I am looking with great interest to the A2DP v. 1.4 which will support music collection browsing, and I am realizing I have questions which the Empeg community surely can help me with

1. Would I be correct in assuming that a smartphone audio output on BT via the A2DP protocol is in fact a audio bit-stream, decoded from MP3/WMA/AAC/Whatever into a... PCM audio stream (+metadata info), I guess? Or, maybe, in some other format? So, would I be correct in assuming that the receiving device, be it a Parrot Asteroid for example, would then do the DAC part?

2. Also, since BT communication is digital, would I be correct in assuming that Bluetooth headsets include a DAC internally?

Thank you!



p.s.: Incidentally, for some reason, I am (positively) surprised that a DAC can be fit into small headsets, considering the good audio quality they seem to have. I am more thinking of Logiech USB wireless (non BT) headsets which I recently bought to use with a Cisco IP Communicator on my laptop; I was not looking fro audio quality, but just for some device which could deliver some build quality to last; but I was blown away by how well they sound. The USB dongle is quite small, so even if the DAC is there, I am amazed.

P.P.S.: Sorry for posting in General section. This clearly belongs to Off Topic. Drakino, feel free to move it there, if possible.

... and one more question: does anybody know if Parrot Asteroid actually supports A2DP v.1.4 or, in general, is capable of browsing through the tunes of your music connection in your phone (assuming it is also compatible with the proper A2DP version)? I can't find that on parrot.com .

I'm not an expert on A2DP by any stretch, but I do use it quite a bit between my phone and a JVC KW-NT50HDT head unit.

The way I understand A2DP to work is there are a bunch of codecs than can be negotiated between devices. There is no PCM bitstream possible over A2DP, so everything is re-encoded in a lossy format before being sent over the Bluetooth link.

In my opinion, audio over A2DP can either sound OK or crappy... never great. The set of hardware you're using seems to be the biggest variable. There is a somewhat new codec called apt-X which is supposed to produce the best sound over A2DP, but I don't own a source or destination A2DP device that supports it. The HTC StereoClip does, but this isn't the type of device you're looking for.

My JVC head unit supports A2DP AVRCP v1.3 profile only, so I cannot browse the music library of a connected device. AVRCP v1.3 provides metadata and playback control only. You would be shocked at how many phones don't support even this much. I would be interested to learn what devices actually support AVRCP v1.4 right now.

That's my experience. I mostly use it to listen to podcasts, and for that it's obviously far more than adequate (podcasts are so compressed already). But when I play music it sounds fine to me.


There's never been a whole lot of interest/support in this area in general. I think the best any car company, for example, has done would be Ford and Microsoft's Sync, which I believe will look at your collection somehow. I'm not sure what it's using for that, though.

I'm still waiting for someone to make a decent simple remote for bluetooth devices (for play/pause, FF, REW, etc).

I had the chance to test drive a Mazda CX-5 with its best sound system inside (sporting 9 Bose speakers and what not, which always look good on paper. I did like how it sounded in the few minutes I tested it, I have to say). It supports A2DP + AVRCP v.1.3 (sorry for my confusing previous post) as it did recognize my phone right away and showed track info on the car central display. I don't think it can display cover art, but I think (not 100% sure) it did have a placeholder for that, which is promising, but who knows. It is indeed possible that my phone (HTC Titan) is not sending cover art over AVRCP .
While in the car and testing the audio system, I did try to browse through my collection, to no avail, BUT I failed to check if the main multi-function control knob did anything (I know, very silly of me). That's also because the dealer knew nothing about the Audio System in the car and just let me play with it and find my way around it for few minutes, which I spent entirely on the buttons and controls on the dashboard and on the steering wheel, forgetting to look anywhere else.

Hopefully the BT link between cars and mobile devices is improving.


This is such a bummer. And I am a bit surprised. I've been using my phone to connect A2DP to my parrot Mki9200, and from it into my stereo system via its Aux input. Sound quality as I perceive it is indeed poorer than the stereo system itself, but surprisingly good. So I was blaming the Aux input part, assuming the BT link could deliver the decoded bitstream untouched from the phone to the Mki9200. Keep in mind that I have quite a few WMA-Lossless tracks on my phone.

