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Frame Rate Conversion with frame blending
Hello.
I work in a post house and we’re about to start processing dailies for a major TV show (#1 rated show on CBS). For the past 3 seasons they’ve been shooting HDCAM-SR, but this year they’ve switched to Arri Alexa.
Sometimes, they’d use an ancillary camera to shoot additional footage (this was sometimes an iPhone) because they’d want to simulate watching it on a TV or computer screen. Their ancillary camera and iPhone both shoot at 29.97, but the main cameras shot at 23.98. This wasn’t a problem for us in the past because since we were delivering tapes to editorial, we just went fed the 29.97 video through a Panasonic UFC to a 23.98 tape.
Now, however, with our tapeless workflow, we have to figure out a way to convert the ancillary footage without using a hardware converter. Resolve is no good since it’ll just slow down the video by 20% (and we still have to sync audio). Both FCP and Compressor just remove 6 random frames from each second.
How can I transcode a 29.97 video to play at 23.98 while frame blending (as opposed to frame removing)?
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7 Replies
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After Effects. Not that I know exactly HOW. Wish I did, that’s something my supervisor at Disney would do when we got stock footage that needed to blend perfectly with our 23.98 footage. He showed me the trick, but I forgot. Next time I need to film him.
Shane
Little Frog Post
Read my blog, Little Frog in High Def -
I think I’m going to send all files I get from ancillary sources through Compressor to make them ProRes first. Then, if they’re at 23.98, I can just use those. If they’re at 29.97, I’ll use Cinema Tools’ Reverse Telecine option to make them 23.98. Time consuming, but I can batch everything so it can run in the background and I can do other things.
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[Alex Mermelstein] “I’ll use Cinema Tools’ Reverse Telecine option to make them 23.98.”
That would work if it had 2:3 cadence, but as this is native 2997, that isn’t likely. There is a way to make 2398 out of 2997 in Compressor, but its a “better” interpolation and can take some time.
jPo
“I always pass on free advice — its never of any use to me” Oscar Wilde.
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Ran a test a little while ago and the final result was identical to what our UFC used to produce. Client has been happy with that for 3 years, so they should be ok with this.
Just in case, though, what compressor settings are used to make the “better” interpolation?
PS: The transcode to ProRes takes 2.5x realtime and then reverse telecine takes 1x realtime.
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Test the Reverse Telecine. It really only works on footage that was 24fps to begin with, telecined to 30. It doesn’t really do well with footage that was shot 30fps to begin with. There is no telecine to remove.
Shane
Little Frog Post
Read my blog, Little Frog in High Def -
[Alex Mermelstein] “what compressor settings are used to make the “better” interpola”
I don’t see the point of using any kind of frame blending or interpolation.
Frame blending will unnecessarily reprocess every single frame and you are not generating any kind of new picture. Nothing to interpolate.
In the end is about dropping “the correct” frames.
Make a test in Compressor with “nearest frame”.
rafael -
Alex, I just had a similar scenario. Our shoot was on iPhones with some film app that shot at a # of frame rates. Our shoot was at 24p, and not 23.976, True 24p. Which gaves us loads of headaches. The footage was actually weird at 24.008 fps or something strange like that. Anyway, this is for broadcast and we had some secondary footage shot with the regular iPhone app at 29.97. Because this is only secondary and the footage used was very quick, like 1-2 sec. worth, we just cut the 29.97 material into the 24p timeline and let FCP pull out the frames. Probably not ideal, as the Compressor method is better, but it has worked for us and the final output at 24p looks just fine.
Our dub house accepted the 24p material then converted to 23.98 and added pulldown for broadcast at 29.97. Nothing was rejected and the spot looks good. But in your case, yes, I would totally convert to ProRes via compressor.
That Filmic Pro app really screwed us with true 24p, but they wanted to use the app to control the iris. For the next one, I’ve urged them to shoot straight 29.97. There is no need for this to be at 24p for the film look since its shot on the iPhone and the spots are for and about cell phones.
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