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25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?

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Phil Hawkins25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Jan 25, 2015 at 1:18:08 pm

Hello all,
I've read a bunch of posts about the 24fps/25fps conversion routes but I couldn't find the answer to an idea I had.

We have a feature film shot at 25fps that we need to convert to 24fps for DCP/delivery.
All fine - we just change the 'interpret footage' setting to 24fps, the video is now longer and we slow down the audio to match and then alter the pitch so it sounds almost the same.

'Almost' being the key word.

I dislike the movie at this slower speed. I know it's only 4% but it really shows to me. I know most people won't even notice the difference having never seen the 25fps version but I just don't like this version.

So, I did an experiment doing the 24fps conversion, rendering out a new "24fps Master" and then in a 24fps timeline in After Effects I sped up the VIDEO by the required amount to get the duration to match the original '25fps' duration and mix. (I know sound doesn't work in FPS, using '25fps mix' as a way of describing the original non-slowed down mix with the correct duration)

Unfortunately the 25fps mix is now out of sync in random places and in sync in others. I guess it's something to do with the way in which After Effects (I've also tried it in Premiere) retimes the footage in a variable fashion?

Is there a way of speeding the footage back up so I can use the original '25fps' mix and it'll remain in sync?
Are there picture issues I may have going forward with this idea?

Any help from cleverer people than myself would be most appreciated.

Best,
Phil


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Phil HawkinsRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Jan 25, 2015 at 1:37:19 pm

Update... I've just tried simply putting the 25fps video onto a 24fps timeline in Premiere and adding the original mix. I've exported a section and the picture seems to play fine, the audio is in sync and the video setting displays as 24FPS.

Is this a solution?


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Ann BensRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Jan 25, 2015 at 2:00:29 pm

[Phil Hawkins] "Is this a solution?"

If it works for you: yes.

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Phil HawkinsRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Jan 25, 2015 at 2:02:20 pm

Thanks... but I would like to know if this is technically correct. Film's go through many QC tests further down the line and I'd rather know now if converting in this way is going to throw up problems. It may appear correct to my eyes but I may be missing something a technician/engineer would know about.


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Chris WrightRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Jan 25, 2015 at 9:48:20 pm

you can slow down the footage or blend the frames, either way, it has to be 24fps for DCP, that's the standard.

1. option 1 for 24fps slowdown. interpret 25fps footage as 25fps then place into 24fps comp.
to preserve audio synchronization but slightly lower the pitch, choose Layer > Time > Time Stretch, and then enter 96 in the Stretch Factor box. video and audio are both stretched

http://helpx.adobe.com/after-effects/using/converting-movies.html#convert_d...


2. option 2
Frame blendingWhen you time-stretch or time-remap a layer to a slower frame rate or to a rate lower than the frame rate of its composition, movement can appear jerky. This jerky appearance results because the layer now has fewer frames per second than the composition. Likewise, the same jerky appearance can occur when you time-stretch or time-remap a layer to a frame rate that is faster than the frame rate of its composition. To create smoother motion when you slow down or speed up a layer, use frame blending. Don’t apply frame blending unless the video of a layer has been re-timed—that is,

http://helpx.adobe.com/after-effects/using/time-stretching-time-remapping.h...

you can also use terranex for good frame blending or twixtor

: Can I Retime Video Without Changing Audio Pitch?
https://forums.creativecow.net/thread/2/956439#956459


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Phil HawkinsRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Jan 26, 2015 at 10:06:36 am

Thanks for these options. I've tried both, especially option 1 which resulted in me not liking the final product because it was too slow for me, even with the pitch change. Call me a perfectionist!

Is the frame blending technique the same as adding a 25FPS video to a 24FPS timeline? I've rendered out and I can't see any jerky movement to the video at all.


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Chris WrightRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Jan 26, 2015 at 12:55:04 pm

maybe frame blending is turned on? a check mark by the appropriate Frame Blending command and Enable Frame Blending button at the top of the Timeline panel. if both are off, then perhaps you just don't notice the slight stutter from the frame mismatch. either way, maybe you used a lot of shutter blur on your project and it blends well or maybe it will be more noticable on the big screen.

The only way to be sure your dcp is good, is play it on the actual machine. it has lots of safeguards and is very very particular how you format your jpeg2000 files.


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Phil HawkinsRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Jan 26, 2015 at 2:04:46 pm

Thanks. I'm going to do a DCP test tomorrow and find out.


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Tero AhlforsRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Jan 26, 2015 at 7:04:54 am

Most channels that have QC will probably fail your movie if you have blended or dropped frames in it. We've done conversions with the interpret footage or Apple's Cinema Tools and then had a proper audio guy retime and pitch the audio.

You could make a 25fps DCP but you might stumble upon a player that doesn't support that framerate. Especially if it's an older one.


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Phil HawkinsRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Jan 26, 2015 at 10:08:14 am

Thanks. The DCP has to be 24FPS as this is the industry standard for delivery.
I can't see any dropped frames to the eye when I watch the rendered out movie. Is there any software that can run a similar QC check to what channel would do so I could check the integrity of movie?


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Riccardo LeoneRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Feb 27, 2016 at 1:22:42 pm

Phil, I'm curious, did it work? I am struggling with the same problem and I just want to figure out the best way to get a DCP that works. How did your DCP perform?


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Tero AhlforsRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Feb 27, 2016 at 5:50:22 pm

[Phil Hawkins] "Is there any software that can run a similar QC check to what channel would do so I could check the integrity of movie?"

You can get the ones that are used professionally, they will cost A LOT.


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Chris WrightRe: 25fps conversion to 24fps - then speed back up picture? Clever or stupid idea?
by on Feb 27, 2016 at 7:26:18 pm

http://www.easydcp.com/product-family.php?id=1

easyDCP Player allows to playback DCP's (Digital Cinema Packages) without specific cinema equipment on a Microsoft PC or MAC.


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