More XL-2 Capture woes

[Jason Hilton]

After finally getting the 24pa capture working, I am having yet another issue. Every forth captured frame displays interlacing. What is going on? I shot at 16x9 24p with 2:3:3:2 pulldown, and captured using the presets with the fps set to 23.98. Why am I getting interlacing?

thanks

-Jason

Setting different capture frame rates doesn't change the interlacing problem.

[Chris Hurd]

Explained by the graphics on page 44 of your XL2 operator's manual. The "interlace" you're seeing is part of the 2:3 pulldown and 2:3:3:2 pulldown processes and is perfectly normal. The interlaced frame in question contains one field from the previous frame and one field from the following frame, so there is a difference in time between these two particular fields which is why it looks like it's interlaced. In 2:3:3:2 mode you have two identical fields, then three, then three more, then two again; at two fields per frame. So it's like this:

Frame 1 -- field A, field A (no time difference between fields)
Frame 2 -- field B, field B (no time difference between fields)
Frame 3 -- field B, field C (different fields, difference in time = interlace)
Frame 4 -- field C, field C (no time difference between fields)
Frame 5 -- field D, field D (no time difference between fields)
Frame 6 -- field E, field E (no time difference between fields)
Frame 7 -- field F, field F (no time difference between fields)
Frame 8 -- field F, field G (different fields, difference in time = interlace)
Frame 9 -- field G, field G (no time difference between fields)
Frame 10 -- field H, field H (no time difference between fields)


Things are working like they're supposed to... you have no woes!
Hope this helps,

[Rob Lohman]

What program did you use to capture this? My capture program does not
allow me to select a framerate since the DV stream controls this, not the
capture program.

Two, in what program are you seeing this issue? If it is in an editing program,
make sure it supports the 24p DV modes and the project is set to 24p with
an advanced inverse pulldown.

[Jason Hilton]

Thanks Chris! Your explaination finally hit home for me. I thought I understood the pulldown, and I have read about it many times, it just never clicked. To answer your question Rob, I'm using FCP 4.5. It allows several options for the capture framerate, but they all seem to work the same. im still looking for a good explaination of this. The manual says to set it to the same as the editing timebase, so I left it at 23.98, because Im editing in a 23.98 timeline.

thanks a lot!

-Jason

[Rob Lohman]

I don't use FCP so I can't help in this case. It is important that FCP does a
reverse pulldown to get the true 24p signal back. However, it may not
decide to do this for the preview screen (I don't know). What happens if
you render out to an uncompressed 24p QuickTime file and play that back
on the Mac? If you step through that, do you still see interlacing? If not
then most likely FCP is working correctly and the preview just is not accurate.

If you still see interlacing it would look like FCP is not doing the reverse
pulldown (correctly).