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ASK DBSTalk: Anyone Get L188 Yet?

Discussion in 'Other HD Receiver Support Forum (811, 921, 942)' started by pdlittle, Sep 8, 2004.

  1. jsanders

    jsanders Hall Of Fame

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    Jan 21, 2004
    Hi Jerry_G,

    I'm not trying to argue with you. I'm trying to collect information about what you are seeing. I never said my TV didn't have overscan, TVs are supposed to have a few % of oveerscan.

    I'm sure that you realize that different signal inputs (480p, 720p, and 1080i) have different overscan settings on various TVs, right?

    The question I have for you is this. If you are watching an SD program on the east coast CBS-HD feed which has gray bars on it, when you stretch your picture, do you see the color in the bars change to black?

    If there is truly underscan happening, then you should see a picture in the middle, surrounded by small gray bars on the sides, surrounded by small black bars afterward. The underscan condition is where the raster on a CRT tv scans the picture with some excess phospher on the tube not being illuminated by the beam. If you are seeing gray bars all the way to the edge of your screen, then there is no underscan of the image. The gray bars to the edge means the raster is scanning and illuminating phospher all the way to the edge.
     
  2. jsanders

    jsanders Hall Of Fame

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    Jan 21, 2004
    We have different hardware, as you noted, but the other difference is the incoming signal. I don't get CBS-HD East Coast Feed. The source material, which in this case adds gray bars. How thick did they make the bars? Is the SD image thinner than other programs or channels?

    If you want to compare overscans, the HDNet test pattern is a common source, given that we all have the screen positions set to the same position from the view preferences. We can't compare with different source material. With the same source material, different connections can be compared, different televisions can be compared.

    You can't tell me that I have more overscan on my television than yours because I don't see gray bars when I watch CBS-HD. My CBS-HD doesn't have gray bars, it is different source material.

    Do you see this problem your seeing while watching other stations and other programs?
     
  3. Jerry G

    Jerry G Icon

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    Jul 12, 2003
    Yes, I fully understand that. But CRTs tend to have more overscan than fixed pixel displays. CRTs suffer from non linearity and other consequences of using a cathod ray tube which gets harder to control at the edges of the image. To compensate for this, they heed more overscan than a fixed pixel display which doesn't have to deal with the problems a CRT display must.

    Yes. But the observations I've made are all with the 921 and 811 outputting all signals as 1080i. So the sets see a 1080i signal regardless of the source. What's relevant here is how the 921 is outputting the signal and how much overscan the viewer's display has.

    NO!

    I fully understand the difference between overscan and underscan. My plasma and LCDs have a small amount of overscan. Your CRT has more overscan than my plasma or LCD. The problem with the 921 is that with a 1080 source the 921 understretches the image when the stretch aspect mode on the 921 is used. If a set, such as yours, has a high enough overscan, the thin bars (be they black from CBS Los Angeles, or gray from CBS New York) resulting from stretching with 4:3 content will not be seen. On my sets, with less overscan than yours, the thin gray or black bars will be seen. I just can't explain it any more simpler than that.
     
  4. Jerry G

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    Jul 12, 2003
    The thickness of the gray bars from CBS NY is the same as the black bars from CBS Los Angeles.

    I no longer have the HDNet test pattern on my 921. I'll try to record it this week. How much overscan does the pattern indicate with your set?

    Now this comment tells me you really didn't read or digest my previous post. Here's what I said:

    "Your Dish CBS HD feed is coming from KCBS in Los Angeles. It's exactly the same feed I get OTA. KCBS uses black bars for 4:3 material"

    I see the exact same source material from CBS LA OTA as you see on Dish's CBS HD west feed. And with 4:3 material from CBS LA, there are thin black bars when I set the 921 to stretch mode.

    Once again, reread my previous post. Yes, with KNBC, which broadcasts 1080i, when I stretch their 4:3 content with the 921, there are thin black side bars.

    It is patently obvious to anyone that has a display that doesn't have too much overscan (mainly fixed pixel displays) that the 921 understretches when receiving a 1080i signal output from the 921 as 1080i. I haven't checked to see if there is understretching if the 921 is set to output 720p. It's somewhat irrelevant to me as I prefer the 921 to output 1080 to my plasma and LCD HD sets.

