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Bluetooth vs. aux input?
d_headshot
post Feb 8 2012, 16:50
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Since a lot of new cars allow you to play music from an iphone via bluetooth, will there be any objective quality loss? I'm assuming no because it's being digitally transmitted but I'm not 100% sure of how it works.
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andy o
post Feb 8 2012, 17:05
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Most bluetooth A2DP (stereo audio) connections use lossy compression. This can be transparent, and with my iPod Touch, it seems to be. With my HP laptop's bluetooth device, there is some distortion introduced which I've narrowed down to either the BT device or the drivers. There is a lossless codec called APT-X used in some BT devices, but I'm not sure any car stereos support it, and of course both devices must support it. I was wondering if the newer iOS devices have it or could be updated, since the newer Macs were.
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kritip
post Feb 8 2012, 17:06
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Wikipedia states it uses this standard.

http://en.wikipedia.org/wiki/Bluetooth_pro...file_.28A2DP.29

It appears it supports multiple codecs, but they must all support this:

http://en.wikipedia.org/wiki/SBC_(codec)

Quality wise, not a clue. I'd probably go for the AUX input, but if it sounds ok over BT, that's all that really matters.
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andy o
post Feb 8 2012, 17:15
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I think the best connection for a car is one of those dedicated "iPod direct" USB connections, like most Pioneers and others have. If you're thinking of buying a new stereo, might just get that. Works with any USB iPod cable (I had it working with a ~$2 ebay cable, so don't mind the "required" cable from Pioneer), it charges your iOS device, and you can control playback from either the unit or the iPod. The only problem I had was that Sound Check didn't work through this connection, but they fixed it with iOS 5 (or something between 4.3 and that).
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JunkieXL
post Feb 8 2012, 21:53
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I use the auxilary input in my car and the phone jack from the iPod. By using the USB you are bypassing the iPods built in decoders IIRC. The device you are plugging it into would then perform the decoding.

There is also the fact that a cable can deliver a larger data feed than a BT device could. There's also no connectivity issues with a cable.
JXL
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saratoga
post Feb 8 2012, 21:58
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QUOTE (JunkieXL @ Feb 8 2012, 15:53) *
I use the auxilary input in my car and the phone jack from the iPod. By using the USB you are bypassing the iPods built in decoders IIRC. The device you are plugging it into would then perform the decoding.


On a lot of stereos this isn't the case. Newer ipods can do PCM over USB if the stereo supports it. Otherwise, you're right, it'll use MSC and decode the files locally.
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andrew_berge
post Feb 9 2012, 00:11
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Correct me if i'm wrong but i'm pretty sure using the AUX instead of bluetooth would extend your battery life as well.
I suppose you'll just have to try each and see what works for you.
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Roseval
post Feb 9 2012, 01:55
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QUOTE (andy o @ Feb 8 2012, 17:05) *
There is a lossless codec called APT-X used in some BT devices


Acoording to http://www.csr.com/products/60/aptx-bluetooth
Compression ratio: 4:1
Audio Format: 16-bit, 44.1kHz (CD-Quality)
Data Rates: 352kbps

I don't think their Bluetooth implementation is lossless.

This post has been edited by Roseval: Feb 9 2012, 01:56


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andy o
post Feb 9 2012, 03:40
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QUOTE (JunkieXL @ Feb 8 2012, 12:53) *
By using the USB you are bypassing the iPods built in decoders IIRC. The device you are plugging it into would then perform the decoding.

That's not true with iOS devices, and I'm not even sure if it's true for other iPods unless the stereo unit can read them as USB disks. AFAIK the two different kinds of connections that use USB to connect to iPod are the old one, which usually requires a proprietary cable and uses USB to power, control and display information, but audio comes out from the dock connector's analog out, and the other one is the "iPod Direct" connection I mentioned, which is simpler and works with any iPod USB cable.
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mzil
post Feb 9 2012, 03:43
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In a car? Is the engine on and there is road noise? If so then one would hardly notice that a tethered, lossless device is any better than a good FM radio station. Besides having a very loud noise floor there's almost no "sound stage" or imaging to speak of because one doesn't sit in the center of a triangular "sweet spot", equidistant to the front L and R speakers, and auto speakers are often just one notch above "intercom quality".

If you listen while parked, engine off, have a state of the art time delay speaker distance compensation system which delays the left front speaker a few milliseconds to compensate that its direct sound path strikes the drivers ears too quickly compared to the front right, correcting this for the driver only and making things even worse for the passenger's seat, and a custom eq set via an RTA used in that specific car model, then you might notice that a tethered connection is better than bluetooth.
---

A cordless connection will allow one to velcro the sound source to the center of the steering wheel making its display and control easy to operate, and when the wheel gets turned over a few times your tether wire doesn't get twisted up, snap, and cause you to crash into a tree. Would that be beneficial? smile.gif

This post has been edited by mzil: Feb 9 2012, 03:45
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andy o
post Feb 9 2012, 03:44
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QUOTE (Roseval @ Feb 8 2012, 16:55) *
QUOTE (andy o @ Feb 8 2012, 17:05) *
There is a lossless codec called APT-X used in some BT devices


Acoording to http://www.csr.com/products/60/aptx-bluetooth
Compression ratio: 4:1
Audio Format: 16-bit, 44.1kHz (CD-Quality)
Data Rates: 352kbps

I don't think their Bluetooth implementation is lossless.

hmm there was another thread where this codec came up, but now that you mention it, I seem to have come upon that page back when I first was reading about it.
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andy o
post Feb 9 2012, 03:49
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QUOTE (mzil @ Feb 8 2012, 18:43) *
A cordless connection will allow one to velcro the sound source to the center of the steering wheel making its display and control easy to operate, and when the wheel gets turned over a few times your tether wire doesn't get twisted up, snap, and cause you to crash into a tree. Would that be beneficial? smile.gif

I'm not sure if you have an iOS device, but the default music player's interface is not exactly car-friendly. In landscape mode there are no controls, so you'll have to have it locked in portrait. When the screen turns off, again, no immediate controls. You have to double-click the home button and then controls will come up with the screen turning on. Unless you want to keep the screen on at all times, but that eats battery, on top of the extra battery you're eating with BT. I think the best way is to buy a cheap music interface app (I use Flick Tunes), keep the screen on all the time, and plugged via USB. The USB Direct stereos are ubiquitous enough nowadays and can be had very cheap. Pioneer has it starting on their second cheapest one.

This post has been edited by andy o: Feb 9 2012, 03:50
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mzil
post Feb 9 2012, 04:23
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Tiny phone displays are much easier for my old eyes to read at hand held distances rather than dashboard/center column instrument column/cup holder mounted distances. The closest thing to that, yet be hands free, is steering wheel distance. [Visor distance is TOO close to read]

Having the display constantly lit, rather than having to wake the phone up with time consuming key taps, would be nice, but only if I could actually read small text easily at that distance. I've tried. I can't. I have to pick the phone up out of my cup holder, (my phone's not an Apple, however) and hold it to read it (and control it, using only one hand and my thumb being "iffy", as my other hand drives). Steering wheel distance would work for my vision, however, and keeps my hands free.

This post has been edited by mzil: Feb 9 2012, 04:41
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