Can Someone Please Explain This To Me?

SWMBO has XM in her car, and it's pretty nice, except that, during the summer, the heavily-leaved trees cause it to cut in and out a lot.

For a long time, I've wondered: remember back in the olden days when we had these contraptions called "compact disc players"? They'd skip a lot. So the portable ones had a feature called "electronic skip protection". It would read ahead on a disc and "store" 20 seconds or more of a song ahead of the current point, and if the player got bumped around, it would rely on this buffer to keep the song from skipping until the jostling stopped.

So, here we are in 2007, and it's all digital. With all the features and crap that satellite radio has, why in the hell can't they set the receivers up to download and store a live buffer, so that when you go under bridges, tunnels and trees, it doesn't cut in and out? Is it a technological limitation of the satellite system? Or have they just not thought of it yet? Or maybe some receivers have it, just not the ones I've seen. What's the deal?

If the signal cuts out, buffering doesn't help...you're just delaying the "skip".

Most of the satellite radio systems I've read about have a transmission buffer to smooth over the small dead zones. However, that isn't going to help much if you are hitting a lot of dead zones or interference.


On top of that, I believe that XM actually transmits 2 or 3 signals at once per channel, each slightly time delayed form each other and this aids in smoothing the transmissions. If you pass under an overpass and lose signal, it means you're only connecting to one of those transmissions to start with.

Bike N Brew said:

If the signal cuts out, buffering doesn't help...you're just delaying the "skip".

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I understand what you're saying, but there's surely some kind of way to make it sync back up with the signal and "reset" the buffer once it reconnects to the satellite---in other words, as long as you're not disconnected from the satellite for longer than the buffer period, then once you're reconnected, it switches from the buffer stream back to the live stream and starts downloading a new buffer.

kornkob said:

Most of the satellite radio systems I've read about have a transmission buffer to smooth over the small dead zones. However, that isn't going to help much if you are hitting a lot of dead zones or interference.


On top of that, I believe that XM actually transmits 2 or 3 signals at once per channel, each slightly time delayed form each other and this aids in smoothing the transmissions. If you pass under an overpass and lose signal, it means you're only connecting to one of those transmissions to start with.

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So if they already have small transmission buffers, couldn't you just increase the onboard memory and set the buffer to, say, 2 minutes?

I've had Sirius for about 4 1/2 years now, it seems a lot worse this year than I had experienced in previous summers. I am, however, travelling more narrow secondary roads with major tree canopies. Also, partially to blame, when I lost my company truck and got a company car, I never put the antenna on the roof, it's just on the dash. Does pretty well, considering, but I do need to get off my butt and roof mount it. On my truck I mounted it on the passenger side, but now to get as clear from the canopy as possible I will mount as far to the driver's side as reasonable.

I wondered the same thing about buffering, suspect they are using a system with the best balance of performance vs. cost.

Could these guys (XM and Sirius) be doing something different this summer vs. previous years, it does seem a bit tougher to get a solid signal, even at my house?

there is buffer built in.....but if you are in a dead spot for longer than the buffer...guess what, it cuts out. I have problems too.....it will be fine eventually

98EXL said:

there is buffer built in.....but if you are in a dead spot for longer than the buffer...guess what, it cuts out. I have problems too.....it will be fine eventually

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There is? It should last for longer than a highway overpass on an interstate, no?

LOVE my iPod... Never had a buffer problem

Evan! said:

There is? It should last for longer than a highway overpass on an interstate, no?

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depends on the hardware I've found.....also antenna size too!

Drunkensatyr said:

LOVE my iPod... Never had a buffer problem

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I love my iPod too. But it's the damnedest thing...I can't pick up XM or Sirius on it to save my life. Maybe it's in the settings?

Evan! said:

I love my iPod too. But it's the damnedest thing...I can't pick up XM or Sirius on it to save my life. Maybe it's in the settings?

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There is a hacked FW revision. 1.2.0 has XM settings, but no Sirius

There's no way I'm paying $13/month for radio.

I'll stick with my CDs.

homebrewer_99 said:

There's no way I'm paying $13/month for radio.

I'll stick with my CDs.

