How is this different from 'Digital Master'? Because this is something I discovered today on my iPhone, and haven't seen before.
When Apple Music flips the switch on lossless, Dolby Atmos, etc., there will be various designations for the available formats of the music you're listening to.
In a nutshell, mastering is the last layer of finish put on a recording. Typically, when something is recorded in a studio, each instrument is recorded to an individual track, so listening to one single track, you might hear a guitar part or a snare drum or whatever. All that is then mixed, meaning putting together different instruments and part, with some louder or softer and placed in a stereo (or, coming momentarily, surround) sound stage. After all that, the final mix is then mastered, which is a bit of art and a bit of highly technical stuff, but the overall recording is tweaked so that it sounds just right coming out of your speakers. Some of that technical stuff involves paying attention to how the recording is to be delivered or played back. Mastering for a vinyl record, for instance, requires technical tricks to be sure that physical limitations of the grooves aren't exceeded, and so forth. Apple Music (up to this point) is delivered in a data-compressed format, and so an "Apple Digital Master" (formerly called "Mastered for iTunes") is done in part to be certain that the process of squeezing the music into a smaller file doesn't cause any undesired artifacts or effects that can be avoided. Think of it as a polishing and quality-control step.
So "Apple Digital Master" looks like it will refer to recordings that have been finished for Apple's AAC compressed file format. Something in Dolby Atmos is also mastered as its last step, but specifically for that format, so it'll have its own "Dolby Atmos" label designating that format, and so forth.
First, the headphones themselves only have individual speaker elements, so there is no integrated spatial element to position the sound sources.
Second, even if there were, your ears are effectively stereo receivers. The spatial element is produced through three mechanisms: (1) differences in volume between left and right ears; (2) difference in sound delays between the sound reaching one ear or the other; and (3) head movements which allow the brain to place the sounds subconsciously.
(1) already exists in stereo sound. (2) can similarly be mastered in stereo mixes if you don’t have to take (3) into account. No new technology is needed for that; but it’s not really worth doing without (3).
So in effect, (3) - spatial audio in terms of head movements - must be part of the Apple spatial music offering. Rather than positioning relative to a screen, the headphones could set forwards as the direction you’re facing when you start the music. It’s easy to exclude the tilt movement of your head as you look down at your phone.
Source: I teach virtual reality filmmaking at university Masters level. Whilst I specialise in image not sound, I’m 99% sure of the above…
Some further thoughts and clarifications... Spatial audio is essentially what stereo always wanted to be, but couldn't.
Let's refer back to binaural audio again, which is an in-ear surround sound technology that's existed for decades. At its most basic, it's the placement of two microphones in the exact same position as two human ears in a mannequin head. Those microphones pick up sounds exactly as a person's ears would. When those sounds are played back directly into a person's ears via headphones or earbuds, the listener is hearing sounds exactly as the mannequin stand-in did.
Remember, with just two eardrums, your brain processes auditory information in three dimensions. You can tell what direction a sound is coming from with just your two ears.
So in a binaural recording, all the minute delays from one ear to another and even the sound-wave shadow of the mannequin head are ported directly to the listener. The result is that the listener hears sounds exactly as the mannequin did. If an original sound was coming from above and behind to the right of the mannequin, the lister will perceive that in the playback.
So why hasn't stereo replicated that all along? Several reasons. First, for binaural audio to work, you have to listen through headphones. The same recording played through a pair of speakers placed in front of you won't recreate the 3D effect. It might even sound a little weird with odd phase distortions, but you can't reproduce the 3D effect when playing a binaural recording through speakers. Second, without advanced computer tech, you can't create a binaural recording without the microphones in the ears of a mannequin head configuration. A bunch of microphones placed near instruments in a recoding studio can't easily be manually mixed to create a binaural output. Even if its could, you have the problem that the same LP, CD or streaming audio source is going to be played back through headphones, earbuds, home stereo speakers, car speakers, etc. So logistically, binaural audio could never become a mainstream thing.
A good sound engineer can, however, carefully mix a studio recording so that play back through either speakers or headphones will create a convincing (or at least interesting) two-dimensional left-to-right sound stage. That's been the gold standard for decades, now. Likewise, a good sound engineer can create a 5.1 surround sound mix that sends just the right thing to each of your five surround speakers to create an auditory soundstage in a planar circle all around you.
