-
720p59.94 to 1080i29.97
-
-
[Sean ONeil] “Do you have a Kona 3? “
Yessir. When I get into the office, I am going to pass the Kona 3 to a ioHD for cross-convert and record it and post it.
Jeremy
-
Nice! That’s exactly what is expected. THis is not 540p, this is two lines of ‘540p’, which equals 1080i.
Thanks a ton for posting this.
Jeremy
-
[JeremyG] “Nice! That’s exactly what is expected. THis is not 540p, this is two lines of ‘540p’, which equals 1080i. “
You really don’t understand this do you. You are focussing on the wrong thing. That video can be 1080i30, it can be 540p60, it could be 320p120, it could be 2160i15. It all depends on how the playback device interprets it. That’s how digital video works. In this case the Quicktime player is interpreting it as 1080i30, and it is wrong of course (why it looks like crap). However, Final Cut, for example, WILL interpret it properly as 540p60 under certain circumstances.
The h264 encoded one I posted earlier will not work so use this one instead, it is the original capture file from the Kona conversion:
https://www.geocities.com/lifterus/test.zipPlay it in Quicktime. Same thing, right. It’s blending mismatched fields together because it is mis-interpreting this as 1080i30 when it is supposed to play back as 540p60.
Now import it into FCP and create a 60p sequence. Drag it in there and do not change sequence settings. Jog through and look at the Canvas. You’ll see 60 p frames per second. A 540p60 picture, which is how this footage is meant to be played back.
I hope you understand now. If not, I don’t know what else to say. Do you think those extra 30 frames appeared magically out of thin air?
[JeremyG] “Re: 720p59.94 to 1080i29.97”
-
[Sean ONeil] “Do you think those extra 30 frames appeared magically out of thin air? “
You are funny, Sean.
Creating a 60p sequence simply shows you what each field is made up of (something that quicktime won’t really display accurately as it won’t display each field, only frames because our computer displays aren’t interlaced). Sure, you can tell digital video to play back at whatever rate you want. I can tell my boss to shove it as well but I bet he won’t go for it. We are talking about 1080i tv here. A 1920×1080 sequence that plays back a 30 frames per second interlaced. This is 1080i30, not 1080p60. If you combine those fields, you will have a 1080i image/frame. I totally get what you are trying to say, and this is the way 1080i works, they way interlaced video has worked for ever, how is the KOna method any different from tv history? By your method, all 1080i is 540p60, I guess that’s not wrong, but it’s not exactly right either.
That’s what I don’t understand that YOU aren’t understanding. Or maybe we are both saying the same thing.
At any rate, thanks for going through with this.
Jeremy
-
[JeremyG] ” This is 1080i30, not 1080p60. “
Nobody’s talking about 1080p.[JeremyG] “By your method, all 1080i is 540p60, I guess that’s not wrong, but it’s not exactly right either.
“
It’s not right or wrong. They’re just different formats within a 1080i video signal. When the Kona does the conversion it’s meant to be played at 540p60. When FCP does the conversion it’s meant to be played at 1080p30. There are two methods of deinterlacing called “Weave” and “Bob”. I suggest Googling them if you aren’t familiar with the terms.“Weave” blends fields A and B together to create thirty 1080 progressive frames. “Bob” displays each field individually as sixty 540 progressive frames. Now you’re probably thinking “TV’s don’t display 540p!”. Actually some do, but you’re right most do not. So after the “Bob” deinterlace, it will apply “line doubling” which is exactly what it sounds like.
Basically, the Kona’s conversion of 720p60 to 1080i is meant for a Bob deinterlace. The FCP’s conversion is meant for a weave deinterlace.
-
[Sean ONeil] “Well after the conversion there’s only one field so there’s nothing to combine. The Kona conversion omits the other field. So you are left with sixty “half-frames”, which when played back properly becomes 540p at sixty frames per second. The full 60fps is maintained but it is only half the resolution of 1080 lines (although in the case of converting from 720p, it would be more like 2/3rds the resolution). Note that the FCP Canvas uses the same method during playback – it omits every other field (cutting the res in half) so you never see jaggies. Does it with SD as well.”
