ff_png_get_nb_channels   71 libavcodec/png.h int ff_png_get_nb_channels(int color_type);
ff_png_get_nb_channels  456 libavcodec/pngdec.c                 s->channels = ff_png_get_nb_channels(s->color_type);
ff_png_get_nb_channels  278 libavcodec/pngenc.c     bits_per_pixel = ff_png_get_nb_channels(color_type) * bit_depth;