[johnnylexus]

I have been considering XM radio in order to pull in "quality" digital radio without commercials for listening on my cans ...

I found this post in a yahoo newsgroup dedicated to XM radio topics:


From: jamespy@s...
Date: Tue Nov 20, 2001 10:22 pm
Subject: The truth about XM radio


I just saw the following posting on the alt.radio.digital newsgroup.
It seems to confirm my suspicions about XM radio's overcompressed
signal.

===================

I'm writing this because there is very little factual information
regarding XM radio as far as how the technology works, and now I know
why.

After eagerly awaiting the release of XM I went out and bought one, got home and activated it online. When I finally had it up and running something immediately didn't sound right, it sounded more like streaming internet radio than "CD quality sound". Every channel sounded as if it were broadcast from inside a tin can, not a multimillion dollar studio.

I had always suspected that XM would do a little compression as to save on valuable bandwidth, but I couldn't believe that they would take it this far down. What I was hearing sounded very compressed for a music only service, when I was expecting something more in line with the fidelity of the Music Choice networks on DirecTV (Not CD quality by far, but still very good). What I was hearing was clearly audible on the cars factory sound system, we're not talking high end stuff here, in fact my car system is probably worse than the average public's.

So I did a little research to see if my suspicions were justified,
and what I found out was appalling. Are you ready for this- the best bitrate that XM broadcasts in is 64Kb/s! This does not constitute CD quality sound no matter what compression CODEC you use (XM uses LDR's ePAC multistream technology that will also be use for IBOC DAB which incidentally will be broadcast on FM at twice the bitrate that XM uses) and does not constitute even a reasonable facsimile of music.

I also discovered that the entire service resides on just over 4Mhz of bandwidth. Do the math people, that means an average of 40Kb/s per channel. This also explains why certain channels sounded horrific while others were merely bad. For instance I found that most of the talk programs sounded better on AM radio than at the 32Kb/s at which they were probably broadcast.

I did some more testing before deciding to take the unit back. I set up the receiver at home and dialed in Radio Free Virgin's streaming internet music player at 100Kb/s (which is probably the best sounding internet streaming radio I have heard) then I switched over to XM. It was no contest the Radio Free Virgin won hands down (which is free by the way). I listened on my studio setup just to be sure of what I was hearing and everything I had suspected was correct of worse.

I had such high hopes for this technology and have been eagerly
awaiting it's arrival for years, and to XM's credit it works
wonderfully even better than I had expected as far as signal loss etc.(at 10,000 watts per satellite they are the most powerful satellites in space), it just sounds like crap. I can't believe that they brought this thing all the way to market expecting people to pay for something that sounds terrible, did anybody at XM listen to this thing before they decided to give the go ahead? I might considerpaying for the service if they cut the number of channels in half and broadcast the good ones at 128 Kb/s, but sad to say mine is going back.

Incidentally I wouldn't hold out any hope for Sirius (assuming they make it to market) sounding any better as they are going to have the exact same bandwidth, just the delivery is a little bit different.

==================

 

[kwkarth]

thanks for the info!! I wonder what brain-dead, greedy, short sighted marketing group pulled this one together??

I also wonder how many frustrated engineers are left in the wake of the development effort for this looser?

You've saved many of us lots of trouble. I wonder how long it will take for the seed money to run out and for the whole thing to collapse?

Thanks again!

 

[johnnylexus]

I'm pretty disappointed about this. I have not personally heard the broadcasts. This info is coming second hand and I am assuming that it is correct. I wish I knew a way to verify the claims that the signals are really as CRAPPY as the poster claims.

 

[gloco]

Looks like were gonna suffer with AM/FM for another half a lifetime, i can't believe they released something so archaic, doesn't make sense!

George

 

[kwkarth]

No, it really doesn't make sense. It can only be explained by greed fortified by a solid dose of stupidity.

 

[Serow]

Man, if this is true, I am very disappointed. I really wanted to give this technology a try, but the costs and uncertain future were making me rethink. Now there's no way I am going to waste my money on this compressed garbage.

 

[Budgie]

What pisses me off about this- If the general public keeps getting exposed to crap sound and told it is state of the art, cd quality sound, people's expectations will get to be so low, they will start to belive that it is good sound. Audiophiles are allready such a small percentage of the population (and on the decrease!) That the future for quality sound products gets to look very bleak, sometimes. I don't want a future where all I can find is a Sony/Bose style boom box getting feed from a super compressed digital format playing Brittney Spear Clones pop super hits.

 

[thomas]

i dunno, i never expected much from the two satellite radio to begin with... Paying somthing like $20 a month + hundreds for new equipment totally defeates the point of radio for me- i use it to discover new music, then buy the cd to listen whenever i want, with good sound quality. If i had to choose between buying CDs and listening to inferior radio, or spending all the money on a premium radio service, i'd choose Cds.

And then there's the format wars, there are two companies competing for the tiny satellite radio market... Now that they've been released, and they suck, i'm sure they'll die even faster...

But i think there's still hope for high quality radio- DAB, as mentioned in that original post. Its FREE, companies have already released integrated decoding chips (receive/decode AM, FM, DAB) that cost about $1, and many local stations (in Toronto) are already brodcasting it... Also, as that article states, it uses twice the bitrate of the satellite systems, so it should sound decent. Sure, 128kb/sec probably won't be "CD-quality", though it can certainly sound very good (similar bitrate to minidisc's ATRAC 3, MDLP 2), and won't have the hiss/high frequency rolloff of analog radio.

But if the radio stations simply put their analog brodcasts through a DAC to turn it into "digital radio", or continue playing the crap they do today, then...

 

[gloco]

Which leads me to say, i'm very happy i own a burner so i can make my own mixes and burn cds that i want for the road. The hell with radio programming!

George