Quote:
Originally Posted by Redbeemer
I called the BMW Genius Hotline this morning regarding this issue and several others I had regarding USB playback on the M235i. First of all, FLAC is not officially supported, although as others have stated and I have personally confirmed, the Harman Kardon head unit will play FLAC files through the USB port. The list of officially supported file formats is numerous, mostly related to Apple products which I don't own or use, but also mp3 and wma (Windows) formats, although I have noted that like many players, it will not play back very high bit rate wma files (haven't verified the upper limit). Probably 192 kbps wma files are a safe bet based on my experience with other players. As for the CD player, my "Genius" had to check with another, more knowledgeable Genius and their consensus was that the CD player does not downsample the 44.1/16 bit WAV files during playback, but likely DOES downsample them (as noted in the post above) when a CD is ripped to the internal hard drive for storage. As to the observed spinning of the CD briefly and then stopping while the track plays, this is likely what is known as "caching" and is actually used in some very high end music servers/players such as Aurender whereby a track or even the entire album is loaded into solid state memory and then read from there for actual playback. There are theoretical advantages to doing this, so, if the BMW head unit is doing this, it does not necessarily indicate any sort of degradation of the music. The one remaining question is whether the head unit somehow downsamples FLAC files contained on a USB drive during playback. I doubt that it does since there is little to be gained by doing so, but I have no way of proving this. I would say one more thing regarding music playback by most any audio system in most cars: generally, their is little to be gained by high quality files (as compared to mp3/wma) given the typical noise levels in many cars, especially high performance cars with noisy exhausts, engines, and wide high performance tires. One might be able to actually tell a difference in audio quality from different files when the car is parked and with some very expensive audio systems, but, even though I am an audiophile and have many high quality audio components at home, for me and my ears, I just want something decent sounding, somewhat above a background music quality to drown out traffic and make the trip less boring. I have owned a pretty high end car audio system (Alpine) and have heard some very expensive systems, but, unless they are at rest or played in something like a Rolls Royce which is tomb-like when moving, I won't waste my money beyond the factory "premium" systems. Sorry, I know I digressed a bit there.  |
You and I think similarly regarding car audio: perfection is impossible because of the many problems with the car environment, from the far-from-ideal 'listening room' to ambient/white noise.
That said, a good system -- clear drivers, ample (but not extreme) and clean power, tonal balance, quality programming -- can still make a huge difference in a car, particularly in the lower and higher registers. There is actually
plenty to be gained by high-quality digital files
if the OEM system is upgraded -- to the point to where the system sounds horrible with lower-quality files
if only parts of the OEM system are upgraded. If you know anything about how compression works, you know that the more compression exists, the more ambient and/or white noise tends to replace the missing frequencies to the human ear. I won't get deep into the theory, but basically the higher the quality of programming, the less your ears are 'distracted' by less-than-perfect acoustics.
The 256Kbps downsampling for CD rips is a fact; it's in print in the manual I specified. Also, the HK and Hi-Fi head units are
exactly the same; it's the drivers and outboard amp that are different. That means the DAC is the same. So don't believe that the HK system has more program-handling capability than the base stereo; it doesn't. All CD transports 'cache' to an extent; that's the nascent definition of oversampling. However, transports typically spin continuously to achieve this at varying RPMs; they don't stop and start like the transport in our HUs does. That behavior has me thinking that the HU does commit each CD file to a memory cache -- but its architecture is only set to do it at 256Kbps based on the ripping, among other things (ears, HD digital file player through the analog AUX input that bypasses the HU's DAC, etc.)