iTunes and 24-Bit Music Files?

A report from CNN suggests that Apple is moving iTunes toward 24-bit music files. What this means is that, instead of using 16-bit CD-quality files (AIFF or WAV files) to convert to the AAC format that iTunes sells, they would use masters which are recorded at 24 bits. But this makes little sense, if Apple were to simply continue to sell files in compressed AAC format.

24-bit files offer only one major improvement over 16-bit files: an increase in dynamic range, or the difference between the softest and loudest parts of music. This difference would, however, be lost if the files were compressed. So the only way that Apple could offer improved quality in the music files they sell is if there were to provide them in Apple Lossless format.

Apple Lossless format does support 24-bit audio, but given the quality of digital-analog converters (DACs) in most computers – Macs included – listeners would not notice much of a difference. While many audiophiles swear by lossless formats, the only possibility to hear a difference between them and lossy formats at decent bit rates is with very expensive audio equipment. (And even then, the placebo effect certainly comes into play.) Users who have an external DAC that supports 24-bit files might see a small improvement, at least as far as the dynamic range is concerned, but other than that, there aren’t many advantages to selling this format for use on computers and iPods. (Some may find this forum post and thread interesting for a heated discussion of the differences between 16- and 24-bit audio.)

The differences between 16-bit and 24-bit files can be somewhat complex, and 24-bit files can take up as much as three times as much disk space as 16-bit files. While Apple may want to get into the “studio master” market – a number of classical labels sell files in 24-bit / 96 khz format – it is likely that only a very small percentage of users would buy such files. The audiophile market is a niche market to start with, and files in this type of format won’t attract many listeners.

This said, if Apple were to offer files in Apple Lossless format as on option, this could attract a group of listeners who refuse to buy compressed music. With file sizes (at 16 bits) of a bit less than twice the size of Apple’s current 256 kbps files, they don’t represent a huge leap in bandwidth and storage space requirements. When burned to CD – if anyone still does that – they reproduce the exact data that was on the original CD. And, since they require more space, it’s possible that users would buy larger capacity iPods.

The trend in music downloads, at least for classical music, is toward lossless files (generally in FLAC format). Apple is a laggard in this respect, despite the fact that they offer their own lossless format. It’s obvious that Apple will make this step one day, but going to 24-bit would be only for a limited number of tracks, and most likely only for those tracks that would attract audiophiles. Lady Gaga in 24 bits still sounds the same.

One more thing: the Apple Lossless format supports 5.1 audio tracks. I’d be far more interested in surround sound than 24-bit audio. While I could only play it on my living room stereo, assuming that it could be correctly streamed through my Apple TV, this would be something that might be more popular. Though not many albums are available in 5.1 mixes yet.

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17 replies
  1. Bruce Wells says:

    Not sure why Apple would bother with 24 bit audio. Most iTunes users buy compressed audio and don’t seem to mind 128k! Full 24 bit audio would be completely lost on the great unwashed masses, especially anyone listening with those crappy white earphones supplied with iPods!

    As to the difference between 24 bit and 16 bit audio, there are two main differences. First, and probably most obvious, is the dynamic range afforded by 24 bit audio. Most humans can hear a wider dynamic range (over 100db) than CD audio (about 90 db), and 24 bis offers the full range humans can hear.

    The other major difference between the 44.1 (samples per second, 16 bits is the size of the sample) and 96 or even 192k samples per second is one word. RESOLUTION! Most haters of high quality audio harp on frequency response. Frequency response is equivalent of the number of colors in an image. Over a certain number, you can’t tell the difference between one image or the other. Resolution is actually how finely the image is reproduced. Going to 96 or 192K is more than doubling, or quadrupling the RESOLUTION. In terms of an image, resolution would be the number of pixels displayed. Imagine looking at a 1024×768 image. On a small screen (ie. crappy Apple earphones), you will not notice anything unusual, and the image will look sharp. Now blow that image up to fill a wall (like getting a really nice set of headphones like AKG K702s) and you begin to see the image is not so sharp. Now add 4 times the number of pixels, and the image is MUCH sharper. RESOLUTION in audio is heard as transparency. It is NOT about frequency response (number of colors in the image), but about reproduction of detail, how real it sounds.

    24 bits recording are amazing in detail. You also don’t need to spend major bucks to hear it either. the AKG K702′s can be had for $250 new, and they sound great, and can be powered by your iPod (but I would recommend a device with more power for best results).

      • Bruce Wells says:

        Sorry if I implied I use 24 bits on an iPod. I only listen to 16/44.1 Apple lossless on my iPod, and yes, good head phones can make a big difference.

        I do listen to 24/192 remasters on my receiver, and they sound amazing. Nothing like 16/44.1, more open, more detail, more dynamic range. Too bad there are not any 24/192 DDD recordings available. I have only found remasters at that rate. I think remasters are limited by the original analog master tapes. I am told by a producer that there is no difference between the 24/192 DVD and the master tape, so that says to me the limiting factor is the 30ips 2 inch master.

  2. Henrik says:

    Most macs support 96/24 on the optical out, and most recievers today, even those at $300, supports it.

    I have a Nuforce uDac, $150, that is both a DAC and a headphone amp, and it works great with 96/24.

    So, no, it does not take expensive equipment to play these files.

