Fundamentals of digital sound III

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Marie-Ange Demory
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Apple just announced a change to its Apple Music service in terms of sound quality. If we relate that to the previous two articles (Part 1 and Part 2) what exactly will Apple do with its music subscription service?

Lossless audio

On the one hand, Apple will make available to its subscribers, the entire music catalog in lossless compression format (initially in ALAC) than it does now (in principle AAC, lossy compression, at 256 kb / s).



There will be 20 million songs in lossless audio format at launch and the catalog will reach 75 million songs by the end of the year.

Apple does not mention sample resolution but does indicate that the sample rate will reach 48kHz (remember CD quality is 44,1kHz). This will particularly affect very high treble enhancement, although most people won't notice it, especially if they don't have adequate, high-quality audio equipment.

High resolution without losses

This is what Apple calls sound where the sample rate ranges from 48kHz to 192kHz. Again, you do not specify the resolution.

In this case, again, the improvement is mainly in the highs. The file size can be much larger - 4 times larger than a 48 kHz file. This means that the user has to select whether he wants one type of audio or the other, bearing in mind that he will use a lot more data from his mobile connection and the storage space on his device.

Now, to take advantage of this high resolution, you need to have a more capable digital-to-analog converter than the one built into Macs, so Apple already warns you that you'll need to purchase a special sound card, such as a USB digital-to-analog converter. ".



For all of this, this option will be much smaller in the number of users. Here I believe that the effort is more for the image than for the business.



Dolby Atmos sound and spatial sound

We will see this later, although this is the point that really makes a difference and will be more noticeable.


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