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If I had a dollar for everytime I heard that, and then heard the exact opposite from the same person about 6 months later....I'd have about $20 bucks

98EXL said:

If I had a dollar for everytime I heard that, and then heard the exact opposite from the same person about 6 months later....I'd have about $20 bucks

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...and I thought you were going to say you'd have a dollar!

homebrewer_99 said:

...and I thought you were going to say you'd have a dollar!

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nah. Really about a dozen or so people have said that to me over the years....then I show them....then they go play with it at the store, then they get it, and now can't live without it.

It's hilarious to me....I've had it from the get-go back in the day

I think it really depends on how much you travel.

My wife got it for really cheap. Like, $50 for the receiver and car kit and 4 months of the service, from woot.com. After the 4 months she was going to get rid of it...that was the plan at least. But when it came up, she just couldn't bring herself to get rid of it. So I see what 98EXL's saying...

I couldn't have imagined paying $15 a month (in Canada) for my XM until I was given one for Christmas. As a gift, I was pretty much obligated to subscribe. My job has a lot of driving associated with it and now I can't imagine not having my XM. I guess I'd make 98EXL one dollar richer had we met last November.

HA! no one believes me. Thanks for the street-cred, err, forum-cred

homebrewer_99 said:

There's no way I'm paying $13/month for radio.

I'll stick with my CDs.

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I think I said that about cable tv once... who needs cable when I have an antennae?

who needs cable or radio when you have the internet (and dvd)? I don't really watch tv, tho...just a few choice shows.

and most radio just sux. XM is better, but i'd rather throw together a mix myself than have a station decide what i'm hearing cuz i'm usually disappointed.

I used to work at Best Buy a couple of years ago (I imagine most of you are past that phase of your life, but never work there, it sucks) and talking to the car audio guys I got pretty much the same story, that it was hard to get people over the subscription fees, buit once they had they were permanently hooked. Kinda like TiVo...

RadicalEd said:

but once they had they were permanently hooked. Kinda like TiVo...

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oh yeah, I have been a TiVo/DVR whore for a few years as well.....

Evan! said:

I think it really depends on how much you travel...

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I've driven in 49 of the 50 States. I take some of my CD collection with me as well as CDs I've burned.

I've driven in cars that had it, but it still didn't appeal to me.

homebrewer_99 said:

I've driven in 49 of the 50 States. I take some of my CD collection with me as well as CDs I've burned.

I've driven in cars that had it, but it still didn't appeal to me.

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so you must be always difficult by going against the grain then huh?

Evan! said:

So if they already have small transmission buffers, couldn't you just increase the onboard memory and set the buffer to, say, 2 minutes?

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Doesn't matter how long your onboard buffer is...if the "skip" is longer than the lag between the time delayed signals, there's no way for you to recover...you'll miss the same piece of music on all 3 transmissions, and there's no way to get it back. It'll never go into the buffer.

I normally listen to Radio 4 which is a speech station or classic FM.

I have only used my ipod two or three times since i got my sirius a year ago. Sirius satellites are in constant orbit, ...or something , so they are moving and you will get better service depending on their position. XM satellites are more stationary, ... or something, i read that somewhere. If the merger goes through i hope that the service will be better, although im not complaining. THere is a tunnel in boston that i get service in, yet, depending on the position of the satellite, some small bridges will make it cut out.

If you spend alot of time in a car i would strongly recomend it, if i was only communiting a few minutes everyday i wouldnt have it. Can not beat 30 hours of howard stern show every day.

Alot of the radios offer a pause button, theroetically you could pause it for however long you were going to be driving beforehand and then have a big enough buffer.

Bike N Brew said:

Doesn't matter how long your onboard buffer is...if the "skip" is longer than the lag between the time delayed signals, there's no way for you to recover...you'll miss the same piece of music on all 3 transmissions, and there's no way to get it back. It'll never go into the buffer.

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That's only IF said "buffer" is comprised of a time delay between three satellite signals.

On the other hand, if it was in the form of storing the upcoming 60 seconds of a signal on onboard flash memory in your receiver, then it could work. What this would mean is that the satellites would have to broadcast a dedicated "buffer signal" that continually rides out ahead of the main transmission for each station. Not impossible to do...and I'd imagine that it (or something like it) gets implemented within 5 years. Because when you're paying $13/month for radio, it really blows to have no signal wherever there are trees.