Quality resolution of downloads

When it was released there were talk about going to higher resolutions on itunes for download.  I also wakely remember someone saying that Itunes would like artist to submit 24 bit files to itunes. Nothing has happened, itunes is still a terrible mp3 service, and I am not giving out money for albums that I can often find cheaper on amazon or other places second hand.

If you search for "mastered for itunes" you can find Apple's talk on the subject in a pdf file. They say all the right things but doing something about it is another matter.

Claus

320kbps MP3 & M4A are basically better than normal MP3 but not anything you would want to listen to in Naim land.

Mastered for iTunes is a meaningless brand slogan eg "the same level of quality that iTunes normally is" but Apple no doubt intend it to mean something better I suppose.

Best

David

AndyP19 posted:

I'm a bit confused in terms of quality resolution.

I get MP3 and 16/44 also, say the first level of hi res at 24/96.

But where would 'Mastered for Itunes' fit in the scale? and what does the term mean used by 7digital ' 320kbps MP3 + 320kbps M4A' 

Thanks

Hi firstly 16/44.1 is the resolution of the PCM fed to the DAC, and is 16 bits at 44.1 kHz sample rate.. and typically stereo. This is the same as CD audio resolution. When file formats are decoded, they can be reconstructed as 16/44.1 PCM streams... however if the reconstruction is from a lossy codec type such as MP3 or AAC, then some of the original information will be missing in the reconstructed PCM data.

MP3 is a lossy encoding compression format that uses psychoacoustic algorithms to encourage the brain to hear the sound as if no audio information has been removed from the original PCM audio. The format can be of various fixed and variable data rates up to a maximum of 320kbps. The higher the number the better the quality and the less loss there is to the audio and the more convincing the audio will sound.

M4A is not an audio encoding format, it’s actually a container format for files and data streams. It stands for MPEG 4 Audio. Within M4A Apple either encode AAC or ALAC. AAC is a lossy codec like MP3 but is more advanced than MP3 and is considered by some to retain more audio information than MP3 for the same data rates. Again as for MP3, the higher the data rate the better.  AAC is the general encoding format on iTunes. ALAC is a compressed lossless file format... not dissimilar to FLAC. With ALAC no information is lost in the compression and can be considered like a compressed version of WAV or AIF where all information is retained... like a computer zip file.

Mastered for iTunes can mean various things, but typically means the master is slightly optimised to help the lossy compression of the AAC encoding process occur more effectively.

Mastered for iTunes basically means that a different mastering technique was applied to raw files. I guess to make them more 'acceptable' when listening to the compresses MP3s. 

High res starts with the bit depth - min 24 bits, rather than outright sampling frequency.

Format is also important - uncompressed is vital. Most popular uncompressed format are: WAW and AIFF. 

Adam Zielinski posted:

Mastered for iTunes basically means that a different mastering technique was applied to raw files. I guess to make them more 'acceptable' when listening to the compresses MP3s. 

High res starts with the bit depth - min 24 bits, rather than outright sampling frequency.

Format is also important - uncompressed is vital. Most popular uncompressed format are: WAW and AIFF. 

Adam means WAV not WAW. But I don't agree that files have to be uncompressed. They have rather to be lossless and FLAC (or if you are in the Apple world totally then ALAC) are the most popular lossless formats.

best

David

Indeed - I meant WAV.

As David wrote - losless is the most important. Uncompressed can be helpful (i.e. FLAC vs WAW debate). Personally I cannot hear a difference between a FLAC and WAW / AIFF. But I still buy uncompressed and rip to uncompressed formats

"Mastered for iTunes" generally means ruined.  As others have explained it's lossy compression. But it also seems to me to be produced with overcooked bass.  It'll sound passable when played on an iPhone with Apple's ear buds but awful on anything of quality. 

Erm, no. According to Apples white paper, "Mastered for iTunes" ideally means high resolution and uncompressed. The latter both dynamically and datawise. Please google this.

You may have the files from the store in mind, which are compressed  with a lossy algorithm. Perhaps a little less bad than MP3, but still...

Thanks for the feedback. What prompted my question was a search for the new album by Dee Dee Bridgewater - Memphis...Yes I'm ready. One of those albums you'd quite like but only if the price is right. With the usual on-line sources at over £11 for the 16 bit/CD version, I saw that itunes had it at a much reduced price with the 'mastered for itunes' tag.

As an example, track one at 4.57 minutes in M4A is 10,045KB and 51,509KB when converted to uncompressed FLAC. (Converting to WAV is 51,476KB). Looking at my library a 5 minute track is circa 50,000KB and on the Naim app it shows FLAC 44.1. Plus the track sounds pretty good.

So question is have I netted effectively a CD quality download at a price a few quid lower than my usual Qobuz/7Digital sources?

From what I've read online, the files available at the iTunes store are 256kb/s AAC encoded i.e. not lossless CD quality. Apparently, the "mastered for iTunes" tag relates to tools provided to mastering engineers to allow them to produce 24 bit lossless files which are capable of being converted to AAC format without causing any clipping/distortion. Whilst these can be re-encoded to flac or wav, you cannot get back what has been removed by the lossy encoding process.

On a positive note, Apple apparently retain the original 24 bit lossless files although, as far as I know, these are not currently available on the iTunes store (which, admittedly, I don't use).