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Skip causing pixelation on HR 24

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by shendley, Apr 11, 2013.

  1. shendley

    shendley Hall Of Fame

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    I recently received a refurbished HR 24 (500 I think) and have noticed something curious. When I skip through commercials there is occasional significant pixilation at random places during the skips. Since I'm skipping through commercials, this is absolutely no problem. I'm just curious about it since I never saw this on my old 24 (100 I think). Anyone else seen this?
     
  2. dpeters11

    dpeters11 Hall Of Fame

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    The big difference on the 500 is it uses a different colorspace, but haven't heard of that causing this type of issue before.
     
  3. Diana C

    Diana C Hall Of Fame DBSTalk Club

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    I've noticed this starting to happen on all our DVRs. I think it is just a difference in the way the software grabs frames during skip (I also notice it when coming out of a slip). The way MPEG compression works is that most of the time each frame only contains the pixels that are different from the previous frame. After a specified number of frames, or when the differences become big enough (whichever comes first), a full frame is transmitted. So, when slipping or skipping, if the software doesn't go to the nearest full frame you'll see a pixelated image. Since it only happens in conjunction with trick play, I don't think it is an issue.
     
  4. shendley

    shendley Hall Of Fame

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    Thanks. A sensible explanation. And, of course, it's not an issue since it only happens when I skip. Just curious.

     
  5. jdspencer

    jdspencer Hall Of Fame

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    My HR24-500 has been doing this for quite awhile. Not a problem since everything is fine after the 30s skip is done.
     
  6. Sea bass

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    + 1.
     
  7. makaiguy

    makaiguy Icon DBSTalk Club

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    That was one of the first differences I noticed when my venerable HR20-700 was replaced by a new HR24-500.
     
  8. RACJ2

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    You can always eliminate that pixilation, which is probably macroblocking, by switching from Skip to Slip.
     
  9. jdspencer

    jdspencer Hall Of Fame

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    Yeah, I went to 30s slip but was so used to 30s skip I couldn't stand it.
    I'll put up with the pixelation.
     
  10. makaiguy

    makaiguy Icon DBSTalk Club

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    ^^^ +1
     
  11. shendley

    shendley Hall Of Fame

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    In Diana C's post above, she said she saw the pixilation coming out of a slip as well as the skip. But even if it did fix it, I'm too used to the skip to switch to the slip. The pixilation doesn't really bother me anyway. I was just curious since I'd never seen it before.
     
  12. Rtm

    Rtm Godfather

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    Same issue for split second on HR24-100 and I'm using 30Skip
     
  13. TomCat

    TomCat Broadcast Engineer

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    That is a very simplified idea of how this works. AVC part 10 can use a GOP that is up to 200 frames long (200 differential frames between full I-frames), but in the interests of faster channel acquisition time extra I-frames are inserted every second or so.

    But none of that matters either, because any digital consumer system that uses any method of jumping non-linearly from one place to another or shuttling from one place to another within media already takes that into account, by only jumping to the nearest I-frame rather than an exact distance (exact number of frames) which might land on a B or P frame, and it does this precisely to prevent the problem of pixillation due to an unreferenced B or P frame which creates a broken or orphaned partial GOP, as well as to make shuttling smoother. Frame-accurate editing systems reprocess B and P frames at the desired edit point as new I-frames, but they do that off line, and a consumer DVR does not have the horsepower to do that on the fly. So if you are seeing this issue, that is not the reason why. It is broken in some other way. HRs jump GOP to GOP, I-frame to I-frame.

    I could understand this issue on a server/client setup like Genie because there is an intermediate bandwidth-related task of moving the content from server to client, but there really should be no reason why an HR24 would do this, short of it being broken or the input content having some issue.
     
  14. Steve

    Steve DIRECTV A-Team

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    Lower...
    IOW, what Diana already explained to us in plain English.
     
  15. Rich

    Rich DBSTalk Club DBSTalk Club

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    Been happening to me for awhile. Minor annoyance.

    Rich
     
  16. Rich

    Rich DBSTalk Club DBSTalk Club

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    Yup, I'm seeing it with my 24-100s too.

    Rich
     
  17. Rich

    Rich DBSTalk Club DBSTalk Club

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    And used brevity to make her point.

    Rich
     
  18. Diana C

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    Gee...thanks...I don't think I've ever been accused of brevity before. ;)
     
  19. jimmie57

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    Diana

    LOL
    All your explanations that I have read are very good. Keep them coming.
     
  20. bobcamp1

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    +1 No other DVR I've seen (Tivo, FIOS, even the crappy TWC box) does this with MPEG2 or MPEG4. I think it's a small bug that's just low on the priority list for now.
     

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