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Change Audio Format to Dolby Digital 5.1 - Output Bitrate?

@HDFan I have 32TB of NAS storage (before redundancy and overheads) so space isn’t a direct concern at the moment. I’ve always found that even vanilla AC3 can sound amazing on good equipment and so have not prioritised audio in my file size considerations. I made an informed choice to use the bitrate budget on higher quality video while still getting excellent audio. Storage space isn’t yet at a premium but I don’t want to end up with thousands of movies that are unnecessarily 2-3000kbps bigger than I need them to be. But what I would like is for the ATV to at least play all my audio without having to fudge workarounds. If it would just play my non-Apple 5.1 tracks without trying to mix them down to stereo then I wouldn’t have to keep changing device settings and this thread wouldn’t exist. Alas…

Thanks for your comments on the Shield. I may well give one a try at some point and just use a throwaway Google account that’s used for nothing else. From what I can tell from my research so far, it will solve my audio woes.
 
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Jim Lahey said:
But then why does DD+ work just fine over ARC when playing Apple content? When I play Apple movies using the same equipment my receiver clearly displays Dolby Digital + (with change audio format set to off).
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Because the HDMI EDID info from the TV tells the Apple TV that Multichannel LPCM is not available (due to the AVR being the audio "sink" over ARC), so it instead uses DD+.

I am not sure if that's the original bitstream from Apple's servers, or if there is a private API the Apple TV can use to mix navigation and Siri audio together; either way, I am guessing Plex and Infuse (have you tried that? The pro version is a dollar per month...) maybe also can't do the same detection and auto toggle a similar output mode.
 
Wombert said:
Because the HDMI EDID info from the TV tells the Apple TV that Multichannel LPCM is not available (due to the AVR being the audio "sink" over ARC), so it instead uses DD+.

I am not sure if that's the original bitstream from Apple's servers, or if there is a private API the Apple TV can use to mix navigation and Siri audio together; either way, I am guessing Plex and Infuse (have you tried that? The pro version is a dollar per month...) maybe also can't do the same detection and auto toggle a similar output mode.
Click to expand...

Thanks. I have tried Infuse and the issue is identical. I know I’m probably being dim but no matter how many explanations people offer, it still doesn’t really make sense to me. Everything that ATV apparently can’t do, it does do when playing Apple’s own media. It won’t even play vanilla AC35.1 much less DD+ audio unless a) I change the audio output or b) it’s an Apple file.

ETA: in any case as I said earlier, I’m going to draw a line under it. I’ve concluded that Apple TV just sucks. Next purchase will almost certainly be something that isn’t constrained by Apple’s standards. By all accounts all I need is something that’s able to pass the bitstream without trying to process it. Shame ATV doesn’t have this as an option. Typical Apple.
 
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Jim Lahey said:
I’ve concluded that Apple TV just sucks.
Click to expand...

I have both the Shield and Roku streaming devices. Both poorly compare with the Apple TV, other than the improved audio with the Shield. It is just unfortunate that your particular Apple TV/Receiver/TV configuration for some reason has some problems.
 
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HDFan said:
I have both the Shield and Roku streaming devices. Both poorly compare with the Apple TV, other than the improved audio with the Shield. It is just unfortunate that your particular Apple TV/Receiver/TV configuration for some reason has some problems.
Click to expand...

You're probably right and I was only venting, really. What continues to baffle me is that Apple-purchased media is able to make it to the receiver as Dolby Digital Plus. Since we know ARC cannot carry 5.1 LPCM then this means that ATV must be sending E-AC3 bitstream out over HDMI, even though we know it cannot (or rather won't) do this. Totally perplexing. First world problems eh...
 
Jim Lahey said:
Since we know ARC cannot carry 5.1 LPCM then this means that ATV must be sending E-AC3 bitstream out over HDMI, even though we know it cannot (or rather won't) do this. Totally perplexing. First world problems eh...
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Even Dolby Labs explained it some time ago, that tvOS will not bitstream.
developer.dolby.com website has meanwhile been completely redesigned, but luckily we can travel back in time using the wayback machine:

Dolby Developer

Dolby Developers
web.archive.org
 
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priitv8 said:
Even Dolby Labs explained it some time ago, that tvOS will not bitstream.
developer.dolby.com website has meanwhile been completely redesigned, but luckily we can travel back in time using the wayback machine:

Dolby Developer

Dolby Developers
web.archive.org
Click to expand...

Thanks. Interesting read but doesn’t explain what’s happening in my system. Only explanation is that my receiver is lying about Dolby Digital Plus from Apple media, which of course makes no sense either. It even sounds slightly better so I’m confident it’s receiving DD+ over ARC.
 
Jim Lahey said:
Thanks. Interesting read but doesn’t explain what’s happening in my system. Only explanation is that my receiver is lying about Dolby Digital Plus from Apple media, which of course makes no sense either. It even sounds slightly better so I’m confident it’s receiving DD+ over ARC.
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It should sound better even if it receives LPCM decoded from DD+ because of the better codec and higher bitrate it uses.
I would love to see the aTV sending native DD+ to your AVR.
Has not happened to me, honestly. And I have used aTV for quite a long time, the 4K model from the year of its introduction.
PS What TV are you using? The very last idea of how can it be is - the TV encodes DD+ for your eARC.
I see no other possibility.
 
priitv8 said:
It should sound better even if it receives LPCM decoded from DD+ because of the better codec and higher bitrate it uses.
I would love to see the aTV sending native DD+ to your AVR.
Has not happened to me, honestly. And I have used aTV for quite a long time, the 4K model from the year of its introduction.
PS What TV are you using? The very last idea of how can it be is - the TV encodes DD+ for your eARC.
I see no other possibility.
Click to expand...

