DD+ can carry Dolby Atmos from smart TV apps to an AVR or Soundbar. Up to around 2015, 2016, few TVs supported this feature, but since the wide-spread use of Atmos in DD+ by streaming services more and more TV manufacturers include this feature.
There is a lot of misinformation about this topic, and I'm moving a recent discussion here from the Vizio 2016 P Series thread, because it was getting too off topic there.
The technical basics: Dolby Digital Plus (short: DD+; technical term: E-AC-3) is an IEC-61937 audio format with a frame rate of 192 kHz, as opposed to the older Dolby Digital (DD; AC-3), which has an IEC frame rate of 48 kHz. DD can carry channel based audio with up to 5.1 channels, while DD+ can carry up to 7.1 channel based, as well as Dolby Atmos object based audio.
The IEC frame rate for compressed audio is equivalent to the sample rate of uncompressed stereo L-PCM audio. One L-PCM stereo sample on HDMI takes up 64 bits (2 * 24 bit plus control bits), and one IEC frame uses 2 * 16 bits of those two 24 bit samples. Therefore data bit rates are 64 times the IEC frame rate.
IEC based interfaces in consumer devices are HDMI, SPDIF (on both RCA and optical connectors) and HDMI ARC. The latter is an audio connection from an HDMI input (e.g. on a TV) to an HDMI output (e.g. on an AVR). It travels the opposite direction from the normal HDMI video/audio connection, hence the name "Audio Return Channel".
HDMI ARC has capability negotiation, using HDMI CEC messages, while SPDIF does not. This means, an ARC source (TV) can determine which audio formats are understood by the ARC receiver (AVR, Soundbar), while an SPDIF source can just try and send stuff and hope for the best. Mainly for this reason, SPDIF is usually limited to the 48 kHz realm (DD, DTS and stereo PCM), and often can not support the 96 and 192 kHz formats (96 kHz PCM, DD+, DTS-HD High Resolution). Cables and connectors are another limiting factor, often not supporting the frequency range for 192 kHz.
ARC is mainly used when an AVR or an HDMI connected Soundbar are used with a TV. Audio that originates from the TV, such as from the tuner, from OTT ("Over The Top") apps like Netflix, Amazon, Vudu, etc., or even from other HDMI inputs to the TV, can be sent to the sound device without the need for an extra cable.
Many TVs have both an SPDIF output as well as ARC on one of the HDMI inputs. This gives users the option to use SPDIF or ARC.
Now, this was all fine and dandy while there was only 48 kHz audio. TVs were built with chips that had just one audio output, and that audio was sent to SPDIF and ARC at the same time. But now there is Atmos. BD and UHD Blu-ray; Vudu, Netflix, iTunes, etc. UHD streams, and other sort of "premium" content comes with "premium" immersive audio, mostly Atmos. A lot of TV maker did not prepare for that, and have been downgrading DD+ content to DD before sending it out on ARC. So, we get plain 2.0 or 5.1 with the spiffy new UHD HDR 4K video.
An increasing number of TVs are starting to support this, in particular Dolby Vision TVs (though not all of the initial ones). Some newer ones, like the LG OLEDs starting with the 2017 models, are even capable of converting Dolby TrueHD with Atmos (from e.g. a Blu-ray player on one of the TV's HDMI inputs) to Atmos in DD+ over ARC.
And, with the release of the HDMI 2.1 specification in late 2017, a new feature has been added: eARC. This "enhanced Audio Return Channel" can support the full audio bandwidth of the HDMI forward direction (IEC frame rate of 768 kHz), and can carry Dolby TrueHD/MAT as well as DTS-HD Master Audio. It basically allows a TV to pass through any audio it receives, to the AVR/Soundbar without any re-encoding. eARC is expected to appear in TVs and AVRs in late 2018 to early 2019.
I'll work on maintaining a list of TVs that support DD+ over ARC, since this information is often hard to find. If you encounter a device, let me know and I'll add it to the lists.
