Temporal Difference Matte

[Chris Northcross]

John, I saw the examples you posted of artwork created using a temporal difference matte and I'm enthralled. Can you walk us through the nuts and bolts of how you created them?

[mark g]

chris,

load a source movie, open temporal image op under the main action menu...open the editor and choose an temporal ip op, and play around, some dont do anything till you process a movie,

T slit scan complete is a good one for producing images like the ones you are looking at

you can also record one action as a PASEQ then process your movie with the new PASEQ

[mark g]

heres the dream sequence from 'spellbound' done using T slit scan complete

spell.jpeg

[Chris Northcross]

Ooooh....shiny! Thanks much Mark!

[Synthetik]

Here's an introduction tip to temporal image operations in version 4.

The Scan Tracker is a lot more flexible than Slit Scan Complete. You can generate a conventional slit scan effects but you can also create slit scan style effects with only a few frames as opposed to the entire movie. You can also use it to build panorama images from video pans. If you are building a panorama image you typically want a canvas bigger in the scan direction than the actual video frame. The coverage control is really useful for pulling additional resolution out of slit scan effects as it's reduced in value. After you pass the sweet spot for a particular video sequence then it will lead to stutter effects.

The temporal rank filter is also very useful for the kind of effects i posted recently.

The temporal ip ops start processing from the current frame of the loaded source movie. Many of the effects have a Symmetry option, which can be used to adjust the temporal processing window in relationship to the current source video frame. This works in conjunction with Size and Frame Inc options. Size specifies the number of frames used for the temporal processing window. Frame Inc specifies the frame spacing between frames used for the effect. So if you used a size of 3 and a frame inc of 10, then only 3 frames would be used for the processing, each spaced 10 frames apart.

Be aware that the 2 options marked complete can take along time to process a single frame since they use every frame in the movie to generate a single output frame. You can use the esc key to manually stop temporal ip ops like this that have the potential to run slow.

If you are using something like the temporal difference matte or motion rank filtering, you would ideally want the camera to not be moving or shaking. So a tripod can be really useful for this when taking the original shot. We may add some motion compensation processing directly in Studio Artist later on to help with this.

[Chris Northcross]

For the interpolation options, could you explain the difference between 0-order, Linear and MaxNLNeigh?

[Synthetik]

Interpolation in this case means interpolating between different video frames at different times, so it's temporal interpolation as opposed to spatial interpolation like you see when resizing the canvas.

0 order means no real interpolation between different frames is taking place. Linear means a linear blend between 2 different frames will be taking place (this is the one you will typically use). MaxNLNeigh is a non-linear interpolation algorithm that tries to preserve edge or texture information. Whether you like the results or not will depend on the kind of frame images you are interpolating between. If there's a lot of busy detail it might give you better results. If there's sky or a lot of flat areas it will probably look noisy and linear will be the way to go.