iTMS: Satisfied with bit-rate?

Posted:
in iPod + iTunes + AppleTV edited January 2014
First off, I live in Australia now, so I haven't actually bought a song from the Store. (But I've been playing around with the interface so I'll be good and ready when the time comes. Oh yes.)



Anyway, I wanted to check with you nice American folks who are in the know: the previews on the iTMS are supposed to be encoded at the same rate as the actual file, right? 128kbps AAC? Are people happy with the quality that they're getting on purchase? If happy, is that comparable-to-CD-quality happy, or happy compared to whatever standard mp3 rip-rate you're using?



I was enthusiastically showing the iTMS off to my father, from whom I inherited whatever little audiophilic capacity I have, so I opened up a preview for one of the songs I tend to use as a benchmark, Eric Clapton's "Change the World". I actually only have one copy of this song, a 128kbps MP3, which has always sounded decent, so I was expecting a small step up in quality with AAC at the same rate, or at the very least for it to sound the same.



However, I noticed with some surprise what I guess is some pretty harsh compression fallout at some points where the vocals hit high notes - it crashed into some sort of ceiling after which there was a tinny, muffled quality and a noticeable warble. My dad didn't notice anything at first until I mentioned it. But here's the thing - shouldn't it at least sound better than an MP3 ripped at the same bit-rate?



This mostly doesn't matter if you're listening to rock, but I listen to a fair bit of jazz and blues and I think you generally get away with less when the music is "unplugged". I hate to be picky (particularly as I am just flat envious of the service - even with the exchange rate, buying a whole album on iTMS would still approach HALF the price of buying a CD in Australia) but for a company that cares about quality control the way Apple does...



Has anyone had any serious objections to the audio quality, audio nut or otherwise? I'm not that much of a nut myself which is why I was surprised that I could hear what I did.
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Comments

  • Reply 1 of 42
    torifiletorifile Posts: 4,024member
    I don't know for sure what the encoding is like on the previews. There's absolutely no reason for us to think that it's at 128kb/s because there's been no indication anyway. I've listened to some previews and I'd imagine that they are less than that, just because they don't sound great. I've bought a couple albums and I can't complain about the quality. I bought the coldplay album and previously I had only heard it at 160 mp3. I think the aac version is better.



    edit: let me also add that the other album I bought was Coltrane's Blue Train and I haven't noticed any problems in the encoding (using my decidedly non-audiophile ears and a good set of headphones).
  • Reply 2 of 42
    banchobancho Posts: 1,517member
    I've been pretty thrilled. The few tracks I purchased so far I had previously only heard on cassette so the 128KB files are stunning in comparison .
  • Reply 3 of 42
    shetlineshetline Posts: 4,695member
    Quote:

    Originally posted by Shanmaneser

    I was enthusiastically showing the iTMS off to my father, from whom I inherited whatever little audiophilic capacity I have, so I opened up a preview for one of the songs I tend to use as a benchmark, Eric Clapton's "Change the World". I actually only have one copy of this song, a 128kbps MP3, which has always sounded decent, so I was expecting a small step up in quality with AAC at the same rate, or at the very least for it to sound the same.



    However, I noticed with some surprise what I guess is some pretty harsh compression fallout at some points where the vocals hit high notes - it crashed into some sort of ceiling after which there was a tinny, muffled quality and a noticeable warble. My dad didn't notice anything at first until I mentioned it. But here's the thing - shouldn't it at least sound better than an MP3 ripped at the same bit-rate?




    I just listened to this same passage. I don't have the same music in any other format for comparison, so I can only say that in isolation it sounded just fine to me. The only thing that sounded like warble to me was a little vibrato. Certainly no part of it sounded harsh or tinny.



    Can you somehow get a hold of the uncompressed source from a CD for comparison? Maybe your MP3 is lacking some audible content that the AAC version doesn't miss, but you've gotten used to the sound of the MP3, so that version sounds better to you.
  • Reply 4 of 42
    Quote:

    I don't know for sure what the encoding is like on the previews. There's absolutely no reason for us to think that it's at 128kb/s because there's been no indication anyway. I've listened to some previews and I'd imagine that they are less than that, just because they don't sound great.



    Right, that was what was worrying me. I'm dead sure I heard Steve Jobs say something in his "keynote" last week that the previews were encoded at the same 'pristine' quality as the purchasable files, ie. 128kbps, but I guess he slipped.



    Same-rate previews would make perfect sense to me - apart from making sure the song is the one you want, it's just very good business sense to let customers have a small taste of the quality of what they're buying. I guess not, though. Maybe it's got something to do with how fast Apple wants shoppers to be able to access preview tracks.



    Anyway, very encouraging, for both the Coltrane and Coldplay reasons (I have A Rush Of Blood To The Head at 160kbps MP3 as well, if you say the AAC is better, that's very comforting!)



