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Discussion Starter · #1 ·
Another thing that has been bothering me about this DVI fiasco is that there is so little HD on either sattelite provider now. For some reason, I can't imagine either DirectTV or DN after implementation of the DVI standard to start beaming us 100's of HD channels. Both of these companies are fairly maxed out as far as bandwidth goes. So how can they justify placing all these locks and restrictions on HD content that they probably want have the bandwidth to send anyways??? Would even spot beaming have the bandwidth to send all movies packages?

There seems to be so many hurdles for us. At over one million HD sets sold, when do we stop being early adopters and start having rights?


Venting Steve


[This message has been edited by SteveHoltam (edited 07-31-2001).]
 

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DBS has 32 transponders per satellite locatation. 1-2 HDTV channels fit per transponder. So that puts a maximum of 64 HDTV channels per satellite location that a person on the ground can see.


There are three major CONUS DBS slots, and most have access to 148 or 61.5. So that is 256 channels to be shared among the 2 providers.


Either HDTV will be adopted by only a few 'premium' stations or DBS will go away as a direct competitor to cable (when or if cable ever gets their act together), or they will have to use the FSS and Ka frequencies too.
 

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Quote:
Originally posted by Advent:
DBS has 32 transponder per satellite. 1-2 HDTV channels fit per transponder. So that puts a maximum of 64 HDTV channels per satellite location that a person on the ground can see.
There was a story a few months ago about a new compression chip that DirecTv might use in its STB. It was MPEG-4, but for the same picture quality, six times as many channels could be sent through a transponder.
http://www.avsforum.com/ubb/Forum11/HTML/013499.html


If it can handle HDTV, only 3.3 Mbps instead of 20 Mbps would be needed for full HDTV resolution. That's not surprising since MPEG-2 is an old technique and the new compression algorithms are much better and cheaper.


Going to DVI for HDTV means they don't have to worry about HDTV compatibility with present STBs. They could take advantage of the transition to start using better compression algorithms and the new chip.


The better compression would make the data rate as low or lower than that for SDTV. This would pave the way for a HDTV future.


[This message has been edited by jackmay (edited 08-01-2001).]
 

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Discussion Starter · #4 ·
ADent - Are you saying that there could be about 256 HD channels if they were to use all possible bandwidth?

And I guess if MPEG-4 was to be used, that would give us about 1500 HD channels!!! That would be amazing. I woudnt mind buying a new recevier for that, but I want my 65857 to come along with me for the ride.


I cant wait till 2011 to see that :)


Steve

 

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The quote from the article is "achieve HDTV resolution from standard DVDs".


DVD bitrate is typically 6Mb/s, though the spec allows up to 9Mb/s. HDTV is 19.4Mb/s max. So it sounds like a 3:1 though it could mean 2:1 compression, using favorable comments from the manufacturers.


And remember most HDTV will use the current standards for quite a while, so DBS will have to take the MPEG2 compressed signal, uncompress, and reencode with MPEG4 then transmit. MPEG, uncompress, MPEG is generally not good, so they will have to bump the bitrate up a bit, so 3:1 (or 2:1) slips again.





[This message has been edited by ADent (edited 08-01-2001).]
 

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Quote:
Originally posted by ADent:
The quote from the article is "achieve HDTV resolution from standard DVDs".


DVD bitrate is typically 6Mb/s, though the spec allows up to 9Mb/s. HDTV is 19.4Mb/s max. So it sounds like a 3:1 though it could mean 2:1 compression, using favorable comments from the manufacturers.


And remember most HDTV will use the current standards for quite a while, so DBS will have to take the MPEG2 compressed signal, uncompress, and reencode with MPEG4 then transmit. MPEG, uncompress, MPEG is generally not good, so they will have to bump the bitrate up a bit, so 3:1 (or 2:1) slips again.
You can't get the compression ratio from the average data rate and peak HDTV rate. The average data rate could go down using MPEG-4. Their statement of 6 to 1 compression over MPEG-2 is possible.


I have seen 80 to 1 compressed color images where it was difficult to see differences between it an the original. I think 10 to 1 MPEG-2 was not that good.


I think the digital master has lossless or very low compression, not MPEG-2 compression. A HDTV movie would be MPEG-4 compressed from the digital master as specified for example by HBO.


