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Discussion Starter · #1 ·
I know this is slightly off-topic here, but I understand it is NOT possible to view a satellite feed (e.g., DirecTV) in a progressive scan type of mode. Is this because the satellite feed is actually transmitted interlaced ?? This would seem odd to me -- I was under the impression (likely incorrectly) that the satellite MPEG-2 stream was similar to that of typical video streams you can watch on the interner, only perhaps at a different bit-rate, etc?? If the satellite feed is actually sent to our receivers in an interlaced scheme then I understand why a progressive scan of the feed is impossible.. but if its sending frames and frame-updates like online video streams then I don't see why you couldn't view sat feeds in a progressive type of mode for a better image quality.


The whole reason I thought about this is because progressive scan DVDs can play virtually any DVD in a progressive scan mode -- is this simply because they have source available to sample enough data to display the whole screen in one pass??


Am I making any sense?? Probably not! :)


-Jeff
 

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It's a common misconception that the video on a DVD is stored as progressive frames - it's not. Whether the source material is 24 frame per second film or 60 "half frame" per second video, it is stored as 60 half frames per second on a DVD (just like any other interlaced NTSC video signal). A progressive scan DVD player contains circuitry that can take these 60 half frames and either reconstruct the original 24 full frames (if film source), or merge the half frames into 30 full frames (if video source). This same process can be applied to any NTSC video signal (satellite, cable, ota). This is what an external "scaler" or "line doubler" does (among other things). While a progressive scan DVD player must still "de-interlace" the video just like an external scaler would, it has a big advantage in that it operates on the digital MPEG source data, which contains flags to let it know which half frames belong together. An external scaler can only look at the analog half frames and try on its own to figure out which ones belong together.
 

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Discussion Starter · #3 ·
Thanks for the info... but does that mean that progressive satellite tv is possible, and if so, why does no one do it?? Wouldn't the picture be a good bit better quality?


When the signal from the satellite reaches our dishes, its still in a pure digital form correct? So it shouldn't suffer from trying to deinterlace an analog signal. Or is the picture quality just not much better between progressive and interfaced (say versus 480i and 480p)? I'm confused because it seems if it were possible to 'progressivize' a sat tv feed then people would do it to try to make the SD signal a little more bearable on a larger screen.


Any additional clarification of my ignorance is appreciated.

Jeff
 

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The only way progressive scan playback is going to improve the interlaced feed is if the TV has an internal reverse 3:2 pulldown to reassemble frames from video which was originally shot/filmed at 24fps. Otherwise, if it doesn't have reverse 3:2 pulldown, it's just going to deinterlace it, and line double it, and then it's going to look worse (softer, with less resolution which is lost during deinterlacing.) You won't see the scan lines, but it's not a fair trade off. This is especially bad for video which was shot interlaced such as with a DV cam. You do NOT want to deinterlace and line double that! You want to view it in its original interlaced format for the best quality. And if you have a progressive DV cam, the video is already progressive (whether through composite, s-video, or DVD player), so you would not want to deinterlace and line double your video which is already progressive also! Personally, I would like an HDTV that lets you manually disable the line doubler.
 

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Quote:
Originally posted by jeff112368
Thanks for the info... but does that mean that progressive satellite tv is possible, and if so, why does no one do it?? Wouldn't the picture be a good bit better quality?


When the signal from the satellite reaches our dishes, its still in a pure digital form correct? So it shouldn't suffer from trying to deinterlace an analog signal. Or is the picture quality just not much better between progressive and interfaced (say versus 480i and 480p)? I'm confused because it seems if it were possible to 'progressivize' a sat tv feed then people would do it to try to make the SD signal a little more bearable on a larger screen.
Most of the programming distributed via satellite originates from ordinary broadcast and cable TV channels, which are 480i from camera on except for material originally shot on film. It is nearly impossible to deinterlace video that originated from an interlaced camera without at least slightly impairing its quality. Film-based stuff, on the other hand, can be deinterlaced perfectly (or near-perfectly), but since this can be done at the receiving end, and most current sets are interlaced anyway, it doesn't make a lot of sense to do it on the transmitting end. In short, if the program wasn't shot on film, you're better off if it stays interlaced, and if it was shot on film, you can do a good job of deinterlacing it at home with the proper equipment.
 

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DVDs can store progressive or interlaced video streams and can switch between the two modes. Flags exist to tell the MPEG decoder what it is dealing with Unfortunately not all DVDs are mastered correctly and the flags are not always set correctly.


Check out all the Chroma bug threads in the DVD forum for more information on progressive scan DVD players.
 

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I wanted to add that the only source for native progressive video isn't from film as was implied here. There are various DV cams that will let you shoot progressively. For example, the new Panansonic AG-DX100 will shoot 480p/24fps or 480p/30fps progressive. There are affordable cams which consumers are buying, so don't overlook them. There are many more in the professional realms as the world moves digital. Computer generated graphics video is usually progressive as well.
 

