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Choppy playback with divx movies.

Discussion in 'Video playback problems' started by divx4ever, Feb 21, 2008.

  1. divx4ever

    divx4ever Member

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    I have recently changed the way I encode divx movies, which results in better quality movies at lower bit rates and smaller file sizes. But I sometimes get playback problems, like the bottom half of the screen sometimes flashes for a second or two, then breaks up.

    I usually encode movies at 720x432 or 720x576, with a bit rate of 1000 for good movies and 800 for others. I use DivX6 with Virtualdubmod with settings for first pass at:
    Home Theatre
    Multipass, 1st Pass 1000
    Balanced (Default)
    SSE4 Full Search Disabled
    Enhanced Multi threading enabled for Intel Quad 6600
    ASC @ 250 frames
    Format in PAL 16:9 out PAL 16:9
    H263 Optimized
    IBlocks disabled

    For second pass I change rate control to Multipass, Nth pass with insane quality then encode video.

    The problem usually arises with movies at 720x576 resolution.

    I don't use any filters, i just crop 72 from top and bottom for 2.35 movies and don't do anything to full screen movies.

    I play my movies on a samsung dvd/divx player to watch on LCD and have never had any problems until now.

    Should full screen movies be PAL 16:9 or PAL 4:3?

    Has anyone had any similar problems to this. I have tried experimenting with format in and out. But no luck!

    Thanks.
     
  2. davexnet

    davexnet Active member

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    It's possible that the max resolution and/or high bitrate is too much
    for the player.

    Shouldn't the avi be encoded with square pixels? For example,
    for full screen, either 640/480 or 720/540 ? Then the video chip
    does the proper processing to scale it to the TV.
     
  3. divx4ever

    divx4ever Member

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    Thanks for your reply,

    I think you might be right. So I either need to get a higher spec player or chop my resolution.

    Should you calculate:

    720/1.3333(4:3)=540
    720/1.7778(16:9)=400 (to the nearest 16)
    720/2.35(Ana)=304 (to the nearest 16)

    That might be the most compatible way of encoding for my player but I will lose quality as the vertical is chopped and changes the PAR.

    I have read a lot about anamorphic in the last few days, and that is where the problem lies I think. Because if you have a resolution of 720x432 or 720x576, i think the horizontal res' gets stretched.
    Because if you want to keep the max resolution I think you have to calculate it like this:

    2.35 movies - Crop 0,72,=432x45/19=1024 Encode 1024x432
    1.33 movies - Crop nil =576x4/3=768 Encode 768x576
    1.78 movies - Crop nil =576x16/9=1024 Encode 1024x576

    If anamorphic resolutions need to be stretched to 1024 or 768, that definately isn't compatible with my player, as you say, because it supports divx up to 720x576. But doesn't the player have to stretch vobs with the same resolution?

    Saving private ryan is a full screen movie at 720x576. Does that mean it's anamorphic and needs to be encoded as 16:9? So you either encode at 1024x576 or 720x400? And set divx to square pixels in and out or 16:9 in and out?

    Another thing which is confusing is, if you load the original demuxed Mpeg or vob into GSpot it tells you at the bottom to resize to 787x432.

    It is a shame because 720x432 and 720x576 are really good quality, but have a flickering at the bottom like bad tracking as someone said in the thread Jumpy Playback.

    Can you tell me if my calculations are right because there are so many conflicting guides on the net.

    Thanks very much!
     

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