Dolby Atmos ups the game by changing that process into an object-oriented thing. With that, you can place (almost) as many speakers as you like around and above you, and the sound engineer decides which direction the sound should come from, and a computational process at playback determines which speakers would be used for which parts of what sounds, based on your actual speaker configuration. You can play back the same Atmos mix through your 7 or 9 speaker configuration at home, or through a whole lot more speakers as they're installed in a movie theater.
The thing that makes Apple's spatial audio revolutionary is the computational processing that happens inside your device that can send sounds to your home theater surround setup, but also can compute those minute delays and sound shadows of binaural audio for playback directly into your ears via your earbuds or headphones. With that under-the-hood processing, playback is tailored to whatever your actual listening setup is, and can even create three-axis surround sound in your earbuds. That's how spatial audio is different from stereo.
The head motion tracking effect used to orient movie sounds to your iPhone screen is just an added thing on top of the rest, and it isn't particularly applicable or necessary for a spatial audio music listening experience. It's useful to tie the sounds to the action on your screen, but for audio-only music, not so much.
First, the headphones themselves only have individual speaker elements, so there is no integrated spatial element to position the sound sources.
Second, even if there were, your ears are effectively stereo receivers. The spatial element is produced through three mechanisms: (1) differences in volume between left and right ears; (2) difference in sound delays between the sound reaching one ear or the other; and (3) head movements which allow the brain to place the sounds subconsciously.
(1) already exists in stereo sound. (2) can similarly be mastered in stereo mixes if you don’t have to take (3) into account. No new technology is needed for that; but it’s not really worth doing without (3).
So in effect, (3) - spatial audio in terms of head movements - must be part of the Apple spatial music offering. Rather than positioning relative to a screen, the headphones could set forwards as the direction you’re facing when you start the music. It’s easy to exclude the tilt movement of your head as you look down at your phone.
Source: I teach virtual reality filmmaking at university Masters level. Whilst I specialise in image not sound, I’m 99% sure of the above…
Look up binaural audio. I provided a link before. Or better yet, watch a movie with Atmos Audio on your iPhone with a pair of AirPods Pro, but hold your head very, very still. The sound will be all around you. That’s spatial audio. They’re processing the Atmos signal into what is effectively binaural output, which your brain interprets as 3D sound. It will be possible to listen to spatial audio Dolby Atmos music tracks with standard headphones. There’s probably not a good way to make the motion sensing thing work when not orienting to an iPhone screen, for the reasons previously mentioned. Apple doesn’t like putting out something that doesn’t “just work,” and orienting audio-only sound without relating it to a screen probably wouldn’t work reliably well enough to get the Apple stamp of approval. We’ll find out for certain on Monday.
Looks like it’s binaural audio for the moment but with full 360 including head tracking in the autumn.
First, the headphones themselves only have individual speaker elements, so there is no integrated spatial element to position the sound sources.
Second, even if there were, your ears are effectively stereo receivers. The spatial element is produced through three mechanisms: (1) differences in volume between left and right ears; (2) difference in sound delays between the sound reaching one ear or the other; and (3) head movements which allow the brain to place the sounds subconsciously.
(1) already exists in stereo sound. (2) can similarly be mastered in stereo mixes if you don’t have to take (3) into account. No new technology is needed for that; but it’s not really worth doing without (3).
So in effect, (3) - spatial audio in terms of head movements - must be part of the Apple spatial music offering. Rather than positioning relative to a screen, the headphones could set forwards as the direction you’re facing when you start the music. It’s easy to exclude the tilt movement of your head as you look down at your phone.
Source: I teach virtual reality filmmaking at university Masters level. Whilst I specialise in image not sound, I’m 99% sure of the above…
Look up binaural audio. I provided a link before. Or better yet, watch a movie with Atmos Audio on your iPhone with a pair of AirPods Pro, but hold your head very, very still. The sound will be all around you. That’s spatial audio. They’re processing the Atmos signal into what is effectively binaural output, which your brain interprets as 3D sound. It will be possible to listen to spatial audio Dolby Atmos music tracks with standard headphones. There’s probably not a good way to make the motion sensing thing work when not orienting to an iPhone screen, for the reasons previously mentioned. Apple doesn’t like putting out something that doesn’t “just work,” and orienting audio-only sound without relating it to a screen probably wouldn’t work reliably well enough to get the Apple stamp of approval. We’ll find out for certain on Monday.
