DTV XM radio sound quality

[FranklyFred]

Does anyone know what quality, bit rate the signal from XM radio on DTV is?

[tzphotos.com]

Does anyone know what quality, bit rate the signal from XM radio on DTV is?

I know it's better than the sound quality you get in the car from the portable version of XM.

I used to have an XM receiver in my car and the DirecTV version sounds like they use less compression. The Car version sounded like a bad MP3.

[jautor]

I had one of the Polk Reference XM home tuners, and the sound quality on the DirecTV feeds was noticably better than the Polk (which should be the best XM receiver). Mostly a difference is stereo imaging quality, but also some 'better' high frequency response...

It convinced me to sell the Polk receiver and replace it with another D* receiver - $5 mirror fee vs. $7 2nd XM receiver fee - and I got another DirecTiVo, so extra record capacity as a bonus!

The only downer is the loss of the non-music channels (sports and comedy) at home... But it was rare I was using those at home anyway (and XM comedy is online).

Jeff

[linuxworks]

fwiw,

when I tune using the opto out of my directivo to my home stereo spdif in, it shows 48k. so for one thing, they're changing the sample rate from 44.1 to 48k. that's problem #1.

problem #2 is that they DE-normalize the amplitude!

I'm not kidding. a normal .wav will usually peak at close to 0dB. audio engineers do try to 'fill the channel' with as much audio level as they can while still not clipping (over 0db).

when I first hooked up dtv and the music service before xm, it was limited to -12dB at peaks! ;(

now it seems to be more like -6db. still not zero but at least its better than a minus twelve!

final insult to injury: there are pops and clicks almost every second on some channels. there's one channel I listen to 'audio visions' (spacey slow music) and you can really hear the bit starvation there ;(

this totally loses any appeal of sat music via DTV. they have done all they can to ruin it - and they succeeded.

[Steve Mehs]

I had one of the Polk Reference XM home tuners, and the sound quality on the DirecTV feeds was noticably better than the Polk (which should be the best XM receiver). Mostly a difference is stereo imaging quality, but also some 'better' high frequency response...

It convinced me to sell the Polk receiver and replace it with another D* receiver - $5 mirror fee vs. $7 2nd XM receiver fee - and I got another DirecTiVo, so extra record capacity as a bonus!

The only downer is the loss of the non-music channels (sports and comedy) at home... But it was rare I was using those at home anyway (and XM comedy is online).

Jeff

The Polk was nothing but an original SkyFi in a component receiver with an toslink output. Pretty much the best sounding way to get XM from their own service is to get an Onkyo, Yahama, Denon or Sony Home Theater receiver with an built in XM tuner that can do Neural.

[AlbertZeroK]

The Polk was nothing but an original SkyFi in a component receiver with an toslink output. Pretty much the best sounding way to get XM from their own service is to get an Onkyo, Yahama, Denon or Sony Home Theater receiver with an built in XM tuner that can do Neural.

Not true. XM sounds best off DirecTV, if you ignore the pops and clicks. SIRIUS sounds best on DISH. SIRIUS on DISH is MPEG2 compression. I think XM is as well. But it's a live feed then pushed onto the satellites using different (better) compression. Also you don't have DirecTV or DISH compressing some channel more than others like SIRIUS and XM do.

[terryfoster]

How about this?

My dad was listening to a Led Zepplin tune and noticed he wasn't receiving a stereo signal. His HR20 is connected to the receiver using an optical digital cable. It's not that it was mono, that would have been an improvement. He lost an entire portion of the song when it would swing to the left or right channel (I don't remember which tune he said it was to know what channel he was missing).

Has anyone else noticed the lack of stereo sound from XM channels?

[tzphotos.com]

How about this?

My dad was listening to a Led Zepplin tune and noticed he wasn't receiving a stereo signal. His HR20 is connected to the receiver using an optical digital cable. It's not that it was mono, that would have been an improvement. He lost an entire portion of the song when it would swing to the left or right channel (I don't remember which tune he said it was to know what channel he was missing).

Has anyone else noticed the lack of stereo sound from XM channels?

Never noticed that problem. Must have been an issue at that moment.

[Steve Mehs]

Not true. XM sounds best off DirecTV, if you ignore the pops and clicks. SIRIUS sounds best on DISH. SIRIUS on DISH is MPEG2 compression. I think XM is as well. But it's a live feed then pushed onto the satellites using different (better) compression. Also you don't have DirecTV or DISH compressing some channel more than others like SIRIUS and XM do.

