[FFmpeg-devel] [FFmpeg-user] How to create trapezoid videos with ffmpeg?

James Darnley james.darnley at gmail.com
Fri Oct 17 23:24:00 CEST 2014


On 2014-10-17 23:09, Nicholas Robbins wrote:
>> So is it possible to make a filter that is basically just a wrapper around 
>> another filter? This hypothetical filter (call it vf_keystone) would just call 
>> vf_perspective with crazy options. Clearly I could just copy the vf_perspective 
>> filter and then insert these changes, but than any future changes to 
>> vf_perspective wouldn't filter down to vf_keystone.
>>
>> Is this possible?

Yes, it is very possible to make a wrapper around another filter.  If
you wanted to do it for this use case I would suggest these steps:
 - Add some more fields to the perspective private context to store user
options.
 - Create a new options table for your "new filter"
 - Add a branch and suitable code in the init function to turn the new
options into the old options.
 - Add a new AVFilter definition for your new filter, have it use the
new options table but the existing functions.


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