    Cassettes, that's a good idea, what's on my old ones...?
  • Reply 5 of 42
    hmurchisonhmurchison Posts: 12,341member
    No I heard just that opposite. The Previews may be at 128kbps but they are smaller for quick previews. AAC has different levels of compression "Profiles" of some sort.



    I've heard numerous reports on maccentral.com about anomalies in the Previews that don't show up with the downloaded file.
  • Reply 6 of 42
    Quote:

    Originally posted by shetline

    The only thing that sounded like warble to me was a little vibrato. Certainly no part of it sounded harsh or tinny.



    Can you somehow get a hold of the uncompressed source from a CD for comparison? Maybe your MP3 is lacking some audible content that the AAC version doesn't miss, but you've gotten used to the sound of the MP3, so that version sounds better to you.




    I take your point, I should get the uncompressed track to compare. Benchmarking at 128 mp3 is a bit obtuse, yeah. But even other tracks, like - oh, "Layla", say - for which I do have CD audio comparison, I'm pretty sure there is something noticeable there.



    This could all be my nitpicky imagination of course. I was just curious about whether the previews are actually representative of what you're going to get, or if I read too much into the press releases. I still can't actually buy a song yet.
  • Reply 7 of 42
    matsumatsu Posts: 6,558member
    I'll rip clapton from CD to a few different formats and play it through my stereo. I wonder if the file system on my CD will read MP3 ad AIFF off the same disc. Just so I can't tell, hear discs switching etc etc...



    I could run AAC from the mac to the reciever, but then they wouldn't be using the same source.



    My impression in the past has been that low bit rates like 128-192 certainly are noticeable, but not unpleasant at 192. At 320, I don't notice too much difference unless I play it back to back against the CD.
  • Reply 8 of 42
    Have you done any extensive blind testing of this? I thought I had pretty good ears for this kind of thing, but did terribly in a 192 vs 320 test not too long ago. Damn placebo effect.
  • Reply 9 of 42
    jlljll Posts: 2,709member
    Quote:

    Originally posted by Matsu

    I could run AAC from the mac to the reciever, but then they wouldn't be using the same source.



    Um, your Mac can play CDs and AIFFs you know
  • Reply 10 of 42
    matsumatsu Posts: 6,558member
    The mac most surely doesn't do as good a job as a dedicated CD player, and it probably doesn't do as well as my DVD/MP3 player either. Computers usually make a shitty source that will mask many inadequacies of a recording. Well, that's not true, they're up to Mid-fi quality.



    Just trying o get a like with like comparison. Same system, same source, differnet formats. Though this isn't anywhere near as rigorous as it needs to be. My DVD player doesn't play back AAC either.



    My buddies nephews make CD's for his car using MP3's converted to AIFF. They sound crappy, very muddled.



    If the point of this tech is that we can make CD's for our use, encoding them using a 128kbps source is a recipe for dissapointment.
  • Reply 11 of 42
    shetlineshetline Posts: 4,695member
    Quote:

    Originally posted by Matsu

    My buddies nephews make CD's for his car using MP3's converted to AIFF. They sound crappy, very muddled.



    Are you saying that the AIFF sounds crappy, just like the MP3, or are you trying to say that the AIFF sounds worse than the MP3 from which it was derived?



    If the latter... that makes no sense. AIFF is just a storage format for uncompressed (or in this case, decompressed) digital audio. Unless you're changing sampling rates along the way, or something unusual like that, an AIFF file contains the same information which gets streamed into a DAC, and then to your ear, as when the original MP3 is played.



    There is generational loss when encoding or reencoding into a lossy format. There is no generational loss from intermediate uncompressed encodings (barring anything unusual like changing sample size or sampling rate along the way).
  • Reply 12 of 42
    matsumatsu Posts: 6,558member
    I'm saying that his nephews steal crappy 128-192 Mp3's on Kazaa, and they encode/export them to AIFF, to make CD's that will play in any CD player, and that those CD's sound muddy/muddled, like crap basically.



    If part of the Appeal of this service is that I can encode the tracks back to AIFF for playback in a (non MP3 capable) stereo, then we need at least 320Kpbs to make a passable transition from MP3 back to AIFF.



    Make sense?
  • Reply 13 of 42
    reidreid Posts: 190member
    This distortion is not necessarily caused by the compression in AAC. More likely, it's a function of the iTunes "Sound Enhancer" and/or "Sound Check" features. When these features are enabled, iTunes reads the digital recording, it looks for spikes in frequency and volume, and attempts to smooth them out.



    Most of the time this is desirable. Because recordings can vary so widely in volume, etc, you could be listening to your library on shuffle and constantly have to be adjusting the volume. However, if you've got a pair of higher-quality speakers or headphones than most people playing music off a computer, you're more likely to notice these artificially imposed cielings.