I know. That's why I said "Pretty much the best sounding way to get XM from their own service is to get an..." XM and DirecTV and XM on AOL Radio have better sound quality then XM themselves, but that's not what I was talking about.

[Radio Enginerd]

fwiw,
when I tune using the opto out of my directivo to my home stereo spdif in, it shows 48k. so for one thing, they're changing the sample rate from 44.1 to 48k. that's problem #1.


How would upsampling 44.1k to a 48k sample rate hurt the quality of the music? You're only increasing the number of times the audio is being sampled therefore increasing the granularity of the audio. Do you have a source at XM or DTV confirming that the original delivery rate is 44.1? The source content, if off CD, was played or ripped at 44.1 but that doesn't mean the air chain for the station(s) in question aren't upsampling the audio for delivery. Regardless, there are many unknowns, non of which effect the audio quality.

My guess: Your DirecTivo upsamples it's optical output to match the sample sample rate it uses for DD.

problem #2 is that they DE-normalize the amplitude!

If thats the case, all they're doing is under modulating the audio where the average peak hits -12. In the digital world, this isn't a bad thing. All you have to do is turn up your receiver to compensate for the slight lack of modulation. It's not like you have to worry about an analog noise floor or anything like that...

The term normalizing/de-normalizing is used when referring to audio editing, not live delivery of audio.

final insult to injury: there are pops and clicks almost every second on some channels. there's one channel I listen to 'audio visions' (spacey slow music) and you can really hear the bit starvation there ;(

I'll have to take your word on that particular channel as I've never listened to it.

this totally loses any appeal of sat music via DTV. they have done all they can to ruin it - and they succeeded.

I think that's a strong and unfair statement. Although it's not perfect, I wouldn't say that DTV is doing everything they can to ruin it. The XM channels are less processed and far better than the feeds you can obtain from an XM radio or online.

[bwaldron]

Although it's not perfect, I wouldn't say that DTV is doing everything they can to ruin it. The XM channels are less processed and far better than the feeds you can obtain from an XM radio or online.

I've definitely found XM via DirecTV to have noticably better sound quality than any XM receiver I've used.

[linuxworks]

How would upsampling 44.1k to a 48k sample rate hurt the quality of the music? You're only increasing the number of times the audio is being sampled therefore increasing the granularity of the audio. Do you have a source at XM or DTV confirming that the original delivery rate is 44.1? The source content, if off CD, was played or ripped at 44.1 but that doesn't mean the air chain for the station(s) in question aren't upsampling the audio for delivery. Regardless, there are many unknowns, non of which effect the audio quality.

My guess: Your DirecTivo upsamples it's optical output to match the sample sample rate it uses for DD.


I don't think you quite understand math errors when doing sample rate conversion. are you familiar with these kinds of artifacts that you get whenever you SRC?

no, you are incorrect - even SRCing 44.1 to 48 IS lossy. its not about fitting 1 quart of water in 1.5quarts container. its about CONVERTING content from one encoding to another. and yes, its lossy and NOT what I want from digital audio! I know it should not have to be like this.

now lets talk about your (also incorrect) view of amplitude levels. no, -12 is NOT normal for PEAK values for digital audio. I did not say average; peak is the name of the game. its not hard or wrong to normalize signals before mastering to final media (your cd). no audio engineer would release a disc that PEAKS at minus 12! or even -6. not even -3, really - that is still too 'junior' of a move for a pro audio engineer.

so what's wrong with just raising volume level? well, again, math errors in amplitude scaling. you take a signal that USED to fill 0000-ffff in 16bit words (say). and that represented its full dynamic range. now your idea is that its OK (!) to scale that dyn range LOWER and then re-encode back to digital format, thus making the audio sit in the 0000-9000 range (to pick some subset of full 16bit range). you have reduced the resolution of the audio (on a 'vertical axis' so to speak) and you have also stretched the sampled data points and re-mapped them to a different horizontal layout (frequency), thus causing more artifacts.

you seriously, now, think that this was OK for them to monkey around with the samplerate and the amplitude levels???

I'm not an audio engineer (although I do have a bit of background in digital audio and spdif circuits) and I'm NOT a golden-ears type. but XM sounds like arse to me on the spdif out of my directivo.

if y'all say this is as GOOD as it can get, well, thanks for the info - now I know not to waste any money ON xm.

