FFmpeg Filtering 介绍

Filtering in FFmpeg is enabled through the libavfilter library.

In libavfilter, a filter can have multiple inputs and multiple outputs. To illustrate the sorts of things that are possible, we consider the following filtergraph:

                [main]
input --> split ---------------------> overlay --> output
            |                             ^
            |[tmp]                  [flip]|
            +-----> crop --> vflip -------+

This filtergraph splits the input stream in two streams, then sends one stream through the crop filter and the vflip filter, before merging it back with the other stream by overlaying it on top. You can use the following command to achieve this:

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The inefficiency of the external diff

However, Vim’s diff mode was seriously lacking. This was basically because it needed to write down temporary files, shell out and run a manual diff command and parse the result back and as one can imagine, this could be slow and was seriously inefficient.

Additionally, this required to have a diff binary available that was able to create ed like style diff, so one could not even fall-back to using git-diff (which is considered to have one of the best tested diff libraries and allows to select different algorithms) for creating those diffs. This lead to the creation of vimscript plugins, that would internally translate a unified diff back into an ed-like diff. Of course this would add an extra performance penalty.

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