So, I'm analyzing the options available to enjoy the Dolby Atmos tracks on headphones connected to a DAC / AMP with USB input.
Actually the streaming platforms that offer Atmos are Amazon Music, Apple Music and Tidal.
However, the matter is not that simple...
For the ideal listening of Dolby Atmos on headphones, a render that uses binaural metadata should be used.
But actually only the Dolby AC4 IMS format constitutes a 2-channel flow encoded in binaural with proper distance metadata.
Here an excerpt from a thread on Dolby Professional Support forum:
In this discussion on Reddit, several users confirm that Apple Spatial Renderer sounds different from the Dolby Binaural one (when headphones are used) probably due to the lack of use of distance metadata.
In fact, Audiomovers sells this add-on for manufacturers to monitor in real time how the track sounds on Apple Renderer.
Here is a couple of YouTube videos of Atmos mixing engineers illustrating the different options: video #1, video #2
Other online sources however seem to clarify that Tidal also offers AC4 IMS like Amazon.
Here a very very exhaustive article that summarise everything.
Leaving aside the customization of HRTF offered by Apple with its pods, from this information one would think that the ideal option for Dolby Atmos in headphones is Amazon Music and Tidal.
But there is one aspect that I cannot clarify.
These apps certainly provide the stream in AC4 IMS when used on mobile devices, as they are 99.9% connected to a headset.
But if I use a DAC / AMP for USB headset connected to a PC, for example, what happens?
It is known that Dolby Access app must be installed from MS Store to use Dolby Atmos on Windows. Since 24H2 version, however, Microsoft has removed the AC3 / EAC3 codecs. This is not a big problem because if ask ChatGPT how to install them it seems feasible (and also for AC4).
However, this should point out that Dolby Access on Windows has a renderer for EAC3, which as explained initially does not use metadata for binaural and therefore is not the best option for headphones.
So it would seem that the best option to listen to Dolby Atmos on a DAC / AMP with USB is to connect it to a mobile device, but it is still not clear how the streaming app detects that device and what Dolby format it streams consequently.
And it should be added that the audio engine of the devices may not be Bit Perfect and may have non-optimal performance in the Sample Rate Conversion or Limiter (possibly present / used).
It is really boring for a user to have to dig so deeply ... Obviously we are still in a phase of development and transition where standards have not established themselves, And where, however, large companies do not want to pay licenses and therefore develop proprietary solutions, favoring the heterogenization of the market (see the recent announcement by Samsung / Google)
What are your experiences?
Does anyone have newer or more in-depth information?
Are there state-of-the-art solutions that escape me?
Actually the streaming platforms that offer Atmos are Amazon Music, Apple Music and Tidal.
However, the matter is not that simple...
For the ideal listening of Dolby Atmos on headphones, a render that uses binaural metadata should be used.
But actually only the Dolby AC4 IMS format constitutes a 2-channel flow encoded in binaural with proper distance metadata.
Here an excerpt from a thread on Dolby Professional Support forum:
Avid also provides an excellent explanation of the Dolby format on the various platforms.Apple uses the DDP JOC (EAC3) codec which doesn't use the binaural render mode distance metadata. Instead it decodes and renders the audio to 7.1.4 ahead of Apple's proprietary Spatial Audio binauralization process. Amazon Music uses the AC4-IMS codec which does use the binaural renderer mode distance metadata. Depending on the content and the distance settings used this can indeed lead to discrepancies in how content sounds on headphones on the two platforms. Conversely sometimes the differences are minimal. I'm not aware of instances of different masters submitted.
In this discussion on Reddit, several users confirm that Apple Spatial Renderer sounds different from the Dolby Binaural one (when headphones are used) probably due to the lack of use of distance metadata.
In fact, Audiomovers sells this add-on for manufacturers to monitor in real time how the track sounds on Apple Renderer.
Here is a couple of YouTube videos of Atmos mixing engineers illustrating the different options: video #1, video #2
Other online sources however seem to clarify that Tidal also offers AC4 IMS like Amazon.
Here a very very exhaustive article that summarise everything.
Leaving aside the customization of HRTF offered by Apple with its pods, from this information one would think that the ideal option for Dolby Atmos in headphones is Amazon Music and Tidal.
But there is one aspect that I cannot clarify.
These apps certainly provide the stream in AC4 IMS when used on mobile devices, as they are 99.9% connected to a headset.
But if I use a DAC / AMP for USB headset connected to a PC, for example, what happens?
It is known that Dolby Access app must be installed from MS Store to use Dolby Atmos on Windows. Since 24H2 version, however, Microsoft has removed the AC3 / EAC3 codecs. This is not a big problem because if ask ChatGPT how to install them it seems feasible (and also for AC4).
However, this should point out that Dolby Access on Windows has a renderer for EAC3, which as explained initially does not use metadata for binaural and therefore is not the best option for headphones.
So it would seem that the best option to listen to Dolby Atmos on a DAC / AMP with USB is to connect it to a mobile device, but it is still not clear how the streaming app detects that device and what Dolby format it streams consequently.
And it should be added that the audio engine of the devices may not be Bit Perfect and may have non-optimal performance in the Sample Rate Conversion or Limiter (possibly present / used).
It is really boring for a user to have to dig so deeply ... Obviously we are still in a phase of development and transition where standards have not established themselves, And where, however, large companies do not want to pay licenses and therefore develop proprietary solutions, favoring the heterogenization of the market (see the recent announcement by Samsung / Google)
What are your experiences?
Does anyone have newer or more in-depth information?
Are there state-of-the-art solutions that escape me?
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