Can Someone Please Explain This To Me?

Evan! · 07-02-2007, 02:40 PM

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?

**FlyingHorse** · 07-02-2007, 02:49 PM

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

**kornkob** · 07-02-2007, 02:55 PM

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.

Evan! · 07-02-2007, 02:58 PM

Quote:

Originally Posted by Bike N Brew

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

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.

Evan! · 07-02-2007, 02:59 PM

Quote:

Originally Posted by kornkob

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.

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

**LouT** · 07-02-2007, 03:03 PM

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?

98EXL · 07-02-2007, 03:15 PM

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

Evan! · 07-02-2007, 03:27 PM

Quote:

Originally Posted by 98EXL

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

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

Drunkensatyr · 07-02-2007, 03:29 PM

LOVE my iPod... Never had a buffer problem

98EXL · 07-02-2007, 03:31 PM

Quote:

Originally Posted by Evan!

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

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