Does HDMI Carry Audio Signals?


HDMI (High-Definition Multimedia Interface) has gained popularity worldwide because it is an effective means of carrying video. This article will explain how HDMI is used for communication in digital networks and whether it can carry audio signals.

Does HDMI carry audio signals? HDMI (High-Definition Multimedia Interface) carries both audio and video. As a multi-media interface, HDMI transmits high-definition uncompressed video data and compressed or uncompressed digital audio data between HDMI-compliant devices.

In this article, we’ll focus the discussion on HDMI and how it carries audio signals.


What Does HDMI Carry?

Let’s begin with the basics. HDMI can carry both audio and video signals. It is known for transmitting high-quality digital video signals and as a digital replacement to older analog video standards. More specifically, HDMI carries uncompressed video.

HDMI is popular for presentations at work or providing news feeds throughout a small area. HDMI is also used for entertainment purposes, so you’ll find HDMI cables attached to your television, allowing you to watch movies or enjoy live streaming of music events.

In addition to digital video, HDMI will effectively carry digital audio (compressed or uncompressed) through the same cable. This allows you to have a more organized look in your personal space or when you’re using digital gear at any event.

The versatility of HDMI cables makes it easy for you to connect your MacBook to another device to play music. You could also connect your television to your PC and enjoy audio files that you’ve saved on the hard drive. In cases where two devices cannot be connected directly via HDMI, an adapter can often be used to facilitate the transmission of audio signals from one to the other.


A Brief Discussion On The Differences Between Digital And Analog Audio

It’s important to reiterate that HDMI does not carry analog audio. Rather, it transfers digital audio. Let’s briefly discuss the differences.

First, I’ll state the difference between sound and audio. Sound is mechanical wave energy (longitudinal sound waves) that propagate through a medium causing variations in pressure within the medium. Audio is made of electrical energy (analog or digital signals) that represent sound electrically.

For more information on the differences between sound and audio, check out my article What Is The Difference Between Sound And Audio?

So audio is a representation of sound that can be stored and played back. Storage, recording and editing/mixing can all be done digitally or in the analog realm.

Analog audio is sound stored, recorded, transferred or played back via electrical, magnetic or mechanical means. Analog audio signals are alternating currents of electrical energy and are regularly converted from one form of energy to another. Take the following examples:

  • A vinyl record is audio stored mechanically in grooves. A phonograph needle/stylus moves within the grooves and the attached cartridge converts the mechanical movement into electrical (analog) audio signals.
  • An audio tape is audio stored magnetically on magnetic tape. As the tape runs across the playhead, the electromagnetic imprint of the tape is read and converted into, once again, electrical (analog) audio signals.

The waveforms of the analog audio are continuous representations of sound.

Digital audio, as we could assume, is made of digital data (binary data). The audio waveform, rather than being continuous, is presented as discrete amplitudes (defined by the bit depth of the digital resolution) at distinct intervals (defined by the sample rate or samples per second).

Analog audio tends to degrade when stored and certainly as it’s reproduced. Analog audio signals also suffer from degradation as they travel through cable and audio devices. Digital audio files can be duplicated infinite times without degradation and can easily be transmitted via streaming services, Bluetooth, HDMI and more.

Analog signals are required for playback, however. Digital signal will not drive headphones or speakers. Only analog signals can do that. Therefore, there are plenty of digital-to-analog converters (and analog-to-digital converters) in audio devices.

So, to wrap up this brief discussion, HDMI carries digital audio, which is easy to transmit. HDMI cables, then, either work or they don’t. They will not affect the audio signal quality since they only transmit digital information.

However, that is not to say that the DAC necessary for playback (or the playback system itself) won’t affect the quality of the audio.

Related articles:
Are Loudspeakers & Monitors Analog Or Digital Audio Devices?
Are Headphones Analog Or Digital Audio Devices?
Are Microphones Analog Or Digital Devices? (Mic Output Designs)


HDMI Audio Specifications

The baseline audio format for HDMI is stereo (uncompressed) PCM. If a device is to send or receive digital audio via HDMI, it must have this format or “greater”.

Other formats are, of course, supported. Here is a list of audio signal formats supported by the HDMI protocol:

  • LPCM
  • Dolby Digital
  • DTS
  • DVD-Audio
  • Dolby Digital Plus
  • Dolby TrueHD
  • DTS-HD High Resolution Audio
  • DTS-HD Master Audio
  • MPCM
  • DSD
  • DST
  • Dolby Atmos
  • DTS:X

HDMI (version 2.0 and above) allows up to 32 channels of uncompressed audio at the following bit depths:

  • 16-bit
  • 20-bit
  • 24-bit

The 32 channels of uncompressed audio can have the following sample rates:

  • 32 kHz
  • 44.1 kHz
  • 48 kHz
  • 88.2 kHz
  • 96 kHz
  • 176.4 kHz
  • 192 kHz

In addition to supporting Dolby TrueHD, DTS-HD, and other superb digital audio formats, HDMI also supports an audio return channel, which can essentially send audio information back and forth from your TV tuner to your receiver. This equalizes audio and video processing delays between different devices automatically, so the picture and sound stay in perfect sync.