    The fact that you don't see thin black bars when stretching 4:3 1080 material doesn't mean that there isn't a significant problem with understretching from the 921. It just means that your display has enough overscan that you don't see it. But other displays with less overscan than your set will see the thin bars.

    When I had my RP HD set, I thought it was great. I thought it was perfect. It was ISF calibrated. It wasn't until I got my plasma that I realized it wasn't as great as I thought. As I mentioned above, there was much more overscan on the CRT set (perhaps it needed to be that way for the reasons I mentioned above) than on my plasma. Linearity was far from perfect, even after an ISF scan. Now direct view CRT HD sets may not be as subject to linearity problems as a RP 3 gun CRT set, but in general overscan will still be greater than a fixed pixel display's overscan.
     
  5. boylehome

    boylehome Hall Of Fame/Supporter

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    Jul 16, 2004
    This is what I think happened. The engineers did some work on the software (L188). They made an adjustment that makes the picture under stretch in size when a station is broadcasting in 480p 4:3 ratio only. The 480i, 720p and 1080i are correct. It just happens with the broadcast of 480p in the 4:3 aspect ratio. It looks fine on the monitor in the regular/natural mode but when you stretch it to a 16:9, it is too short from side to side but the aspect doesn't overstretch the images which are proportionate in size and shape. I have noticed that some stations can manipulate the aspect ratio. One of my local OTA stations seems to have a switching problem. They have a 4:3 aspect for program but they have condensed it so it is more like a 3:4 aspect and the images say of people are very stretched vertically. I think that different monitors will have slightly aspect appearances, and lastly, we are all correct in what we have been thinking, but we just have a different aspect in front of us.
     
  6. Bogney

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    Jul 11, 2003
    I believe you have this backwards. Most televisions (especially old vacuum tube sets) were not capable maintaining anything close to a 0% horizontal overscan. The broadcasters knew this and came up with a "safe title area". Anything deemed important was supposed to be away from the edges so that even a set with a huge amount of overscan would see the information. However, the is nothing inappropriate with the video outside this safe area. (One exception might be at the top edge of the picture where there is the possibility of seeing some vertical interval information on some stations).

    Jerry G- Your analysis of the horizontal stretch modes is 100% correct. 720p video is accurately stretched. 1080i video is not nearly stretched as much. This has nothing to do with overscan on anyones TV. It is just more obvious on a near 0% overscan set watching CBS east which has gray side bars.
     
  7. Jerry G

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    Jul 12, 2003
    Thanks for the confirmation. Just to add, the understretch will occur with any 4:3 content being broadcast as 1080 when the stretch mode is applied and if the station is not first altering the 4:3 image by zooming it as some ABC stations do with their 4:3 material. Of course, the understretch exists even with widescreen material, but it doesn't come into play as no one would stretch widescreen content.

    My concern here is that the Eldon engineers may not be using a plasma or LCD to evaluate how much they stretch the image. If they are using a CRT display, they may not see the understretch that those us with plasmas or LCDs (or any set with only a small amount of overscan) will see. The engineers need to evaluate the stretch on a plasma or LCD set.
     
  8. Jerry G

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    Jul 12, 2003
    No. This is not correct. I haven't carefully looked at any 480p sourced 4:3 material. But the stretch is insufficient with a 1080i signal. The image is NOT correctly stretched with a 1080 signal. It is correctly stretched with a 720p signal (it actually may be slightly overstretched with 720p, but it's so small as to be of minimal significance).

    When the 921 first appeared, 1080i was stretched correctly, but SD sat broadcasts were vastly overstretched. This was fixed somewhere along the line, but somehow, the fix changed the 1080 stretch which was vastly overstretched. In attempting to fix it, the engineers overdid it and slightly understretched a 1080 signal. Now they need to concentrate on a 1080 signal and get it right and fix the understretching.
     
  9. boylehome

    boylehome Hall Of Fame/Supporter

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    Jul 16, 2004
    Between Jerry G, Jsanders, and Boylehome, we can STRETCH this topic forever :)

    Anyway, yes. The stretch is incorrect in 1080i, 740p, and 480p whenever the transmission from the broadcaster is transmitting 480p with a 4:3 aspect ratio.
     