AVRs and Soundbars that support ARC and Atmos are generally capable of accepting Atmos in DD+ over ARC. If exceptions are found, then I'll add them to the list, too.
Please find the lists below.
There is a lot of misinformation about this topic, and I'm moving a recent discussion here from the Vizio 2016 P Series thread, because it was getting too off topic there.
The technical basics: Dolby Digital Plus (short: DD+; technical term: E-AC-3) is an IEC-61937 audio format with a frame rate of 192 kHz, as opposed to the older Dolby Digital (DD; AC-3), which has an IEC frame rate of 48 kHz. DD can carry channel based audio with up to 5.1 channels, while DD+ can carry up to 7.1 channel based, as well as Dolby Atmos object based audio.
The IEC frame rate for compressed audio is equivalent to the sample rate of uncompressed stereo L-PCM audio. One L-PCM stereo sample on HDMI takes up 64 bits (2 * 24 bit plus control bits), and one IEC frame uses 2 * 16 bits of those two 24 bit samples. Therefore data bit rates are 64 times the IEC frame rate.
IEC based interfaces in consumer devices are HDMI, SPDIF (on both RCA and optical connectors) and HDMI ARC. The latter is an audio connection from an HDMI input (e.g. on a TV) to an HDMI output (e.g. on an AVR). It travels the opposite direction from the normal HDMI video/audio connection, hence the name "Audio Return Channel".
HDMI ARC has capability negotiation, using HDMI CEC messages, while SPDIF does not. This means, an ARC source (TV) can determine which audio formats are understood by the ARC receiver (AVR, Soundbar), while an SPDIF source can just try and send stuff and hope for the best. Mainly for this reason, SPDIF is usually limited to the 48 kHz realm (DD, DTS and stereo PCM), and often can not support the 96 and 192 kHz formats (96 kHz PCM, DD+, DTS-HD High Resolution). Cables and connectors are another limiting factor, often not supporting the frequency range for 192 kHz.
ARC is mainly used when an AVR or an HDMI connected Soundbar are used with a TV. Audio that originates from the TV, such as from the tuner, from OTT ("Over The Top") apps like Netflix, Amazon, Vudu, etc., or even from other HDMI inputs to the TV, can be sent to the sound device without the need for an extra cable.
Many TVs have both an SPDIF output as well as ARC on one of the HDMI inputs. This gives users the option to use SPDIF or ARC.
Now, this was all fine and dandy while there was only 48 kHz audio. TVs were built with chips that had just one audio output, and that audio was sent to SPDIF and ARC at the same time. But now there is Atmos. BD and UHD Blu-ray; Vudu, Netflix, iTunes, etc. UHD streams, and other sort of "premium" content comes with "premium" immersive audio, mostly Atmos. A lot of TV maker did not prepare for that, and have been downgrading DD+ content to DD before sending it out on ARC. So, we get plain 2.0 or 5.1 with the spiffy new UHD HDR 4K video.
An increasing number of TVs are starting to support this, in particular Dolby Vision TVs (though not all of the initial ones). Some newer ones, like the LG OLEDs starting with the 2017 models, are even capable of converting Dolby TrueHD with Atmos (from e.g. a Blu-ray player on one of the TV's HDMI inputs) to Atmos in DD+ over ARC.
And, with the release of the HDMI 2.1 specification in late 2017, a new feature has been added: eARC. This "enhanced Audio Return Channel" can support the full audio bandwidth of the HDMI forward direction (IEC frame rate of 768 kHz), and can carry Dolby TrueHD/MAT as well as DTS-HD Master Audio. It basically allows a TV to pass through any audio it receives, to the AVR/Soundbar without any re-encoding. eARC is expected to appear in TVs and AVRs in late 2018 to early 2019.
I'll work on maintaining a list of TVs that support DD+ over ARC, since this information is often hard to find. If you encounter a device, let me know and I'll add it to the lists.
AVRs and Soundbars that support ARC and Atmos are generally capable of accepting Atmos in DD+ over ARC. If exceptions are found, then I'll add them to the list, too.
Please find the lists below.