      • Bruce Wells says:

        I will disagree. Most $300 receivers are good enough for 24/96k audio to hear a difference. Plug in a good set of headphones and you can hear the difference.

        The big issue is the D to A converter you use. Most people use the built in one in the DVD player, which are good enough. Any analog receiver will do a decent job amplifying the output. The other issue is the speakers you use. I put together a $500 system, DVD player, cheap surround sound receiver and decent speakers, and it sounds great.

        But most people don’t care about audio quality, as they buy compressed music off iTunes. Still not sure how selling 24 bits files will help.

        • kirk says:

          Yes, I was going to mention DACs and speakers, but you didn’t, so I didn’t. :-)

          My point is that you need well-above-average equipment to get any difference from such files. Most people don’t have that quality equipment.

          • Bruce Wells says:

            Yes, agreed. Most people don’t have the system, not that is costs a lot, but most people just don’t care, which is why they download 128 or 256k files from iTunes and think it is OK.

            Once you hear good audio, you can’t go back to 128. I can’t listen to 128k for more than a few minutes. Also, a lot of modern pop (what most people listen to) is compressed to begin with.

            A great use of 24/192 audio would be to record a great orchestra, but to date, I have not seen a full DDD recording in 24/192. Most are remasters of analog, or 24/96k. Not sure why people are not recording in 24/192 as the norm. Always easy to down sample.

  3. kirk says:

    Well, iTunes has been 256 kbps for about two years now.

    And, for those who might not understand, when you say pop music is compressed, it’s dynamic compression, not file size compression.

    Personally, I’m fine with compressed music. I have decent equipment, and I can’t hear the difference between 160 kbps AAC and CDs – I’ve done blind listening tests, and there’s no difference for me. But I do have a DAC, so the quality of the playback is certainly better than what most people use to decode their digital files.

  4. PierOz says:

    Hi Kirk,

    there is an interesting thread on computer audiophile about the capacity of ipods to play high resolution files, they downsample everything to 16 bits.

    so not only would Apple have to increase their server capacity but they would also have to modify their hardware (ipods, ipad, airport…) to allow them to handle 24bit files…quite unlikely

    Although I have a few High Resolution files that I play through a firewire interface (Focusrite), I agree that for most people it wouldn’t make any sense to sell 24 bit music. A much more meaningful move commercially would be to sell cd quality files in Lossless with booklets in PDF files. That makes sense with the progressive abandonment of cd.
    Websites such as Qobuz and HDTracks seems to be doing rather well, and I have the impression that compared to physical formats the average price for lossless format is cheaper. So it’s all benefit for the consumer.

    Perhaps the announcement is also rather an indication that Apple is looking into making changes to iTunes so that it can play different resolution natively, thus changing the Audio-midi settings instantly. For mow you have to change it manually, relaunch iTunes, or set it to the higher possible sample rate.



  5. PierOz says:

    Just one more comment about the ‘loudness war’, I agree most of mainstream pop and rock recordings are awfully dynamically compressed (Thriller, all Alicia Keys, the last Emilie Simon…everything, damn!). More that a criminal offence to good taste and good music, I wonder if it is not potentially a matter of public health…poor ears : (
    Maybe with 24 bit files we could have access to uncompressed (dynamic compression) version of these great albums…


    • Bruce Wells says:

      They compress songs so they sound “punchy” on the radio, or on poor systems, like car stereos, or both!

      Some of the modern rock I have ripped recently looks like a fat sausage in an editor, as opposed to a more feathery profile of the older songs. I am sure the original is not recorded compressed like that, so maybe there is hope for the “box set reissue” when the record company wants to get some more revenue out of the back catalog.

      I must say, they do sound better on crappy equipment.

      • kirk says:

        I seem to recall some musician or producer saying he listened to mixes in the studio on crappy equipment because that’s how most listeners heard the music.

  6. Stephen Mackenzie says:

    My first generation iPod classic refuses to play 24/96 files at all. I don’t have any issues at all with iTunes store music at all, sounds fine to me. But it would be fun to try some higher res stuff, especially for classical music…

  7. Ian Goos says:

    I’m in favor of the choice between 16 bit and 24 bit music on iTunes. However I would have chosen a push for surround sound support instead of 24 bit.
    Additionally, I’m afraid I’m not sensitive enough to hear the difference with the music I listen to from 16 bit to 24 bit. I suspect I’d fall into the placebo influenced category. But the real problem I would face is verifiability. I’d have to take the manufacturer’s or someone else’s word for 24 bit support.
    I think ultimately I would hope for 24 bit support but not be aware that I needed factors X Y & Z in place to support it, and not sensitive to it, I might think I’m listening to 24 bit but not really. (I had this problem with a dish network receiver capable of surround sound but only over optical—at least my end audio receiver never recognized surround sound over RCA, not even an analog version of it. The main difference was it was obvious when the surround sound was present and not mixed down to all the speakers.)

    It’s not going to be the same quality jump as standard def to high def video is—at least not to my ears.

    • kirk says:

      Surround sound: the problem is, files like that won’t work on iPods, so you’d need two copies of each file, just as when you download an HD movie/TV show and get an SD copy as well.

      Verifiability: Apple could add bit info in the Summary pane; they already have sample rate.

      But I agree; the vast majority of people wouldn’t hear it, which is why I strongly doubt that Apple will go in this direction.


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