How to configure different ALSA defaults for capture through one device and playback through another?

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07-10-2024

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Playing and Recording on Different Devices with ALSA: A Guide to Configuration

The Problem: Ever wanted to use one sound card for playback and another for recording? For example, you might have a high-quality USB audio interface for recording but prefer to listen to your audio through your computer's built-in speakers. This seemingly simple task can become a bit tricky with ALSA, the Advanced Linux Sound Architecture.

The Solution: Fortunately, ALSA offers a degree of flexibility in configuring your sound devices. This article will walk you through the steps to set up separate default devices for capture (recording) and playback.

The Scenario: Imagine you have a USB microphone connected to your computer, and you'd like to record audio through it while simultaneously listening to music through your computer's built-in speakers.

Original Code (Sample):

# Example: Set default playback to 'hw:1,0' and capture to 'hw:0,0'
amixer cset name='PCM'  'hw:1,0'
amixer cset name='Capture'  'hw:0,0'

Explanation:

• amixer: This command is used for configuring ALSA mixers.
• cset name='PCM': This sets the default playback device to the specified device.
• cset name='Capture': This sets the default capture device.
• hw:1,0: This refers to the second sound card (indexed as 1) and its first device (indexed as 0).
• hw:0,0: This refers to the first sound card (indexed as 0) and its first device (indexed as 0).

Identifying Your Devices:

Before diving into configuration, you'll need to identify the correct device names for both your playback and capture devices. Run the following command to list available ALSA devices:

aplay -l

This will output a list of devices along with their names and capabilities.

Configuration Options:

1. Using amixer Commands:

   • The commands shown in the "Original Code" section are a basic starting point. You can adapt them to match your specific device names.
   • You may need to run these commands every time you boot your system, as they are not persistent.
   • For a more permanent solution, you can add these commands to your system's startup scripts.

2. Using asound.conf:

   • This configuration file allows for a more comprehensive and persistent setup.

   • You can create or modify the asound.conf file in /etc/asound.conf.

   • Example configuration:

     pcm.capture {
       type hw
       card 0
       device 0
     }
     pcm.playback {
       type hw
       card 1
       device 0
     }
     

     • Replace card 0 and card 1 with the actual card indices of your recording and playback devices, respectively.

Additional Tips:

• Test your configuration: After making changes, test your setup by recording audio and playing it back. Verify that the sound is coming from the intended devices.
• Refer to the ALSA documentation: For detailed configuration options and advanced settings, refer to the official ALSA documentation: https://www.alsa-project.org/
• Use graphical tools: Several GUI tools, such as alsamixer, can simplify configuration and provide a visual interface for managing ALSA settings.

Conclusion:

By understanding the basic commands and configuration options, you can easily customize your audio experience with ALSA. Whether you're a musician, a podcaster, or simply want to enjoy your favorite music while recording, configuring separate capture and playback devices will provide you with the flexibility you need.