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Thread: Jaggy lines question?

  1. #1

    Default Jaggy lines question?

    I've filmed some stuff in HD and have sucessfully downconverted to SD to go onto a regular DVD.

    When played on a widescreen tv and on the computer I notice very subtle jaggyness on the straight lines. (bars,railings, brickwork Etc.)

    The real problem is that when the camera moves quickly everything gets very blurred and hard to see. (not blured as in out of focus, almost as if the picture breaks up a little) but returns to fine on the still shots

    The problem isn't huge but I was wondering if there was a solutions to this to remove or further reduce them the effect. Perhaps a field order or de interlacing.

  2. #2
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    It sounds like interlacing and is more noticable when you pan the camera. Try de-interlacing it and make another copy, was the HD footage interlaced or progressive?

  3. #3

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    Hi NikoSony

    Footage was interlaced.

    I shall make a de interlaced copy and try again. However the footage should be deinterlaced as I checked that option when I downconverted the footage from HD to SD.

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    Can you put up a screen grab in your next post of the video as interlaced combing as it is called has a very distinctive look.

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    Hi Starkie

    Your problem is purely the fact that HD interlaces with Upper Field first and DV uses Lower Field first.

    You have to de-interlace the footage!!! My 'puter cannot handle big AVCHD files so I'm forced to transcode the footage to HDV (m2t format) with UpShift and when I do that I select the interlace mode as progressive so there is no interlacing on the source footage!! Otherwise set your NLE so it de-interlaces the footage during editing (I use Vegas and set de-interlace to "interpolate")

    I have been told elsewhere that it's far better to de-interlace in your NLE rather than de-interlace somewhere else as you lose resolution!! Can anyone confirm that????

    Ideally, if you camera can shoot in progressive mode then do that if you are going to output to SD. That way you lose nothing!!

    When I switched to HD, my very first clip had terrible interlacing lines on the TV!!!

    Chris

  6. #6

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    Hi Guys,

    my apologies NIKOSONY I didnt get chance to look at the posts and wont be ale to screen grab till monday. I have tried de interlacing the downconverted SD files and they look a little worse.

    Mr. Softweigh your point seems a valid one!

    I downconverted the HD to SD and I did deinterlace the footage in the conversion. I suppose this is whats causing the messy looking movement as when I stick it into premiere and export, deinterlacing a second time, it looks worse, not deinterlacing at all makes it look ok but with the fuzzy jaggy badness.

    I will reinvestigate on monday, downconverting without de interlacing and leaving the deinterlacing until it leaves Premiere.

    Cheers for the help guys!

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    Hi Starkie

    I actually find it's better to keep the source footage in HD and then just render to SD Widescreen. If you leave the HD footage interlaced then when it gets downsized it will pick up the comb effect on all moving edges!!

    I still am trying to find out whether it's better to de-interlace before it gets to the NLE and also whether it's better to de-interlace as progressive or interpolate!!!

    So far I have got fairly good results from progressive footage but I need to check whether I need to do the de-interlace in the transcoder or let the NLE do it???

    I'll keep you updated on what I find out. Some say do it before and some say let the NLE do it so I will have to find out what works best!!!

    Chris

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    I've found that when filming in HDV or AVCHD, keeping everything in HD until the very last stage, burning the dvd and not de-interlacing, I have no jaggies on a television screen and keep the best quality. However, when viewing the footage on the 'puter, those jaggies were there.
    For computer screen viewed stuff I keep everything in 1080i right the way through and only de-interlace when making the final file.

    In my "experiments" I found a noticeable reduction in picture quality when filming in progressive compared to interlaced, especially on "freeze frame". This was particularly noticeavle with AVCHD. I used to be a "progressive" fan but now I'm not so sure...

  9. #9
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    Hi Gaffer

    I'm using Sony Vegas 9 and if I bring my HDV footage in as interlaced and let the software do the de-interlacing right at the end I get a ton of jaggies!!!
    Admittedly they are not so bad on the TV but they are still there because of the downsizing from 1440x1080 to 720x576. However if I de-interlace before the NLE I get absolutely no jaggies on the TV BUT a much softer image!!!
    (as you say you DO lose PQ!!!!)

    There doesn't seem to be a really good way to keep the HD quality and have a sharp SD video unless you are prepared to put up with the jaggies!!!

    Chris

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    Hmmmm, not a problem with Final Cut or, at least, not that I've found. Strange as Vegas seems to be an excellent software used by a lot of the pros here.

    This does seem to be a "suck it and see" thread with as many solutions are there are users.

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