Fdecimate and Avi-DVD Encodes

[Pookie]

I have a 25fps 720x576 AVI file that I'd like to make into an NTSC DVD Mpeg2. Does it make sense via AviSynth to do something like

FDecimate(rate=23.976)
Lanczos4Resize(720,480)

then run a pulldown on the resulting Mpeg2 file ?

TIA

[Guest]

No. DGPulldown can go directly from 25fps to 29.97. The only requirement is that the video be progressive. You'll have to deinterlace or IVTC if it is not.

[Pookie]

Thanks, Don. I'll just deinterlace if necessary,resize, keep it at 25fps, then run DGpulldown 25->29.97.

[Guest]

Originally posted by Pookie
Thanks, Don. I'll just resize, deinterlace if necessary, keep it at 25fps, then run DGpulldown 25->29.97. Be careful. You should either deinterlace before resizing (easiest), or resize using a proper interlaced resizing method before deinterlacing.

At the risk of sounding oxygen starved, wouldn't a change from 25 fps progressive to 23.976 progressive be a more natural conversion ? The frame rates are so close to each other. FDecimate will make it jerky if you do that. There's really no downside to the DGPulldown method, so why add additional processing steps that cause degradation?

[Pookie]

Once again, thanks. As I thought about it, I realized the extra step 25->23.97 was not needed, since either would have to end up at 29.97.

Deinterlace->Resize->Keep Frame Rate at 25->encode progressive->DgPulldown 25-29.97

[Pookie]

Hey, just did the above and it works perfectly. The resulting mpeg plays smoothly and the audio is synced correctly, just like it is on the 25fps AVI source. :) WhooHoo!

[Guest]

Thank the framers of the MPEG2 specification for building in the flexibility to allow such tricks.