Open Other > ALSA Audio

shotcut · September 2, 2019, 10:16pm

Opens a raw audio capture device using ALSA (Advanced Linux Sound Architecture).
This allows Shotcut to capture audio directly from an ALSA PCM device instead of importing an audio file.

This feature is Linux-specific and intended for advanced or low-level audio capture.

What ALSA is

ALSA is the low-level audio subsystem of the Linux kernel.
It provides direct access to sound hardware through PCM (Pulse Code Modulation) devices.

Unlike PulseAudio (or PipeWire), ALSA:

Operates closer to the hardware
Provides minimal abstraction
Does not handle mixing, routing, or device management automatically

Shotcut accesses ALSA through FFmpeg.

Important context

On Linux, Timeline > Record Audio uses PulseAudio (or PipeWire), not ALSA. Microphone selection and routing are expected to be configured at the desktop/system level. Shotcut does not provide internal ALSA or PulseAudio configuration panels.

Controls

PCM Device (input)

Specifies the ALSA PCM device name to open.

Default value: default
This refers to the system’s default ALSA capture device

Advanced users may enter explicit ALSA device identifiers, such as:

hw:0,0
plughw:1,0

If an invalid or unsupported device is specified, capture will fail.

Channels (0 - 8)

Specifies the number of audio channels to capture.

1 — Mono
2 — Stereo (default)
Higher values — Multi-channel capture (if supported by the device)

The device must support the requested channel count.

Scope and behavior

Linux-only feature
Captures audio only
Appears as a live source
No internal level controls
No automatic device selection

This capture path bypasses desktop audio routing.

Typical use cases

Capturing audio from:
- USB audio interfaces
- Professional sound cards
- External mixers
Low-latency or direct hardware access
Advanced workflows where PulseAudio/PipeWire is not setup
Technical testing or diagnostics

Usage notes and warnings

ALSA device names are system-dependent
Incorrect PCM device strings will cause silent failure
No automatic resampling or mixing is provided

Relationship to PulseAudio / PipeWire

PulseAudio (or PipeWire) sits on top of ALSA
Timeline > Record Audio uses PulseAudio
ALSA device capture is a direct, bypass path

If recording fails via ALSA, a common workaround is to:

Close any other process using ALSA because often the device cannot be used by more than one process, which is a big reason why PulseAudio, PipeWire, and JACK exists.
Record audio using a dedicated ALSA-capable application
Import the resulting audio file into Shotcut

Limitations

No device discovery UI
No level meters
No internal routing or mixing
Requires ALSA knowledge
Behavior depends on kernel driver and hardware support