gstreamer: Fix usage of default size for fixation

Pipeline managers sets a default value to StreamConfiguration::size. The
original fixation code was attempting to use it, but as it was truncating
the caps to its first structure it would never actually find a best match.

In this patch, instead of truncating, we weight various matches using the
product of the width and height delta. We also split delta from ranges
apart and prefer fixed size over them as ranges are not reliable.

This patch also removes the related todo, as it seems that libcamera core
won't go further then providing this default value and won't be sorting the
format and size lists.

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 47 insertions, 4 deletions

diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp
index f7e0e1c8..0af91c1a 100644
--- a/src/gstreamer/gstlibcamera-utils.cpp
+++ b/src/gstreamer/gstlibcamera-utils.cpp
@@ -136,14 +136,57 @@ gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,
 					 GstCaps *caps)
 {
 	GstVideoFormat gst_format = pixel_format_to_gst_format(stream_cfg.pixelFormat);
+	guint i;
+	gint best_fixed = -1, best_in_range = -1;
+	GstStructure *s;
+
+	/*
+	 * These are delta weight computed from:
+	 *   ABS(width - stream_cfg.size.width) * ABS(height - stream_cfg.size.height)
+	 */
+	guint best_fixed_delta = G_MAXUINT;
+	guint best_in_range_delta = G_MAXUINT;
 
 	/* First fixate the caps using default configuration value. */
 	g_assert(gst_caps_is_writable(caps));
-	caps = gst_caps_truncate(caps);
-	GstStructure *s = gst_caps_get_structure(caps, 0);
 
-	gst_structure_fixate_field_nearest_int(s, "width", stream_cfg.size.width);
-	gst_structure_fixate_field_nearest_int(s, "height", stream_cfg.size.height);
+	/* Lookup the structure for a close match to the stream_cfg.size */
+	for (i = 0; i < gst_caps_get_size(caps); i++) {
+		s = gst_caps_get_structure(caps, i);
+		gint width, height;
+		guint delta;
+
+		if (gst_structure_has_field_typed(s, "width", G_TYPE_INT) &&
+		    gst_structure_has_field_typed(s, "height", G_TYPE_INT)) {
+			gst_structure_get_int(s, "width", &width);
+			gst_structure_get_int(s, "height", &height);
+
+			delta = ABS(width - (gint)stream_cfg.size.width) * ABS(height - (gint)stream_cfg.size.height);
+
+			if (delta < best_fixed_delta) {
+				best_fixed_delta = delta;
+				best_fixed = i;
+			}
+		} else {
+			gst_structure_fixate_field_nearest_int(s, "width", stream_cfg.size.width);
+			gst_structure_fixate_field_nearest_int(s, "height", stream_cfg.size.height);
+			gst_structure_get_int(s, "width", &width);
+			gst_structure_get_int(s, "height", &height);
+
+			delta = ABS(width - (gint)stream_cfg.size.width) * ABS(height - (gint)stream_cfg.size.height);
+
+			if (delta < best_in_range_delta) {
+				best_in_range_delta = delta;
+				best_in_range = i;
+			}
+		}
+	}
+
+	/* Prefer reliable fixed value over ranges */
+	if (best_fixed >= 0)
+		s = gst_caps_get_structure(caps, best_fixed);
+	else
+		s = gst_caps_get_structure(caps, best_in_range);
 
 	if (gst_structure_has_name(s, "video/x-raw")) {
 		const gchar *format = gst_video_format_to_string(gst_format);