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Old 24th May 2017, 10:35   #11  |  Link
hello_hello
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Join Date: Mar 2011
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Quote:
Originally Posted by Katie Boundary View Post
Yes, I know. However, there are a LOT of discs out there that are almost but not quite pure film - they'll be 99.78% film or 99.12% film or whatever, and I'd like to know just what kind of butchery might be performed on the video if I run such content through forced film.
You'll have frames with combing.

Quote:
Originally Posted by Katie Boundary View Post
Yes but I'm asking how it chooses which frames to drop.
I only tried this because the question was asked and I was curious and thought I might learn something. Katie will probably still be too busy ignoring.

I indexed an NTSC DVD for a look. It was actually PAL converted to NTSC using field blending, but it was handy and that should mean it's 100% video (no pulldown flags) so I created a d2v file using force film and again without it. The d2v files declared it to be 100% video.
I compared the two by opening them with Avisynth and stepped through the frames. The 23.976fps (force film) version obviously had every fifth frame missing relative to the 29.97fps version. It doesn't seem any more clever than that.

I've never been a fan of force film myself. I recall having problems when I was quite an NTSC novice with a particular DVD because it had a few small sections with hard-coded pulldown while the majority used pulldown flags and there was combing in the sections with hard-coded pulldown. Since then I've always honoured pulldown flags and taken the TFM().TDecimate() route and more recently, for hybrid sources, I've been using TIVTC for VFR encoding. x264 is VFR aware if you give it a timecodes file so it's not that hard. Harder for mpeg2/Xvid. Not VCD compatible.
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