Re: [Avid-L2] Europe here calling: p50 -> p25 - i25

I think perhaps there's a consideration being made for something that doesn't necessarily need considering. I would say the 'half one shot, half the next shot' on an interlaced frame is just fine for being played back in an interlaced world. That is in fact exactly how 23.976p becomes 29.97i in the US.

frames A / B / C / D in 23.976p

become

AA / BB / BC / CD / DD in 29.97i

And everyone is happy.

EXCEPT 

the people who want to go and use that interlaced file on progressive streaming services or internet platforms. Then they often blend the frames together and drop one, and you get a stutter at best and weird half and half frames at worst.

However, if you have an interlaced delivery, and it is going to an interlaced playback platform, then having those blended frames (edits with a frame of one shot and a frame of another shot) are OK. You may be thinking that you need to keep all those edits "clean" but that can be torturous to maintain. I would, as Knut said, edit in 50p and finish in 50p, and convert that 50p master to 25i at the end for that specific delivery. If that delivery is asking you for clean edits on your interlaced frames, it then becomes clear that they intend to subsequently re-encode your 25i air master for 25p web/streaming, and they can go to heck.

On Wed, Oct 6, 2021 at 10:22 PM Jo's Mailinglists <lists@filter-media.net> wrote:

John -

Well, what we did already is a successful transfer from p50 to i25 - edited in Avid, tranfered to DaVinci Resolve (DVR) and therefrom put out at i25.

By our experience, pending on the handling of frame rate conversion in DVR, if you opt for "frame blending" (instead of "nearest / Optical flow) in fact the p50 timeline in an i25 timeline will end upt not psf but frame-blended frame #00 & frame #01 where frame #00 is upper and #01 is lower field (we aren not talking NTSC-DV where fields are reordered from upper to lower field first).

Turning back into Avid: my expectation is: preparing a sequence for the editor, all edits have to be at ":" (not at "." - by Avid lacking displaying a 50 fps TC). -> If there is an edit on "." in a 50 Edit Timebase" we are all fine, however, if you switch that sequnce to "Edit Timebase 25) you are not able to catch the edit done in the 50 fps timeline - it will be one frame ahead or late to the edit you did in the 50 fps timeline. This will phonk your edit for further process.

?

Jochen "Jo" Hermann

filter Media Postproduction

Salzburg, Austria

On 7. Oct 2021, at 02:46, John Moore <bigfish@pacbell.net> wrote:

Years back I asked how 720P 59.94 was converted into 1080i 59.94.  I thought each frame would become a field but that was never confirmed and it was suggested that each 720 frame did not become a field but just every other frame was converted to an interlaced psf.  I'm not really sure what happens when 720P is converted to 1080i.  If I ask the same question in your 50P/25i world what is the answer there.  Does each frame of the 50P become a field?  50P means 50 discrete frames per second, correct?  Or is it two Frames from the same moment in time?.  I think it's the former not the later but please confirm or correct.  Bottom line is if each frame is a unique moment in time no matter which 50P frame  you chose there will always be a blended frame.  The big draw for 720P for ABC was that it had crisper motion like interlace does.

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