But ARC cannot carry multichannel LPCM so how is my AVR receiving it from Apple TV? :oops:

My TV is an LG C9 65" OLED with ARC set to passthrough. It's also set to eARC but that's immaterial since my AVR (Sony STR-DN1040) doesn't support it. I did wonder, as you say, if the TV is re-encoding DD+ LPCM from ATV to bitstream before sending it out to my receiver for decoding. But if that is the case then why does it only do so for Apple media? ??

I don't think this will ever be fully resolved without a new AVR that will let me passthrough 2160p 4:4:4 to the LG, but honestly even then I'd be lacking DTS bitstream out from the Apple TV.
 
Funny that you say that you also have Sony AVR. I used DN1080 previously, now it is a ZA5000ES.
I did never see DD+ being reported from aTV. As I said earlier, I never used it via ARC, only directly connected to HDMI in on the AVR.
PS even regular ARC can be configured to output DD+ (at least on my Bravia that's the way you could get Atmos from the internal apps to AVR).
PPS According to LG help, the ARC output might be re-encoded to Dolby Digital, as I understand. I also do not know anything about LG tellys, but I wonder, how will it behave if aTV sees it as Atmos-accepting sink and you ask it to forward received MAT2.0 (LPCM) signal to ARC? If you ask why only Apple-sourced content, then the reason may be as simple as it has proper Atmos metadata set in MP4 headers.
 

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The final solution to get everything working optimally plus enabling DTS bitstream will eventually have to be a new AVR and using something other than Apple TV as the client device. Until then I shall just continue as I am. It's an ageing but substantial setup with great speakers and a B&W PV1D subwoofer so to be honest there's nothing it does that sounds bad ?
 
I agree. In my case, I use appleTV for compressed audio mainly (i.e. DD and DD+), music I can also use ALAC lossless and newly Apple Music in lossless or lossy Atmos. Both are good to my ears.
For lossless TrueHD Atmos and Dolby vision, I use Sony UHD bluray player.
 
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Jim Lahey said:
Hello. Although my AV system is fully capable of playback of the more modern audio formats - up to but not including Atmos - when using the Apple TV Plex client I have to change audio format to AC3 5.1 or it will only output stereo PCM to my receiver irrespective of the format of the file coming from the Plex Server. That is the thrust of the issue but it's not the purpose of this topic. Since my gear is a very capable if ageing separates system then it always sounds great anyway, even with trusty old vanilla 5.1.

My question to you good people is this: out of curiosity, when the Change Audio Format is switched in settings to Dolby Digital 5.1, what is the output bitrate of the stream? I'm hoping it's at least 384kbps as per the older DVD typical norm? I would like to know the maximum bitrate of this AC3 downmix on ATV because it's relevant when I'm encoding HEVC videos from my purchased Blu-rays...no point ripping passthrough audio tracks with mega bitrates if I cant hear them, as it's just wasted file size. I can always re-rip them at a later time if my audio situation changes.

If anyone can shed some light on the Plex issue then that's a bonus. It is only the Plex app - Dolby Digital Plus etc. plays just fine from iTunes or ATV+ sources without me having to use this workaround.

TLDR; what is the maximum bitrate of Apple TV's Dolby Digital 5.1 mixdown capability?
Click to expand...
Very good question. I've been searching the net for the exact information. What is the bitrate, when you fx. via Infuse put an DTS-HD Master Audo signal or TreuHD Signal, and let Apple TV change the foermat. Is the the maximum, 640, when the original is on par or over that? I simply can't find any answers anywhere...
 
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This is what I see, when playing DTS:X MA audio from Plex server via Infuse client on tvOS.
According to my calculations, this amounts to:
48k x 8 x 24 = 9216kbps

Here's the MediaInfo report of the source file:
Code: 
General
ID                                       : 0 (0x0)
Complete name                            : /Volumes/iTunes/Non-iTunes Media/Tests & Demos/DTS.Demo.Disc.Vol.24.2020.2160p/02-Wolf Warrior 2 UHD.m2ts
Format                                   : BDAV
Format/Info                              : Blu-ray Video
File size                                : 1.59 GiB
Duration                                 : 3 min 22 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 67.5 Mb/s
Maximum Overall bit rate                 : 109 Mb/s


Video
ID                                       : 4113 (0x1011)
Menu ID                                  : 1 (0x1)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2086, HDR10 compatible
Codec ID                                 : 36
Duration                                 : 3 min 21 s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 2)
Bit depth                                : 10 bits
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : BT.2020
Mastering display luminance              : min: 0.0050 cd/m2, max: 1000 cd/m2


Audio #1
ID                                       : 4352 (0x1100)
Menu ID                                  : 1 (0x1)
Format                                   : DTS XLL X
Format/Info                              : Digital Theater Systems
Commercial name                          : DTS-HD Master Audio
Muxing mode                              : Stream extension
Codec ID                                 : 134
Duration                                 : 3 min 21 s
Bit rate mode                            : Variable
Channel(s)                               : Object Based
Channel layout                           : Object Based


Audio #2
ID                                       : 4353 (0x1101)
Menu ID                                  : 1 (0x1)
Format                                   : DTS XLL
Format/Info                              : Digital Theater Systems
Commercial name                          : DTS-HD Master Audio
Muxing mode                              : Stream extension
Codec ID                                 : 134
Duration                                 : 3 min 21 s
Bit rate mode                            : Variable
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 93.750 FPS (512 SPF)
Bit depth                                : 24 bits
Compression mode                         : Lossless

PS I will need to check, if Vertex can display DD5.1 bitrate from HDMI.
 

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