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In "HDTV for the Cable Masses" new hardware is described that allows cable operators to squeeze four HDTV channels into 6-MHz slots instead of today's two channels with 256 QAM technology. Lots of complaints about overcompression of standard channels on cable systems (and DBS) to stretch limited bandwidth, but so far not many about HDTV. Any opinions how fidelity for an already 'squeezed' over-the-air 19.39 Mbps for HDTV, delivered via cable, will hold up? -- John
 

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Agree. If you go to Terayon's site , they point out earlier versions of their hardware is already used by many cable firms, including mine, Time Warner.


Cisco also claims its video router is used by Time Warner and others to multiplex X-number of channels into 6-MHz slots. Speculation here: So perhaps cable companies have been giving HDTV a fixed ~38 Mbps (2 HDTV programs) per 6 MHz slot up to now. For non-HDTV cable delivery, say 10:1 compression per slot, the standard programming is multiplexed and the bits/program 'rate shaped' depending on its content (details, motion). But now, says Terayon, we've got hardware for 'cherry picking' or rate shaping HDTV programming, too. Their phrasing: "The DM 3200HD sets a new rate shaping benchmark as it can rate shape up to four HD streams into a channel at 256 QAM (Quadrature Amplitude

Modulation) with no discernable loss of picture quality."

Wonder if that discernable is akin to MP3 audio versus CD-quality audio? -- John
 

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In other posts here members (Rich Peterson?) have already stated that DirectTV was using a stat mux for HDTV. Is this any different?


- Tom
 

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This illustrates the good thing about having different HDTV delivery systems. As long as DTV OTA keeps providing HDTV, we'll always know what's what. I think it will help keep cable & sat 'honest', so to speak, as far as HDTV delivery goes.
 

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Discussion Starter · #6 ·
Some of this recent hardware publicity might just be competition between different forms of statistical multiplexing (stat mux). This, as the Cisco Q&A site above points out, is simply assigning different bit rates to multiplexed channels as the detail and motion varies within them.


Terayon assures us that squeezing 4 HDTV channels into a slot (6 MHz for cable) won't perceptibly degrade images compared to 2 HDTV channels per slot. To verify that, it would be nice to have lots of independent observers study a 4th action/detail HDTV movie while three other action/detail HDTV movies share the same bandwidth. Terayon might be telling it like it is, but then again we're still hearing that multicasting on HDTV channels shouldn't influence image quality.


Rather than trying to squeeze more and more originally ~19-Mbps channels (~17 Mbps video) into 6-MHz cable slots, industry should be creating lower-cost methods of extending optical fibers to TV sets. With that virtually unlimited bandwidth, cable companies could go the other way: piping HDTV at perhaps 55 Mbps per channel to viewers (all using Toshiba's upcoming true-1080X1920 LCOS RPTV or its equivalent. :) ) -- John
 

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Quote:
(all using Toshiba's upcoming true-1080X1920 LCOS RPTV or its equivalent. )
As part of the must-carry provisions I think the cable companies should be required to provide each subscriber one of these, along with the STB. ;)


Then it would be obvious when they stealth down-rez to save bandwidth or mollify movie moguls. I will volunteer to take the first one.


- Tom
 
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