PF_ALPHA          347 libavfilter/vf_decimate.c #define PF(suf)         PF_NOALPHA(suf), PF_ALPHA(suf)
PF_ALPHA          224 libavfilter/vf_psnr.c #define PF(suf)         PF_NOALPHA(suf), PF_ALPHA(suf)