Apple goes Hires

[Vincent Kars]

Some stir on the audio forums.
Apple published http://images.apple.com/itunes/mastered-for-itunes/docs/mastered_for_itunes.pdf

You will find sentences like:

Best Practices for Mastering for iTunes
Our latest high resolution encoding process ensures that your music is transparently and
faithfully distributed in the way you intended it to be heard. However, before you submit
songs to iTunes for encoding, there are some best practices you can follow to ensure
that your audio is optimized for iTunes.

Provide High Resolution Masters
To take best advantage of our latest encoders send us the highest resolution master file
possible, appropriate to the medium and the project.
An ideal master will have 24-bit 96kHz resolution. These files contain more detail from
which our encoders can create more accurate encodes. However, any resolution above
16-bit 44.1kHz, including sample rates of 48kHz, 88.2kHz, 96kHz, and 192kHz, will benefit
from our encoding process.

If you stop reading there, you will think they want to publish the recordings with the original bit depth and sample rate
If you read a bit more:

Apple’s latest encoding methodology is a two-step process. The first step in the
encoding path is to use state-of-the-art, mastering-quality Sample Rate Conversion (SRC)
to resample the master file to a sample rate of 44.1kHz.
Because this SRC outputs a 32-bit floating-point file, it can preserve values that might
otherwise fall outside of the permitted frequency range. This critical intermediary step
prevents any aliasing or clipping that could otherwise occur in SRC. It is this 32-bit
floating file that’s used as the input to the encoder and is one key reason for such
stunning results.
Our encoders then use every bit of resolution available, preserving all the dynamic range
of a 24-bit source file and eliminating the need for dithering. The advantage of this is
twofold. Not only does it obviate the need of adding dither noise, it also lets the
encoders work more efficiently as they don’t need to waste resources encoding this
unwanted and unnecessary noise.

Or if starting with WAV LPCM file at 48kHz or 96kHz sample rate:
1. To downsample to 44.1kHz LPCM using optimal sample rate conversion and add
Sound Check information, in Terminal, type on one line:
afconvert source.wav -d LEF32@44100 -f caff --
soundcheck-generate --src-complexity bats -r 127
intermediate.caf

Apple goes for 24 bit / 44.1 kHz, Redbook without dither, regardless of the sample rate of the master.
No 96 kHz I’m afraid.
Can’t expect them to support a sample rate most of their hardware can’t stomach.

 

[Phelonious Ponk]

digital without dither? It's only a matter of time when we're looking back nostalgically at digital with noise, remembering how it sounded so much more spacious and natural. All kidding aside, if the cd isn't already dead, this is a shot to the head. They get this out and I'll never buy a new one again.

Haven't I heard a few of our resident experts say that word length is the more important of the two numbers? Evidently Tomlinson Holman agrees.

Tim

 

[Phelonious Ponk]

Vincent, have you seen the "Mastered for iTunes" section on the iTunes store? It doesn't talk about resolution specifically. I may have to try a couple of things out this weekend,

Tim

 

[Vincent Kars]

No, I read the PDF only.
A possible interpretation is that they do want to have the masters in full resolution for future use but at the present will offer 24/44.1 only.

 

[LL21]

OK...let me ask a question for the tech-saavy and audio producers here.

First, my BACKGROUND
- I have a Zanden Signature DAC...16/44.1 only. but far and away my favorite digital DAC that i have heard...including ARC CD7/8, DCS Elgar Stack, DCS Scarlatti Stack, Emm Labs CDSA, Wadia 7, Esoteric X-01SE, Krell 505, plus a few others. I acknowledge quite a few above have far better detailing, but none brings me the music [the way i enjoy it] like the Zanden.

- the ONLY thing that makes me upgrade digital is hi-res.

QUESTION:

- is the current 24-bit, 192khz upsampling enough...or are we going to find out in 3 years that 32-bit is the way to go?
- I try to upgrade on average 7-yrs...and buying second-hand SOTA, i am usually quite happy with that in preamps, amps, speakers, etc...
- But i have struggled with digital and thus have had my Zanden DAC for 5 years and am debating whether i should trade now while it retains quite a lot of its original value...and go for some second-hand SOTA 24-bit DAC...or just wait 3+ more years because 32-bit is really where its at.

i have no idea and appreciate any guidance!!!

Thanks for any guidance.

 

[amirm]

I glanced through the pdf. Alas, I don't see any relationship to providing consumers higher resolution files as I think you are saying Vincent.

The article talks about an important thing: sample rate conversion errors manifest in much more degradation when the file is compressed. Aliasing error adds to the high-frequency content that the codec needs to compress, reducing compression efficiency and resulting in more compression artifacts. I happen to stumble on this while managing our codec team 12 years ago when I realized the resampler in Windows was causing far more degradation than when I used to a pro audio tool to do the conversion. So we added our own high-quality resampler to our encoder. That is what they are asking people to do now. And point out to another advantage that by keeping the target results in higher resolution, then dither noise is not added resulting in some efficiency loss due to that.

 

[amirm]

- is the current 24-bit, 192khz upsampling enough...or are we going to find out in 3 years that 32-bit is the way to go?

