I did some searching, and couldn't find any mention of this particular issue. I thought it might help someone.

I've only had a little time to play with the audio in my 2013 R58 I bought 3 weeks ago (standard boost system). But I have a long commute and I listen to audiobooks on mp3, so that was the first thing I got going. I had previously been using a Sansa Clip+ feeding an Aux Input in my 2003 Cooper.

I tested playing mp3 files on a flashdrive connected to the USB port without much optimism. I was pleased to find that the system remembered where I had left off, even if I removed the flashdrive, drove the car without it, then reconnected it. Not bad!

But then I discovered that many of the audiobook files caused an "unreadable" error, while others worked just fine. Lots of things about a file that the Mini might not like: Bit rate, Mode (stereo/joint stereo/mono), VBR, etc. It was just a matter of identifying the culprit(s). After some detective work involving creating mp3 files with varying attributes and noting which ones failed, I figured it out.

It was the Frequency.

People who only listen to music probably wouldn't run into this, as 99% of music mp3s you'll find (or create) are frequency 44100. It's the standard frequency used for music CDs as well.

But when some people create spoken-word mp3s, they figure they don't need to encode a full spectrum of sound, just that of a speaking voice. So to shrink the file size, they may cut back on the bit rate, and/or use VBR, and/or use mono instead of stereo, and/or...use a lower frequency. Like 22050 or 24000.

So I've determined that the following are ok, as far as I can tell:

Bit rate 32-256 (haven't tried higher, but manual says >256 may not play)
VBR (Variable Bit Rate) seems to be good.
Mono/Joint Stereo/Stereo all seem to work fine.

But it MUST be encoded at 44100. Or it will be "unreadable".

Non-44100 files can easily be converted though. I use a freeware program called MP3 Quality Modifier and convert non-44100 files to mono/64kbps/CBR/44100. Does the job.

Anyway, I thought maybe some other audiobook listeners might benefit from this.

 

Hey, that is great info. Thanks for posting, would be nice if your post was stickyed..