From 350f89859501fbe759634e77733ecba2c97fd06d Mon Sep 17 00:00:00 2001 From: Vito Caputo Date: Thu, 14 Nov 2019 23:06:52 -0800 Subject: snow: add a simple tv snow / white noise module I wanted to add some noise to the rtv module and figured why not just add a snow module and make rtv pass through it briefly when switching modules. It's not interesting by itself, but as more composite/meta modules like rtv get made it might be handy beyond rtv. --- src/modules/snow/snow.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) create mode 100644 src/modules/snow/snow.c (limited to 'src/modules/snow/snow.c') diff --git a/src/modules/snow/snow.c b/src/modules/snow/snow.c new file mode 100644 index 0000000..f3c20d5 --- /dev/null +++ b/src/modules/snow/snow.c @@ -0,0 +1,51 @@ +#include +#include +#include + +#include "fb.h" +#include "rototiller.h" + +/* Copyright (C) 2019 - Vito Caputo */ + +/* This implements white noise / snow just using rand() */ + +/* To avoid the contention around rand() I'm just using rand_r() + * in an entirely racy fashion with a single seed from the threaded + * render_fragment(). It should really be per-cpu but the module + * api doesn't currently send down a cpu identifier to the render + * function, so TODO in the future add that. + */ +static int snow_seed; + +static int snow_fragmenter(void *context, const fb_fragment_t *fragment, unsigned num, fb_fragment_t *res_fragment) +{ + return fb_fragment_slice_single(fragment, 32, num, res_fragment); +} + + +static void snow_prepare_frame(void *context, unsigned n_cpus, fb_fragment_t *fragment, rototiller_fragmenter_t *res_fragmenter) +{ + *res_fragmenter = snow_fragmenter; +} + + +static void snow_render_fragment(void *context, fb_fragment_t *fragment) +{ + for (unsigned y = fragment->y; y < fragment->y + fragment->height; y++) { + for (unsigned x = fragment->x; x < fragment->x + fragment->width; x++) { + uint32_t pixel = rand_r(&snow_seed) % 256; + + fb_fragment_put_pixel_unchecked(fragment, x, y, pixel << 16 | pixel << 8 | pixel); + } + } +} + + +rototiller_module_t snow_module = { + .prepare_frame = snow_prepare_frame, + .render_fragment = snow_render_fragment, + .name = "snow", + .description = "TV snow / white noise", + .author = "Vito Caputo ", + .license = "GPLv2", +}; -- cgit v1.2.3