VideoHelp Forum

Our website is made possible by displaying online advertisements to our visitors. Consider supporting us by disable your adblocker or Try ConvertXtoDVD and convert all your movies to DVD. Free trial ! :)
+ Reply to Thread
Results 1 to 4 of 4
Thread

Threaded View

  1. Member
    Join Date
    Sep 2006
    Location
    Ohio, United States
    Search Comp PM
    Sorry if this is the wrong place to post this. Can someone suggest a better place?

    What I mean is localized distortions, most noticeable in faces, in video displayed on LCT-TV's from some CATV/Satellite sources. (I had a CRT TV until recently and never noticed these artifacts, although perhaps they were present.) This is most apparent when a face is large on the screen. I see this most often on analog SD channels that appear to have relatively low quality to begin with, compared to other channels. A good example is movies on the AMC channel -- specifically the "Lonesome Dove" series recently broadcast.

    Examples:
    1. Left and right cheek may seem to move relative to each other in an unnatural way.
    2. When head turns, the width of the face varies in an unnatural way.
    3. When head nods, the top and bottom of the face don't move together in a natural way.

    I would suspect my setup (TiVo HD, SamSung 40" LCD-HDTV and CATV source) except I have seen the same effect on completely different setups (e.g., 32" Zenith LCD-HDTV and Satellite source).

    Has anyone else noticed such artifacts? I suspect they actually may be MPEG4 stream encoding deficiencies.

    I've seen "judder" from film content and this doesn't seem to match that effect at all.
    Quote Quote  
  2. It's a result of too much temporal noise reduction at the source, maybe exacerbated a little by the HDTV.
    Quote Quote  
  3. Member
    Join Date
    Sep 2006
    Location
    Ohio, United States
    Search Comp PM
    Originally Posted by jagabo
    It's a result of too much temporal noise reduction at the source, maybe exacerbated a little by the HDTV.
    Is this done for the obvious reason: to reduce the encoded stream bitrate?
    Quote Quote  
  4. Originally Posted by dlflannery
    Originally Posted by jagabo
    It's a result of too much temporal noise reduction at the source, maybe exacerbated a little by the HDTV.
    Is this done for the obvious reason: to reduce the encoded stream bitrate?
    I assume that is the primary reason. It may also be a misguided attempt to impress viewers with reduced static/grain noise. I don't know if it's at the ultimate source (eg, AMC) or the cable/sat company.

    Also note that noise reduction is a part of MPEG 2 and MPEG 4 encoding. And, as mentioned, many HDTVs will use noise reduction filters. So what you're seeing is likely the sum of several filterings.
    Quote Quote  



Similar Threads