We cannot reproduce better than 20 bits today or anytime in the future. General noise in our electronics keeps us from having more accuracy. There are 32 bit DACs out there but that just means that you can feed them 32-bit samples, not that it can represent them. I am not seeing anything obsoleting 24-bit/192 KHz. Almost all digital music product occurs at that sampling rate and lower.

- But i have struggled with digital and thus have had my Zanden DAC for 5 years and am debating whether i should trade now while it retains quite a lot of its original value...and go for some second-hand SOTA 24-bit DAC...or just wait 3+ more years because 32-bit is really where its at.

DAC specs like that have no meaning as I mentioned above. We would need measurements and/or listening tests.

 

[Vincent Kars]

An ideal master will have 24-bit 96kHz resolution. These files contain more detail from
which our encoders can create more accurate encodes. However, any resolution above
16-bit 44.1kHz, including sample rates of 48kHz, 88.2kHz, 96kHz, and 192kHz, will benefit
from our encoding process.
Don’t upsample files to a higher resolution than their original format. Upsampling won’t
recover or add information to an audio file. Don’t provide files that have been
downsampled and dithered for a CD. This degrades the file’s audio quality.
As technology advances and bandwidth, storage, battery life, and processor power
increase, keeping the highest quality masters available in our systems allows for full
advantage of future improvements to your music. Also, though it may not be apparent
because there may not always be a physical, tangible master created in LP or CD format,
the iTunes catalog forms an important part of the world’s historical and cultural record.
These masters matter—especially given the move into the cloud on post-PC devices.

Maybe a bit too much exegesis but you can read the underlined part as an attempt by Apple to get the original masters

 

[Vincent Kars]

First of all it is not about up-sampling (by the software or the DAC) but about the availability of recordings with a native sample rate > 44.1 kHz.
The catalogue is small and will probably remain that the next years.

Some hardware accept 32 float.
If post processing is needed this might save one integer to float conversion

 

[LL21]

Amir and Vincent,

thank you both very much...extremely helpful. Sounds like there is time here for me. I can keep my 16/44.1 and let the hi-res catalogue grow a little bit. Or if i did go with 24/192 now, it does not appear likely to be outmoded for some time. ie, no rush...take my time choosing digital upgrades, and meanwhile, enjoy my favorite 16/44.1 DAC.

Many thanks!!!!!!!!!!!!!!

 

[Vincent Kars]

If you like the Zanden (NOS I guess) maybe the Metrum is an option: http://www.6moons.com/audioreviews/aprilmusic8/6.html
NOS but capable of highres

 

[LL21]

If you like the Zanden (NOS I guess) maybe the Metrum is an option: http://www.6moons.com/audioreviews/aprilmusic8/6.html
NOS but capable of highres

Thanks...based on several recommendations, i am thinking about the STahl-Tek Vekian Opus. i have heard the Vekian which was exceptionally good in detail retrieval without overhighlighting anything...but the Opus apparently adds an organic touch which takes it back to the 'magic' element for which i hold onto my Zanden. All to be determined...and of course, also depends on trade-in values, etc.

 

[Phelonious Ponk]

I listened to a bunch of "mastered for iTunes" cuts this morning and purchased a few. They do, indeed, sound good, but let's not forget that these are artists/producers concerned enough about quality sound to be pioneers in providing Apple with the best possible masters to create AACs from (Goat Rodeo, Wilco, Herbie Hancock, Philip Glass, Pink Floyd, Diana Krall, the London Symphonies latest Beethoven and Mahler symphonies....no pop tarts). So their stuff probably sounds pretty good anyway. And it is, indeed about Apple getting the best raw material to make AAC files from. The "Mastered for iTunes" files are, in fact 256kbps.

And yes, they sound very good. 256kbps or not, Some of the best mastering of Amy Winehouse I've heard is there...

Tim

 

[MarinJim]

OK...let me ask a question for the tech-saavy and audio producers here.

First, my BACKGROUND
- I have a Zanden Signature DAC...16/44.1 only. but far and away my favorite digital DAC that i have heard...including ARC CD7/8, DCS Elgar Stack, DCS Scarlatti Stack, Emm Labs CDSA, Wadia 7, Esoteric X-01SE, Krell 505, plus a few others. I acknowledge quite a few above have far better detailing, but none brings me the music [the way i enjoy it] like the Zanden.

- the ONLY thing that makes me upgrade digital is hi-res.

QUESTION:

- is the current 24-bit, 192khz upsampling enough...or are we going to find out in 3 years that 32-bit is the way to go?
- I try to upgrade on average 7-yrs...and buying second-hand SOTA, i am usually quite happy with that in preamps, amps, speakers, etc...
- But i have struggled with digital and thus have had my Zanden DAC for 5 years and am debating whether i should trade now while it retains quite a lot of its original value...and go for some second-hand SOTA 24-bit DAC...or just wait 3+ more years because 32-bit is really where its at.

i have no idea and appreciate any guidance!!!

Thanks for any guidance.

I bought a GNSC Wadia S7i because Wadia is in the upgrade game for it's customers. So, my recommendation is to go with a company that does the same. If, you can find one that you love their sound also.