Dolby Atmos is quickly becoming featured on high-end speakers and even soundbars (more on that in our guide). But if you are planning on using HDMI ARC to send sound from your TV, you may want to first understand Atmos and HDMI ARC’s limitations for a couple of reasons. One question people commonly have is whether HDMI ARC can send a Dolby Atmos signal.
HDMI ARC can send Dolby Atmos with the Dolby Digital Plus audio codec. You need to make sure that both devices support HDMI ARC and that the TV is capable of sending Dolby Digital Plus, not just Dolby Digital through HDMI ARC. You can typically find this information under the supported audio codecs in the TV’s user manual. If both devices support HDMI eARC, then Dolby Atmos is definitely supported.
Dolby Atmos gives consumers access to a type of surround sound that was once only available in cinemas. This relatively new technology may be unique, but it does come with its hiccups. One issue arises when trying to transfer the heavy load of data from one device to another.
The HDMI ARC Standard and Dolby Atmos
HDMI ARC, which we’ve explored at length in another article, has allowed for audio to travel from your device to your soundbar, speakers, or audio receiver without the need to run another cable. It takes advantage of HDMI capabilities and bandwidth maximums. While technically it is not supposed to transfer surround sound data, because of the high-bandwidth capabilities, it can.
HDMI standards change, and in the most recent release of 2.1, eARC was introduced which remedies a lot of ARC and Atmos issues, but more on that later. However, because the ARC feature has become popular in the last few years, TV manufacturers have started to add ARC ports that support a version of Dolby Atmos.
How to Tell if your TV Supports Dolby Atmos
Finding out whether you have a TV that can support this function can be tricky. In general, most TV’s made after 2017-2018 will usually support Dolby Digital Plus (lossy or compressed Dolby Atmos) with HDMI ARC. Look at the user manual because there might be information that helps you find out if your TV is compatible. Look under “Audio Codecs” and see if Dolby Digital Plus is listed.
Dolby Atmos isn’t technically an audio codec, it is still reliant on the Dolby Digital Plus or Dolby TrueHD audio codecs. There is a difference between these two, and only one is supported by ARC standard. Dolby Digital Plus, for example, is supported by ARC standard but does compress the audio through lossy format, and not lossless. Dolby TrueHD, on the other hand, is lossless but is not supported by HDMI ARC (but is supported by HDMI eARC).
The Difference between Dolby Digital Plus vs. Dolby TrueHD
Dolby Atmos uses either Dolby Digital Plus or Dolby TrueHD to handle the actual audio which is done in a couple of different ways. Regardless of how it’s done, there are limitations to these audio codecs and that’s the amount of bandwidth available to transfer the data. These two factors will determine whether your system will need to compress the audio or leave it uncompressed. Here is the difference between compression types:
- Lossy – The file is compressed, but it is not the same as the original file when it is unpacked.
- Lossless – When the audio is compressed and then unpacked it returns to the original master. What lossy does is essentially remove the fragments of audio in the master that won’t be notibly different.
This allows for a reduction in the size of the data. When this happens, data is compromised. Compare that to lossless compressions where the end result is basically the same quality as the original. This means that no data is compromised, and you are hearing the studio master. Lossless compression does not reduce the data’s size, which means it can be a very data-intensive audio format.
What this means for the Dolby audio codecs is that Dolby Digital Plus allows for quality audio formats like Dolby Atmos to be used on equipment not rated for the aggressive bandwidth and processing needs. If you are using standard ARC, it is the only way to transfer the audio and speaker metadata. Dolby TrueHD needs more bandwidth and more processing power to operate.
The HDMI ARC Standard can support 1-3 Mbps of data, whereas HDMI eARC can support up to 37 Mbps.
As you can see, there is a considerable difference between the two formats. This is why ARC can only support the compressed lossy format of Dolby Digital Plus and why only eARC is capable of handling Dolby TrueHD. Also, it’s worth mentioning that there is a way to tell if you’re truly getting the Dolby Atmos Sound, which we’ll explore in the section below.
How to Tell if You’re Getting Dolby Atmos Sound
Once you have all your connections figured out, you will need to test to confirm if your Atmos setup is functioning. This can be a little trickier than you think. What happens is that when your system does not support Atmos, it will typically upmix the audio to either 5.1 or 7.1 surround sound. This will mean you are still getting a surround sound experience but not a Dolby Atmos experience. Keep in mind that there are a lot of variables that could cause issues. For Dolby Atmos to work with HDMI ARC, you will need to have:
- A TV that supports Dolby Digital Plus through HDMI ARC or has an HDMI eARC port.
- A soundbar or AV system that supports Dolby Atmos.
- An HDMI cable that can support the bandwidth of Dolby codecs (which shouldn’t be a big issue.)
- A streaming service or media type that uses Dolby Atmos.
If you find a kink anywhere along the line, your audio will only be transmitted in surround sound. If you know what to listen for, this can be easy to identify. Dolby Atmos has a couple of features that help the technology stand out and be easily identified by a discerning ear. Listen for the following:
- Sound coming from above – This is one of the hallmarks of Dolby Atmos; the upward-firing speakers or ceiling speakers give the impression of audio coming from directly above you.
- Sounds move across the room – Because Atmos doesn’t stick sounds on only one channel, they can be designed to move across the room like natural sound does, but not just side to side.
If you still aren’t sure you are getting Atmos sound, you can always check your soundbar or AV receiver. More often than not, they will display which audio channel they are on. In this case, it should say “Dolby Atmos” or “Atmos.”
There is a lot to digest when it comes to the world of audio. Between lossless and lossy, Dolby Atmos and Dolby Digital Plus, ARC and eARC, there is a lot to understand. Thankfully, technology is improving, and these audio systems are commonly being supported. As it stands now, ARC can support Atmos using Dolby Digital Plus compression. If you have a TV with eARC, you can get the full lossless Dolby Atmos experience. For a more comprehensive look at ARC and eARC make sure you check out this video here.