Popping Sounds while listening to BMW Premium Sound System via USB port

Dear Readers:

I am using the latest iPod Touch (4G) via the USB port in the BMW 2011 5-series. I am experiencing popping and crackling sounds as if I were playing a vinyl record from the old days. I do NOT experience this with my old 2nd generation iPod Touch. Now I have to tote both of them with me…

Any explanations come to mind?


Some words of wisdom from Jim Morrison come to mind:

“Keep your eyes on the road and your hands upon the wheel.”

I would first substitute a different connecting cable. It that doesn’t change things, borrow if you can a different new iPod fom a friend to see if the problem is in the iPod or car. That’s the usual electronic chain game you play to isolate and replace. If your’s works in another car, you may be looking a compatibility problem. I doubt it but trying your old again with the new cable and new iPod with the old…if they are still lying around. I’m leaning toward a connection problem.

Usually this type of problem is cable related. Try a different cable…or even a different IPod/IPhone…etc.

I bet it is some sort of IOS issue with the bleeding edge touch. They had a similar issue with IOS 4.1
Apple no doubt is coming out with an upgrade at some point that fixes it.

Try turning all apps off , possibly resetting the device and then just play music to see if that fixes it.
The more applications you have running, they harder a processor has to work because it has to get to all of them in a very specific time to make sure they are serviced. In the case of music applications, that app can be starving for processor time and thus cause weird noises to be played.

If you change the device only and it fixes it then it’s obviously the device.

I have tried several Apple cords that insert directly into the USB port, not the BMW multiprong cable, and no difference: the 2G is fine but pops and crackles with the 4G.

I am not sure where to get a different iPod touch with the same OS5 in order to test this hypothesis.

I do not understand why there should be a difference if I am only using the iPod only to listen to music only in the car. Should I contact the dealer for a software update, or is this an Apple, Inc. issue??


I would try to reproduce the issue on a set of portable speakers and if you can reproduce the difference then take it to an apple genius bar.

Of course, there could be something wrong with your iPod. Maybe ask someone with the same model to give it a quick try to eliminate that possibility.

I’d then make sure you have the latest update by both apple and BMW.
With USB, your sound goes through a different hardware/software path than if you’re just using your bud plug. If that iPod software isn’t serviced quickly enough, you can get all sorts of weird problems on the other end because it expects a stream of sound data. If it doesn’t get that for even a fraction of a second, you’d get no sound (a pop when the sounds abruptly starts again) or possibly a repeat of what they just played or maybe some random noise - it depends on how they implemented it.
Long story short, it will sound like crap.

It could also be an electrical problem somewhere (ground loop maybe) but then you’d likely hear it on the other device as well.

Edit: this link may be of use to you. http://www.bmw.com/com/en/owners/navigation/bluetooth/bluetooth_software_update_vin.jsp

The car should be under warranty. Take it to the dealer and have them replace the sound system if need be.

Why would you replace the sound system for a faulty iPod?

There are quite a few reasons this might be occurring.

Does your BMW sound system have an AUX input? If so, have you tried directly piping the audio into the sound system AUX input rather than using the USB port?

First thing I’d do is to restart/reset the iPod. That often fixes these little bugs.

I assume that the iPod otherwise plays music well. IE, both the headphones and built in speaker sound correct. If yes, I’d try something else that plays via the dock connector. Best Buy (or similar) will often have plug in speaker sets that use the dock connector that you can just plug it in to test, though you might have to feign interest in buying the device while testing. If that also fails, then its a problem with the iPod. If it passes, then its a problem with the iPod/bmw interface and you’ll possibly be waiting for a software update to fix.

edit: I’d also turn the sound equalizer on the iPod off. It’s probably not the problem, but its one more thing to check.

Testing the iPod on an amplified speaker at Best Buy is not going to solve this problem. Plugging the iPod into the aux port on the BMW probably will stop the popping noise. The speaker out port on the iPod is analog, the USB out is digital. The problem probably lies in the Codec used in the BMW and the format used in the iPod.

