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Old 01-07-2007, 07:18 PM   #1
dnewhous
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Question Minimum and maximum bit rate satellite broadcast

I know that the bit rate on the satellite broadcast varies from channel to channel. What are the lowest and the highest bit rates available? You have to measure this by the time it takes to record the material on one of those portable receivers.
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Old 01-08-2007, 08:33 AM   #2
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Your question was a little vague.

Bit rate per channel? Decompressed?

It's a little hard to answer. Sirius uses a dynamic bandwidth allocation scheme. Their codec gives priority to music channels, but not the same bandwidth for each. Older, monophonic music, for example, is generally streamed at a lower bandwidth. Even the latest music is not always being broadcast. Promotional announcements (which they don't consider commercials, but, IMO, they really are) are (hopefully) streamed at a low bitrate.

Offhand, I would be stunned to find out any channel is streamed with a bitrate greater than 48K.

Sorry this is all guesstimation. Perhaps someone with greater techinical insight can give more specific answers.
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Old 01-09-2007, 04:20 PM   #3
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You can figure out actual bitrates from the satellite using the S50 since you can "see" the file sizes on the device. Howard 100 comes down around 44kbit if I remember correctly
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Old 01-09-2007, 04:52 PM   #4
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From what I understand, he has exceptionally greater bw than other talk/news/sports. I think it's in his contract.
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Old 01-09-2007, 06:53 PM   #5
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I was vague, but your replies have given me sufficient answer anway. Thank you very much.
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Old 01-11-2007, 12:17 AM   #6
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Quote:
Originally Posted by Capn Ramius
From what I understand, he has exceptionally greater bw than other talk/news/sports. I think it's in his contract.
I believe that Howard 100 is given the same priority as channels like Sirius Hits 1... which is a bit much for talk channels...
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Old 01-11-2007, 10:46 AM   #7
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Maybe so. OTOH, if he's worth $500M, he's worth a little extra bw, too.
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Old 01-16-2007, 11:03 PM   #8
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Howard has always been picky about how he sounds. I'm sure he would be very upset with the standard talk channel bandwidth.
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Old 01-17-2007, 04:54 PM   #9
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Quote:
Originally Posted by VDCHawk
Howard has always been picky about how he sounds. I'm sure he would be very upset with the standard talk channel bandwidth.
What about the setting in the middle (not quite a talk channel, but not full quality music channel either; some of the music channels run this... sounds less bright and SLIGHTLY more mono). Seeing as the majority of his show is talking, I think that would work.

With his sound quality now, his channel sounds just as good as Hits 1!
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Old 01-17-2007, 06:39 PM   #10
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Lets be real, this is the guy that uses compression on his voice, and has used the same megaphone for 20 years.
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Old 01-18-2007, 10:06 AM   #11
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Quote:
Originally Posted by Capn Ramius
It's a little hard to answer. Sirius uses a dynamic bandwidth allocation scheme.
...
Sorry this is all guesstimation. Perhaps someone with greater techinical insight can give more specific answers.
You're not kidding about guesstimation.
The dynamic allocation scheme is not in use at this time.
All the channels are using static bit rates today.
The actual allocations change from time to time but not often.

You're describing the new "hierarchical modulation" technique that has been in use by satellite television for a little more than a decade now which Sirius and XM announced support for last year. It's not implemented yet, as it requires new receivers for everyone who hasn't already upgraded to the new generation units like Stratus, Sportster4/3, Starmate 4/3, etc.
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Old 01-18-2007, 10:08 AM   #12
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Quote:
Originally Posted by snakester
I believe that Howard 100 is given the same priority as channels like Sirius Hits 1... which is a bit much for talk channels...
Howard 100 uses a very high bit rate but is lower than Sirius Hits 1.
Howard 101 uses a slighly lower bit rate than Howard 100 does.
Both are much higher than most of the other talk channels except possibly Maxim which plays lots of music.
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Old 01-18-2007, 01:01 PM   #13
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Quote:
Originally Posted by aegrotatio
You're not kidding about guesstimation.
The dynamic allocation scheme is not in use at this time.
All the channels are using static bit rates today.
The actual allocations change from time to time but not often.

You're describing the new "hierarchical modulation" technique...
Got any links to support this? I'm not saying you're wrong, just that I hadn't read anything about Sirius switching to a static bandwidth allocation.

No, I'm not. The hierarchical modulation scheme, as I understand it, allows for greater compression with better (or at least, not much worse) sound quality, so that some video can be streamed, too. I was addressing the current bandwidth allocation, which is what the OP was asking.
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Old 01-19-2007, 04:49 PM   #14
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Quote:
Originally Posted by Capn Ramius
The hierarchical modulation scheme, as I understand it, allows for greater compression with better (or at least, not much worse) sound quality, so that some video can be streamed, too.
Hierarchical modulation is a digital transmission method and has nothing to do with data compression. Currently Sirius uses Quadrature Phase-Shift Keying (QPSK) modulation. With QPSK modulation the carrier has 4 defined phase shifts, or symbols in its constellation. With 4 symbols, each transition represents the encoding of 2 binary bits. Adding symbols to the modulation constellation increases the data capacity of the carrier without increasing the required bandwidth. But there is a tradeoff. As additional symbols are added, it become increasingly difficult to distinguish each symbol from the adjacent ones. This produces higher error rates as the signal quality drops.

Hierarchical modulation, as it applies to Sirius, will add 2 symbols to the existing 4. However, since the data encoding for these 2 new symbols is fully independent from the original data stream, it's really not a form of 6-PSK modulation. Using HM adds a 2nd data stream to the transmission without requiring additional spectrum. But, the HM symbols appear as gaussian noise imposed upon the QPSK data. So they are trading off S/N for additional capacity.

Over 19 months ago Sirius claimed they would have HM services operational in the 2nd half of 2006. That didn't happen and I'm guessing it's due to not having the required chipset modifications in production. They have barely mentioned the topic of HM in the last 12 months.
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Old 01-22-2007, 09:05 AM   #15
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What a great explanation of QPSK and HM!

I don't neccessarily agree with all the ramifications you suggest.

I still don't understand how you got HM from what I posted earlier.

Too bad you don't have any links to support what you said earlier about static vs. dynamic bandwidth allocation being used by Sirius.
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