Any other HDTV would be recorded in a very lightly compression format and then compressed to MPEG-4. In the switch to DVI, DBS can use any format. They probably don't need to use MPEG-2 for anything.


The DVI and 5C interfaces don't require MPEG-2. Some people are saying there is not much MPEG-2 HDTV material out there anyway.
 

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Quote:
Any other HDTV would be recorded in a very lightly compression format and then compressed to MPEG-4. In the switch to DVI, DBS can use any format. They probably don't need to use MPEG-2 for anything.


The DVI and 5C interfaces don't require MPEG-2. Some people are saying there is not much MPEG-2 HDTV material out there anyway.
That is true for DVI but I thought Firewire/5c was limited in bandwidth and had to be transmitted in a compressed format. That would mean that any TV or VCR receiving it would have to be able to decode that format. Which I think means standard ATSC/mpeg2 for now. Any STB that received anything else would have to recode/recompress to mpeg2 on the fly for firewire. Wouldn't it?


- Tom




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Quote:
Originally posted by trbarry:
That is true for DVI but I thought Firewire/5c was limited in bandwidth and had to be transmitted in a compressed format. That would mean that any TV or VCR receiving it would have to be able to decode that format. Which I think means standard ATSC/mpeg2 for now. Any STB that received anything else would have to recode/recompress to mpeg2 on the fly for firewire. Wouldn't it?
The video master at the studio is not compressed very much. To send the HDTV signal, it would compress the digital master video with MPEG-4 as it does now with MPEG-2.


The difference is that the HDTV would be compressed six times as much as MPEG-2 without any additional loss of video quality. A new compression standard will appear soon which will at least double that amount of compression with no additional loss


The MPEG-4 would be encrypted by 5C just like MPEG-2 would be encrypted. It just bits to the encryption and the format of the bits is not important. When the 5C arrives at the STB, it would be decrypted and decompressed to become the DVI signal which does not depend on the compression scheme used. Firewire / 5C also does not require MPEG-2, it just passes bits no matter how they have been processed.


The 5C bits could also be passed to the recorder to store the bits no matter what encryption and compression standard is used.


This assumes that DirecTv and Dish adopt the new decompression chip in the STBs that implement 5C and DVI. It would be a major advantage for them to do this at the introduction of 5C and DVI so that they could have 6 times as many HDTV channels for the future.


If they don't use the new chip, they are setting themselves up for a major transition problem in the future when SDTV is no longer considered adequate just like black and white TV is now not considered adequate. The transition now would be relatively painless since the HDTV STBs must be replaced anyway.


The chip also decompresses MPEG-1 and MPEG-2 which means it could still work with the existing SDTV channels. Of course you would not be able to receive MPEG-4 HDTV with your present STB but that may be true anyway because of 5C being used for everything.

 

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Quote:
The MPEG-4 would be encrypted by 5C just like MPEG-2 would be encrypted. It just bits to the encryption and the format of the bits is not important. When the 5C arrives at the STB, it would be decrypted and decompressed to become the DVI signal which does not depend on the compression scheme used. Firewire / 5C also does not require MPEG-2, it just passes bits no matter how they have been processed.


The 5C bits could also be passed to the recorder to store the bits no matter what encryption and compression standard is used.
Maybe I'm missing something here. Bits is bits, and the recorder could store them. But how would it ever get played. Who besides the STB has an mpeg4 decoder? Does the recorder pass it back to the STB for decode?


I certainly agree the satellite companies have an advantage because they can switch to new or proprietary compression methods. I just can't figure out how the STB's could output something new unless some other box could decode it.


- Tom





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Quote:
Originally posted by trbarry:
Maybe I'm missing something here. Bits is bits, and the recorder could store them. But how would it ever get played. Who besides the STB has an mpeg4 decoder? Does the recorder pass it back to the STB for decode?
Someone else has said that the STB will receive the bits back from the recorder and output the DVI signal to the display. The STB which will be able to handle MPEG-2 and MPEG-4 would the central converter from 5C, MPEG what ever to DVI


This probably mean there will be separate 5C to DVI boxes if there is an upgrade to a new compression standard or new capability for some channels.


Some companies will of course also make 5C to DVI boxes claiming that their bit produce a better picture than the bits coming out of your lowly STB.


[This message has been edited by jackmay (edited 08-02-2001).]
 
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