[linuxworks]

[i]The term normalizing/de-normalizing is used when referring to audio editing, not live delivery of audio.[i]

technically, you are right - in a way.

to normalize you have to have to WHOLE wave history in front of you. you then (as step 1) find the max value and then scale all others (step 2) to make that new max value 'all effs' (max integer) and so you do need a 2 step process.

UNLESS they have already guessed or calculated or just DEFINED what the max level should be and they artificially lowered the output - for 'content management' reasons.

seriously guys, I can think of no other reason than to garbage-up the audio stream and make it LESS attractive to tape and keep a copy of. the fades from one song to another is one deterrant, making the setlists NOT available online is another deterrant and the destruction of clean audio by doing horiz AND vertical compression/remapping only ruins what is left of the audio signal.

there is no technical reason I can think of why lowering volume level (on a non AM signal - we -are- out of the 1960's afterall) would be a good thing. but lowering it DOES raise distortion and also DISALLOWS bit-perfect copies of the source.

the source was almost always 44.1 and peaks at 0db. what comes over xm on dtv is most certainly NOT 44.1 at 0db.

you make your own conclusions. but if this is how xm sells 'digital audio' I want no part of paying for that 'product'.

we almost have to accept very bitstarved and lossy video over satellite. but to have to accept the same kind of stuff for audio - that makes no sense to me. none. audio is easy enough to get in full 44.1/0db format.

[Radio Enginerd]

no, you are incorrect - even SRCing 44.1 to 48 IS lossy. its not about fitting 1 quart of water in 1.5quarts container. its about CONVERTING content from one encoding to another. and yes, its lossy and NOT what I want from digital audio! I know it should not have to be like this.

This is insignificant to the average ear though.

now lets talk about your (also incorrect) view of amplitude levels. no, -12 is NOT normal for PEAK values for digital audio. I did not say average; peak is the name of the game. its not hard or wrong to normalize signals before mastering to final media (your cd). no audio engineer would release a disc that PEAKS at minus 12! or even -6. not even -3, really - that is still too 'junior' of a move for a pro audio engineer.


I never said that -12 was NORMAL for peak values, I stated that I agree that it was UNDER modulated. We're not talking about a mastered CD. We're talking about the ever changing live delivery of audio. I agree, you would never master at -12dB, that's ridiculous.

I don't work for DTV but I happen to think they chose -12dB because of the lack of processing on the audio itself. My "guess" is that they wanted to eliminate digital clipping. I didn't say it was the best way to do it, just commented that it's insignificant. Yes, I'm a super nerd and I've looked at audio out of my HR-20 versus audio out of my DVD player and there is a difference. I don't think I was arguing that.

you seriously, now, think that this was OK for them to monkey around with the samplerate and the amplitude levels???

I don't think they have a choice. Could you imagine the overhead for them to send the XM channels down uncompressed? You raise fair arguments but when the quality of the audio stream coming out of your DTV box beats the audio quality you can get out of an XM Radio, online or even FM, does the end user even know the difference? I think in most cases the answer is NO.

Thanks for the stimulating chat.

[Radio Enginerd]

you make your own conclusions. but if this is how xm sells 'digital audio' I want no part of paying for that 'product'.

I would never pay for XM or Sirius for what you get out the box. That we totally agree on. :)

UNLESS they have already guessed or calculated or just DEFINED what the max level should be and they artificially lowered the output - for 'content management' reasons.

I don't think DTV is using anything to do dynamic processing and if they are, it's minimal. They're probably using some kind of digital signal processor to do some leveling. One would hope there adjusting the output attenuation of that device and feeding that into the uplink. With peaks at -12 it would appear they have left a lot of head room.

[Dolly]

All of you are taking way over my head :confused: But I will add one thing. I wish D had a way you could just drop the music channels. If I want music, I will turn on a radio. I see no point in a TV having music channels :eek2:

[tonyd79]

I am ignoring the numbers posted cause I don't quite understand them.

XM in my Pilot sounds better than at home but I think Honda tweaked the acoustics.

However, listen to the XM feed when Channel 95 is displaying the DirecTV logo and then go to the same XM channel in the 800s (I think it is usually a classic rock station). You can hear the difference.

So, that tells me that the XM source is better than what we get normally since 95 is delivered via an HD channel. It sounds spectacular there. Even when just using straight stereo.

