Apple TV and Dolby Digital Output (posts from 'Music streaming on Apple Music in 5.1' thread)

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Cheezmo

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Yes you said "upconverted" which isn't entirely accurate.
Upconverted is accurate, as is your description of the original quality.

Nothing to argue about here, the DD+ lossy source is upconverted by the AppleTV to lossless for delivery to the processor. Your two posts complement each other.
 

JediJoker

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Nothing to argue about here, the DD+ lossy source is upconverted by the AppleTV to lossless for delivery to the processor.
An inaccurate description. It is not "upconverted:" it is simply decoded by the Apple TV from lossy to lossless, without any information added or extrapolated. "Upconversion" implies the latter.
 

marcb

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An inaccurate description. It is not "upconverted:" it is simply decoded by the Apple TV from lossy to lossless, without any information added or extrapolated. "Upconversion" implies the latter.
Upconverted implies it was upconverted from lossy to lossless. If you take something from .mp3 to lossless PCM, you’re upconverting it - even though no “info” is being added or extrapolated. Exactly the same with going from DD+ to PCM.. But if you want to split microscopic hairs and call it “convert”, have at it Webster.

The end result is it goes from a lossy DD+ source to 24/48 PCM. Which is what I wrote - and you perfectly understood.
 

JediJoker

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Upconverted implies it was upconverted from lossy to lossless. If you take something from .mp3 to lossless PCM, you’re upconverting it - even though no “info” is being added or extrapolated. Exactly the same with going from DD+ to PCM.. But if you want to split microscopic hairs and call it “convert”, have at it Webster.

The end result is it goes from a lossy DD+ source to 24/48 PCM. Which is what I wrote - and you perfectly understood.
Sorry, but you're just wrong as far as terminology is concerned. When you play back an MP3, it is decoded to uncompressed PCM before it hits the DAC. If it weren't, all you'd hear would be noise. Doing this at a file level—or what the Apple TV does for DD+ streams it passes to HDMI—is no different. "Upconversion" is the term used for when a lower resolution source is converted to a higher resolution output with additional processing intended to improve upon the source, such as upconverting standard resolution video to HD or 4K. In audio, upsampling is a form of upconversion. This is not that.
 

EricKalet

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Sorry, but you're just wrong as far as terminology is concerned. When you play back an MP3, it is decoded to uncompressed PCM before it hits the DAC. If it weren't, all you'd hear would be noise. Doing this at a file level—or what the Apple TV does for DD+ streams it passes to HDMI—is no different. "Upconversion" is the term used for when a lower resolution source is converted to a higher resolution output with additional processing intended to improve upon the source, such as upconverting standard resolution video to HD or 4K. In audio, upsampling is a form of upconversion. This is not that.
Thank you for this explanation, exactly spot on.
 

marcb

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Sorry, but you're just wrong as far as terminology is concerned. When you play back an MP3, it is decoded to uncompressed PCM before it hits the DAC. If it weren't, all you'd hear would be noise. Doing this at a file level—or what the Apple TV does for DD+ streams it passes to HDMI—is no different. "Upconversion" is the term used for when a lower resolution source is converted to a higher resolution output with additional processing intended to improve upon the source, such as upconverting standard resolution video to HD or 4K. In audio, upsampling is a form of upconversion. This is not that.
Sorry but you and EricKalet are wrong. Image processing is not the same as audio processing and is not useful as an analogy.

Audio decoding is unpacking and uncompressing a file or stream. So when the original audio source is lossy compressed into a DD+ file, it is encoded. When the compressed file is unpacked, it is decoded.

Converting is taking an audio file and converting it to a different digital audio format or analog signal. In this case, that would be taking the uncompressed , but still lossy decoded DD+ and losslessly converting that lossy unpacked file to PCM. If it goes from a higher resolution to a lower resolution, it is downconverted. If it is lower resolution to a higher resolution - even if the extra bits are just empty - it is upconverted. This can happen manually or - as is the case with Apple TV - automatically in real-time. Every software tool I know of which takes something from one format to another calls it conversion, not encoding/decoding.

Additional processing is additional processing.

You can call the entire process of unpacking the DD+ and turning it into PCM “decoding” if you want. But it’s really a two-step process albeit a nuanced one.

Regardless, you are playing a pedantic game of semantics with no practical purpose.
 
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EricKalet

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You can call the entire process of unpacking the DD+ and turning it into PCM “decoding” if you want. But it’s really a two-step process albeit a nuanced one.

Regardless, you are playing a pedantic game of semantics with no practical purpose.
If it's coded as 48/16 and decoded as 48/16 then there is no up or down conversion or additional processing. But really it's a game of potato vs. potato. Let's move on shall we?

Pot-pot.jpg
 

marcb

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If it's coded as 48/16 and decoded as 48/16 then there is no up or down conversion or additional processing. But really it's a game of potato vs. potato. Let's move on shall we?

View attachment 74167
That’s really cool how you again say I’m wrong, then say it’s really splitting hairs, then act like you’re taking the high road.

It is streamed by the AppleTV at 24 bit, not 16 bit btw. I stand by my original post.
 

EricKalet

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That’s really cool how you again say I’m wrong, then say it’s really splitting hairs, then act like you’re taking the high road.

It is streamed by the AppleTV at 24 bit, not 16 bit btw. I stand by my original post.
I can not find anywhere on Dolby's site or Apple site that Dolby Digital E-AC-3 (DD+) is streamed by ATV at 24 bit.

I did find this and highlighted what stands out to me as the final say on how DD+ is handled by audio equipment: "By means of an elegant conversion process, Dolby Digital Plus bitstreams, regardless of their source bit rate, are repackaged into a standard Dolby Digital format at 640 kbps. The conversion process does not decode the signal to PCM and reencode it, therefore avoiding the introduction of compounding coding artifacts." https://professional.dolby.com/globalassets/dolby-digital-plus/dolby-digital-plus-audio-coding-tech-paper.pdf
 
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