How to add a new filter to ffmpeg library

Question

I am trying to add functionality to FFmpeg library. The issue is that in developer guide there are just general instruction on how to do it. I know that when I want to add something to ffmpeg I need to register the new functionality and rebuild the library so I can then call it somehow like so:

ffmpeg -i input.avi -vf "myfilter" out.avi

I do not want to officialy contribute. I would like to try to create the extra functionality and test it. The question is - is there any scelet file where the basic structure would be ready and you would just get a pointer to a new frame and processed it? Some directions or anything, because the source files are kinda hard to read without understanding its functions it calls inside.

Answer 1

The document in the repo is worth a read: ffmpeg\doc\writing_filters.txt

The steps are:

1. Add an appropriate line to the: ffmpeg\libavfilter\Makefile

   OBJS-$(CONFIG_MCSCALE_CUDA_FILTER) += vf_mcscale_cuda.o vf_mcscale_cuda.ptx.o scale_eval.o

2. Add an appropriate line to the: ffmpeg\libacfilter\allfilters.c

   extern AVFilter ff_vf_mcscale_cuda;

3. The change in (2) does not become recognized until ./configure scans the files again to configure the build, so run Configure and when you next run make the filter should be generated. Happy days.