  10. Jerry G

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    Jul 12, 2003
    Yup. I'm afraid we're going to have to do so until the Eldon engineers are lucky enough to get it right. I say luck, because the way this stretch has been butchered and mis-engineered over the past 8 months, I find it hard to believe that they are trying to fix this by any other means other than by a hit or miss approach. Add the complete inability to fix the OTA recording issues and I really have to wonder how seriously Dish and Eldon are taking the 921 problems.

    I think we're stuck with an unfixable machine that Dish would just as soon abandon and not sink any more money into. What a disaster Dish has been between the failed 105 HD Superdish fiasco and now the 921. All I can do is bide my time until DirecTV adds more HD and then junk my Dish equipment and move to DirecTV. They really seem to be a much more competent company than Dish.
     
  11. Bogney

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    Jul 11, 2003
    That is actually 8am EDT, not 5am EST.
    HDNet overscan numbers. 921 in 720p mode with DVI cable feeding a Fujitsu P50.

    Left=2
    Right=2
    Top=1
    Bottom=3
     
  12. Jerry G

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    Jul 12, 2003
    I've set my 921 to record the HDNet Test Pattern this Tuesday morning, so I can report my numbers Tuesday evening.

    You should also report the numbers when you set the 921 to stretch, assuming the numbers remain on the screen.

    I checked for understretching when setting the 921 to output 720p and 480p to my Pioneer plasma and Mits LCD HD set. The understretch is present with outputs also, so it's not just limited to a 1080 921 output of a 1080 signal. It also happens when the 921 outputs 720p (as you've noted) and 480p.
     
  13. Bogney

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    Jul 11, 2003
    The numbers only go as high as 14. If they continued, I would approximate it to read 21 both on the left and right while in the stretch mode.
     
  14. jsanders

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    Jan 21, 2004
    The NTSC standard for video is 525 scan lines and 720 "dots" per line. With that in mind, there are only 480 viewable scan lines for an NTSC broadcast. Also, the colorburst information is pushed on each horizontal line just after the horizontal sync signal. Overscan is part of the specification. They put macrovision copy protection in the overscan lines. If you watch *some* stations, you will see some random information on the left side of the screen if you watch an NTSC broadcast. The spec says to set overscan to about 5%.

    Attached is a picture showing the stuff that overscan is used to get rid of, there is weird stuff on both sides and the bottom of the frame. It came from this website: http://scanline.ca/overscan/
     

    Attached Files:

  15. Bogney

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    Jul 11, 2003
    This all sounds impressive but is it meaningful in this case? My monitor allows me to shift the image so that I can see the left or right edge of the frame. On all HD channels the edge is perfectly clean. There is no "crap" (as the author on the website calls it). Therefore, it would seem to me that the least amount of overscan would be desirable.

    Even the standard def channels on Dish seem to be mostly free of this contamination on the left and right edge. It should be obvious if there were any problems since the image is centered in the 16:9 frame. There is effectively no overscan in this situation.
     
  16. jsanders

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    Jan 21, 2004

    It is now time to explain why this is meaningful.

    You said that your overscan numbers from the HDNet test pattern were:

    Left=2
    Right=2
    Top=1
    Bottom=3


    You have a tiny bit of overscan but not much. First, you need to be very careful about the HDNet test pattern. Those numbers are not percentages. They do not coincide with video essentials numbers which are percentages. I think what they did here is to describe how many uniform segments there are in each direction, horizontal and vertical. It appears that each number represents about 10 actual lines when compared to the video essentials calibrated test pattern. Let's say you want 4% overscan. For horizontal, you want 1920 x .04 = 76.8, or 7.68 on the HDNet pattern. 1080 x .04 = 43.2, or 4.32 on the HDNet pattern. Notice that to maintain a 16 x 9 aspect ratio, you need numbers that are bigger in the horizontal direction than the vertical?

