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iPhone AAC vs. Aptx and Aptx-hd real world

Discussion in 'Sound Science' started by neil74, Oct 4, 2017.
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  1. bigshot
    If you're streaming AAC 256 VBR from Google Play, the sound quality is identical to when you play the same songs in lossless at home. If there is a difference, it's because your portable equipment isn't as good as your home equipment, not because of the file itself. I'm not familiar with AptX HD, but I would imagine that would sound the same too.

    By the way, AAC 256 VBR has the same dynamic range as a CD. High bitrate AAC has the same frequency response too. I don't know if you're aware of it, but VBR allows you to redistribute bandwidth and if needed actually *exceed* the data rate you have it set for. if you encode AAC 320 VBR, the data rate can go as high as 460, if the music requires it. (I don't know what kind of music would though. I find that 256 VBR is plenty for any kind of music.) That might make you feel good if you want to judge sound quality by the numbers.
     
  2. PiSkyHiFi
    The first line.... It's just wrong ok ?

    If I'm streaming AAC 256 from Google Play, the sound quality is identical to lossless.

    No.

    Just plain no.... before you go any further rambling on with justifications for compressed perfection (audibly transparent in your terms)

    You need to accept that the information is different and you should hopefully understand by now that I'm not even vaguely interested in even risking wondering if the codec is to blame for any particular sound issue I may be having.

    You should be getting some hint here that I have also been through the whole VBR thing... it's a useful encoding feature - this is all debates from 10 years ago.

    AAC VBR 256 does not have the same dynamic range as CD, the basic limit of CD is 96 dB and with good dithering, possibly up to 120 dB. Any lossy codec using that as a source will be reduced in quality - below 96, because it's no longer bit-for-bit once you pass through AAC, so dithering above 96 dB is lost.
    Measurable by my ear at a moments notice - probably not.
    Measurable by my ear under other conditions - probably not.

    Am I prepared to accept that my ears dynamic range is in flux... it's never the same way twice and I can even focus on different parts of the sound to varying degrees upon subsequent listening. I fully intend on burning sound that is beyond my hearing into my brain, simply because then I can know that my ears will have good days and bad and my sound equipment will be there for them to help them hear whatever they can on that listen.

    My sound equipment could always do with improvement, I'm very glad to remove lossy from the equation for when I'm testing.

    I don't judge the sound quality by the numbers, because they should be pushed well out my range so I don't have to.

    I won't be convinced that I should return to lossy...... because I have FLACS and space on my phone.... They are better than what can be streamed at present, even if I can't always hear that they are better - listening and improving are daily events for me and the equipment I have.

    Just using AAC is going backwards for me - like doing a whole bunch of work that might make no difference to my music or possibly make it a little worse.

    You should try addressing things I've said if you disagree - I can clearly see your point already.
     
  3. bigshot
    AAC 256 VBR is audibly identical to lossless. I posted evidence of that in this post... https://www.head-fi.org/threads/iph...tx-hd-real-world.861978/page-13#post-14377431

    You say it isn't audibly identical. How about posting some evidence to support that?

    You're in sound science forum right now. We don't just say what we believe. We are expected to back up what we say. If you would like to back up your claim that you can easily tell the difference between lossy and lossless, I have a FLAC file I can send you with three different lossy codecs at three different data rates, along with a lossless file. I will happily send it to you to listen to. All you have to do is rank the samples from best to worst. They you'll know whether what you say is correct.
     
    Last edited: Jul 23, 2018
    PetZoundz and Jearly410 like this.
  4. PiSkyHiFi
    Rather than repeat yourself silly, try reading some of the points I've made already about how inaccurate you are being, like for instance, let's take it one point at a time, the dynamic range of AAC VBR for example. You say it's the same as a CD, but that is impossible by the very nature of it being lossy from a CD source.... I don't need to say more on that, it's proven, done, I went further to explain how using good mastering, one can do better than 96 dB for CD, but if you run it through a lossy codec, you get no benefit from dithering at all - this is just basic logic.

    You are very focused on audibly transparent - Have you noticed at all that I haven't disagreed with that? Have you noticed that I am trying to get you to see beyond your AAC bias for just a minute? To see that barely sufficient is not the latest marketing phrase?

    Let's look at 192 KHz for a second... complete waste of space for me, since both my ears and any possible equipment can simply not retrieve that much detail, it's overkill, but I have nothing against it.

    Now let's flick back to AAC.... barely sufficient for most people is it's tag line.

    Redbook CD - it just is and personally I'm OK with everything being at this level but many would like to see more detail, you're keen on slightly less information.

    Since you probably ignored most of what I said, let's look at AAC seriously...

    It's a fantastic codec, mostly transparent at 256 Kbps, stretches up to 18 to 19 KHz in terms of detail, much better than MP3. Not the most transparent, I think Opus is more advanced although it is different.

    You don't mean audibly transparent, you mean indistinguishable on the same equipment from the PCM source - audibly transparent would be the holy grail of sound equipment, being present as if the sound system wasn't even there, as if the sound source itself was there instead - that's transparent.

    Most people listening to their AAC files are doing so on equipment that isn't even close to transparent.

