iPhone AAC vs. Aptx and Aptx-hd real world

Discussion in 'Sound Science' started by neil74, Oct 4, 2017.

  1. neil74
    The info on the interweb is both plentiful and vague on the comparative bitrates of APTX, AAC and SBC but as I understand AAC is capped at around 256 kbps and APTX around 350 kbps?

    I regularly switch between iOS and Android I am curious as to the real world limitations of wireless headphones on an iPhone vs APTX equipped droids? e.g. using Apple Music and it's 256 kbps AAC should mean no loss but I'm unsure how higher bitrate stuff like Spotify 328 kbps or the standard Tidal 328 kbps AACs would compare and how much of a bottleneck the AAC codec would be on an iPhone?

    With aptx-hd now available on both phones and headphones I am wondering how much of a real world quality advantage Androids now have with wireless headphones?
     
  2. bigshot
    AAC goes up to 320 and if you do AAC 320 VBR, it can actually go above 320 if necessary. It really isn't though, because AAC is audibly transparent at 256. Once a codec reaches audible transparency, throwing more bitrate at it won't make the music sound better. So good enough truly is good enough.
     
    JaeYoon and neil74 like this.
  3. pinnahertz
    The Apple A2DP includes the mandatory SBC codec, which can run up over 320k, but usually is bumped down much lower. Apple also includes AAC at 250K. Android A2DP also includes SBC with similar bitrate chokes, but throws in AptX at some reasonbly high rate, possibly up to 320k, but I couldn't confirm that.
     
  4. neil74
    All things being equal I am wondering though if this is black and white?

    1 - iPhone 256 kbps AAC files piped straight over ACC so in theory no encoding. Spotify on an iPhone would presumably need to be re-encoded first. So an advantage to apple music on an iPhone?
    2 - On Android with aptx those same 256 kbps AAC files would need to be encoded too so spotify may have the edge here?

    For the above 2 scenarios the non-aptx iphone with native AAC files could actually be the better sounding combo?
     
  5. jfvny
    I just got a pair of bluetooth headphones capable of AAC and was interested to test this out! I'm new-ish to describing sound though, so please bear with me

    equipment used: AIAIAI TMA-2 H05-S01-E06 (the most "neutral" combination they have), iPhone 8, AAC 256 kbps (Apple music) vs MP3 320 Kbps (played through the default iOS quicktime player), track used (link here) (cos it starts out quiet, and there's a number of vocal nuances throughout)

    pre-test: Just to make sure my iPhone was using the AAC bluetooth codec (or is it profile?), I played the same track from my Surface pro (regurlar bluetooth profile, can't remember if it's SBC or A2DP) on iTunes vs from my iPhone. The iPhone playback win hands down. (edit: after longer use, I'm finding that not all tracks sound different to me for SBC vs AAC; take from that what you will)

    Short answer, both were equally good!
    Long answer, there seems to be some differences in both tracks: the AAC one seems to have slightly less volume difference for the quick low-to-high vocal portions, but slightly more detail in the vibratos. Might be something to do with the players themselves, or the source tracks, and was really minor anyways. So I assume the 320kbps MP3 is still getting encoded to AAC to be transmitted since it doesn't lose out (and Apple certainly doesn't use the aptx codec)? Which is pretty good, cos I half expected Apple to just ignore mp3s. Whether it works for the Spotify app (or others) I can't say though, since I don't have Spotify premium.

    edit: just for fun, I tried it with an AIFF (Apple's lossless format) vs the aforementioned AAC file; and there's no discernible difference either
     
    Last edited: Nov 10, 2017
  6. bigshot
    That sounds like a very small difference in volume between samples. If one track is slightly quieter than the other, your ears will perceive less dynamics than if it's slightly louder. Encoders will sometimes adjust the overall level of a track to prevent clipping on a hot mastered song.
     
  7. jfvny
    Yeah that was probably what happened
    Thanks for clarifying!
     

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