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Conform 25fps Canon footage to 24p

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Drew Lahat
Conform 25fps Canon footage to 24p
on Mar 13, 2017 at 7:40:07 am
Last Edited By Drew Lahat on Mar 13, 2017 at 7:43:16 am

This shouldn't be a rare need, but Google makes me feel as if I'm the first soul in the world tackling it.

I'm prepping post for an independent documentary feature shot in different continents. Finishing in 23.976p. Among the dozens of hours of footage there are 9 hours and 50-100 clips from a Canon C300, shot at 25fps. I'm looking for a way to batch-conform the clips including the frame rate conform (with the resulting 4.01% slowdown) and pitch shift. We have interviews of the film's hero in both 24p and 25p, so that's one valid reason to want his voice to stay consistent and not be 0.7 semitones lower.

This is tricky. Premiere is no good for batch processing, Media Encoder won't do even the fps conform let alone pitch shift, Audition may process QT's but is uber-slow, AE screws the audio, and even DaVinci Resolve won't help either. I'm gonna dive into ffmpeg tomorrow, but wanted to see if anyone had other ideas to throw out.

I think I'll utilize the Canon XF utility to herd the clips and merge spanned clips (always a sticky issue). Then wield ffmpeg to conform the frame rate and pitch-shift the audio. With a bit of luck (or hours of teeth-grinding) I could get Premiere-ready clips with the correct frame rate, metadata and synced audio without even transcoding the video.


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Blaise Douros
Re: Conform 25fps Canon footage to 24p
on Mar 13, 2017 at 11:46:49 pm

Import your footage to Premiere. Select all your 25P clips, and color-code them to a certain color--let's say Orange. Then, Modify > Interpret Footage to 23.976. Now you have footage that is native framerate, with slowed-down audio, color-coded orange for easy recognition.

Edit your doc. Keep everything that is your 25P orange colored clips on one audio track. In the meantime, test out the pitch-shifting algorithms of as many different software packages as possible.

Once you've got Picture Lock, crunch out an audio-only track of your 25P orange clips. Run it through your favorite pitch conversion software. Add another audio track in Premiere, mute the old orange ones, and import your pitch-shifted track to replace them.

Now you're done!

This workflow minimizes your transcoding, and keeps the audio round-trip to one single pass.


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Drew Lahat
Re: Conform 25fps Canon footage to 24p
on Mar 14, 2017 at 7:38:00 am

Definitely a good workaround, Blaise, using Premiere's current capabilities. For some reason I thought I had past issues with interpreting multiple clips (might've been in AE)... but tested it and it's easy.

Not stoked on the need to keep an eye on those clips through feature-length timelines and dozens of versions, but it's definitely doable. I'm currently the only editor on the project, this isn't a reality show where dozens of freelancers come and go.

This also takes care of the most important aspect - timing. It's nearly impossible to conform to 4%-slowed footage at the end of the editorial process, since the edits` timing is all off. The drawback is the need for an orderly picture lock and online phase. With this director there may be a dozen festival screenings before we actually get to a picture lock...

Also John, great find! A little hidden feature in AME I wasn't aware of. Now we just need a few more options implemented like generic AU/VST plug-in "effect" and we'd be all set.


Still looking into doing this with ffmpeg/mencoder. There are advantages for having all the footage sorted out in the front end, from the get go.


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Drew Lahat
Re: Conform 25fps Canon footage to 24p
on Mar 14, 2017 at 7:44:10 am

Blaise, what would you do with the timecode? Looks like for conformed TC, Premiere retains the original timebase, including in the source player - unless you change it.

E.g. if you conform a 30fps clip to 24fps and step through it, you'll see many duplicate frames. But it appears that it's not a video issue, it's the source player relying on the TC time base. If you cut it into a 24fps sequence, all the frames should "fall" into the right place in a 1:1 relation.

As said, it's changeable: Modify > Timecode > Time Display Format allows changing the time base. Of course this changes the clip's timecode.

So what's "better", a mismatched clip time reference (between TC frames and real video frames), or a mismatch between the TC inside Premiere and the raw camera footage TC?...


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Blaise Douros
Re: Conform 25fps Canon footage to 24p
on Mar 14, 2017 at 6:13:25 pm

I would say it's better to conform both the footage and timecode so you can work seamlessly within the timeline--you just have to record it in your production notes. Anyone trying to re-create a sequence will have to conform the footage to 23.976 anyway, so make the timecode conform a required step in the process, too. Otherwise, if you leave the timecode in the other timebase, you risk having to parse out weirdo fractional frames from the "stretched" timecode. Ain't nobody got time for that. If you were transcoding/conforming, it would do this anyway by default.

I just much prefer this method to transcoding because it saves time, money, storage space, and only requires good record-keeping, which is cheap (and you should probably be doing it anyway!). I think you just make a space in your production binder for post-production process notes, and call it good.


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John Pale
Re: Conform 25fps Canon footage to 24p
on Mar 14, 2017 at 4:51:12 am

Media Encoder can do the frame rate conform.

Right click on the file name (the line with the text in white above the settings pulldowns with blue text)

Select "Interpret Footage"


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