So, you are saying that the BT/A2CP capable phone would need to take a music file (Mp3/WMA/Whatever) decodeit and re-encode it in some format that can be delivered over BT/A2CP, and sent (to the MKi9200 in my case).

As far as I know, this is how it works.

It's funny you mention the MKi9200. My friend has one and I'm thinking of using it (well, the MKi9100) as my main head unit. I have a vision where most media is streamed from a phone or tablet permanently mounted in the car. The MKi series is ideal because it's able to be placed out of the way and not take up too much dash space.

For the past month, I have been using A2DP 100% of the time in my Suzuki to test how feasible it would be to rely solely on media streaming (Google Play Music, Pandora, etc). Like I said before, the sound between my CM10 Galaxy S III and JVC is just OK. Certainly acceptable in my daily driver with lots of road noise and low-end speakers.

I'm going to take things one step further this weekend and mount a Nexus 7 in the car. I will tether via Wi-Fi to my phone for now since the Nexus doesn't have a cellular radio. If it works out alright, I'm going to then see what it would take to mount the Nexus 7 in the dash. The Parrot MKi would be my new head unit in this scenario. I would link the Nexus to the Parrot over A2DP rather than Aux because I could still use my steering wheel controls. I would also have metadata on the Parrot display dependent on the app.

The Parrot is also ideal because it has an iPod interface. I have an old 160GB Classic I can leave hooked up in the glove box. It would make a good secondary audio source.

My wife's new-to-her 2011 Hyundai Elantra connects perfectly fine with my iPhone 4 and will pick up the phone and play music through the car's audio system. But there's absolutely no ability to control the playback from the car's controls. There's supposed to be, but it simply doesn't work.

BT has a lot of promise, but I can't think of a single product or combination of products where you can see it all come together like you'd infer from its specs on paper.

I don't know if the CA and US spec Elantra is different, but this guy claims AVRCP profile isn't included on the non-NAV models. So, if that's what you have, not being able to use the car's buttons to control the iPhone is exactly how it's supposed to work.

In my case, the JVC head in my Saab and Suzuki supports AVRCP 1.3 and both cars have steering wheel controls hooked up to the head unit. I can skip, reverse, and pause playback from either the steering wheel controls, the JVC touchscreen, or the phone itself. Those functions also work in 3rd party music apps such as Pandora and Slacker. Needless to say, it's very convenient when the phone is in your pocket.

EDIT: Link in above post is actually about 2011 Sonatas. It may not relate to the Elantra.

Parrot MKi9200 is a really nice device. Very reliable. It never failed on me in any way.

In my car, I have an Alpine iDA-X100 connected to an iPod classic 160GB, and I also have a Parrot MKi9200 connected to the Alpine unit via Aux.

I originally bough the Parrot to be used as a BT interface to my Phone, exclusively as hands free system.

However, I use my HTC Titan as my main music player when I am around, it contains a nice and well thought of selection from my collection, so even though it is not big enough (16GB only) to contain all of it, it contains most of my favorite tracks. And, it contains my playlists. So, I ended up using the HTC Titan connected via A2CP to the MKi9200 more than the iPod.
Which tells you a lot about how poorly implemented the iDA-X100 GUI in controlling the iPod is: I did try hard to get used to it, but having to browse through my collection is so painful I basically only skip tracks forwards and backwards. So, Parrot it is most times. At least, I can resume play where I left when I get in the car and when I get out. And I have my playlists.

So, if I were you, I'd either go with the MKi9200 or I would go directly with a Parrot Asteroid as a central main unit. Which I am actually considering in case I decide to give the MKi9200 to my girlfriend for her car.

Because of this thread (thanks), I've done some more digging on A2DP. I think I came across a great hack that applies to folks using a rooted Android device.

Here's a snippet from /system/etc/bluetooth/audio.conf in CM9 and CM10:

Basically, SBC stands or subband codec and is the only codec that's required to pass audio over A2DP. Perhaps it can sound good if you mess with the bitrates, but I'm just going to assume it sounds like crap because that's my experience with it.

