Dolby AC-4

[Edawg553]

I recently purchased a new Sony OLED with an ATSC 3.0 tuner, which picks up next gen 4k stations in my area. The audio being broadcast on the ATSC 3.0 channels is Dolby AC-4. I currently have a Denon AVR-X3400H. The TV is in earc and is set to pass through everything, however the receive just displays the audio signal as Dolby Digital. I am unable to determine if there is an audio difference between Dolby Digital AC-3 (on the HD station) vs Dolby Digital AC-4 (on the ATSC 3.0 station).

Does anyone know, is the Denon receiver even decoding the AC-4 signal? Are receivers able to get a software update to decode AC-4? Thanks.

 

[everettT]

I recently purchased a new Sony OLED with an ATSC 3.0 tuner, which picks up next gen 4k stations in my area. The audio being broadcast on the ATSC 3.0 channels is Dolby AC-4. I currently have a Denon AVR-X3400H. The TV is in earc and is set to pass through everything, however the receive just displays the audio signal as Dolby Digital. I am unable to determine if there is an audio difference between Dolby Digital AC-3 (on the HD station) vs Dolby Digital AC-4 (on the ATSC 3.0 station).

Does anyone know, is the Denon receiver even decoding the AC-4 signal? Are receivers able to get a software update to decode AC-4? Thanks.

AC-4 can be from Dolby digital to Dolby Atmos, depends on the broadcast. The Denon can decode all Dolby formats (consumer), so you don't seem to have an issue.

 

[Edawg553]

Thanks. I don't have any audio issues and am able to hear audio audio on the ATSC 3.0 stations through my receiver. I just wanted to make sure I was actually listening to the newer AC-4 codec, which I must be if the Denon is able to decode all Dolby formats.

 

[everettT]

Thanks. I don't have any audio issues and am able to hear audio audio on the ATSC 3.0 stations through my receiver. I just wanted to make sure I was actually listening to the newer AC-4 codec, which I must be if the Denon is able to decode all Dolby formats.

The codec is a minimum and a maximum for Dolby. Look at the tech specs in the wiki

Dolby AC-4 - Wikipedia

en.m.wikipedia.org

 

[Edawg553]

That would make sense that the current Dolby decoders would be able to decode AC-4. I guess I was a little confused when I read ATSC 3.0 Dolby Audio Handbook February 2020 publication which discussed AC-4 Decoders.

Bottom of page 11: "At the time of this publication, only one ATSC 3.0-capable IRD (Integrated Receiver/
Decoder) with AC-4 decoding capability is commercially available (DS Broadcast BGD4100)
which can provide PCM audio to an external AC-3 or E-AC-3 encoder. The AC-4 to AC-3 or
E-AC-3 transcode functionality can also be accomplished using the AC-4 pro-decoder and
AC-3/E-AC-3 encoder SDKs, which are available."

The above makes me wonder if my TV is converting the AC-4 to an AC-3 stream before sending it to my receiver?

There is additional talk about the Dolby Multi-Stream Decoder MS12 (page 12). It goes on to talk about the MS12 v2.3 to meet the minimum requirements to provide the next gen audio experience. Is there a way for me to check if my TV or Denon have MS12? and if so, identify which version it is? Obviously I would assume at least my TV and/or receiver has some version of MS12, otherwise I wouldn't be hearing any audio.

 

[Trebdp83]

https://professional.dolby.com/siteassets/technologies/dolbt_atmos_ac-4_whitepaper.pdf