25/30p to interlaced

Nigel Traill · July 15th, 2005, 08:55 PM

I've just been reading a thread about turning 1080i to 24p, but for most people considering the JVC to record footage for broadcast, surely the big issue is: Will I have a great looking product when I convert from progressive to one form of interlaced or other (SD or HD)?

I know we can shoot 576/480i on the JVC - but what if we want to utilise the advantages of HDV 720p and still deliver SD.

While the interchangeability of lens' is certainly a creative advantage - does the JVC offer a real image quality advantage when we will have to convert 720p to interlaced without the required 50/60 frames per second?

JVC converts progressive to interlaced by extracting the odd lines from progressive frame one and even lines from progressive frame two - but this will not be as good an interlaced image as one created from 50/60 progressive footage - there must be a visual cost to the back-and-forward sharing of images.

As the interlaced images are broadcast we see half the action from one progressive frame, then half the image from the next progressive frame, then we see the other half of that next progressive frame, then half of the image from the progressive frame after it, then the other half of that frame, and so on. Sounds like a half-arsed solution when we are used to seeing images updated 50/60 times a second.

Sure - persistence of vision and all that, but when there is action on screen, it will have to look different to what we are used to - and probably not in a good way.

If we are creating content for broadcast in the next couple of years, how many of us really need 25/30p?

Cheers,

Nigel Traill

Ken Hodson · July 16th, 2005, 03:48 AM

Have you ever seen a film on TV?
Thats 24p downsampled and converted to 50/60i.
Looks pretty good ;>)

Tommy James · July 16th, 2005, 10:10 AM

actually the conversion of 720p to 1080i is an almost lossless conversion. Unlike converting interlace to progressive which requires deinterlacing which means that you have to interpolate information that does not exist and you end up with that horrible doctored look which is just a cheap paint job.

When going from progressive to interlace no deinterlacing is required and the image is preserved in its native format. Of course there will be no temporal displacements between the odd and even half frames but who wants interlaced combing artifacts ? Interlacing is like using a saw that is not big enough to cut the board and you have to flip the board over finish the cut and the two cuts never match.

Judder does not look good when converted to interlace but with the JVC motion smoothing technology judder should be eliminated.

Nigel Traill · July 16th, 2005, 10:31 AM

Quote:

Originally Posted by Ken Hodson

Have you ever seen a film on TV?
Thats 24p downsampled and converted to 50/60i.
Looks pretty good ;>)

Ken,

Yeah, I thought about that after I'd posted - good point.

Nigel

July 15th, 2005, 08:55 PM	#1
Nigel Traill New Boot Join Date: Jun 2005 Posts: 21	25/30p to interlaced - will it work well? I've just been reading a thread about turning 1080i to 24p, but for most people considering the JVC to record footage for broadcast, surely the big issue is: Will I have a great looking product when I convert from progressive to one form of interlaced or other (SD or HD)? I know we can shoot 576/480i on the JVC - but what if we want to utilise the advantages of HDV 720p and still deliver SD. While the interchangeability of lens' is certainly a creative advantage - does the JVC offer a real image quality advantage when we will have to convert 720p to interlaced without the required 50/60 frames per second? JVC converts progressive to interlaced by extracting the odd lines from progressive frame one and even lines from progressive frame two - but this will not be as good an interlaced image as one created from 50/60 progressive footage - there must be a visual cost to the back-and-forward sharing of images. As the interlaced images are broadcast we see half the action from one progressive frame, then half the image from the next progressive frame, then we see the other half of that next progressive frame, then half of the image from the progressive frame after it, then the other half of that frame, and so on. Sounds like a half-arsed solution when we are used to seeing images updated 50/60 times a second. Sure - persistence of vision and all that, but when there is action on screen, it will have to look different to what we are used to - and probably not in a good way. If we are creating content for broadcast in the next couple of years, how many of us really need 25/30p? Cheers, Nigel Traill

July 16th, 2005, 03:48 AM	#2
Ken Hodson Trustee Join Date: Aug 2003 Location: Vancouver BC Canada Posts: 1,315	Have you ever seen a film on TV? Thats 24p downsampled and converted to 50/60i. Looks pretty good ;>) __________________ Damnit Jim, I'm a film maker not a sysytems tech.

July 16th, 2005, 10:10 AM	#3
Tommy James suspended -- contact admin Join Date: May 2005 Posts: 214	actually the conversion of 720p to 1080i is an almost lossless conversion. Unlike converting interlace to progressive which requires deinterlacing which means that you have to interpolate information that does not exist and you end up with that horrible doctored look which is just a cheap paint job. When going from progressive to interlace no deinterlacing is required and the image is preserved in its native format. Of course there will be no temporal displacements between the odd and even half frames but who wants interlaced combing artifacts ? Interlacing is like using a saw that is not big enough to cut the board and you have to flip the board over finish the cut and the two cuts never match. Judder does not look good when converted to interlace but with the JVC motion smoothing technology judder should be eliminated.