    Try turning off one or both of those options in iTunes Preferences, and see if the music sounds better to you.
  • Reply 14 of 42
    jlljll Posts: 2,709member
    Quote:

    Originally posted by Matsu

    I'm saying that his nephews steal crappy 128-192 Mp3's on Kazaa, and they encode/export them to AIFF, to make CD's that will play in any CD player, and that those CD's sound muddy/muddled, like crap basically.



    If part of the Appeal of this service is that I can encode the tracks back to AIFF for playback in a (non MP3 capable) stereo, then we need at least 320Kpbs to make a passable transition from MP3 back to AIFF.



    Make sense?




    If the mp3 sounds crappy, the AIFF will sound crappy too.



    I think that 128bit AACs sound great, and I've compared them to the original CD on my stereo.



    But when you burn them onto CDs, make sure that you are burning them at low speed - 1x preferably.
  • Reply 15 of 42
    matsumatsu Posts: 6,558member
    Every time you encode/re-encode, there will be generational loses in quality. Making an AIFF CD from an MP3 source will not sound as good as making a straight copy of the CD track. Compression doesn't squeeze anything, it throws things out. This might fool our ears, but it doesn't fool your CD player. The resultant CD is in essence mastered from a lower quality source, it's not only as bad as the MP3 it cam from, it's worse! It might sound OK, but the "fidelity" to the original is greatly comprimised each time a recording is transfered to another format using lossy schemes.



    It's not like copying an MP3 (bit for bit), those will sound identical no matter how often they're copied. If you re-create an AIFF from an MP3, what was lost in the original encoding is gone. It's re-invented in a sense (by your software) to remake a playable track in whatever format, but the result is even further from the original recording.
  • Reply 16 of 42
    shetlineshetline Posts: 4,695member
    Quote:

    Originally posted by Matsu

    Every time you encode/re-encode, there will be generational loses in quality.



    True.



    Making an AIFF CD from an MP3 source will not sound as good as making a straight copy of the CD track.



    Well, mostly true except that a standard CD is not an "AIFF CD" -- it's a Redbook standard CD, and it doesn't store AIFF files. If an AIFF file is encoded at 44.1 KHz stereo with 16-bit samples, the numeric data in the file will, however, be equivalent to what gets stored on a standard CD.



    Compression doesn't squeeze anything, it throws things out.



    True enough.



    This might fool our ears, but it doesn't fool your CD player.



    Now what the heck is this supposed to mean?



    Let's take it for granted that a given MP3 file has succeeded at "fooling your ears". You can't directly play the MP3 file in its compressed form... it always has to be decompressed before being fed to a digital-to-analog converter (DAC). When you decompress the MP3, it is turned into the very same audio data whether you immediately feed that signal into a DAC, and then into speakers and your ears, or if you write that data to a CD as an intermediate step.



    All else being equal at playback time... DAC quality as good, speakers as good... if the MP3 fools your ears, the CD made from the MP3 will also fool your ears.



    The resultant CD is in essence mastered from a lower quality source, it's not only as bad as the MP3 it cam from, it's worse!



    Worse than the original CD, yes. Not worse than the MP3. If the MP3 succeeded in fooling your ears, the CD made from that MP3 has just as much capability to do so. The CD simply has become an intermediate buffer for the very same data you'd have been listening to when listening to the original MP3.



    It might sound OK, but the "fidelity" to the original is greatly comprimised each time a recording is transfered to another format using lossy schemes.



    Aye, there's the rub. That second-generation CD might manage to sound as good as a first generation CD, but it makes a poor source for a second round of ripping and encoding. Encoding noise that was below the threshold of human perception the first time around will get added into a new cycle of encoding noise. The total encoding noise might then reach audibility.
  • Reply 17 of 42
    buonrottobuonrotto Posts: 6,368member
    I'm listening to some Suzanne Vega from the iTunes Music Store, and it's damn good encoding. i'm of course not listening to this stuff on great speakers, but it's coming across to my damaged ears as being pretty crisp and clear. I did hear some Van Hlaen stuff at the Store that sounded por though, but for the most part, the stuff sounds quite good.
  • Reply 18 of 42
    eugeneeugene Posts: 8,254member
    Is it satisfactory? Yes, but I'd be much happier with a bit more leeway. On some tracks you really notice how vocals and instruments munge up each other.
  • Reply 19 of 42
    paulpaul Posts: 5,278member
    Quote:

    Originally posted by Eugene

    Is it satisfactory? Yes, but I'd be much happier with a bit more leeway. On some tracks you really notice how vocals and instruments munge up each other.



    any more leeway and you get into possible problems with piracy... i say if after 3 months of the windows version being out and there is no major piracy problems from exclusive tracks then apple will be allowed to offer better quality rips (I hope they have already planned for this \)
  • Reply 20 of 42
    nebrienebrie Posts: 483member
    .
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