720p59.94 to 1080i29.97

[Jeremy Garchow]

[Sean ONeil] “Yeah but how do you know it’s not down-rezzing to 540 first then line-doubling it to be 1080?”

I don’t but i bet it’s the exact same process as 720p60. I bet the footage goes to 720p60 first then to 1080i. Since this footage has a 2:2 pattern each interlaced frame will be two fields of the same redundant frames. I guess 1080psf30 would more accurate.

Can’t wait to see the results, what test frame will you use?

[Sean Oneil]

I just tested a 1080i conversion from 3 sources. 720p30, 1080psf, and 1080p30. All is kosher. Nothing to worry about. It does the conversion while maintaining the full spatial quality.

Can’t post a video but here are the test patterns if you’re interested:
https://www.tigerdave.com/test_patterns.htm

It’s an overscan pattern that also works as a resolution tester (notice the alternating horizontal lines).

[Gary Adcock]

[Sean ONeil] “I just tested a 1080i conversion from 3 sources. 720p30, 1080psf, and 1080p30. All is kosher. Nothing to worry about. It does the conversion while maintaining the full spatial quality.”

Sean

I liked this question so much I asked the guys at AJA to let me know.

I will post what I can when I get back in the US.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD

[Jeremy Garchow]

1080i conversion from 1080psf and 1080p30? What did you convert to?

[Sean Oneil]

[JeremyG] “1080i conversion from 1080psf and 1080p30? What did you convert to? “

To 1080i.

[Sean Oneil]

[gary adcock] “I liked this question so much I asked the guys at AJA to let me know. “

Cool, but that wasn’t a question :). That was me saying I tested it out using res patterns and all is good. Nothing to worry about. The Kona 3 does in fact maintain the highest spatial quality possible during those conversions.

[Jeremy Garchow]

Then explain to me the conversion from 1080p29.97 to 1080i29.97. Should be identical, no?

Wouldn’t the p frames just get segmented to two fields?

Jeremy

[Sean Oneil]

[JeremyG] “Wouldn’t the p frames just get segmented to two fields? “

Yes I would assume that is how it works. All that matters is that it maintains the full 1080 lines (or 720 lines) for every type of HD cross-conversion except when going from 720p60->1080i (in which case it loses resolution in favor of keeping the 60fps).

[Jeremy Garchow]

[Sean ONeil] “(in which case it loses resolution in favor of keeping the 60fps). “

Space. Time. We have a winner.

[Tom Brooks]

I’m lost. Or am I? I guess time and more study will tell, but I think I see this the way Jeremy is describing it. To me, the Kona is doing the only thing that makes sense to do with the 720p60. The result is that each frame is made into a field for the 1080. Each field is half of the frame. They are interlaced on playback. They are deinterlaced by the display monitor. A good monitor will use some sort of motion adaptive or motion compensated deinterlacing algorithm.

To my mind, 1080i is always going to be, in effect or in a manner of speaking, “540p60” as it is displayed on a progressive monitor. That is only a way of verbally describing the deinterlacing that the monitor is doing. If a camera is to record 1080i it will record fields that are half the resolution of the full frame. The fields will always be interlaced. As a result, any motion that happens during a 60th of a second will create some sort of artifact. If the camera shoots a still object, it will appear to have the full resolution and the deinterlacer in your monitor will loaf along using weave. If the camera moves, the deinterlacer will have do some fancy stuff to avoid ugly artifacts.

One interesting point that all of this brings up is that any of the formats that sacrifice frame rate to achieve progressive frames (24P and 30P) also end up preserving all 1080 lines of resolution at all times (as long as you keep them away from interlaced NTSC displays). But at the expense of motion smoothness or frame rate. Right? Ha ha, lucky I’m capturing hour-long clips today.