Atmos

[cosmoxl]

3.9.2 still cannot get my Denon receiver to recognize atmos stream. also, no tv art is showing in library, Cant find any specific setting to passthrough atmos track.

It works only for EAC-3 Atmos tracks.

Would u elaborate what are the different kinds of Atmos tracks?

there is atmos with trueHD and atmos with DD+ (eac3).

[xkwwwx]

3.9.2 still cannot get my Denon receiver to recognize atmos stream. also, no tv art is showing in library, Cant find any specific setting to passthrough atmos track.

It works only for EAC-3 Atmos tracks.

Would u elaborate what are the different kinds of Atmos tracks?

A_TRUEHD. mostly. I now understand that Apple TV cannot play this codec. Hoping the next release can at least convert it to EAC-3.

[Jarvismeier]

It works only for EAC-3 Atmos tracks.

Would u elaborate what are the different kinds of Atmos tracks?

A_TRUEHD. mostly. I now understand that Apple TV cannot play this codec. Hoping the next release can at least convert it to EAC-3.

From my understanding the container that atmos is attached to has to be done during the mastering of the audio track. You can’t simply extract the metadata from a TrueHD stream and reattach it to an eac-3 stream. Best case scenario is to have MrMC decode the atmos track and send it as a DolbyMAT 2.0 LPCM stream.

[xkwwwx]

Maybe the team can find a way to transcodeTrueHD+Atmos to EAC3+ Atmos?

[davilla]

fun fact, the AppleTV 4K internally understands the following:

"session available formats" = "{ { [ 32/48000/2 lpcm ], [ 32/48000/6 lpcm ], [ 32/48000/8 lpcm ], [ 16/192000/2 cc+3 ], [ 16/176400/2 cc+3 ], [ 16/192000/2 cd+3 ], [ 16/176400/2 cd+3 ], [ 16/192000/2 cec3 ], [ 16/176400/2 cec3 ], [ 16/768000/2 mtat ], [ 16/48000/32 mtb+ ], [ 16/768000/2 mtbt ], [ 16/48000/32 mtc+ ], [ 16/44100/32 mtc+ ], [ 16/768000/2 mtct ], [ 16/705600/2 mtct ] } }";

Note the sample rates which go up to 192000.
Of particular interest is "mtb+" which it uses when outputting eac3/atmos.

AVPlayer will take a eac3/atmos raw file and output Dolby Atmos. Probing show that it sees three "tracks", ec3, atmos/12 channels and atmos/16 channels.

I suspect ACAudioPlayer will also output Dolby Atmos.

However, AVSampleBufferAudioRenderer just plays the eac3 part when one inputs eac3/atmos. From what I see, there is no public method that can switch tracks.
Same results when feeding an AudioUnit/kAudioUnitSubType_RemoteIO.

Somehow, AVPlayer detects and enables atmos decoding eac3/atmos. Still investigating

[luckynd]

Hi Davilla,

Any progress on this topic?

Thx

[rogbott]

With an ATV4k running tvOS 13, if I rip a movie that has an Atmos TrueHD track, will it be decoded to LPCM and therefore lose the Atmos data or does it get converted to Dolby MAT and keep the Atmos data intact? I read that DD+ Atmos is fully supported which I am assuming means that it is being transcoded to Dolby MAT for the streaming services, but was unsure if this transcoding capability is leveraged across the board by other apps and formats.

[cosmoxl]

With an ATV4k running tvOS 13, if I rip a movie that has an Atmos TrueHD track, will it be decoded to LPCM and therefore lose the Atmos data or does it get converted to Dolby MAT and keep the Atmos data intact? I read that DD+ Atmos is fully supported which I am assuming means that it is being transcoded to Dolby MAT for the streaming services, but was unsure if this transcoding capability is leveraged across the board by other apps and formats.

yeah, truehd would lose atmos at the moment. maybe some conversion will come in the future? only davilla knows.

[rogbott]

yeah, truehd would lose atmos at the moment. maybe some conversion will come in the future? only davilla knows.

Thanks for the quick reply. I had a sinking feeling that was the case and I bet that Apple hasn't opened up the transcoding possibilities beyond Netflix and other streaming apps. Fingers crossed they allow third-party non-streaming video players to get access to it.

[oviano]

fun fact, the AppleTV 4K internally understands the following:

"session available formats" = "{ { [ 32/48000/2 lpcm ], [ 32/48000/6 lpcm ], [ 32/48000/8 lpcm ], [ 16/192000/2 cc+3 ], [ 16/176400/2 cc+3 ], [ 16/192000/2 cd+3 ], [ 16/176400/2 cd+3 ], [ 16/192000/2 cec3 ], [ 16/176400/2 cec3 ], [ 16/768000/2 mtat ], [ 16/48000/32 mtb+ ], [ 16/768000/2 mtbt ], [ 16/48000/32 mtc+ ], [ 16/44100/32 mtc+ ], [ 16/768000/2 mtct ], [ 16/705600/2 mtct ] } }";

Note the sample rates which go up to 192000.
Of particular interest is "mtb+" which it uses when outputting eac3/atmos.

AVPlayer will take a eac3/atmos raw file and output Dolby Atmos. Probing show that it sees three "tracks", ec3, atmos/12 channels and atmos/16 channels.

I suspect ACAudioPlayer will also output Dolby Atmos.

However, AVSampleBufferAudioRenderer just plays the eac3 part when one inputs eac3/atmos. From what I see, there is no public method that can switch tracks.
Same results when feeding an AudioUnit/kAudioUnitSubType_RemoteIO.

Somehow, AVPlayer detects and enables atmos decoding eac3/atmos. Still investigating

Although not a user of MrMC, I have been trying to use some of the CoreAudio APIs on a video player project to play Atmos from a raw eac3 bitstream on Apple TV and am running into the same problems.

AVAudioPlayer and AudioQueue seem to trigger only regular Dolby Digital on my TV, whereas AVPlayer when given an MKV containing the same audio track is able to trigger Atmos on the TV. So whether it is track selection or something else, it seems that this logic is only present in AVPlayer, and not in the audio-specific APIs, which is annoying!