VAR_NB_IN_CHANNELS  231 libavfilter/aeval.c     eval->var_values[VAR_NB_IN_CHANNELS] = NAN;
VAR_NB_IN_CHANNELS  383 libavfilter/aeval.c     eval->nb_in_channels = eval->var_values[VAR_NB_IN_CHANNELS] = inlink->channels;