sndusbaudio

snd-usb-audio is a Linux kernel driver in the ALSA subsystem that provides support for USB audio devices. It exposes each USB sound interface as an ALSA sound card, enabling playback and capture through standard ALSA interfaces and, via higher-level sound servers such as PulseAudio or PipeWire, to applications.

The driver supports USB Audio Class 1 and USB Audio Class 2 devices, including common peripherals such as USB headphones, USB microphones, external USB DACs, and multi-channel interfaces. It handles isochronous data transfer, negotiates sample formats, channels, and sample rates, and can adjust hardware clocking to maintain synchronization during playback and recording.

Configuration and usage: On most systems the driver loads automatically when a USB audio device is connected. It is loaded as the kernel module snd-usb-audio. Users can list devices with aplay -l and select devices through ALSA mixers or via PulseAudio/PipeWire.

Limitations and quirks: Some devices require device-specific quirks or firmware; not all features are supported equally across devices; latency can vary and may require tuning of buffer sizes and sample rates; certain USB devices report multiple interfaces which can appear as several cards.

Development and maintenance: The driver is part of the ALSA project and is maintained within the Linux kernel. Ongoing work focuses on better support for new USB Audio devices, improved latency, and power management. Maintainers include contributors from the ALSA community, with Jaroslav Kysela historically a key maintainer.