XM radio quality specs

Factual Questions
1

For about 5 months now I have had a XM capable radio in my car, I have not enabled the XM portion of it as of yet. I did research the XM website to find out about the audio quality, and as best as I can tell it says “CD like quality”. I emailed the XM support, and they told me exact specifications are “not public information”.

I am a semi intelligent person, and I just find it hard to believe that “CD like quality” is being pushed out digitally to sunscribers. A clean, non mp3’d audio track of 5 minutes long is pretty sizeable, 20MB or more, that rules out that aspect. I know there must be some type of compression going on, with decompression happening in the car, or they would have been doing this a long time ago with regular FM radio waves.

I estimate it is on the order of a 128kb stream, which is really not that great, and not at all CD quality. Then again, I can easily tell any mp3 from a original CD, no matter how high a bit rate it is encoded at. The lows are washy and the highys are flat, the whole thing is muted. I know some of you will argue XM is good, and that is probably true, I am interested in knowing the exact specification, as well as a link to where that spec is. I googled the FCC on it, as well as many other sites, and I can just not find info on the technology behind the service.

thanks

2

As long as it is significantly better than radio quality, I plan on getting it as soon as I can afford it.

Can’t wait for a portable version too.

3

I have found multiple sources, but none of them I would consider authorative. However, all of them say bitrates from 40-64kbs with 64 being the absolute maximum.

A 64kbs stream would certainly underwhelm me.

4

In the owner’s manuals on XM’s website there’s a section “Introducing XM Satellite Radio” and under that there’s “Technology” and under that they say “Furthermore the AMBE voice compression software…”

Do a google on “AMBE voice compression software” and you’ll see a link to the website of the company that makes it. It’s a start, anyway.

Also, “CD like” can mean anything. On XM’s site I’ve seen digital mentioned quite a few times, but not “CD-like”. I didn’t look very hard, though.

5

I used to have satellite TV - that’s a MPEG format and the bandwidth required for both video and sound has got to be greater than audio-only for XM. Why should the quality suck?

The music-only stations sounded just fine on my home stereo from that service and didn’t have the noisy environment of the car to combat.

-B