The Kona makes fields of half the resolution of the frame–60 per second. These are the same fields that are broadcast daily on the networks that use 1080i. It’s 1080i the way it is designed to be. The way those fields look on your TV depends on the type of TV and the type of deinterlacing it employs. The Kona is not omitting anything, just reformatting. The Kona is not creating a progressive format (540p), it is creating a 1080 line interlaced format as expected.
Your description, in a roundabout way, describes the shortcomings (and advantages) of all interlaced formats when compared to progressive formats of the same frame rate. Interlacing is a way of reducing the bandwidth that must be broadcast while maintaining the perception of high resolution.
A progressive display, as almost all are in the age of HD, has to deinterlace the 1080 60i stream to achieve, as you say, proper playback. Here’s where bob, weave, motion adaptive, and motion compensated deinterlacing methods come into play. Your description of the 1080i conversion done by the Kona as 540p describes a simple bob deinterlacing method. The Kona is obviously not DOING that deinterlacing. That would be done by a progressive display device upon playback of the 1080i program. The FCP Canvas uses this simple “bob” deinterlacing unless it is set to 100%, in which case I guess it changes to a simple “weave” (hence the comb or “mouse teeth” artifact).
Wikipedia’s (go to Poynton if you like) article on deinterlacing says: “The best deinterlacers combine all of the methods mentioned above. The fields are bobbed, so the frame rate is then kept. Motion compensation is done. In the areas that it cannot find a motion match, it falls back on selective blending.” That’s why 1080 60i looks better on an HD monitor than it does in the Canvas–better deinterlacing.
I personally have to “let 1080i be 1080i.” From there I can think about how various devices handle the interlaced format.
-
Tom, we’re mostly in agreement. I never said the Kona deinterlaced anything. I said it doesn’t care because it just sees a 1080i signal. What I am saying is that the Kona’s method for converting 720p (by first scaling to 60 half frames as oppose to 30 full frames) is not some kind of industry standard. It’s just one of two ways to do it. I’ll refer to them as “Method 1” and “Method 2”.
“Method 1” is meant for to be deinterlaced using Bob and/or line doubling. “Method 2” is meant to be deinterlaced using weave or inverse telecine.
When you say this:
[Tom Brooks] “Your description, in a roundabout way, describes the shortcomings (and advantages) of all interlaced formats when compared to progressive formats of the same frame rate. Interlacing is a way of reducing the bandwidth that must be broadcast while maintaining the perception of high resolution.”
I get the impression you think all 1080i conversions are done this way. That is absolutely not true. If the source footage is not 60fps to begin with, then “Method 1” is vastly inferior to “Method 2”. You lose half the resolution yet gain nothing because the footage wasn’t 60fps to begin with. That is not good. When an HDCamSR deck has a 1080psf24 tape loaded, and it is spitting out a 1080i signal from it’s converter board, I assure you it is using “Method 2”.I am now curious how the Kona creates 1080i footage when the source is not 60fps. 720p30 or 1080psf24 for example. If it still scales these source types using “Method 1”, then that is a problem. A huge problem. In fact, not that anyone here would listen, but I would say if that is the case people should absolutely never, ever use the Kona 3 to convert 1080i from another HD source. Hopefully it’s smart enough to know better. I’ll test it Monday using a pixel test pattern.
-
720p30 will result in 1080p30.
-
[JeremyG] “720p30 will result in 1080p30.”
Yeah but how do you know it’s not down-rezzing to 540 first then line-doubling it to be 1080? There’s no way to really know without using a test pattern (which I’ll do Monday).
720p30 is the same timing signal as 720p60. It just has 30 redundant frames added to it, so each frame is displayed twice.
My point being, when converting this to 1080i, the Kona 3 quite possibly does pull 1 field per frame just like it does with 60fps 720p. “Method 1” as I’m calling it. Since there’s only 30fps to begin with, it would look no different than if it used “Method 2”. Hence your statement above. Only the resolution quality would be a little degraded – impossible to tell without a test pattern or an A/B comparison.
Reply to this Discussion! Login or Sign Up