gth824p

I just got my UMI system installed on my 2008 C300 and tried Navi. and audio streaming.

Navi seems cool and straightfoward.

However, the audio quality of bluetooth audio stream seems very poor.
Ipod and new Aux. input seem to work much better tho..
I just don't like the idea of keeping my iphone in glove box for Ipod or Aux. connection. Bluetooth seems perfect with no cable hassle,,,

Do you, who already installed the UMI, have the same problem????

Diesel Benz

The SW update to Navigation 20 or Nav +4 in the US should fix BT streaming issues. I've installed UMI to our 204 but I have not bothered to have the SW updated (it would cost quite a lot for me).

NickCats

I had the UMI installed last year and I agree, the sound quality of the bluetooth streaming is extremely poor. But, is this a Mercedes issue or an iPhone issue ?

Acapulco Bill

In the best of cases A2DP Bluetooth bandwidth is less than half a standard CD bitrate. Add to this less than perfect reception, and the UMI or the Audio (20) head's conversion of the Bluetooth signal to the digital audio format eventually decoded into an analog signal, and there is lots of information loss here. This is neither an iPhone or a Mercedes issue, the sound is the sum of two or more compromised standards of information transmission.
There are Bluetooth enabled stereo headsets and speakerphones that work with the iPhone and others, however these are bandwidth limited and also show reduced audio quality.
In the future the Bluetooth standard may include bandwidth sufficient to send and receive audio CD quality information (1.411 Mb/sec), for the moment it is recommended to listen to quality sound by investing in an inexpensive iPod, and hooking it up permanently in the car via aux or better still, the iPod interface, which gives you an excellent display and control of funcions, plus seleccion of tunes.

gth824p

Thanks all for your replies.

I decide to use just USB memory key.. Bluetooth seems cool but music from USB sounds much much better..

Acapulco Bill

Can you select your music from the USB on the UMI?

gth824p

I can select songs by dialing the control knob on center.

JaCe88

Good thread guys. Answered my Q of whether using the iPod USB cable was better or worse than using Bluetooth audio streaming which sounded a bit lacking.

encoder

Bill, couple thoughts on this, from a technical perspective.

First, it's true that A2DP wouldn't be able to transmit uncompressed CD quality audio. But that seems like a red herring to me, because the AAC or MP3 files you're transmitting from your iPhone, iPod or Android, are not uncompressed CD audio. If you've got an MP3 encoded at 320kbps, that audio is being transmitted as-is over the A2DP link. That is, no on-the-fly transcoding is taking place. I suppose I'll caveat that by saying that sure, a device could transcode the audio before sending over BT and still meet the BT spec but I don't know of any device that would do that.

Second, while there might be some reception issues, I've never experienced any. And even if you do, it's a digital signal: you're not going to hear general degredation of music quality, you'd hear "skips" and pauses in the music.

Now, within the BT receiver, it's turning this digital signal into something that it passes off to the audio hardware. Is it converting the signal to analog? Is it passing it still in its digital form? I have no idea. For me, having a a BT A2DP reciver in my glove box that hooks into line-in, it's certainly converting to analog and then feeding the analog signal over the mini jack. But in cases of built-in A2DP, I'm not sure.

I'm a software guy, not a sound guy, but these are the things I know about it from a software POV.

JaCe88

From my various Googling/forum researching, isn't the SBC codec used over Bluetooth for audio streaming a lower quality compression algorithm compared to say, MP3? i.e. 320kbps may sound good for mp3, but will need to be reencoded for transmission to a device which does not support that codec over Bluetooth? Or am I confused? That was my understanding as to why the bluetooth streaming sounded tinny and shrill compared to using the iPod cable on the HK system.

Ref: http://www.wirelessaudioblog.com/wab...-a2dp-ste.html

encoder

Ooh, good find. I stand corrected: I've implemented BT for data transmission (specifically in my case handheld scanners) but I've never done any A2DP work and didn't think there was any transcoding taking place.

Anecdotally, I am myself pretty happy with my BT audio, but it's definitely not great.

JaCe88

I think the benefits of using a cable are definitely worth it. I also realised today that trying to use an iPod Touch over bluetooth causes issues if you have your system connected to your iPhone for mobile phone calls... that is, it disconnects from the iPhone and reports "NO SERVICE" on the display.

sammyboi

Guys, I think UMI is a rip off from Mercedes. I've installed one myself and I find it appalling. The navi was the only good thing, even though the visual display on my W204 is small, at least the navi system works well on it. Bluetooth music streaming is the real teething problem. I am certain that the bluetooth telephone system in my w204 is able to support bluetooth music streaming with today's technology; even cheap in-car music sytems can achieve this easily, yet Mercedes decided that they should separate bluetooth music streaming from bluetooth telephone so that they can sell the UMI as another package option. Fine, if they deicded to do that they should've done it better. In many instances the UMI will say 'bluetooth busy' and will not connect to the mobile phone at all to stream music. The status will persist until you switch off the engine for a long time and let the UMI shut off completely and reload the next time you drive. This was driving me mad for a while as it costed quite a bit.... but i did find a temporary solution:

Well, if this happens to any of you, try connect your handset to UMI directly from your phone. I use an iphone myself, and when my UMI says 'bluetooth busy' and won't let me start a connection with my phone, i go into my phone's bluetooth settings, and click onto the UMI name in my bluetooth list and link it from there instead.

In addition, i dunno if any of you guys know about this, i was messing around with the control knobs next to the gearbox, and if you press down all three buttons altogether for about 5 seconds (left button, the circular knob, the right button), it will bring you to a configuration page where you can adjust some settings from there. I did find the bluetooth music quality quite bad aswell, but I adjusted the volume a bit from there and it seemed to have improved a lil bit. Maybe you guys can mess around with it too.


Sigh, I just think that why was i paying 1st class price to get this installed but am only getting a 3rd class quality product. Other third party in-car entertainment systems are so advanced yet so cheap! Only i I wasn't conerned about keeping the originality of the car... i definitely wouldnt have picked UMI.

NickCats

You may want to take your car to the dealer - I have never had a problem with a "bluetooth busy" error ( I am using an iPhone 3gs ) - have you upgraded the software in your phone recently ?

( I have had some problems though - I have found that turning my iPhone off and back on again usually fixes whatever is causing the issue )

I also have gone into the settings and increased the volume for streaming and it helped immensely...

I love the full iPod control and the ability to play music from a USB thumb drive.

Nick

sammyboi

Hi Nick, i think my bluetooth busy problem lies within the UMI unit itself as it happens not just to my iphone but also my previous handset nokia N97. But it doesn't happen all the time so even my dealer couldn't doagnose the problem. Also i've asked whether my UMI unit has any software and map update and they said no (im uk based). This sounds a bit strange as i heard that some ppl in the States can update their UMI from the dealer. Anyhow thanks for ur reply i juz santed to share my experience with the UMI unit thats all

ChrisB.

Had my UMI installed about a month ago. Overall very happy with it. The opening screen says "Navigation 20" does this mean i have the latest software? Would the dealer automatically installed any updates?