Selur's Little Message Board

What would be the best settings to create extra frames/fields with a PAL 25i to 1080i upscale?

Are you sure you need 1080i? It's relatively uncommon.
What target format?
You want to create 29.97 interlaced frames (=59.94 fields) or 29.97 telecined (= 24 progressive fields with 3:2 pullup) output?

It's a 1990s UK TV programme, shot on video, upscaled for a Blu-ray release. We need to retain the made-for-TV look as much as possible.

okay, but that does not answer all the questions.

It was shot on PAL 25fps interlaced video so we won't need 29.97 telecined. We need 29.97 interlaced frames (=59.94 fields)

Okay, I have never tried this, but what I would try is telling Hybrid to handle interlaced filtering by deinterlacing with QTGMC (set 'Filtering->Misc->Script->Filter interlace handling' to 'QTGMC(prest="Fast)'). Then Interpolate to 29.97 fps using 'Filtering->Vapousynth->Frame->Frame Interpolation->Interframe/SVP' and tell the encoder to encode interlaced output.
One could also first Bob deinterlace, then use sRestore and then tell the encoder that one wanted to encode interlaced, but that probably won't work atm. in Hybrid. (wanted to fix it for ages, but I never found the time for it, since it never seemed important,.. )

Cu Selur

Thank you, I will try this later and will report back tomorrow when it has completed. Do I need to deinterlace with QTGMC at all?

Quality wise it's better for frame interpolation.

After some more thinking best would probably to:
a. Bob deinterlace with QTGMC (to 50p)
b. Frame interpolate to 60p
c. then create interlaced content
but Hybrid can't do this atm. you would need to write a manual script for this.

Cu Selur

Thanks - Can anybody help me out with the script?

What does the "Vapoursynth Script View" show if you open it?