This adds low resolution proxy support to the blender sequencer, so
that even HD editing should be possible on slower machines.
The proxies are stored as directories of JPEG-files and are only
activated, if you use preview-resolution rendering.
For your final render, just switch back to full resolution and
the original files are used again.
It enables even proxying of whole effect pipelines and scene-strips
(but you have to your own custom directory for file storage then,
since blender has no filename, which could be taken as a sensible
default directory reference)
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