I changed the file to look like this a few days ago:

The sound is much more full, and it's not just a placebo effect. I'm currently using CM10 nightlies and flashing every day. My dirty flash routine is:

• Clear cache
• Clear dalvik cache
• Format /system
• Flash ROM
• Flash Gapps
• Fix permissions
• Reboot

Because I wipe the /system partition, I have to redo the A2DP modification every day. Yesterday, I was driving home with A2DP and it sounded poor again. Sure enough, I forgot to reboot again after editing the audio.conf file. Once I rebooted, I had good sound again.

Now, I'm not saying it's great. I haven't compared to wired AUX input from the phone, but it is noticeably better with MPEG12Sources set on in the stock Play Music app and Pandora. I don't know if the phone is now simply passing the MP3 file over the bluetooth link or actually re-encoding on the fly, but I'm happy with the results. I'm not certain why something like this would be set to off by default. Perhaps it's a licensing issue?

I would be interested in hearing from other Android users here trying this out. I edit the file in Root Explorer ($4), but I guess you can do it from ADB if you have a command line text editor installed.

The phone is passing the MP3 file over the bluetooth link. The (probable) reason that this behaviour is off by default, is that it doesn't degrade well if the available bandwidth goes down.

SBC isn't a very good codec, in the sense that at any given bitrate MP3 will sound better, but it has the very desirable property that it's easy to suddenly change the bitrate it uses in case of radio congestion or smog. So if, say, other bluetooth gadgets wander into range and the available bandwidth goes down, SBC will degrade smoothly and you'll just get worse-sounding audio until the congestion clears. If it's sending the MP3 directly, it can't (reasonably) re-encode the MP3 and so audio will drop out completely.

Peter

What about system sounds that aren't typically MP3s? Most sounds in Android are OGG encoded and they will play fine at the same time as streaming MP3. Is the phone re-encoding to MP3 on the fly in this case or is it sending MP3 and SBC streams at the same time?

I have the clear impression that my WMALossless tracks sound better than the 320bps MP3s, when I play them via BT from my phone over to the car sound system (via the Parrot MKi9200). If I understand correctly what has been said in this thread, that would not make much sense, would it?

Now, my impressions mean little because they're different tracks, from different CDs. But, at home the original CDs don't sound THAT different (that's one test I made out of curiosity).

I plan to make MP3s and WMALossless of the same tracks and test.

Should my impressions be confirmed, I would not know how to explain it.
Is it possible that WMALossless are trated differently? Or, maybe when re-encoded by A2DP to be sent over BT the result is better somehow? or maybe MP3s are re-encoded and WMALossess are not?

From what I can tell, there is some flexibility with how the SBC encoded content is streamed. You can manually set something in Android that forces a higher bitrate. Perhaps your phone is already doing this? I imagine that some stock ROMs might do that if they're optimized for your hardware (Bluetooth v3, v4, etc.)

I haven't messed with that at all since discovering the mpeg12sources thing. I will say that Pandora streaming from my Nexus 7 sounds better than Pandora streaming from my CM10 SGS3. Maybe I should look into this more....

It's hard to keep track of all this because, when on the Nexus 7, Pandora thinks it's connected via WiFi rather than cellular data. That fact alone could produce better audio from that source.

All the tests above were done from a HTC Titan with Windows Phone 7.5 . I will indeed try with the S3 at some point.
But again, today I've been driving for 2hrs, and music via BT sounded really good, which keeps surprising me. I have no clue what the Titan+MKi9200 are doing - and possibly I will never know, and in addition to that I am feeding my Alpine via Aux. Level is lower than when playing the iPod via the Alpine, but other than that, it's just good! I would not even be able to tell which of the two sources is better, in all honesty. I'd expect a much lower quality from BT sources, all considered. Maybe my stereo setup needs more tuning. It's getting old, after all...

I have a LG Quantum C900 running WP7.5 I can test with. Maybe I will give it a listen this week.