With HDMI transmission of sound, you will experience less quality loss and enjoy theatre-quality experiences when you’re playing music or enjoying the latest blockbuster film.


Compressed And Uncompressed Audio

HDMI can easily transmit both compressed and uncompressed audio. Most of the time, audio files are compressed to save space, allowing you to store several music files on your MacBook or other relatively small gear. HDMI cables don’t have a problem with compressed files.

HDMI actually performs better than component video cable when you’re considering the quality of surround sound facilitated by it. Despite that, sometimes it may take a few adjustments before sound is transmitted properly using HDMI when you’ve connected your TV or computer.


Reduce Delays

When audio and video devices cannot communicate well, the result is often poor synchronization and a less-than-ideal experience.

With HDMI, you won’t have to worry as much about delays due to the devices being different. Thanks largely to the return audio path, the audio-video sync won’t slip out of sync due to the HDMI cable.

In terms of setup time (let’s call it real-world delay), the simplicity of a single cable makes hooking up HDMI-compatible AV equipment super easy, thereby reducing the “delay” or time it takes to set up (and tear down) your systems.

Most gadgets nowadays are built to use HDMI. You can freely play audio with HDMI on all of these. As far as the future is concerned, it’s likely that this means of transmission will be utilized for a while.


Using The Correct Settings

While HDMI works well with different types of devices, you’ll always have to ensure that the settings are correct for each one that you’re using.

Perhaps you’re reading this article because you’re not getting any audio transfer with your HDMI cable properly connected. The issues are likely with the devices themselves rather than the cable.

If your computer’s settings aren’t correct, you won’t hear any sound. It’s often not the fault of the cable, and your device should be adjusted to fix the sound.

Ensuring the device settings are properly set will usually allow you to enjoy good sound quality with HDMI. Of course, there are times when you’re unable to hear the audio (or see video) because the HDMI cable that you’re using could be faulty. In that case, you can simply change the cable to enjoy clear audio.

If you’re using a cable box with your device, you’ll usually need to flip a switch to indicate that you want sound sent out through the HDMI cable instead of some other cable that’s attached. Similarly, on your computer, you’ll need to change the audio settings to ensure sound is sent through the HDMI cable to the external device.


HDMI Vs Optical Cables

HDMI and optical cables both transmit digital audio, and you’ll usually find one of them used to connect two digital devices. If you’re using multi-channel audio, like Dolby Digital, you won’t usually notice a difference in sound quality.

However, this seeming equity between HDMI and optical cables disappears when you’re not using a multi-channel source. When high-resolution audio is available, HDMI is the preferred choice. It was designed for this type of situation, and allows for a better listening experience than optical cables.

HDMI can be used with several high-resolution formats, including Blu-Ray. It can also transmit DTS HD Master Audio and Dolby TrueHD.

Some older devices do not support HDMI, so we won’t benefit from the high-quality digital audio transferring. Additionally, if you’re connecting an audio transmitter and loudspeakers within the system, HDMI is not usually necessary or even an option.

Although HDMI is very good at transferring audio, it’s not always necessary to use it if you only plan to send audio and don’t need to use video. Most pro audio and Hi-Fi equipment does not bother with HDMI, as there are plenty of other audio-specific connections on the market that work tremendously well.


Related Questions

Are AUX (Auxiliary) connectors & headphone jacks the same? The construction of the aux connector and the headphone jack is often the same: 3.5mm (1/8″) TRS. However, the “auxiliary connector” is universal for audio while the “headphone jack” is, by its name, suited for headphones. Headphone jacks also come in different sizes and wiring schemes.

Further reading: Are AUX (Auxiliary) Connectors & Headphone Jacks The Same?

How do we connect speakers of all types to our computers? How we connect an external speaker to a computer depends on the type of speaker. Bluetooth speakers are connected wirelessly via Bluetooth; USB speakers connect via USB cables, and typical speakers require some sort of interface (whether internal or external) to connect to a computer.

Further reading: How To Connect Speakers To A Computer (All Speaker Types)

Arthur

Arthur is the owner of Fox Media Tech and author of My New Microphone. He's an audio engineer by trade and works on contract in his home country of Canada. When not blogging on MNM, he's likely hiking outdoors and blogging at Hikers' Movement (hikersmovement.com) or composing music for media. Check out his Pond5 and AudioJungle accounts.

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