    What if there was a minor detail in a music file that was so delicate that it took 100 listens before you even noticed it? Well, that happens to me all the time because I'm human and I need the equipment to consistently perform better than my ears to be pleasantly surprised and I am consistently surprised by minor details every day, I can never hear them all on repeated listening either.

    Given that's how my ears work, what are the odds that I can hear a lot more than an ABX test would reveal? They are quite good given I'm going to need to listen to the thing at least 100 times before I can really get into that recording at all.

    Why would I want to listen to a piece 100 times only to discover nothing new because the file was only barely sufficient in terms of sound information I can recognise?

    You would claim that I am unlikely to ever hear anything more from a recording with more information than AAC 256 and yet, I love being surprised by detail I hadn't heard before, it happens, would that happen the same way with PCM as AAC ? hard to say, but at least I'm prepared to say it's possible.

    It's a very minor detail to argue, but I am the one remaining open minded, you seem convinced that anything better than AAC 256 is a waste of space.

    One day in the distant future, Apple will just drop AAC in favour of lossless, simply because hardware has no issues with it any longer.

    That is exactly where the future of audio compression is going.

    You must know that you've drawn the line at barely sufficient and for what..... more space?
     
  5. bigshot
    You can play tag with me as much as you want, but I've offered evidence that AAC 256 VBR is audibly transparent. I'm just waiting for you to step up to bat and offer some sort of evidence to back up your claims that it isn't. I've done controlled listening tests comparing AAC and lossless. I've read numerous other controlled tests conducted by other people, all coming to the same conclusion I did. Why should I just take your word for it if you haven't made any effort to find out the truth for yourself? You can feel free to go on your gut instincts if you'd like. That's your prerogative. But that doesn't mean anything to me. For an opinion to have validity for other people it has to be verifiable and repeatable. This is sound science.

    If you really want me to, I can go through your post and answer your misconceptions point by point and provide more links. But you didn't follow the links I've already given you that said that AAC 256 VBR is audibly transparent... The compressed audio sounds *exactly* like the uncompressed file on high end or low end equipment... to trained ears, musician's ears, to audio enthusiast's ears and to your mom's ears... under any normal circumstance in which you might be listening to music. It is audibly interchangeable with lossless and it is a fraction of the file size. It's efficient. It streams easily. There's no sacrifice at all.

    Redbook is audibly identical to SACD and 24/96 too. I would be happy to provide evidence of that too. I've done tests myself on a pro-tools workstation and have found other people's tests that validate that opinion too. I'd be happy to share that info with you as well.

    Sometimes "common knowledge" in audiophile circles doesn't hold up under close examination. A lot of what you read about consumer audio is thinly veiled sales pitch. Welcome to Sound Science. Sorry about your preconceptions.
     
    Last edited: Jul 23, 2018
  6. PiSkyHiFi
    You're waiting for Godot there... You've offered nothing but repetitive claims and when I challenge you on a mistake, you just hammer away as if you were right the whole time.

    You made mistakes.

    Go back and correct them before I pay any attention, that's sound science.
     
  7. Glmoneydawg
    I was you for a few decades.....recently sold my $10,000 dac and the cd drive that went with it for a very nice profit (feel a little guilty lol)replaced both with a Cambridge CXU......not a full on science nerd but i can assure you there is no difference.I am not ashamed to admit i have a turntable,records,expensive cables(i know lol)Stop chasing you're tail my friend. ....you will never catch it....unless you're the guy that bought my DAC then its cool.:wink:
     
    Last edited: Jul 23, 2018
  8. PiSkyHiFi
    I've never been that person, science nerd yes.

    Chasing my tale? I'm not your friend, I'm just trying to communicate here.

    I witnessed the moment I heard MP3 bight the dust because I heard the difference on the Beyerdynamic T1 for the first time.

    I don't need a Denon cat 6 cable to know that compressed audio isn't the purpose of my sound system.
     
  9. Glmoneydawg
    Thats unfortunate ....i may be the the person who is closest to you and your beliefs in the sound science forum....good luck to you.
     
  10. PiSkyHiFi
    Cheers, I think, not sure if being sarcastic though.

    It's simple, I draw the line at redbook and leave it there with solid science backing up why you shouldn't need any more and why saving space is no longer a factor! AAC at 256 is just barely adequate compared to redbook, it's all the rage because of streaming, but it's still just barely adequate.

    Let me put it this way then, to get to AAC 256, you must first have PCM. That's compulsory. Now just skip the part where you reduce information. Done.
     
  11. Steve999
    I am listening to some ridiculous Samsung bluetooth speaker with a glowy tube on top that was on like a 1/4 price sale at Best Buy a few years ago because no one would buy it. I am listening Itzhak Perlman or however you spell it over 256kbps Itunes Plus. I just ripped it. I rip a CD a night just as a leisure activity. I am about 90 or 95 percent through my library. The AAC file is getting from my computer to this speaker over some mangled early bluetooth protocol or CODEC or container with egregious transcodings I am sure. My kids are always occupying the space with my nice stereo playing video games or on a computer or taking a nap or something or asking me some kind of question. So I am in another room listening to this abomination. It's all jittery but the tube sounds nice and warm.

