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I was always curouis how much they actually compressed this signal? I assume its constant bitrate and not variable. Anyone know what its set at for either company?
 

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This is top secret info for both providers. From what I understand, both providers do use variable compression rates. Sports supposedly get more bandwidth than news or other static images, premium channels get more than standard, PPV gets the most.


As both providers have added channels (ex. local into local), these compression rates have been adjusted to try and fit a gallon of programming into the 1/2 gallon of bandwidth they have. Better compression equipment and experience has helped to some degree, but the days of DBS meaning better picture quality are over, except for HDTV.


For now, both DBS systems pass HDTV along without additional compression. How long this lasts is anyone's guess.




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Quote:
Originally posted by Savageone79:
I was always curouis how much they actually compressed this signal? I assume its constant bitrate and not variable. Anyone know what its set at for either company?
Assuming you're referring to their HD signals, both services claim a bit for bit pass through. In other words, whatever they receive from the programmer gets passed through unaltered. An HBO spokesperson told me their maximum bit rate was around 13+ megabits/second. CBS is typically closer to 19 Mbits/second, I believe.




[This message has been edited by cwood (edited 09-21-2001).]
 

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Terrestrial TV (OTA) is a fixed rate of 19.39 M bits per second (MBPS)


Satellite places two HD programs per transponder. One transponder can carry UP TO 24 MBPS. Therefore one Satellite channel can be up to 12 MBPS. I know this is what Direct TV is doing from a meeting I had with them in a previous life.


Typical compression rates are 35:1 to 50:1 give or take 200% I can not be more precise because cable and satellite play games with the compression ratio, not just through statistical multiplexing, but with the sinister motive of putting more programs in the same space. They raise the compression ratio and lower the picture quality until they get enough complaints where they figure are at the threshold of where they the average person will notice a degradation in picture quality. They do this periodically. The problem is if you get used to crap then it accepted, so when the compression rate is raised again the reference for a good picture is already crap. They do not use focus groups for this, they depend on subscribers calling and complaining about the picture. I sat on a DTV Q&A panel in New York and had one of the top executives of cable explain this mode of operation to the listeners.

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Jim Burns www.dtvconsultants.com


[This message has been edited by Jim Burns (edited 09-22-2001).]
 

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Discussion Starter · #5 ·
No i knew what HD was i was interested in what their standard programming is compressed at. It would seem to me that it is even lower then SVCD Qaulity which to me says they must be at like VCD bitrates for some of thier channels to get it to look that bad.
 

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The small dish compression disease has made its way to digital cable. When will this crap stop?


HDTV is not immune to it either, bit rates are being reduced already. Most people really don't care as long as picture appears on their screen.
 

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What I forgot to mention in my post was the point!


Call you sat or cable provider and tell them the picture sucks. This may take a couple of calls, ask for the supervisor if the person on the other end of the phone has no idea what you are talking about.



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Jim Burns
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