ff_png_get_nb_channels   62 libavcodec/png.h int ff_png_get_nb_channels(int color_type);
ff_png_get_nb_channels  595 libavcodec/pngdec.c         s->channels       = ff_png_get_nb_channels(s->color_type);
ff_png_get_nb_channels  348 libavcodec/pngenc.c     bits_per_pixel = ff_png_get_nb_channels(color_type) * bit_depth;