Does anyone know the maximum bitrate that the iPhone 6 supports for playing audio files via bluetooth to something like a car or bluetooth headphones? Would this differ between streaming audio (like Spotify Extreme quality at 320kbps) and music files that reside on your iPhone in Apple Music or other Music apps like Spotify.
Is the phone generally the limiting factor or is it more likey to be the car or headphones?
iPhone 6 Plus, iOS 8.1.1
I did a search on the BT spec, but does that mean an iPhone supports all of the bitrates?
There is a doc called "Bluetooth Accessory Design Guidelines for Apple Products". https://developer.apple.com/hardwaredrivers/BluetoothDesignGuidelines.pdf
But that doc is from Sep 2013 and may be obsolete - but there doesn't appear to be a later version.
With respect to audio I found the following: MPEG-2/4 AAC Codec Information Elements for iOS devices - 264,630 bps. So does that mean the maximum bit rate is 264kbps? If so is my phone then downsampling higher bit rate files/streams like the 320 kbps Extreme quality Spotify files/streams?
Unless your headphones cost over $1,000, they will be the limiting factor in frequency response and dynamic range. Similarly, for cars, unless they are also high end, the speakers will be the limiting factor. Even then, there simply isn't enough room in a car for high end reproduction quality, and the acoustics of a car interior really stink. Next, you need to consider audio source. MP3s are of such a high compression ratio that the source material will be the limiting factor. The maximum bitrate for Bluetooth is 768 Kbps, but you can find a lengthy discussion of it here: http://www.electronicsweekly.com/news/design/communications/bluetooth-gets-audio -quality-overhaul-2008-09/
Finally, the real limit is human hearing. Frequency range for humans is theoretically 20 Hz to 20 KHz, but it begins to be limited at the high end above age 8, and most people over 40 can't hear frequencies over 8 KHz, so the actual sound reproduction quality isn't that important.
My question is just more limited in scope - I am more concerned about whether my phone (an iPhone 6+) and BT playback devices can support higher rate MP3s/AACs files with bitrates around 320kbps. I realize that there are many other limitations with regards to the actual audio quality but I want to know if the bitrate between phone and car can even support this bitrate.
I am pretty sure that the iPhone 6 and 6+ can support higher bitrates than previous generations, but I don't remember seeign the exact number. That article you linked to is seven years old so it, obviously, will not have any infor specific to the iPhone at all.
Bitrate alone is a poor representation of audio quality. MP3 and AAC will sound very different at the same bitrate, especially when this bitrate is low. Dolby Laboratories reports that AAC at 96 kbit/s sounds better than MP3 at 128 kbit/s. Also bitrate can be constant or variable. It is said that MP3 cannot compete with 256 kbit/s AAC.
In a car, the road noise prevents any good hi-fi experience. In a car, it is however a good idea to equalize the signal and set the balance / fader settings correctly. Good audio systems will have separate tweeters as high as possible and should be directed to the listener's ears.
Do a Google search for the audio specifications of BT 4.0 and / or A2DP if you want to know the supported bit rates.
Maximum bitrate for bluetooth audio with 6+
