add vcf/noise

Similar idea as "noise" in testcard2 (to add entropy for compression
testing when using artificial source).

configure.ac

@@ -3485,6 +3485,7 @@ if test "$build_default" != no || test "$req_files" = all; then
         src/capture_filter/matrix.o
         src/capture_filter/matrix2.o
         src/capture_filter/mirror.o
+        src/capture_filter/noise.o
         src/capture_filter/override_prop.o
         src/capture_filter/preview.o
         src/capture_filter/ratelimit.o

src/capture_filter/noise.c

@@ -0,0 +1,168 @@
+/**
+ * @file   capture_filter/noise.c
+ * @author Martin Pulec <martin.pulec@cesnet.cz>
+ */
+/*
+ * Copyright (c) 2025 CESNET, zájmové sdružení právnických osob
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, is permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of CESNET nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software without
+ *    specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+ * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <limits.h> // for UCHAR_MAX, UINT_MAX
+#include <stdlib.h> // for calloc, free, strtol
+#include <string.h> // for memcpy, strchr, strcmp, strdup, strtok_r
+
+#include "capture_filter.h"  // for CAPTURE_FILTER_ABI_VERSION, capture_fil...
+#include "debug.h"           // for LOG_LEVEL_ERROR, MSG
+#include "lib_common.h"      // for REGISTER_MODULE, library_class
+#include "types.h"           // for tile, video_frame, video_frame_callbacks
+#include "utils/color_out.h" // for color_printf, TBOLD, TRED
+#include "utils/macros.h"    // for IS_KEY_PREFIX
+#include "utils/random.h"    // for ug_rand
+#include "video_frame.h"     // for vf_alloc_desc, video_desc_from_frame
+struct module;
+
+#define MOD_NAME "[cf/noise] "
+
+#if __STDC_VERSION__ < 202311L
+#define nullptr NULL
+#endif
+
+static void done(void *state);
+
+enum {
+        DEFAULT_MAGNITUDE = 30,
+};
+
+struct state_noise {
+        unsigned magnitude;
+};
+
+static void
+usage()
+{
+        color_printf(TRED(TBOLD("noise")) " capture filter adds white noise\n");
+        color_printf("\n");
+
+        color_printf("THe main use case is for testing (to add entropy for compression).\n");
+        color_printf("See also \"noise\" parameter of " TBOLD("testcard2") ".\n");
+        color_printf("\n");
+
+        color_printf("Usage:\n");
+        color_printf(
+            "\t" TBOLD(TRED("-F noise") "[:magnitude=<m>]") " (default %d)\n",
+            DEFAULT_MAGNITUDE);
+        color_printf("\t" TBOLD("-F noise:help") "\n");
+}
+
+static int
+parse_fmt(struct state_noise *s, char *ccfg)
+{
+        if (strcmp(ccfg, "help") == 0) {
+                return 1;
+        }
+        char *item   = nullptr;
+        char *endptr = nullptr;
+        while ((item = strtok_r(ccfg, ":", &endptr)) != nullptr) {
+                ccfg = nullptr;
+                if (IS_KEY_PREFIX(item, "magnitude")) {
+                        char *endptr = nullptr;
+                        const long val =
+                            strtol(strchr(item, '=') + 1, &endptr, 0);
+                        if (val <= 0 || val > UINT_MAX || *endptr != '\0') {
+                                MSG(ERROR, "Wrong value given: %ld!\n", val);
+                                return -1;
+                        }
+                        s->magnitude = val;
+                } else {
+                        MSG(ERROR, "Unknown option: %s!", item);
+                        return -1;
+                }
+        }
+        return 0;
+}
+
+static int
+init(struct module *parent, const char *cfg, void **state)
+{
+        (void) parent;
+        struct state_noise *s = calloc(1, sizeof(struct state_noise));
+        s->magnitude          = DEFAULT_MAGNITUDE;
+        char *ccfg            = strdup(cfg);
+        int   rc              = parse_fmt(s, ccfg);
+        free(ccfg);
+        if (rc != 0) {
+                usage();
+                done(s);
+                return rc;
+        }
+
+        *state = s;
+        return 0;
+}
+
+static void
+done(void *state)
+{
+        free(state);
+}
+
+static struct video_frame *
+filter(void *state, struct video_frame *in)
+{
+        struct state_noise *s = state;
+
+        struct video_frame *out = vf_alloc_desc_data(video_desc_from_frame(in));
+        out->callbacks.dispose  = vf_free;
+
+        unsigned char *out_data = (unsigned char *) out->tiles[0].data;
+
+        memcpy(out_data, in->tiles[0].data, in->tiles[0].data_len);
+
+        const unsigned char *const end = out_data + in->tiles[0].data_len;
+        out_data += (ug_rand() % s->magnitude);
+        while (out_data < end) {
+                *out_data = ug_rand() % (UCHAR_MAX + 1);
+                out_data += 1 + (ug_rand() % s->magnitude);
+        }
+
+        VIDEO_FRAME_DISPOSE(in);
+
+        return out;
+}
+
+static const struct capture_filter_info capture_filter_noise = {
+        .init   = init,
+        .done   = done,
+        .filter = filter,
+};
+
+REGISTER_MODULE(noise, &capture_filter_noise, LIBRARY_CLASS_CAPTURE_FILTER,
+                CAPTURE_FILTER_ABI_VERSION);