Looks like it’s binaural audio for the moment but with full 360 including head tracking in the autumn.
I’ll be interested to see how they pull the latter off.
Also, binaural output is “full 360.” You can hear sounds coming from any direction on three axes. It just doesn’t have the “dynamic head tracking” feature.
Comments
In a nutshell, mastering is the last layer of finish put on a recording. Typically, when something is recorded in a studio, each instrument is recorded to an individual track, so listening to one single track, you might hear a guitar part or a snare drum or whatever. All that is then mixed, meaning putting together different instruments and part, with some louder or softer and placed in a stereo (or, coming momentarily, surround) sound stage. After all that, the final mix is then mastered, which is a bit of art and a bit of highly technical stuff, but the overall recording is tweaked so that it sounds just right coming out of your speakers. Some of that technical stuff involves paying attention to how the recording is to be delivered or played back. Mastering for a vinyl record, for instance, requires technical tricks to be sure that physical limitations of the grooves aren't exceeded, and so forth. Apple Music (up to this point) is delivered in a data-compressed format, and so an "Apple Digital Master" (formerly called "Mastered for iTunes") is done in part to be certain that the process of squeezing the music into a smaller file doesn't cause any undesired artifacts or effects that can be avoided. Think of it as a polishing and quality-control step.
So "Apple Digital Master" looks like it will refer to recordings that have been finished for Apple's AAC compressed file format. Something in Dolby Atmos is also mastered as its last step, but specifically for that format, so it'll have its own "Dolby Atmos" label designating that format, and so forth.
Let's refer back to binaural audio again, which is an in-ear surround sound technology that's existed for decades. At its most basic, it's the placement of two microphones in the exact same position as two human ears in a mannequin head. Those microphones pick up sounds exactly as a person's ears would. When those sounds are played back directly into a person's ears via headphones or earbuds, the listener is hearing sounds exactly as the mannequin stand-in did.
Remember, with just two eardrums, your brain processes auditory information in three dimensions. You can tell what direction a sound is coming from with just your two ears.
So in a binaural recording, all the minute delays from one ear to another and even the sound-wave shadow of the mannequin head are ported directly to the listener. The result is that the listener hears sounds exactly as the mannequin did. If an original sound was coming from above and behind to the right of the mannequin, the lister will perceive that in the playback.
So why hasn't stereo replicated that all along? Several reasons. First, for binaural audio to work, you have to listen through headphones. The same recording played through a pair of speakers placed in front of you won't recreate the 3D effect. It might even sound a little weird with odd phase distortions, but you can't reproduce the 3D effect when playing a binaural recording through speakers. Second, without advanced computer tech, you can't create a binaural recording without the microphones in the ears of a mannequin head configuration. A bunch of microphones placed near instruments in a recoding studio can't easily be manually mixed to create a binaural output. Even if its could, you have the problem that the same LP, CD or streaming audio source is going to be played back through headphones, earbuds, home stereo speakers, car speakers, etc. So logistically, binaural audio could never become a mainstream thing.
A good sound engineer can, however, carefully mix a studio recording so that play back through either speakers or headphones will create a convincing (or at least interesting) two-dimensional left-to-right sound stage. That's been the gold standard for decades, now. Likewise, a good sound engineer can create a 5.1 surround sound mix that sends just the right thing to each of your five surround speakers to create an auditory soundstage in a planar circle all around you.
Dolby Atmos ups the game by changing that process into an object-oriented thing. With that, you can place (almost) as many speakers as you like around and above you, and the sound engineer decides which direction the sound should come from, and a computational process at playback determines which speakers would be used for which parts of what sounds, based on your actual speaker configuration. You can play back the same Atmos mix through your 7 or 9 speaker configuration at home, or through a whole lot more speakers as they're installed in a movie theater.
The thing that makes Apple's spatial audio revolutionary is the computational processing that happens inside your device that can send sounds to your home theater surround setup, but also can compute those minute delays and sound shadows of binaural audio for playback directly into your ears via your earbuds or headphones. With that under-the-hood processing, playback is tailored to whatever your actual listening setup is, and can even create three-axis surround sound in your earbuds. That's how spatial audio is different from stereo.
The head motion tracking effect used to orient movie sounds to your iPhone screen is just an added thing on top of the rest, and it isn't particularly applicable or necessary for a spatial audio music listening experience. It's useful to tie the sounds to the action on your screen, but for audio-only music, not so much.