Masks falling out of sync on export

[stephenb92059306]

Hey guys,

I'm having some serious troubles trying to figure out a solution to my problem. I've been tasked to mask out people from CCTV footage. Everyone is masked and blurred out now however when i export a video file the masks seem to be out of sync compared to what i see within after effects. Naturally this is a problem as people need to be hidden completely.

Out of sync maybe isnt the right term as things are fine within certain portions of the video whereas at other points the mask just pops out of sync for a frame of two.

The footage i was given is a strange frame rate playing at 24.670fps. Im not sure if this is the underlying issue. Ive tried different approaches to fix it by exporting the video using intraframe codecs and having a keyframe every 1 frame. But the problem still persists.

Another curious thing is that the footage itself comes with a baked in timecode. And on export im seeing TC for certain frames which actually do not appear when viewing the footage inside of after effects. I feel the problem is related to how AE is interpreting the footage and the problems are stemming from here.

What should i do to try and combat this? Should i export the raw files again using an intraframe codec and conform the framerate to something standard like 25fps?

Foolishly i began editing the footage in AE using the raw files within giving much thought to it. It's clearly come back to bite me now

I appreciate any help with this

[Rick Gerard]

This kind of problem is fairly common with off speed footage.

Check the interpretation of the original footage and conform it to 25 fps. If there is audio it will be slightly off speed but it shouldn't matter very much. Make sure your composition is also 25 fps. Everything should line up just fine now.

If you are still having problems the footage may be interlaced. Timecode poppin on and off the frame tells me this might be the case. If the footage is interlaced you must separate fields and check to make sure you have the correct field order. You check field order by temporarily doubling the frame rate of the comp (50) and then step through the footage one frame at a time. If the motion is always in the right direction they the field order is correct. If the footage ping pong's every other frame then the field order is reversed. Once you have set the correct field order change your comp frame rate back to normal (25).

[stephenb92059306]

https://forums.adobe.com/people/Rick+Gerard  wrote
Check the interpretation of the original footage and conform it to 25 fps. 
If you are still having problems the footage may be interlaced. Timecode poppin on and off the frame tells me this might be the case. If the footage is interlaced you must separate fields and check to make sure you have the correct field order. You check field order by temporarily doubling the frame rate of the comp (50) and then step through the footage one frame at a time. If the motion is always in the right direction they the field order is correct. If the footage ping pong's every other frame then the field order is reversed. Once you have set the correct field order change your comp frame rate back to normal (25). 

Is the interpretation you mention simply just changing the frame rate within AE?

I tried the 50fps method and things seem to be ok, the only thing i noticed is that every second frame is a still with no movement within the frame. No ping pong going on

[Rick Gerard]

If you have duplicate frames when you change the comp to 50 fps then the footage is not interlaced. Simply re-interpreting the footage to 25 should solve your problems. A Frame is a Frame in AE and even if the true frame rate drifts, setting the interpretation to the same frame rate as your comp should give you perfect frame for frame matches.

Transcoding is only necessary if the original footage is a form of MPEG that is having a hard time decompressing by the CPU. MPEG (h.264 and a bunch of other consumer formats) is usually compressed of a couple of real frames and some made up frames in between that are mathematically reconstructed by the processor. Personally, I seldom use HandBreak because the output options are so limited. It is my last resort. AME usually does a great job transcoding, just make sure you pick a format that is not going to re-compress the already compressed colors and degrade the image.

In 90% of the cases I have ever worked with, just fixing the frame rate interpretation solves the problem. If you must transcode to fix MPEG problems then I would use AME first and render an image sequence.

[Roei Tzoref · Accepted solution]

The footage i was given is a strange frame rate playing at 24.670fps

probably due to variable frame rate of the the footage. use handbrake to transcode it to constant frame rate. the re-import, set the composition frame rate at the proper frame rate and carry on.

[stephenb92059306]

https://forums.adobe.com/people/Roei+Tzoref  wrote

probably due to variable frame rate of the the footage. use handbrake to transcode it to constant frame rate. the re-import, set the composition frame rate at the proper frame rate and carry on.

Is there a specific codec i should export out of handbrake? I think ill do this for all clips going forward just to be safe. Seeing as the footage is close to 25fps i assume this is the best frame rate to export the footage out of handbrake from?

[Roei Tzoref]

yep 25fps is a good bet.

try this workflow here: Re: Iphone clips are in slow motion when imported

[stephenb92059306]

Thank you very much. I'll definitely use this process for all the clips in the future.