XM's Audio Processing Upgrade
Those of you who are also XM Radio subscribers may or may not have been aware of the recent audio processing upgrade implemented at XM Radio's transmission facility in Washington D.C.While ostensibly a technology improvement, the primary reason for the upgrade may be directed toward appeasing the seemingly unending customer complaints related to audio quality. This topic often makes its appearance as XM SQ or XM Signal Quality, in the various online discussion (and bashing) groups.
XM originally started broadcasting using Telos Systems Omnia-3 audio processing equipment. The Telos equipment was eventually superceded with processing gear designed and developed by Neural Audio. Audio processing is used to compress and limit the dynamic range of program material prior to CT-AAC encoding.
Some XM listeners may recall that the Neural equipment upgrade back then was attended with with much hoopla and fanfare. We were led to believe that the Neural stuff was the ne plus ultra of codec enhancing audio processing and was going to do wonders. Well ... the jury was always out on that one and it often seemed like the Neural equipment made things worse, rather than better! Compounding the problem was XM's never ending parameter tweaking of the processing compression and equalization settings.
On Sat. Aug. 4 and Sun. Aug. 5, newly installed Neural processing equipment was turned-up on select music channels. No changes to the CT-AAC encoding equipment were said to have been made. Noteworthy with the upgrade, is improved audio clarity. We can now clearly hear what CT-AAC encoding really sounds like! Although the equipment is new in a chronological sense, it many aspects it sounds more like traditional processing gear, similar to the Optimod 6200 processing that Sirius has been using with their encoding apparatus.
Any improvements are welcome. I let my subscription lapse on my portable unit since I started listening to it for quot;freequot; through my Direct TV system hooked up to the stereo. I have noticed that some of the channels sound better than others, the jazz and classical channels sound surprisingly good. I do miss the portable unit, especially hooked up to my car system though. Maybe I will get it turned back on.
I was thinking the other day either I'm getting used to the crappy sound that xm puts out or it's getting better somehow. I have a polk xm tuner, run it though an expander and finally through some tube gear. I have no problem listening to it all day and I'm glad to hear they're trying to improve the sound quality on their end as well.
jhal
Pretty sure that DirecTV gets the 70 or so program streams -before- they go through the processing. That would mean that you are out of the loop in terms of hearing the processing effects (lucky you). DirecTV most likely gets the raw XM content over a fiber and then transcodes it into their format of choice (MPEG-II).
Originally Posted by applesaucejhal
Pretty sure that DirecTV gets the 70 or so program streams -before- they go through the processing. That would mean that you are out of the loop in terms of hearing the processing effects (lucky you). DirecTV most likely gets the raw XM content over a fiber and then transcodes it into their format of choice (MPEG-II).
When I get my portable receiver (Delphi My-Fi) hooked back up, I will run it into the stereo and do an quot;A-Bquot; comparison test and post my results.
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