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pythagoras · 01-07-2011, 00:31

If the problem is because of this, which I suspect it is,
"Field order
[15] An NTSC "frame" consists of an "even" field followed by an "odd" field. As far as the reception of an analog signal is concerned, this is purely a matter of convention and, it makes no difference. It's rather like the broken lines running down the middle of a road, it doesn't matter whether it is a line/space pair or a space/line pair, the effect to a driver is exactly the same.
The introduction of digital television formats has changed things somewhat. Most digital TV formats, including the popular DVD format, record NTSC originated video with the even field first in the recorded frame (the development of DVD took place in regions that traditionally utilize NTSC). However, this frame sequence has migrated through to the so-called PAL format (actually a technically incorrect description) of digital video with the result that the even field is often recorded first in the frame (the European 625 line system is specified as odd frame first). This is no longer a matter of convention because a frame of digital video is a distinct entity on the recorded medium. This means that when reproducing many non NTSC based digital formats (including DVD) it is necessary to reverse the field order otherwise an unacceptable shuddering "comb" effect occurs on moving objects as they are shown ahead in one field and then jump back in the next.
This has also become a hazard where non NTSC progressive video is transcoded to interlaced and vice versa. Systems that recover progressive frames or transcode video should ensure that the "Field Order" is obeyed, otherwise the recovered frame will consist of a field from one frame and a field from an adjacent frame, resulting in "comb" interlacing artifacts. This can often be observed in PC based video playing utilities if an inappropriate choice of de-interlacing algorithm is made."

It will effect every TV, however processing will make it worse as processing relies on recieving the frames in the correct order. I suspect plasma TV's will mask this problem pretty well also.

Regards

John.

01-07-2011, 00:31	#424
pythagoras cf.addict Join Date: Nov 2003 Location: Wigan Age: 64 Posts: 486	Re: TiVo Picture Quality If the problem is because of this, which I suspect it is, "Field order [15] An NTSC "frame" consists of an "even" field followed by an "odd" field. As far as the reception of an analog signal is concerned, this is purely a matter of convention and, it makes no difference. It's rather like the broken lines running down the middle of a road, it doesn't matter whether it is a line/space pair or a space/line pair, the effect to a driver is exactly the same. The introduction of digital television formats has changed things somewhat. Most digital TV formats, including the popular DVD format, record NTSC originated video with the even field first in the recorded frame (the development of DVD took place in regions that traditionally utilize NTSC). However, this frame sequence has migrated through to the so-called PAL format (actually a technically incorrect description) of digital video with the result that the even field is often recorded first in the frame (the European 625 line system is specified as odd frame first). This is no longer a matter of convention because a frame of digital video is a distinct entity on the recorded medium. This means that when reproducing many non NTSC based digital formats (including DVD) it is necessary to reverse the field order otherwise an unacceptable shuddering "comb" effect occurs on moving objects as they are shown ahead in one field and then jump back in the next. This has also become a hazard where non NTSC progressive video is transcoded to interlaced and vice versa. Systems that recover progressive frames or transcode video should ensure that the "Field Order" is obeyed, otherwise the recovered frame will consist of a field from one frame and a field from an adjacent frame, resulting in "comb" interlacing artifacts. This can often be observed in PC based video playing utilities if an inappropriate choice of de-interlacing algorithm is made." It will effect every TV, however processing will make it worse as processing relies on recieving the frames in the correct order. I suspect plasma TV's will mask this problem pretty well also. Regards John.