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Atmos finally decoded in PC/Mac

voodooless

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There are 2 reasons to prefer Atmos in TrueHD:
1) TrueHD is lossless, the difference when you listen in High quality HT is really big.
Any objective data on that?
2) Streaming audio is Dynamic compressed to follow ITU 1770/1771 or EBU128 specs. Good for TV and soundbar, not for High quality HT listening.
Atmos contains all the metadata to apply dynamic range compression, that does not mean it’s baked in. Usually you can just turn it off in the player software (which it it by default anyway), or have your AVR apply it.
 

somebodyelse

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Digimaster

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Any objective data on that?

Atmos contains all the metadata to apply dynamic range compression, that does not mean it’s baked in. Usually you can just turn it off in the player software (which it it by default anyway), or have your AVR apply it.
I can assure you that in streaming audio Dynamic compression is baked in. I've worked for years in audio industry and we delivered to streaming providers a different audio mix respect to "native" theatrical mix. The only place where you can find it, it's the Disc (BD or UHD-BD). When we speak about Atmos, it means TrueHD.

About lossy compression and "objective" data: MP3 or AAC audio sounds the same of PCM audio? I don't think so...
 

Digimaster

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Thinking so doesn’t make it objectively true…
Lossy compression is lossy. In this word, there's all you need to know.
Maybe, in the future, audio from streaming providers will be high quality audio for ultimate HT experience (and I hope so). At this time, it's not.
 

Digimaster

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No, I need to know if a human can tell the difference. So far, you've not given any evidence that they can.
I'm human and I can. Many humans in the world can do it, as you can read in many Forums in many Countries. Reviewers all around the world can hear the difference between lossy and lossless track of the same movie. All we are wrong?
Anyway, the issue about Dynamic compression is not a lossy vs. lossless matter and it's another reason (maybe more important) to don't discard Atmos in TrueHD decoding.
 

voodooless

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I'm human and I can. Many humans in the world can do it, as you can read in many Forums in many Countries.
Those are hardly ever controlled tests. Let's exclude MP3 here because it's known to be not transparent and obsolete anyway. We're talking Dolby Digital Plus specifically here. You can add high bitrate AAC as well if you like. Ever blind-tested that?
Reviewers all around the world can hear the difference between lossy and lossless track of the same movie. All we are wrong?
The same people also claim to hear differences in cables and DAC's that sound worlds apart, so how much should I rely on these subjective opinions?
 

3ll3d00d

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The question is at what bitrate does it become perceptually different? Modern tracks are , as far as I recall, 640Kbps precisely because that is the point at which people cannot tell the difference. The other difference is that DD+ tracks invariably have dialnorm metadata embedded which is typically undefeatable (hence extra care is required to actually volume match). More detail in https://www.avsforum.com/threads/defeating-dialnorm.3253654/
 

voodooless

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Last time I looked, Asio4all relies on external sync
I do see a resampling option, but you could be right. Otherwise, CamilaDSP could do it. I think it can also act as a virtual soundcard with an arbitrary number of channels.
 

somebodyelse

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I do see a resampling option, but you could be right. Otherwise, CamilaDSP could do it. I think it can also act as a virtual soundcard with an arbitrary number of channels.
As I understand it CamillaDSP's resampling is on the input end, and it can't keep different output devices in sync. You need output devices with a separate master clock for that, or some other mechanism.
 

voodooless

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As I understand it CamillaDSP's resampling is on the input end, and it can't keep different output devices in sync.
No software solution can do that for you. If you want to aggregate random sound cards, the only option is to resample the data.
 

VoidX

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that would be excellent; any thoughts on how you'll sync their respective clocks?
By calibration. Initialization offset is constant, and dilation can be measured and corrected on the fly by counting the number of samples requested by each sound card.

This is good for studio applications being able to use heavily multichannel ASIO, but passing 8+ channels to any system device is still not possible on windows. This is why I'd handle the sound cards with separate direct connections.

so...decode to multichannel PCM in PC, then HDMI out to pre/amp (or AVR) HDMI in, then to speakers? Is that what we are talking about?
You can completely bypass an AVR, but old 7.1 systems without Atmos support can now also be used as 5.1.2.

I read that Google is trying to develop a open source multi channel codec
Many others are, but none will reach the popularity of Atmos, it will stay for a long time. It's so integrated to the industry that even Dolby is unable to change AC-3 to AC-4.

Right, I mean applying e.g., room correction either in the PC downstream of decoding, or in a box between PC and speakers.
That's also a goal of the project to apply EQ on the Atmos bitstream to be able to use some higher quality calibration than what's in AVRs.

There are 2 reasons to prefer Atmos in TrueHD:
1) TrueHD is lossless, the difference when you listen in High quality HT is really big.
2) Streaming audio is Dynamic compressed to follow ITU 1770/1771 or EBU128 specs. Good for TV and soundbar, not for High quality HT listening.
So, please, don't discard Atmos in TrueHD: it's the only Atmos for HT ultimate experience.
Luckily the DRC is in the metadata, and can be easily bypassed, just throw away the values. This is not possible on an AVR, so the difference will indeed be great there, but we blind tested the DRC bypass method in a high-end HT demo room, and it passed as transparent.
 

Digimaster

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No, I need to know if a human can tell the difference. So far, you've not given any evidence that they can.
Fair enough. But you can't give any evidence that they can't. So, please and again, don't discard TrueHD because, at this time, it's the state of the art of Dolby Atmos at home: if you can't guess that lossless is better than lossy, then consider the dynamic compression issue.
 
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Digimaster

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Luckily the DRC is in the metadata, and can be easily bypassed, just throw away the values. This is not possible on an AVR, so the difference will indeed be great there, but we blind tested the DRC bypass method in a high-end HT demo room, and it passed as transparent.
No, the issue with audio from streaming providers is that audio is dynamic compressed in the master, as I've written. DRC can be bypassed or ignored, but the issue remains.
This is the main reason to decoding Dolby Atmos in TrueHD (there is another one, as I've written, but everyone can decide the value to give it)
A note: Disney is sadly famous to limit the dynamic on their audio tracks on BD and UHD-BD, because in this way they can use the same tracks for Streaming and Disc...;)
 

tifune

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Many others are, but none will reach the popularity of Atmos, it will stay for a long time. It's so integrated to the industry that even Dolby is unable to change AC-3 to AC-4.

This is interesting, can you recommend any links or articles on it?
 

Digimaster

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Ah, is that just a Windows limitation then?
Yes, but not only: if you find an AVR that accept more than 8 channels (PCM) by HDMI (it would be absolutely possibile, as per HDMI 2.0b and 2.1 specs), you win a Caraibic holiday...
 
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