FX Cut

On Tue, 2005-07-05 at 11:38 -0400, Dan Dennedy wrote: > what is a “fx cut?”

I will be providing more detailed docs once the functionality has fully stabilised (creation and interfacing wise). Hope the following helps for now:

An FX Cut is an experimental serialised form of a filter.

The idea is that they can be placed on a track in the same way as you can place a normal clip or cut, but they affect the video or audio from the tracks above, like:

   T0: | video1 | video2 |
   T1:    | greyscale |

Here, the greyscale effect is applied over the overlapping region of both video1 and video2.

Soon, you will also be able to use them in the normal attach and filter way (currently not supported).

They’re made up of a dummy producer (which is normally discarded at runtime) and attached effects.

A simple example would be something like:

<?xml version="1.0" encoding="utf-8"?>
<mlt title="Greyscale">
  <producer in="0" out="499">
    <property name="markup">Greyscale</property>
    <property name="mlt_service">pango</property>
    <property name="meta.fx_cut">1</property>
        <filter mlt_service="greyscale" />

Save that as greyscale.mlt and run:

melt colour:blue -track greyscale.mlt

Standalone, the idea is that they could provide a little indication of what the effect does (could be text which is then changed by the effect) or it could be a small animation via the dummy producer. When they are used in a multitrack, the dummy is hidden (which is why melt won’t be able to play that directly).

Transitions can also be introduced via the same approach, though they need to wrapped by the new ‘transition’ filter (this is part of a general attempt to remove the usage distinction between filters and transitions and simplify the multitrack container).



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