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Old 31st December 2022, 17:56   #1  |  Link
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Resizing at the same time as de-interlacing with QTGMC

Hi, I am archiving some old miniDV footage (PAL). It was shot in 16:9 mode. I am de-inerlacing it, and converting pixels to square. Below is my script.

Question: is it possible to optimise the script? For example, is it possible to perform upsizing from 720x432 to 768x432 within the QTGMC script itself? I am trying to avoid two consequtive destructive operations, and would like to join them into one if possible.

SetFilterMTMode("DEFAULT_MT_MODE", 2)
Crop(0, 66, 720, 432)
LanczosResize(768, 432)
I hope my question makes sense. Thank you for your answers in advance.
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Old 7th January 2023, 05:54   #2  |  Link
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It's not possible to avoid doing it in two steps, as the de-interlacing has to be done before the resizing (well technically before any height resizing but it still has to be done in two steps as QTGMC doesn't resize).

Are you sure your resizing is correct though? I'm fairly sure DV follows the ITU-R Rec.601 standard, which means a 4:3 image should be contained within 702x576 pixels (although it's often rounded to 704x576) rather than 720x576, so if you don't crop anything from the sides the resizing is 786x576 (rounded), or after cropping from the height in your case, it'd be 786x432.

You can try this function if you want to check out the difference with accurate cropping.
Used the following way it'll crop the height and resize the width according to the SAR/PAR.

The generic SAR for 768x432.
CropResize(0,0, 0,66,720,432, InSAR=16.0/15.0, Resizer="LanczosResize", ResizeWO=true)

The 128:117 SAR from the table in the second link above for 784x432.
It's actually 720*(128:117)=787.69, so the script will crop about one and a half pixels each side and resize to 784x432.
CropResize(0,0, 0,66,720,432, InSAR=12.0/11.0, Resizer="LanczosResize", ResizeWO=true)

And another link on SAR/PAR.

Last edited by hello_hello; 7th January 2023 at 06:00.
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