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Discussion Starter · #1 ·
I realize most of us here don't care as much about SDTV/480i. But this still seemed to be the right forum to post because it's the HD STB's I'm interested in here.


It seems there is a lot more discussion of multi-casting recently. We may not like that, but it looks like it is going to happen somewhat anyway. A side effect of that will likely be an increase in the number of available digital SDTV/480i channels. And at least on OTA TV these will likely be sent with a width of 640 or greater, unlike the typical digital satellite & cable channels where they often shrink it.


So on the wild chance there might even be something interesting on some of those channels I guess it would be useful to discuss how the various STB's handle them.


Most particularly, I'm curious about deinterlacing, scaling, and inverse telecine.


Deinterlacing 1080i HDTV is still fairly expensive to do well. But, due mostly to the mass roll out of affordable progressive DVD players, the extra technology to deinterlace 480i is widely available. Chips from Sage/Faroudja and others can do a very good job, and are inexpensive. Due to DVD Forum restrictions many of the progressive DVD players may not yet be scaling to 1080i/720p, but most of the HD STB's already can do that for 480i/480p.


So, finally on to my question. Are there any STB's that can actually do a good job with all this? That is, do any have the Sage or other chips to automatically use inverse telecine or deinterlace and then convert to 1080i/720p? It seems to me that SDTV channels should be able to look as good as progressive scaled DVD if the box was good and the bit rate was sufficient. And there are no silly rules limiting it to 480 lines of scaled output.


Or don't they care much when the source is just digital 480i?


- Tom
 

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Tom,


Of the 9 digital stations I can receive over the air, only 3 are doing actual HD. The rest are broadcasting 480i.


My stb is last year's Sony HD-200. My tv's native HD scanrate is 1080i. My set has no DVI inputs so I'm using component cables.


The box offers several choices as far as upconversion of 480i digital (or ntsc for that matter) broadcasts.


It can upconvert 480i to 1080i (or 720p if you choose) or it can be set to upconvert it to 480p only. Using the 1080i upconvert disables the aspect ratio controls on my tv, but the box has it's own which I can use to stretch/zoom 4/3 material. When not using stretch modes the box has the option of black or gray sidebars.


When using the graybar mode on the box, my local digital sd channels look very good upconverted by the box to 1080i. DirecTV 480i channels are variable from mediocre to almost as good as local ota, depending on the digital compression used by D*. Using the stretch/zoom modes on the stb degrades overall pq somewhat.


I've also played with setting the box to output 480i to 480p, enabling the set's stretch/zoom modes. This also looks very good, and makes overcompressed D* channels look better than when using the 1080i upconvert. This does cause the tv to have to shift scanrates when switching between HD and SD channels however, not a real problem but I like to avoid making the set do this.


Using either method, SD locals don't look as good as HD of course, but they do look much better than the same channels over my analog cable.

If I don't apply any stretch or zoom modes the pq is about like DVD on better channels, LD on the channels who are cheaping out on thier analog/digital conversion.


It looks like some of the local SD digitals are sending an analog signal over the air to thier digital upconverters--the same analog picture defects are showing up on the digital feed. Others are much better.


As far as 3/2 pulldown or inverse telecine or whatever, I don't know what's going on inside the box. I do know I've never seen any combing or other signs of poor de-interlacing when watching 480i digital channels upconverted to either 480p or 1080i by the box.
 

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I've got a SAT520 Zenith that's an LG box like the Sony. It has a great upconverter for NTSC. I've compared it to the Samsung 160, Hughes e86 and DTC-100. The SAT520's upconversion was far superior to the other's in my setup.
 

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Discussion Starter · #4 ·
Anyone know what deinterlacing technology these boxes are using?


- Tom
 
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