HDMI Audio Output in Ubuntu

by Ruri Ranbe
Multimedia presentations often require more flexible audio capabilities than a general all-purpose PC can provide.


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Most small businesses use Microsoft Windows as their main operating system, but Ubuntu is sometimes used as an alternative due to its user-friendly interface and -- more importantly -- lack of licensing or subscription fees. A significant number of hardware devices are compatible with Ubuntu and will work without requiring additional configuration. Some high-definition multimedia interface (HDMI) cards, however, while outputting a video feed, will fail to produce audio due to a missing or outdated module, or invalid settings.

HDMI Basics

Before the advent of HDMI, digital video interface (DVI) and video graphics array (VGA) were used to output video on a monitor. Both DVI and VGA are still in common use, but only DVI produces a digital signal -- VGA, on the other hand, is an analog interface. HDMI can be considered an extension, or superset, of DVI; it uses the same technology to produce digital video. Unlike DVI, however, it can also carry an audio signal. As a result, video cards with integrated HDMI can also transmit audio to an external device.


Drivers enable the operating system to interact with the hardware devices installed to the PC. Advanced Linux sound architecture (ALSA) is an application programming interface with integrated sound drivers that improves device support on Linux operating systems. If ALSA is missing or outdated, Ubuntu might not be able to utilize the audio features of the HDMI video card. Install or update the ALSA modules via Synaptic Package Manager or through Terminal to improve sound support on the OS.


AlsaMixer enables users to configure the sound levels on a particular audio device. Users can turn on, mute and increase or decrease sound levels for pulse-code modulation (PCM), a method of encoding developed to transmit digital audio over an analog format. PCM is used to output sound on modern HDMI cards. If PCM is muted in AlsaMixer, HDMI cards won't produce audio. Executing the command "sudo alsamixer" (without quotes) from the Terminal will launch the application. You can use the directional pad to select "PCM." Press "M" to unmute sound; press the up arrow to increase volume.

Device Configuration

Ubuntu uses profiles to configure the behavior of sound devices. If the incorrect profile is selected for an HDMI device, Ubuntu will fail to utilize the high-definition audio capabilities of the card. You can configure profiles in Sound Preferences, accessible via the System and Preferences menus. Click the Hardware tab to see the different audio devices installed to the computer and then click the HDMI card. If the profile "Digital Stereo (HDMI) Output" is not selected from the associated drop-down menu, the card won't be able to produce digital sound.

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