added dummy I420->UYVY decompress

As there is no line decoder for I420, because it is a planar format,
added regular decompress to be able to display simple uncompressed I420
as in the this command: `uv -t testcard:c=I420 -d gl`

Author: MartinPulec

configure.ac

@@ -3348,6 +3348,7 @@ if test "$build_default" != no; then
         src/video_capture/import.o
         src/video_capture/switcher.o
         src/video_capture/ug_input.o
+        src/video_decompress/i420.o
         src/video_display/aggregate.o
         src/video_display/dump.o
         src/video_display/multiplier.o

src/video_decompress/i420.c

@@ -0,0 +1,130 @@
+/**
+ * @file   video_decompress/i420.c
+ * @author Martin Pulec     <pulec@cesnet.cz>
+ *
+ * implementation of I420->UYVY "decompression", because for the planar
+ * format there is no line decoder and when the display iw unable to display
+ * I420 directly, it is not possible to present it.
+ *
+ * As this is implementation is quite short, it can also hold as a decompress
+ * module template.
+ */
+/*
+ * Copyright (c) 2024 CESNET z.s.p.o.
+ * 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 <assert.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+#include "lib_common.h"
+#include "types.h"
+#include "video_codec.h"
+#include "video_decompress.h"
+
+struct i420_decompress_state {
+        struct video_desc desc;
+};
+
+static void *
+i420_decompress_init(void)
+{
+        return malloc(sizeof(struct i420_decompress_state));
+}
+
+static int
+i420_decompress_reconfigure(void *state, struct video_desc desc, int rshift,
+                            int gshift, int bshift, int pitch,
+                            codec_t out_codec)
+{
+        (void) rshift, (void) gshift, (void) bshift;
+        assert(out_codec == UYVY);
+        assert(pitch == (int) desc.width * 2); // implement other ir needed
+        struct i420_decompress_state *s = state;
+        s->desc                         = desc;
+        return true;
+}
+
+static decompress_status
+i420_decompress(void *state, unsigned char *dst, unsigned char *buffer,
+                unsigned int src_len, int frame_seq,
+                struct video_frame_callbacks *callbacks,
+                struct pixfmt_desc           *internal_prop)
+{
+        (void) src_len, (void) frame_seq, (void) callbacks,
+            (void) internal_prop;
+        struct i420_decompress_state *s = state;
+        i420_8_to_uyvy((int) s->desc.width, (int) s->desc.height, buffer, dst);
+        return DECODER_GOT_FRAME;
+}
+
+static int
+i420_decompress_get_property(void *state, int property, void *val, size_t *len)
+{
+        (void) state;
+
+        if (property == DECOMPRESS_PROPERTY_ACCEPTS_CORRUPTED_FRAME) {
+                assert(*len >= sizeof(int));
+                *(int *) val = true;
+                *len         = sizeof(int);
+                return true;
+        }
+        return false;
+}
+
+static void
+i420_decompress_done(void *state)
+{
+        free(state);
+}
+
+static int
+i420_decompress_get_priority(codec_t compression, struct pixfmt_desc internal,
+                             codec_t ugc)
+{
+        (void) internal;
+        enum {
+                PRIO_NA     = -1,
+                PRIO_NORMAL = 500,
+        };
+        // probing (ugc==VC_NONE) is skipped (optional, not necessary)
+        return compression == I420 && ugc == UYVY ? PRIO_NORMAL : PRIO_NA;
+}
+
+static const struct video_decompress_info i420_info = {
+        i420_decompress_init, i420_decompress_reconfigure,
+        i420_decompress,      i420_decompress_get_property,
+        i420_decompress_done, i420_decompress_get_priority,
+};
+
+REGISTER_MODULE(i420, &i420_info, LIBRARY_CLASS_VIDEO_DECOMPRESS,
+                VIDEO_DECOMPRESS_ABI_VERSION);