[General Topics] Menneisyys:
UPDATE (06/24/2009 23.47 CET):

1.)	Unfortunately, there’s a lot of misinformation surrounding the A2DP support of OS3. For example, PCMag has published the following:

“One new feature, stereo Bluetooth, bombs. Music on our Altec Lansing BackBeat headphones was so full of hisses and distortion it was laughable—almost as if Apple was saying, "This is why we hate stereo Bluetooth." The headphones weren't the problem, as the same music files sounded much better on a BlackBerry Storm.”

As you may have guessed, this is far from the entire truth. Anyone knowing a little bit of stereo Bluetooth in general knows one shouldn’t judge a given handset based on a test with only one pair of BT stereo headphones. An example: most? all? Nokia S60 phones don’t support the pause / resume functionality of older Plantronics A2DP models. Based on only one test (with, say, the Plantronics 590), a reviewer could only say “Hey, the N95 is really bad because it doesn’t support pausing / resuming!” Which isn’t true because there are headsets (for example, the Altec Lansing BackBeat 903/906) where the pause/resume is supported.

Not to mention I couldn’t discern any “hisses” or “distortion” with the sound produced by the BackBeat. There was some distortion of the highs compared to the sound of some other headphones (for example, the Pulsar 590), but this could easily be explained by the 590’s strong cutting (not really playing back) the highs. One thing is certain: the BackBeat + iPhone 3G combo sounds way better than pre-WM6 Windows Mobile phones / PDA’s equipped with the Microsoft Bluetooth stack. There is no comparison. There definitely isn’t “laughable” “hiss” and “distortion” compared to other mobile platforms (or, using the built-in A2DP support of Windows 7) either. I’m not sure whether the author of the PCMag article, Sascha Segan, has a single pair of A2DP headphones or has ever tested the A2DP support on other, alternative platforms with more than one pair of headphones. I seriously doubt it. All in all, just ignore what he says on the matter.

Also note that the JKOnTheRun folks also mention this article. A commenter there states he has absolutely no problems with the 3G and the Backbeat 903 either.

Let’s turn back to the BackBeat. Today, I’ve made a lot of long-time tests with it and, during them, I’ve found out something of real interest.

When playing back anything streamed (and you stream via Wi-Fi and not 3G – that is, the cellular connection) in both the built-in YouTube client and third-party apps like netTV Lite, all my other headphones (except for the Voyager 855, which I didn’t test in this respect) introduce severe skippings and pauses. (Here, under “pauses”, I mean completely missing audio sometimes for seconds, while the video is played back without problems.) Also, for some reason, loading (pre-catching) YouTube files seems to be much-much slower than without any A2DP headphones or with the BackBeat – all this using the same access point and under exactly the same circumstances. With the BackBeat, I have never run into any serious skippings or long(er) pauses. (I’ve only encountered two short [about 0.2 sec] pauses during the 3-4 hours I’ve spent on playing back YouTube clips.)

As soon as the YouTube files are fully re-cached, skips stop with the other headphones. This may mean it’s the Bluetooth aerial unit that is trying to take over the Wi-Fi aerial unit – as was the case with several, older Windows Mobile phones before Bluetooth 1.2. These old WinMo PDA’s, generally, either completely disabled using Bluetooth and Wi-Fi at the same time or have resulted in major performance problems (heavily decreased Wi-Fi and Bluetooth speed) when enabling them both. I think the stuttering problem while, concurrently, downloading / streaming via Wi-Fi with the iPhone may be related to this.

Frankly, I don’t know why the BackBeat behaves much-much better than my other headphones.

2.)	I’ve benchmarked (with the “Benchmark” app in the AppStore) the CPU usage of A2DP. It’s acceptable: while playing back AAC songs in iPod via the speaker, the speed of the iPhone 3G decreases to 84% and doing the same via Bluetooth A2DP results in around 70%. That is, there is some CPU usage – but, fortunately, nowhere as large as with, say, Samsung CPU’s on Windows Mobile, where A2DP could easily result in taking no less than 50% of the CPU cycles on the 400 MHz models.

3.)	Two minor corrections of my original article:

-	with Symbian S60, you can dynamically change the sound output hardware; it’s only Windows Mobile that you can’t do this

-	the pause/resume function does work with the Voyager 855. That is, in my tests, only Cellink’s (otherwise, pretty bad) headphones didn’t work together with the iPhone 3G.