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• compile own ffmpeg filter

  20 juin 2023, par lfk

  I'm trying compile my own ffmpeg filter using official tutorial. My filter uses C++ code. I made header file and adapted my C++ function definition for C. Now I'm trying compile with command make -j<libavfilter> ffmpeg</libavfilter>, but receiving an error message

  


  


  gcc -Llibavcodec -Llibavdevice -Llibavfilter -Llibavformat
-Llibavresample -Llibavutil -Llibpostproc -Llibswscale -Llibswresample -Wl,—as-needed -Wl,-z,noexecstack -Wl,—warn-common -Wl,-rpath-link=libpostproc:libswresample:libswscale:libavfilter:libavdevice:libavformat:libavcodec:libavutil:libavresample
-o ffmpeg_g fftools/ffmpeg_opt.o fftools/ffmpeg_filter.o fftools/ffmpeg_hw.o fftools/cmdutils.o fftools/ffmpeg.o -lavdevice
-lavfilter -lavformat -lavcodec -lswresample -lswscale -lavutil -lm -pthread -lm -lm -lz -pthread -lm -lz -lm -lm -pthread -lm libavfilter/libavfilter.a(vf_foobar.o) : In function `filter_frame' :
/home/joeyes/ffmpeg_sources/ffmpeg/libavfilter/vf_foobar.c:302 :
undefined reference to MyFunction.c
collect2 : ld returned 1 exit status
*** [ffmpeg_g] Error 1

  


  


  For compilation I added OBJS-$(CONFIG_FOOBAR_FILTER) += vf_foobar.o MyCode.o to /libavfilter/makefile

  


  Also I put MyCode.h & MyCode.cpp to /libavfilter folder

  


• ffmpeg xfade custom transition expression - Fetch pixel value at specifc x, y from vid1, vid2 ?

  25 janvier 2021, par jsaluja

  I am using xfade with transition=custom, and trying to build expression.
I am referring to official documentation https://ffmpeg.org/ffprobe-all.html#xfade

  


  Per my understanding, expression should return pixel value of merged video

  


  I built a few custom transitions using expressions that return some combination of A, B

  


  For eg.,

  


  "custom:expr='if(gt(P, abs(X/W - 0.5)), A, B)'"
"custom:expr='lerp(A, B, 1 - P)'"


  


  For the next set of transitions, I want to fetch the pixel values from source, target video at specific positions, and combine them in my expressions

  


  I tried using a0(X, Y), b0(X, Y) etc inside of

  


  xfade=transition=custom:expr='r....


  


  I ran into exceptions with ffmpeg complaining it doesn't understand the expression.

  


  Can someone clarify, how i can fetch pixel values as specific position from source, target video and combine them in expression ?

  


• How to fetch pixel value at specifc x, y from vid1, vid2 in ffmpeg xfade custom transition expression

  25 janvier 2021, par jsaluja

  I am using xfade with transition=custom, and trying to build expression.
I am referring to official documentation https://ffmpeg.org/ffprobe-all.html#xfade

  


  Per my understanding, expression should return pixel value of merged video

  


  I built a few custom transitions using expressions that return some combination of A, B

  


  For eg.,

  


  "custom:expr='if(gt(P, abs(X/W - 0.5)), A, B)'"
"custom:expr='lerp(A, B, 1 - P)'"


  


  For the next set of transitions, I want to fetch the pixel values from source, target video at specific positions, and combine them in my expressions

  


  I tried using a0(X, Y), b0(X, Y) etc inside of

  


  xfade=transition=custom:expr='r....


  


  I ran into exceptions with ffmpeg complaining it doesn't understand the expression.

  


  Can someone clarify, how i can fetch pixel values as specific position from source, target video and combine them in expression ?