[linuxworks]

xm on dtv is convenient since I already have an opto cable run from the tivo box to my home stereo. and, IN THEORY, spdif should give me a very clean sound. that is, if you assume no one monkeys around with the source bits.

and it clearly seems they have. the sample rate is easy enough to observe (reads 48k on my home stereo; and when I force a 44.1k signal from my m-audio spdif sound card, I certainly see 44 read out on the stereo display, so I know its not kept fixed at 48 for the display ;)

that is odd part #1. but to artificially lower the signal level - I just can't understand that. unless they play some bit round-robin game on the downlink where they assign the upper few bits of dyn range (that was robbed from you) to a pool of bits and they can derive more channels that way (?). totally guessing here, but why else bit-starve? otoh, this is still 'just audio' here - bitstarving audio streams seems almost pointless as you need MUCH more for video than audio - by far.

its near impossible to find true spdif outs on xm and sirius receivers. there were some early hacks at the start but those boxes aren't current anymore.

it sure seems that paranoia about home taping is what is really going on here. intentional mutilation of the signal for anti-taping reasons. why else? I can't see any other logical reason for this.

[Radio Enginerd]

All of you are taking way over my head :confused: But I will add one thing. I wish D had a way you could just drop the music channels. If I want music, I will turn on a radio. I see no point in a TV having music channels :eek2:

My apologies, our rant was bordering on rude.

[Lags]

For my car, I have a Roady2 and I use the cassette adapter. Great sound (compared to FM modulated).

At home, the I think the XM channels on DTV sound great too. I have the sound coming through a Sony receiver and Paradigm speakers. I play them all the time, no complaints on the sound quality.

I don't notice any sound degradation of XM channels through DTV.

[linuxworks]

if anyone wants, I could probably find an excerpt taped copy of an xm show 'hearts of space' from the audiovisions channel. I intended to keep a few back copies of those (background music, easy to fall asleep to, LOL!) but the pops and clicks every few seconds just totally ruined it for me, so I stopped even bothering taping that show. but I may have a copy around - or I could make another copy at-will. on quiet passages, the clicking in the audio stream is worse than FM ever was! there's no reason for it. maybe you don't hear it since some content masks the clicks and pops. but if you tune to a classical station with a piano solo, for example, I bet you'll hear the bit losses very easily. a click is not hard to hear - no golden ears needed for that test!

[Dolly]

My apologies, our rant was bordering on rude.
:lol: I liked the rant I just couldn't understand it all :confused: My remark didn't mean your rant was bordering on rude at all. I simply meant I think those of us not interested in music on TV should be able to "opt out" and maybe get a little discount in our D bill--haha no way
:nono2:

[Steve Mehs]

Dish and DirecTV would lose a lot of money if they didn't have the audio only channels, think of how many commercial establishments out there have commercial accounts with DirecTV or Dish to provide background music to patrons. I’m guessing the audio channels cost the providers very little to carry.

[Radio Enginerd]

Dish and DirecTV would lose a lot of money if they didn't have the audio only channels, think of how many commercial establishments out there have commercial accounts with DirecTV or Dish to provide background music to patrons. I’m guessing the audio channels cost the providers very little to carry.

You're probably right, but I think the point he was trying to make is the ability to "opt out" on the channels to perhaps save money on your programing package.

[Radio Enginerd]

Dish and DirecTV would lose a lot of money if they didn't have the audio only channels, think of how many commercial establishments out there have commercial accounts with DirecTV or Dish to provide background music to patrons. I’m guessing the audio channels cost the providers very little to carry.

So I just re-read your signature and it's clear you are a satellite radio advocate. How much do your sub(s) set you back and what do you think of the sound quality (through DTV/Dish and the radio itself)?

[Steve Mehs]

A month, I pay $26.93 for XM (3 receivers) and $19.94 for Sirius (2 receivers). I have a plug and play receiver for each in my SUV at all times, a plug and play receiver at home at all times and my new home theater receiver has a built in XM tuner. Not including my Sony Home Theater Receiver I have about $1K invested in various satellite radio hardware not to mention another $50 in paraphernalia that I use to promote the two services (decals, t-shirts, hats).

