de interlacing 1080i

[kujija]

hi folks , i want to ask sm questions abt deinterlacing when editing. i live in pal land and i have been capturing 1080i 25 fps hdtv . my problem lies here my lcd monitor went kaput last month and have been using my old crt for now. does capturing video in crt is same quality as doing in lcd new monitors. ive been capturing stuff and when u look at it it looks a normal progressive video , however when you zoom it to original size i can see small horizontal lines ner eyes face and smear marks all over. does this mean i have to deinterlace it? i use megui for conversion and when i auto analyse deinterlace the result is always partially interlaced. am i doing ir the right way. btw i use amarectv and ut lossless for capturing. and my question is does that mice teeth partially interlaced becomes fine when in lcd monitor? or do i have to deinterlace it .thanking you

[jagabo]

What monitor you use has nothing to do with video capture. The comb artifacts you are seeing is normal for interlaced video. You don't need to deinterlace -- just use a player that deinterlaces on-th-fly. If you're processing and re-encoding interlaced video you have to be careful to use interlace aware filters and encoders. Or deinterlace before applying other filters -- especially any resizing on the vertical axis. If you're encoding interlaced video be sure to set the encoder to interlaced mode. If you've deinterlaced set the encoder to progressive (non-interlaced) mode.

[kujija]

thank you mate . yeah i can deinterlace on the fly videos thru any player but instead of selecting deinterlace everytime i want to view it i want to deinterllace thru megui or handbrake and get it over with . so right i dont need to deinterlace the combing jagged horizontal artifacts as it will look.smooth when playing only if u pause and carefully view it its there. coming to setting interlaced option in megui avs i dint get it can u please elaboarate it p

[jagabo]

I don't use megui so I don't know how well it deinterlaces or what options it has. But here are some things you should be aware of:

1) There is no perfect way to deinterlace. When you deinterlace you may lose as much as half the temporal resolution and half the spacial resolution. The best deinterlacers do better than that but they still aren't perfect and will create some artifacts. For example, if you deinterlace 25i to 25p you will lose half the temporal resolution (25 pictures per second rather than 50 half pictures per second -- a severe loss for high action material like live sports) and some of the spacial resolution (how much depends on the deinterlacer used and the nature of the video itself).

2) If you deinterlace now you are locking in the loss of quality of that deinterlacer forever. As on-the-fly deinterlacing gets better in the future, playback of your interlaced video will improve. Every DVD/BD player and TV supports interlaced video because that has been the broadcast standard since inception.

3) Some interlaced video may actually be progressive fields stored out of phase. This is quite common with PAL video. Instead of 1T + 1B, 2T + 2B, 3T + 3B... you have 1B + 2T, 2B + 3T, 3B + 4T... That can easily be restored ot progressive frames by repacking the fields. NTSC is often 23.976 fps progessive stored as 29.97 fps interlaced after 3:2 pulldown (ie, "telecined". That can be "inverse telecined" back to 23.976 fps progressive.

4) Material that has gone through PAL to NTSC, or NTSC to PAL, conversion often has blended fields. To restore the original progressive frames requires advanced handling that isn't available in simple programs like megui, or even the commercial video editors like Premiere, Vegas, etc.

5) The best deinterlacer at the current time is QTGMC in AviSynth. A distant second is Yadif (in AviSynth and many of the free converters).

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6) "Smart bob" deinterlacing, like QTGMC will give you a 50p video from 25i. That is good for smooth motion but some players can't handle it. For example, Blu-ray players can't play 1920x1080 at 50 fps. Old computers can't play it smoothly. And Youtube will reduce it to 25 fps (they plan to start offering support for 50p and 60p this fall).

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