Jerkiness in Digital TV w/ 40H80

Discussion in 'Archived Threads 2001-2004' started by Miguel Paredes, Dec 10, 2001.

  1. Miguel Paredes

    Dec 5, 2000
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    Not sure if this was addressed or not, so sorry if it has been - could someone post a link to the thread?

    When watching some digital channels with my 40h80, I notice that some shows, especially HBO documentary shows, are very jerky, almost as if it's out of synch. Since I don't have another TV to compare with, does anyone know what this is or if it's due to my 40h80 or something else?

    I'm connecting to the cable box with S-video.

    Thanks in advance.
  2. Allan Jayne

    Allan Jayne Cinematographer

    Nov 1, 1998
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    That's a tough question.
    There is always the slight chance two pieces of equipment cannot get along with each other.
    You may be able to rule out some things but it is hard to prove who is at fault. Even if you could prove who is at fault, there may be no way around it.
    The idiosyncrasy may be so unique that connecting the composite output of the DTV receiver to the composite input of the same TV (or connecting through a VCR) works OK.
    One of the stumbling blocks in U.S. video is that it is officially 59.94 fields per second (frames per second for progressive scan) instead of 60. 99.99 percent of equipment works correctly despite this but there is the occasional exception.
    Everything you suggestd about the cause of the problem is possible except, it is not a case of 24 fps coming out of the DTV receiver. Since you said that things work OK for some channels, the S-video itself is not the problem and S-video for U.S. TV sets is always the same (approx) 60 fields per second.
    I have a TV (with some digital processing of the video) that works OK with my VCR and LD player. I have an external doubler that works OK playing into my computer monitor. When I connect the doubler to the TV I get an occasional minute but noticeable jerk every 5 seconds or so, suggesting a dropped frame.
    By the way, digital cable compresses the video, different channels and even different shows may be compressed differently. The more compression, the more likely that motion will be blurred. The better doublers take hints from the video (analyzing tiny segments of scan lines, or pixels) The digital compression, as well as snow on analog video from far away stations, can prevent the doubler from doing its best job.
    For analog TV sets, the horizontal and vertical hold are among the controls used to get the TV to sync. with the broadcast signal. As TV sets and also broadcast signals got better and more consistent, these controls tended to be on the back of the TV set instead of up front. There may be comparable settings in the service menu for digital TV sets, I don't know what they are called.
    Other video hints:

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