The sound quality could be better, but I can tolerate it (obviously). The content is superb, what I get out of satellite radio by far outweighs any flaws in sound quality or monthly fees. I get a music experience that takes me far beyond what I ever listened to. Before I got XM and Sirius I only listened to current hard rock. Now I listen to everything from Southern Gospel to Electronica to Alterative Country. Nowhere else on the planet can I get the variety of satellite radio, and have it be commercial free and uncensored. That is something dinosaur radio and their new gimmick HD Radio can’t give me and which is why I will never listen or support a medium where selling ads outweighs the importance of music. Woohoo a ‘local’ radio station plays 5 songs in a row, big deal. I have no use for dinasour radio.

I ditched Dish before Sirius was added, but I hear Sirius all the time at my uncles house. The audio quality is excellent, blows away Sirius itself. I ditched DirecTV a few months after XM was added. From my listening, while XM on DirecTV does sound better then XM itself, the whole thing was a disappointment compared with what I was expecting. There seem to be a lot of little quarks with XM on DirecTV that aren’t present on XMs own service. I’d say Sirius on Dish sounds more rich then Music Choice on cable, but Music Choice sounds cleaner. I don’t know if that really makes sense or not, and I can’t really do an A/B comparison on the same set up, but that’s how I generally feel.

Next weekend is the Auto Show here in Buffalo. I guess there’s going to be a booth for HD Radio. I’ll be wearing my Sirius hat and XM t-shirt promoting satellite radio on the floor. I wonder if any of the ‘local’ radio stations will be there for stupid contests or spin the wheel and win a nifty prize. I’ll make sure to get noticed.

[tzphotos.com]

Steve,

With all that money you have invested in Satellite radio I can see why you talk about it the way you do. I just don't have time to listen to that much radio. The local stations do it for me.

I sometime use the XM on the DirecTV for background at home(Christmas for instance), but can sit there and listen to the stations when I have HD to watch.

Enlighten me. You talk how great the satellite channels are. Which XM channels should I test drive on my DirecTV? (No Country music please)

Thanks,
Tom

[Steve Mehs]

I came to XM with the thought I'd only listen to 3 channels, Bone Yard, Liquid Metal and Squizz. That's it, nothing else ever considered. For some reason I started exploring new genres and now I listen to a bunch of different stuff. That is the greatest value of satellite radio, IMO. I can’t really recommended what to listen to, my #2 most listened to station is Enlighten, and Southern Gospel is an offshoot of country. We all have different tastes and preferences. Some people are turned off by XM because XM goes deep and plays songs that never got popular or bands that aren’t being played on regular radio. While Sirius is more hit orientated.

The common thing is ‘XM sucks because they play obscure crap no ones ever heard of’ or ‘Sirius sucks because they play the hit songs over and over’. Well being a living, breathing creature, sometimes I do want to hear that obscure crap, and sometimes I want to hear familiar songs over and over. Depends on what I feel like at the moment.

I keep this in a Word file since this question is asked a lot on the satellite radio boards I visit. Here’s what I listen to on each service.

XM
The 60s, The 80s, Big Tracks, Bone Yard, BPM, Enlighten, Flight 26, Hear Music, Liquid Metal, Lucy, The Message, Squizz, The System, Watercolors, X Country, America Right, NHL Home Ice, Old Time Radio, The Virus, XM Comedy

Sirius
Area 33, The Beat, Bluegrass, Buzzsaw, Classic Rewind, Hard Attack, Octane, Prime Country, Revolution, Super Shuffle, Spirit, Howard 100, Howard 101, NFL Radio, Playboy Radio, Raw Dog, Sirius Patriot

Music Choice is for the stuff neither XM or Sirius have like Party Favorites, Solid Gold Oldies and Sounds of the Season.

[tzphotos.com]

Steve,

Thanks for the response. When I find time I will give XM a listen. I know what you are saying about obscure music. We have a station in Chicago(WXRT) that plays strange off the wall music(IMO). XRT plays both local and national groups that you won't find on the Nationally run networks. We have a couple of other stations that play local music, but also mix in more popular rock.

Again, I will check out the XM stations.

[Dolly]

Dish and DirecTV would lose a lot of money if they didn't have the audio only channels, think of how many commercial establishments out there have commercial accounts with DirecTV or Dish to provide background music to patrons. I’m guessing the audio channels cost the providers very little to carry.
I wasn't thinking of that service being provided to commercial establishments. What I was saying is I don't think I should have to have those stations myself, if I don't want them. Maybe put them in a package of their own for people who have D and want the music. Then that way those of us who don't want the music don't have to have it :)
But I can't see D doing that :(