Here is a somewhat convoluted scenario for which I'm seeking some advice:The context is a multicam recording of a long theatre play; a 1080i/50 project with most master clips being also 1080i/50, but some being 1080p/25: an unattended camera has produced static 4k 25p mp4 video, ideal to do some serious pan & scan reframing using Frameflex without excessive resolution loss.Obviously, 25p clips in a 50i project create a slightly less smooth video (default motion adapter), but I bumbed against an unexpected and more serious side-effect (perfectly explainable and technically justified).Imagine a scene where a character is moving across the stage, say right to left; Using Frameflex keyframes, I implement virtual camera pan to follow the character: so the frame moves gently right to left to follow the character, but slightly slower to smooth out the movement. In the resulting image, the character still moves right to left but very subtly, while the background of the stage appears to move left to right (you're still following me ?).Rendering and playing back, I noticed that the character was moving with excessive stuttering (excessive strobing effect), much like incorrect field ordering in interlaced video...And stepping field by field through the video, I observed this:field A : reference imagefield A': background moves slightly to the right, character is fixed relative to the background (because it is filmed in 25p, it moves relative to the background only every other field), so it moves along slightly to the *right*field B : background moves slightly to the right, character moves to the left relative to the background, and only slightly to the *left* in the image (=his [frame] move to the left minus the [field] pan move to the right)field B': same as A'repeat...The result is indeed much like incorrect field ordering, where the subject moves forward then slightly backward, then forward then slightly backward, and so on (while the background moves very smoothly backward).The explanation is that the pan generated using frameflex is rendered according to the project format, i.e. field by field, while the movements in the video are filmed frame by frame.My first idea to work around this problem was to force rendering of the Frameflex effect for the offending clips in 1080p/25 (by temporarily switching the project format), but that doesn't work as the render is no longer valid when switching back to 1080i/50, and the above symptom comes back.So I see two other workarounds:1) add a Timewarp effect, set to Fluidmotion. Best progressive-to-interlaced method, but two drawbacks: render times are astronomic (okay, source is 70 mbps 4k MP4, but only 25% CPU utilization on my Core-i7 3740QM: thank you QT AMA [:'(] !) and the result is not always pleasing depending on the complexity of the background behind the moving character (I can't afford to start editing the motion vectors manually)...Timewarp/Blended Interpolated isn't visually pleasing in my case as it seems to introduce too much motion blur.2) do not use any position animation with Frameflex: keep each clip static...(bye bye virtual camera operator)Ok this is probably an unusual, clumsy workflow, but any way to workaround the above side effect more efficiently/elegantly is welcome ! Did I overlook an obvious solution ?Ideally I would like to have the virtual camera move rendered as progressive (like the underlying video), but interlaced render is also okay (like with a Timewarp/Fluidmotion effect) as long as the stutter side-effect isn't too apparent.Note: switching the project permanently to 25p isn't an option.
Quickest: Use mixdowns in 50i project and add a 100% interpolated input interlaced output progressive timewarp adapter
Better: Switch to 25p and do your video mixdowns (retains resolution of video but temporal motion of frameflex will be 25 steps per second, rather than 50). Switch back to 50i and mixdown remains.
Best: Get Avid to give us the option of changing temporal interpolation of it's effects (this request predates progressive projects when trying to match film originated material).
Also you can lose the motion adapters for P sources in an I timeline. Modify the source clips to be 'interlaced' (even though they are progressive) and refresh motion adapters for the sequence.
TrevorA:Better: Switch to 25p and do your video mixdowns (retains resolution of video but temporal motion of frameflex will be 25 steps per second, rather than 50). Switch back to 50i and mixdown remains.
Absolutely !
but I need to assess the extra time it takes to do mixdown of ~50 "problematic" 25p clips in a 1.5 hour sequence (that's why I initially attempted render w/o mixdown in 25p mode). Could be an acceptable compromise though.
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