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Quote:
Originally posted by ADGrant
DVDs can store progressive or interlaced video streams and can switch between the two modes. Flags exist to tell the MPEG decoder what it is dealing with Unfortunately not all DVDs are mastered correctly and the flags are not always set correctly.
This mostly has to do with frame rate rather than progressive or interlaced. That is, whether the source was 24 fps (film) or 30 fps (video).
 

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Most movies on DirecTV are broadcasted as 24 progressive frames and converted 60fps 480i in the STB. A Showtime engineer was on Dish's Charlie Chat and stated that Showtime HD is broadcast as 24 1080p frames and converted to 1080i in the Dish 6000 STB.


It is possible to view Directv in Progressive Scan. I believe there are HD STBs that output 480p, as well as 720p and 1080i.
 

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Quote:
Originally posted by Marc Alexander
Most movies on DirecTV are broadcasted as 24 progressive frames and converted 60fps 480i in the STB. A Showtime engineer was on Dish's Charlie Chat and stated that Showtime HD is broadcast as 24 1080p frames and converted to 1080i in the Dish 6000 STB.


It is possible to view Directv in Progressive Scan. I believe there are HD STBs that output 480p, as well as 720p and 1080i.
Yes, there are combo HD/DirecTV STBs that will convert DirecTV signals to any of those formats. I find it hard to believe, by the way, that Dish would transmit anything in 1080p; it would be really inefficient to do that and downconvert to 1080i at the STB. Are you sure he didn't say that Showtime sent the signal to Dish in 1080p and Dish then converted it to 1080i for transmission? Even that seems odd, but it would make a bit more sense.
 

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Quote:
Originally posted by MDRiggs
Yes, there are combo HD/DirecTV STBs that will convert DirecTV signals to any of those formats. I find it hard to believe, by the way, that Dish would transmit anything in 1080p; it would be really inefficient to do that and downconvert to 1080i at the STB. Are you sure he didn't say that Showtime sent the signal to Dish in 1080p and Dish then converted it to 1080i for transmission? Even that seems odd, but it would make a bit more sense.
It would only be inefficient if the 1080p were being sent at 60fps. In that case half the information would be thrown away when each 540 line half frame was generated. Since it's being sent at 24fps and the STB has to generate both half frames 30 times a second, there is no wasted information (and bandwidth is all important).


Probably the only reason DVDs weren't this way (480p at 24fps) is that they felt it was more important to reduce the cost of the circuitry in the DVD players, and the DVDs held enough data that a little extra bandwidth was a fair tradeoff.
 

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Quote:
Originally posted by gregvaughan
It would only be inefficient if the 1080p were being sent at 60fps. In that case half the information would be thrown away when each 540 line half frame was generated. Since it's being sent at 24fps and the STB has to generate both half frames 30 times a second, there is no wasted information (and bandwidth is all important).


Probably the only reason DVDs weren't this way (480p at 24fps) is that they felt it was more important to reduce the cost of the circuitry in the DVD players, and the DVDs held enough data that a little extra bandwidth was a fair tradeoff.
Good point--forgot about that. On the other hand, my understanding is that MPEG is more efficient with interlaced signals than with progressive and that this is one reason DVDs are predominantly coded interlaced rather than progressive.
 

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Discussion Starter · #14 ·
Quote:
Originally posted by MDRiggs
Yes, there are combo HD/DirecTV STBs that will convert DirecTV signals to any of those formats. I find it hard to believe, by the way, that Dish would transmit anything in 1080p; it would be really inefficient to do that and downconvert to 1080i at the STB. Are you sure he didn't say that Showtime sent the signal to Dish in 1080p and Dish then converted it to 1080i for transmission? Even that seems odd, but it would make a bit more sense.
I guess the question is then: Do the HD/DirecTV STBs that convert DirecTV signals into progressive modes produce a significantly better picture quality when watching SD signals from DirecTV ?? If so, I would be surprised since I've heard no mention of it, yet I've heard many complaints regarding general SD PQ on large projection sets. If a fancy sat receiver could increase the PQ on my set with SD sat signals, then I'd sure pay for it! Anybody??
 

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Quote:
Originally posted by jeff112368
I guess the question is then: Do the HD/DirecTV STBs that convert DirecTV signals into progressive modes produce a significantly better picture quality when watching SD signals from DirecTV ?? If so, I would be surprised since I've heard no mention of it, yet I've heard many complaints regarding general SD PQ on large projection sets. If a fancy sat receiver could increase the PQ on my set with SD sat signals, then I'd sure pay for it! Anybody??
Generally speaking, you're going to be better off with interlaced display of programs that originate at the camera in interlaced form. So for most regular TV, converting to progressive is likely to be at least a slight step down in quality rather than a step up. Programs originated on film are a different story, since it is possible to deinterlace them essentially perfectly without losing temporal resolution or introducing artifacts. In other words, it depends.
 

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I am kinda dumb... but my DTC100 outputs 540p on SDTV via the VGA outputs, and it looks soft compared to the S-Video output of my UltimateTV.


I'm also using a Mits 46805, which does not do reverse 3:2 pulldown internally.


UltimateTV still looks pretty acceptable.
 
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