    Here is an absurd review of this beautiful strangeness:

    https://www.whathifi.com/samsung/da-e750/review

    If you are interested the review makes bizarre comparisons between the Apple Airplay sound, the bluetooth sound, and the Aptx bluetooth sound, and wired streaming by ethernet cable. The review is jaw-droppingly silly. This astonishing contraption also takes USB inputs and who knows probably some other stuff. It's the swiss army knife of input options. It also docks Apple and Android stuff.

    Seriously, I cannot for the life of me hear the difference between 256k Itunes Plus and the source on anything. I have all of the original CDs in vinyl jackets so they don't take up too much space if I get freaked out about it. I always used whatever was best at the time over the last 15 or 20 years from Lame MP3 to Fraunhofer or whoever and sometimes to some other CODEC just to goof around, and that's the form it's still in, unless Apple Music provided me an automatic upgrade to AAC 256kbps for free, which it did do for an awful lot of music, and is an awesome perk for my $10 a month. But at the time I was ripping I always made sure the result was transparent (the same sound to my ears) to me the best I could, with some margin for error.

    I underclocked my PC and put my graphics card in silent mode so they don't interfere with the music. This much is true!

    Actually it's a mid-fi speaker but the sound is really, really nice for what it is. And it looks awesome. Seriously, Best Buy could not sell the stupid thing and I just dropped by once in a while and watched the price drop and drop and drop. It has a woofer on the bottom and a bass port on the back in case you wonder where the bass comes from.

    And the other point is what about the music? I am going to worry about some little knick-knack detail that only 1 in 508 young, talented and experienced people can make out after two hours of listening to a short and particularly demanding sample? Or am I going to listen to the music as music? We are living in an age of hifi I never even dreamed of when a turntable was the best source I could have access to. Now, as far as sources and audio files are concerned, we are in the age of way beyond good enough.

    My CDs will be lying around in vinyl jackets for posterity, if anyone cares.

    By the way a point of interest: Even Itunes Plus AAC @ 256kbps will run over 320kbps in complex passages. I have seen it as Foobar displays the bitrate in real time.

    If someone can hear the difference between 256kbps AAC Itunes Plus and the original CD or lossless file and they want to put up evidence that it's so I'm cool with that.


    upload_2018-7-23_22-29-9.png
     
    Last edited: Jul 24, 2018
  12. bigshot
    Let's simplify this. One question at a time.... AAC is audibly identical to redbook. If it sounds exactly the same, how is it any worse than redbook? Just give me answers to that one question- concise and to the point. Bullet points are fine.
     
    Last edited: Jul 24, 2018
  13. PiSkyHiFi
    You can't even examine your own fallacies, which you will need to do if you want to put me in a box of your design.

    Can CD audio reach a higher dynamic range than 96 dB in any way? - Yes, through careful mastering down to Redbook, error diffusion can mathematically allow a higher dynamic range (but only slightly)

    What happens if one bit is different than it should be in many locations? The dynamic range above the theoretical limit of 96 dB is now impossible, because the error diffusion has been lost.

    AAC does not have as high a dynamic range as Redbook period - whether we can always hear that is a separate question, one I have painstakingly tried to address while you keep pulling out the same broken box.

    Here's my suggestion, if you actually care about fixing the box you're in, go back and read things properly and stop presenting me with the same tired old box to climb in.

    I bet you're going to paint scenario with audible transparency and never even consider that starting with AAC being a reduced form of the PCM is the correct path to describing it successfully - You might say a reduced form that is audibly transparent, but you haven't.... you've pretty much tried to cover up the differences the whole time, as if it's impossible to have a difference that takes time with repeated listening to hear, but it isn't impossible, just not very likely because the differences are small.

    Here's the kicker though, scientifically, I'm the one claiming that AAC vs CD being mathematically different is enough to warrant justification of why the sound will be audibly the same to anyone.

    I am not the one making claims against the math, I'm the one willing to deconstruct the math to find out what's really happening.

    The onus is on you to define your terms - audibly transparent for instance, you said you made sure your equipment was transparent before the tests, but that doesn't make any sense because equipment can only be more or less transparent, since no equipment exists that is perfectly transparent - i.e. like the sound source was in the room with no sound system. transparency is a relative thing in sound systems.

    My main point is that the time for all this is now up.

    We don't need to compress audio in a lossy format for storage any more, because space is abundant, store them as a FLAC, then you don't even need to discuss the relative merits of adding artifacts that you may or may not hear.
     
  14. bigshot
    One simple question. One simple answer. All these paragraph breaks and digressions aren't making any points. They're just exhausting me and making me not want to read your posts. Be concise. Give a clear argument to support your position. Don't wiggle. If you can give me a solid argument in your favor, I'll acknowledge it. I'm not trying to make points myself any more. I'm just trying to get you to answer a simple question...

    If you agree that AAC 256 VBR sounds exactly the same as lossless, what advantage is there to maintaining your music library in lossless?
     
    Last edited: Jul 24, 2018
  15. PiSkyHiFi
    See the box you put me in ? Its broken. I've told you one clear mistake, address it or not.
     
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