deinterlacing effect at DVinfo.net

Carlos Porras · December 1st, 2004, 03:33 PM

Could someone please explain to me what effect has the "deinterlace" option in the NL editors when working with 24p (2:3) footage?

If the video is going to be displayed on a regular TV set, thru a regular dvd player, should I "deinterlace" it for a more "progressive look" of not?

I appreciate comments,

thanks.

A. J. deLange · December 1st, 2004, 07:57 PM

I'll take a stab at this. It doesn't matter whether the material was shot in 30i,30p, 24p or anything else. When it is ready to be viewed on an NTSC television it is converted to 30i which means that the frame, whatever its source, will be split into two fields which will be recorded and displayed subsequently. If the source video was 30p that means that a single picture was taken every 30th of a second. This picture will be separated into high and low fields when displayed on a TV set. You still get the whole picture - it's just presented in two parts written 1 60th of a second apart. If the source video was 30i then the image was captured as two fields captured 1/60 of a second apart. Thus a moving object will appear in two different places in a 30i image corresponding to the amount it moved in 1/60th of a second. If you display this image progressively, i.e. present both frames at once, then the two displaced images will be seen and this is most annoying. Thus the NLE and photo editors have a deinterleave function which will remove either the high or low field leaving every other line blank. These software packages usually fill the blank lines by interpolation between the retained lines. There is no need to deinterleave in any image that was captured progressively (30p, 24p) because both fields come from the same exposure. To deinterleave would accomplish nothing but throwing away half the vertical resolution of the image.
[Note: 24p with 2:3:3:2 puldown will have 1 frame in five with the two fields from separate images. With 2:3 pulldown 2 frames in five will have fields from different images.]

Carlos Porras · December 2nd, 2004, 01:29 PM

Thanks a lot for the explanation A.J.!!!

Pete Bauer · December 3rd, 2004, 12:18 PM

A.J. -- good explanation. The only comment I'd make is that where you used "30i" I think it is customarily called "60i." But your understanding of the process is otherwise the same as mine.

A. J. deLange · December 3rd, 2004, 01:59 PM

Pete,

Yes, you're quite right. I kept thinking something looked funny in my post.

December 1st, 2004, 03:33 PM	#1
Carlos Porras New Boot Join Date: Oct 2004 Location: Mexico Posts: 13	deinterlacing effect Could someone please explain to me what effect has the "deinterlace" option in the NL editors when working with 24p (2:3) footage? If the video is going to be displayed on a regular TV set, thru a regular dvd player, should I "deinterlace" it for a more "progressive look" of not? I appreciate comments, thanks.

December 3rd, 2004, 12:18 PM	#4
Pete Bauer Wrangler Join Date: May 2003 Location: Eagle River, AK Posts: 4,100	A.J. -- good explanation. The only comment I'd make is that where you used "30i" I think it is customarily called "60i." But your understanding of the process is otherwise the same as mine. __________________ Pete Bauer The most beautiful thing we can experience is the mysterious. It is the source of all true art and science. Albert Einstein Trying to solve a DV mystery? You may find the answer behind the SEARCH function ... or be able to join a discussion already in progress!

December 1st, 2004, 07:57 PM	#2
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	I'll take a stab at this. It doesn't matter whether the material was shot in 30i,30p, 24p or anything else. When it is ready to be viewed on an NTSC television it is converted to 30i which means that the frame, whatever its source, will be split into two fields which will be recorded and displayed subsequently. If the source video was 30p that means that a single picture was taken every 30th of a second. This picture will be separated into high and low fields when displayed on a TV set. You still get the whole picture - it's just presented in two parts written 1 60th of a second apart. If the source video was 30i then the image was captured as two fields captured 1/60 of a second apart. Thus a moving object will appear in two different places in a 30i image corresponding to the amount it moved in 1/60th of a second. If you display this image progressively, i.e. present both frames at once, then the two displaced images will be seen and this is most annoying. Thus the NLE and photo editors have a deinterleave function which will remove either the high or low field leaving every other line blank. These software packages usually fill the blank lines by interpolation between the retained lines. There is no need to deinterleave in any image that was captured progressively (30p, 24p) because both fields come from the same exposure. To deinterleave would accomplish nothing but throwing away half the vertical resolution of the image. [Note: 24p with 2:3:3:2 puldown will have 1 frame in five with the two fields from separate images. With 2:3 pulldown 2 frames in five will have fields from different images.]

December 2nd, 2004, 01:29 PM	#3
Carlos Porras New Boot Join Date: Oct 2004 Location: Mexico Posts: 13	Thanks a lot for the explanation A.J.!!!

December 3rd, 2004, 01:59 PM	#5
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	Pete, Yes, you're quite right. I kept thinking something looked funny in my post.