Do you use a computer with iTunes on it to either download or copy from disc to the hard drive before loading them onto your iPod. If so, load a new song onto both iPods from the same computer, then play from both iPods on the BMW. iTunes is always updating something in its software and it may have made a change in the Codec, particularly how it handles long strings of zeros during pauses in the music.

The term is called zero suppression or zero code suppression. In order to keep both ends in sync, ones have to be placed in a long string of zeros. It is done in a certain pattern so that the codec on the other end recognizes the pattern and turns the ones into zeros again. Apple may have modified its zero code suppression in the newer iPods and the BMW codec may not recognize it.

BTW, do I understand you correctly that you tested the G2 iPod with the USB and not the iPod adapter?

Right, at the loss of all the nice things that the USB interface gives. If there’s a bad solder connection for the dock connector, it would be nice to correctly diagnose this.

Dear Readers,

I turned off the location services and push function of the iPod Touch G4, and 99% of the popping and crackling sounds have gone away. I did not realize that these functions of the apps tax the iPod processor so much so to interfere with playing the music through iPod cord male end. Is not the signal coming from this component digital?

I do have an Apple, Inc approved iHome radio with the iPod Dock feature and did not hear the popping and crackling while the location and push services were still on. While these functions were on, the iPod demonstrated delays when I using a given app, although the delays were much shorter than with my G2. Seems that this updated processor is still not sufficiently powerful?

Am I simply experiencing a touchy iPod interface with the BMW that is more complicated than a software update for the car?

Thanks to everyone for your contributions!!

Every single applet you use on a device is lobbying for processor time. USB sound needs to be serviced periodically. It shovels sound out to the device but in chunks, maybe only enough to play a fraction of a second at one time. Since sound requires service at some predetermined rate, we refer to it as a ‘real time’ application.
When the applet that serves up sound isn’t being ‘gotten to’ within less than that time, you’ll hear it. That’s called ‘latency’. Depending on how the other side deals with that latency, you’d most likely hear a pop. Remember, it ran out of data but can’t make up sounds so it stops playing and then, when it abruptly gets data again, it pops. It is like muting and unmuting the sound very quickly, for a fraction of a milli second.

It is inherent of the operating system design. Windows, Linux, etc all have similar issues except that they have many more resources than a portable device does so you don’t hear it as readily.
The way that’s often fixed by a manufacturer is by shoveling more data out to the device at one time so it is less likely to run out of data to play or make the operating system more efficient in dealing with ‘real time’ tasks.

Long story short:
For now, until they figure out a fix, just shut down the applications you’re not using.
Did you try that^ update in the link for the BMW? It could be that they made the buffer too short so it starves for data sometimes. It could also be on that end and/or just a matter of compatibility, its buffer being too short for the amount of data the iPod sends out.
That update can’t hurt. They clearly fixed something.

Yup, I do this stuff for a living.

As a test, go into the setting screen, and turn off the wireless network adapter, and then into the general, network settings, and turn off the cellular data. This will basically shut down even those background tasks that are still chomping for cpu time, as with no network at all, they have nothing to do. If this solves all your issues, you need to check and see what apps are running in the background.

You can turn off location services altogether, but that won’t stop everything. With a future update, Apple, Inc will be removing a software app that reportedly monitors everything that happens within the IOS (and if you have reporting turned on, it sends chunks of data for analysis). This should have a reasonable impact in your noise level. That software is reported not to monitor everything you do (like texting, etc), but it does. It tracks every “keypress”, which includes texting, but supposedly doesn’t report everything back to the provider.

What iOS are you running on the two devices? I just purchased a 2012 Kia Optima and experiencing similar issues. Theories on the forums for it are similar to here in that it’s Apples software that is the root of the issue, but if your two devices have the same OS then that theory would hold less water.