sysprog21 / vsnd

Virtual Linux soundcard driver

Virtual Soundcard Driver for Linux Kernel

vsnd implements a Linux device driver that introduces a virtual soundcard. Typically, a sound card is a hardware component that enables computers to play audio files. This virtual soundcard, however, is designed to transmit audio PCM data received from various programs directly into a FIFO file.

Prerequisites

The following packages must be installed before building vsnd.

To compile the kernel driver successfully, package versions of currently used kernel, kernel-devel and kernel-headers need to be matched.

$ sudo apt install linux-headers-$(uname -r)

Additional packages are required for verification purpose.

$ sudo apt install alsa-utils ffmpeg

Build and Run

After running make, you should be able to generate the file vsnd.ko.

Before loading this kernel module, you have to satisfy its dependency:

$ sudo modprobe snd_pcm

A FIFO file is required during kernel module initialization and is used for transmitting audio PCM data.

$ mkfifo /tmp/audio.pcm

The module can be loaded to Linux kernel by runnning the command:

$ sudo insmod vsnd.ko out_fifo_name=/tmp/audio.pcm

Then, use aplay to check the soundcard device provided by vsnd.

$ aplay -l

Reference output:

card 0: vsnd [vsnd], device 0: vsnd PCM [vsnd PCM]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

See scripts/verify.sh for automated test.

License

vsndis released under the MIT license. Use of this source code is governed by a MIT-style license that can be found in the LICENSE file.

Reference

• The ALSA Driver API