mirror of
https://github.com/Brandon-Rozek/website.git
synced 2024-11-28 12:23:39 -05:00
87 lines
2.4 KiB
Markdown
87 lines
2.4 KiB
Markdown
---
|
|
title: "Record Output Audio via Terminal"
|
|
date: 2020-03-01T10:38:06-05:00
|
|
draft: false
|
|
tags: [ "Linux", "Audio-Video" ]
|
|
---
|
|
|
|
This post is specific to `PulseAudio` on Linux.
|
|
|
|
I know of GUI based solutions like [PulseAudio Volume Control](https://freedesktop.org/software/pulseaudio/pavucontrol/) that lets you set up monitor devices. But, what if you want to do this through the terminal?
|
|
|
|
Luckily, [b-ak](https://askubuntu.com/a/850174) on AskUbuntu gave an elegant answer to this question!
|
|
|
|
First make sure you have `pulseaudio-utils` installed,
|
|
|
|
```bash
|
|
sudo apt install pulseaudio-utils
|
|
```
|
|
|
|
Next we need to search for the speaker we wish to monitor
|
|
|
|
```bash
|
|
pacmd list-sinks | grep -e 'name:' \
|
|
-e 'index' \
|
|
-e 'Speakers'
|
|
```
|
|
|
|
It will output something similar to this:
|
|
|
|
```bash
|
|
* index: 0
|
|
name: <alsa_output.pci-0000_00_1b.0.analog-stereo>
|
|
analog-output-speaker: Speakers (priority 10000, latency offset 0 usec, available: unknown)
|
|
```
|
|
|
|
From here note the name in `<>` of the speaker you wish to monitor. For example for my output above, I wish to monitor `alsa_output.pci-0000_00_1b.0.analog-stereo`.
|
|
|
|
Next we will use the `parec` command to record the raw audio stream from the PulseAudio server.
|
|
|
|
```bash
|
|
parec --device alsa_output.pci-0000_00_1b.0.analog-stereo.monitor | encoder_command
|
|
```
|
|
|
|
Notice the addition of `.monitor` at the end of the device.
|
|
|
|
## `lame`
|
|
|
|
For the `encoder_command`, b-ak used `lame`.
|
|
|
|
```bash
|
|
lame -r -V0 - out.mp3
|
|
```
|
|
|
|
This command takes in a raw pcm `-r` and enables variable bit rates for the highest quality `-V0`. From there it encodes it and puts it in `out.mp3`.
|
|
|
|
Now `lame` actually makes a couple assumptions about your raw pcm if you didn't specify additional arguments:
|
|
|
|
- The Raw PCM is formatted in signed 16-bit little endian samples
|
|
- The Raw PCM has 2 channels
|
|
|
|
If you're assumptions don't meet the above, then you will need to add additional arguments.
|
|
|
|
## `ffmpeg`
|
|
|
|
We can replace `lame` with the more featureful `ffmpeg` if we take note of the same assumptions above.
|
|
|
|
```bash
|
|
ffmpeg -f s16le \
|
|
-ac 2 \
|
|
-i pipe:0 \
|
|
-b:a 0 \
|
|
out.mp3
|
|
```
|
|
|
|
Where we can replace the `.mp3` with whatever file extension `ffmpeg` supports.
|
|
|
|
Now to show the entire command
|
|
|
|
```bash
|
|
parec --device alsa_output.pci-0000_00_1b.0.analog-stereo.monitor | \
|
|
ffmpeg -f s16le \
|
|
-ac 2 \
|
|
-i pipe:0 \
|
|
-b:a 0 \
|
|
out.mp3
|
|
```
|
|
|