M_PI_2            131 libavfilter/af_flanger.c                            s->max_samples - 2., 3 * M_PI_2);
M_PI_2            169 libavfilter/vf_vignette.c     s->angle = av_clipf(av_expr_eval(s->angle_pexpr, s->var_values, NULL), 0, M_PI_2);
M_PI_2             48 libavutil/mathematics.h #ifndef M_PI_2