I think I can see a reason for the difference in our results. From what you saying when you reinterpret the footage to LFF from UFF you are doing it in a correct and proper manner and creating new files. You say there is a line shift which accounts for the reinterpreting you are doing.
In my case there is no re interpreting at all. I'm taking the exact same file and telling Avid to bring it in as UFF and then LFF. I am deliberately trying to make wrong field order and when I do I see the jaggies. It sounds to me like your workflow is the correct way to reinterpret the footage to a different field order. That would explain why you don't see the jaggies because your system is correctly interpreting and handling the file accordingly. I'm simulating a case of incorrect reverse field order and you are demonstrating the proper way to convert/reinterpret field order. In this case it seems Avid just takes the field order I tell it with no reinterpreting hence the jaggies.
---In avid-l2@yahoogroups.com, <speckydave@...> wrote :D.The aliasing you're seeing doesn't make any sense to me, and if any system was to handle this kind of thing well, I would expect it to be Avid.John,I re-interpreted the UFF export to change the field order to LFF, edited into a sequence and rendered as UFF, which Premiere appears to have done by shifting the frame (both fields) down by one line - so odd lines become even lines and vice versa. Which, to my mind, is a perfectly logical way to switch fields around to maintain their original sequence when playing them out over a stream that has has the opposite field order - and exactly what I would have hoped to see when editing LFF footage into a UFF sequence on any system. (I think the top or second line was duplicated to cover the resulting line of blanking at the top from the one-line shift.)
The diagonal line I used was 45 degrees, so any aliasing would show up nicely. Although I didn't mention, it was inside a circle too. (No aliasing anywhere around that either.) The image was created in Photoshop and saved as a png with alpha and overlaid on 1080 50i footage in Premiere (I don't have access to an Avid at the moment.)On 9 November 2015 at 19:16, bigfish@... [Avid-L2] <Avid-L2@yahoogroups.com> wrote:Okay I just made a diagonal line with 3 different lines from very slight slope of maybe 5 degree angle, medium slope of approx 45 degrees and steep of about 80 degrees. I exported the the lines image made in title tool as a jpeg. When I import that back in as odd upper field first it plays back with a smooth line on the slight slope. When I import the same still as even lower and play it back the slight slope line is broken and jaggy. That is what I was expecting to see. I don't know what to say either. I didn't really access the vertical shift but it behaved as I would have expected. This is playing SDI out to a moderate Panasonic LCD screen in an Avid 1080 59.94 project.
I can suggest that perhaps the line you used was too steep. I didn't notice much difference in the steeper lines. Also the difference was only noticeable in play. When parked on a single field there was no difference for obvious reasons. I'm not trying to be right here but I did see the behavior I had expected to see. The bottom line is as already said the temporal studder/judder is way more noticable that this slight stair stepping.
---In avid-l2@yahoogroups.com, <speckydave@...> wrote :The diagonal line is still NOT aliased in any version though.However... if you then take the incorrectly interpreted video (now set to play Lower-Field-First) and put it in a Premiere timeline set to play back Upper-Field-First, THEN there has to be transposition (switch) of fields. Comparing the LFF version with the original (correct) UFF version appears to show that *both* fields (i.e. the whole frame) has shifted down by one line as part of this process. The result is that the clip still plays back with reverse field order (i.e. horrible shuddering) in a UFF sequence, so that if I were to export this, I would have a UFF export containing a clip that plays back with a horrible reverse field-order problem. That's how it gets baked in and, sadly, broadcast by people with a lack of properly trained QC department. (Or a newsroom with no time to properly QC at all.)When I said I was viewing on a broadcast monitor, I meant just that: HD-SDI feed to a Sony PVM. I'm well aware of the playback differences of computer screens and broadcast monitors, which is why I waited until I was in work with access to a broadcast setup before I was able to properly test this. (Playback on a computer screen will show you either both fields at once, or a deinterlaced preview, so field order is irrelevant.)I'm not sure how I can describe this any better than I already have. When you set the field order interpretation for a file, you are telling your computer which half of the frame to play first: Upper or Lower. You're NOT telling it to take either half of the frame and shift it into the position of the other frame.D.On 9 November 2015 at 17:41, bigfish@... [Avid-L2] <Avid-L2@yahoogroups.com> wrote:What monitor did you view the diagonal line on? Was it an external sdi feed monitor or the computer screen. It was mentioned in this thread that you can't see the reverse field order on the computer monitor so I wonder it that might mask something. I just don't see how if field 2 plays back first it has to be scanned at a field one time that mean the video information is filling the lines for field on which are offset from field two. Not sure how the half line start would play into it.
---In avid-l2@yahoogroups.com, <speckydave@...> wrote :Just tested this on a broadcast monitor by adding a big diagonal line across some upper-field HD footage. Exported as QuickTime ProRes upper-field, which I them imported into Premiere and played back: smooth motion and no aliasing while interpreted as upper-field. When I switched the interpretation to lower-field, I got all the horrible shuddering from fields being played in the wrong order, but the static diagonal line showed no aliasing at all.I would say your assumption about fields being re-positioned is wrong. When someone mis-interprets upper-field-first footage as lower-field-first, they just get the fields played in the wrong order. That's it. No re-positioning. Just (in this case) the lower field played first, then the upper field.
I would have thought that to take the upper field and shift it down a line to the lower field position and vice versa would be quite a deliberate process. I can't right now think of a way to *accidentally* tell the system to actually reposition the fields like this (though since there generally tends to be a way to easily screw anything up, I don't doubt that it can be done with a single bad keystroke...).D.On 9 November 2015 at 01:24, bigfish@... [Avid-L2] <Avid-L2@yahoogroups.com> wrote:If the fields are in reverse order then they are not playing in the same field the are intended for. Think of a diagonal line. I am assuming that with wrong field order Field 2 plays first and is positioned on the lines intended for Field 1 and Field 1 plays second in the lines intended for Field 2. That would mean the horizontal scan lines are inverted too. To me that would create the stair stepping even on a static frame.
Posted by: David Ross <speckydave@gmail.com>
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