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HR24 vs H24 PQ Difference

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by acostapimps, Feb 6, 2013.

  1. acostapimps

    acostapimps Hall Of Famer

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    I've notice that the H24 HD receiver picture quality looks sharper and more text detailed than the HR24, and I'm using the same HDMI cable directly to Samsung Plasma TV, On the HR24 I've used an EHD WD 1 TB and picture quality is not that great during dark scenes but its not too bad, I see some artifacts in gray background and white and soft and some black crush picture I believe that's the word, And I'm using the same TV settings on both receivers. What is the issue so to speak on the HR24 than the H24?
     
  2. dpeters11

    dpeters11 Hall Of Fame

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    Is one a -500? That's the only thing I can think of, it uses a different color space.
     
  3. acostapimps

    acostapimps Hall Of Famer

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    Both -200
     
  4. joed32

    joed32 Hall Of Fame

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    Are you using the same input on the TV to test them or two separate inputs. The inputs are calibrated independently and won't be exactly the same.
     
  5. acostapimps

    acostapimps Hall Of Famer

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    They're both on same TV input on the same calibrated settings that I haven't change.
     
  6. smitbret

    smitbret Legend

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    Could be a lot of things. You may have different max resolutions set up on one or the other. Native mode may be turned for one and not the other, causing the TV to up/downsample, creating artifacts. If you are not checking within the same broadcast, it could just be that that network or show simply wasn't encoded as efficiently, etc.
     
  7. acostapimps

    acostapimps Hall Of Famer

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    I understand some local channels have different ways of broadcasting resolutions, but when I connect the HR24 it looks softer than the HD receiver on the same channel which I don't understand, maybe the resolution is different for those receivers, but I can try to connect the HR24 without the EHD, by the way both have native off with only 1080i and 1080p checked on both
     
  8. TomCat

    TomCat Broadcast Engineer

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    I can guarantee you that the resolution is the same, as is everything else, all the way from the uplink to the output of the decoder (note that this is not the same as the output of the DVR or STB). There is no possible way to change that while inside the compressed digital domain without purposeful math being done. (also note that all MPEG AVC decoders for consumer gear are designed to operate exactly the same, meaning the math done there must be the same).

    It also appears that there are no differences from the HDMI transmit chip forward through to the TV (assuming you are using HDMI). And again, all of that happens while inside the digital domain as well (note that this does not include all of the processing inside the TV).

    So what does that leave us? It leaves (A) whatever processing is inside the DVR or STB between the decoder output and the HDMI tx input, and (B) whatever processing is after the HDMI rx chip in your TV, before it goes through the general processing that both inputs go through (of course in either case the tx and rx processes may share their dies with other processes, meaning the post or pre processing may be resident on those chips along with the tx or rx processes).

    Not a lot happens in either location, but there is indeed some purposeful math involved there, and there can be slight differences in how RGB and Y Pr Pb are handled, as both are protocols transported by HDMI, and some DVRs/STBs use RGB while some use Y Pr Pb; that protocol uses a matrix encode/decode to create the three channels, and RGB does not.

    But one would not expect that to affect actual resolution, and my best guess is that it does not; resolution is pretty well locked away in the pixel map where it can't be compromised. But it could still appear that way.

    One would also expect that the math being done is accurate in either case. But it that were true they should by all rights look the same. Apparently they don't. It is discouraging that improper math might be done in either system, but that does not mean it is not improper. It seems like a sad day when basic processes such as this might alter PQ in ways that it shouldn't, and if so, the manufacturers should be ashamed of themselves at a minimum.

    I think (at least from what I can glean from the discussions on this forum) what might be happening is a difference in how luminance is handled, which might affect gamma, or brightness and contrast. And that could be a difference either in the DVR, in the TV, or both. But it is hard to imagine that there could be differences anywhere other than these two tiny areas of the signal chain; digital delivery is designed so that there will not be opportunities for change, for the most part, which is one of the chief reasons digital exists in these systems.

    So even though the TV inputs are matched, it might take a little tweaking to equalize whatever is different about one source compared to the other. I would try that; throw out the concept of the settings having to be the same, and start to tweak them to match each other by eye.

    If my suspicions are correct, this will fix some or most of the differences you see. If truly a gamma difference, maybe not. Perception is a funny thing; it is not unusual to perceive different resolution or a better or worse PQ when the difference may be something simple like gamma or brightness and contrast settings, which are otherwise unrelated to resolution and PQ. That fault in human perception is exactly why the factory settings on all TVs are set to "torch" mode, so they will be brighter with exaggerated color, which gives the false first impression on side-by-side comparison that one TV might be better than another.
     

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