    So, with your numbers of 2, 2, 1, 3, my approximation is that you have .926% overscan on the top, 2.77% on the bottom, and 1.04% on the right and left sides. What this means is that you have an aspect ratio that isn't quite 16x9 (1.77), it is slightly wider, 1880x1040 (1.8). Things are actually a tad more stretched, but probably not very perceptable.

    Here is point. With an average of 1% overscan, you may well see weird stuff when you stretch an SD picture because the garbage around the edge of the pictures will still be visible when the image is stretched with 1% overscan. It stretches 480 lines x 720 pixels to 1080 lines x 1920 pixels in the 1080i case. If some of those lines and pixels are garbage, this will show up on the edge of the stretched screen that has no overscan. In this case, your source material may be covering up the garbage that sometimes appears with an extra thick gray bar. You stretch the picture, and you see a little gray bar sliver because you have almost no overscan.

    It doesn't matter if you are using Dish Network or DirecTV, the source material is the problem.

    I think boylehome has some insight when he said, "I have noticed that some stations can manipulate the aspect ratio. ... They have a 4:3 aspect for program but they have condensed it so it is more like a 3:4 aspect and the images say of people are very stretched vertically."

    This is why Mark asked if you see this consistently on all stations and all programs, or if it was just this one station, or even just one program. I don't believe that question was ever answered.

    At this point, I don't think what you are seeing is a bug.
     
  17. Jerry G

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    Jul 12, 2003
    I've already answered the question. The understretch occurs on every 1080i station I receive on the 921, whether OTA or via Dish.

    It is a "bug" or whatever you want to call it. Don't you remember when the 921 went from a correct stretch to a vast overstretch of 1080 material? And now when they tried to fix it, they overcorrected, resulting in understretching. If you don't want to call it a bug, fine. Then call it a misadjustment in the code. Call it whatever you'd like, but the degree of stretch is slightly short of what it should be. For those stations that don't intentionally alter the 4:3 image, it's NOT a problem with the station. It's a problem with the 921. At this point, I don't think there is any way to convince you of this. You're taking the attitude of if you don't see it, then it doesn't exist. You're trying to find any way to explain this other than accepting the fact that it's a problem with the 921's code and you don't see it because your CRT display has much more overscan than my (and others') plasma and LCD displays have.

    Additionally, if it's the station's problem, then why does stretching the same 4:3 1080 image with the 811 not reveal thin side bars as the 921 stretch does? Oh, excuse me I forgot, it's a problem with the immature 811 versus the mature 921. Ya, right. If it's a problem with the station, then you're saying that the 811 is overstretching while the 921 is stretching correctly, and that's just not true. And if it's a problem with the station or my set, then why was there a time when the 921 correctly stretched 4:3 content broadcast as 921? I hope you're not going to say that all these stations made changes in how they broadcast 4:3 material. The evidence that there is a problem with the 921's 1080 stretch is overwhelming and yet you continue to fight it with every fiber of your being. Unbelievable.

    BTW, where are your HDNet test pattern numbers? Regardless of what they indicate, they are still a way to compare overscan. Please post them. I will as soon as I can record the test pattern.
     
  18. jsanders

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    Jan 21, 2004

    Okay, I don't recall you said that, and that information is *very* important! If it happens on all of the stations, then it is a problem. If you could post some pictures of this happening on various channels and various programs demonstrating this, it would be much appreciated.

    I have not been attacking your character with my responses, please keep your arguments to facts. Second guessing someone else is valueless.
     
  19. boylehome

    boylehome Hall Of Fame/Supporter

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    Jul 16, 2004
    I notice the problem with other stations as well. The, "understretch" is the same on the 921 when these stations broadcast in 480p with a 4:3 aspect. In checking my 6000, the aspect ratios are correct (they properly fill the screen). It seems that the 921 has a variation with a broadcast in 480p with a 4:3 aspect regardless if your using 1080i, 720p, or 480p. Any other theories?
     
  20. Jerry G

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    Jul 12, 2003
    jsanders,

    Do you intend to post your overscan/underscan numbers from the HDNet pattern? Bogney did so. If all went well, my 921 recorded the pattern this morning and I'll check it tonight and post my numbers. But if you don't post your numbers, this is all a waste of time.

    Thanks.
     

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