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```
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## Replacing Audio
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Once you're done touching up the audio (`touchup.mp3`), you'll want to replace the existing audio with it.
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```bash
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ffmpeg -i input_video.mkv \
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-i touchup.mp3 \
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-c:v copy \
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-map 0:v:0 \
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-map 1:a:0 \
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output_video.mp4
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```
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| Argument | Description |
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| ---------------------- | ------------------------------------------------------------ |
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| `-i` | Inputs |
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| `-c:v copy` | Make this a copy operation |
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| `-c:v copy -map 0:v:0` | Map the video from the first input to the first video output |
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| `-map 1:a:0` | Map the audio from the second input to the first video output |
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