Washington – Multiple paths are available to output audio content from future over-the-air ATSC 3.0 TV broadcasts to home audio equipment, but it will be up to individual TV suppliers to implement them, the Advanced Television Systems Committee (ATSC) said.
Dolby, DTS, and an alliance of Fraunhofer, Qualcomm and Technicolor have proposed three competing audio standards for future ATSC 3.0 broadcasts. The three proposed formats will be able to deliver 2.0- and 5.1-channel audio to TVs as well as “3D” object-based surround sound supporting 7.1+4 and 22.2 speaker systems. Dolby’s technology is called AC-4. DTS’s technology is DTS:X. And the alliance’s technology is called MPEG-H.
Here’s what Dolby and DTS had to say about how ATSC 3.0 audio could be fed to audio products in a home theater system:
Dolby: The company’s AC-4 soundtracks could be output as two-channel, 5.1-channel, or object-based audio through a TV’s HDMI audio return channel (ARC) to a home audio product, a spokesperson said. Two-channel linear PCM could also be passed through a TV’s optical output.
To play back multichannel content through a home audio system, a format conversion to a codec supported by an AVR “would take place in the TV,” the spokesperson said.
If the AC-4 soundtrack incorporates object-based audio, the soundtrack could be decoded by an HDMI-connected A/V receiver incorporating Dolby Atmos decoder. Object-based metadata would pass through the HDMI cable to the AVR.
“One of the things we have done, because the current generation of Dolby Atmos AVRs doesn’t include Dolby AC-4 decoders yet, is to support passing the decoded objects and their metadata over HDMI to the AVR to then render for the home theater system,” the spokesperson said.
In the future, Dolby envisions native Dolby AC-4 decoding in AVRs, “which will enable a direct bitstream pass-through and decoding on the AVR.” In the meantime, “we want to protect the investment of people buying Dolby Atmos AVRs today when the new broadcast standards roll out.”
In further detailing its proposal, Dolby pointed out that the bandwidth of AC-4 streams is about half the size of Dolby Digital Plus, which is used for streaming services.
DTS: “Once a TV, settop box, or other receiving device receives the ATSC 3.0 signal, the audio could be handled in one of three ways,” the company said:
- “decoded on the receiving device;
- “passed through the receiving device and out the device’s HDMI out connection; and
- “transcoded to DTS 5.1 and passed out the device’s optical or HDMI ARC connection.”
DTS also pointed out that, like today, DTV broadcasters will send “whatever they choose from the yet-to-be defined specification.” If a broadcaster transmits “an immersive audio broadcast featuring objects, it could be rendered and played back on a 5.1- or two-channel system” because “the format is sending the highest quality / largest configuration of audio and then playing back what is appropriate for the consumer device,” DTS explained.
That is “much like today’s broadcasts where 5.1 is sent out, and most TVs play out stereo. Only one signal is sent, but multiple playback configurations are possible based on the abilities of the format and decoder.”
The company didn’t say whether object-based DTS:X broadcasts would be decoded by the DTS:X decoders that will be available in A/V receivers. “We will provide details related to AVRs as part of the official DTS:X unveiling,” the company said.