gst: Add utility to convert StreamFormats to GstCaps

This transforms the basic information found in StreamFormats to GstCaps.
This can be handy to reply to early caps query or inside a device
provider. Note that we ignored generated range as they are harmful to
caps negotiation. We also don't simplify the caps for readability
reasons, so some of the discrete value may be included in a range.

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

3 files changed, 125 insertions, 0 deletions

diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp
new file mode 100644
index 00000000..386ec364
--- /dev/null
+++ b/src/gstreamer/gstlibcamera-utils.cpp
@@ -0,0 +1,105 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Collabora Ltd.
+ *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
+ *
+ * gstlibcamera-utils.c - GStreamer libcamera Utility Function
+ */
+
+#include "gstlibcamera-utils.h"
+
+#include <linux/drm_fourcc.h>
+
+using namespace libcamera;
+
+static struct {
+	GstVideoFormat gst_format;
+	guint drm_fourcc;
+} format_map[] = {
+	{ GST_VIDEO_FORMAT_ENCODED, DRM_FORMAT_MJPEG },
+	{ GST_VIDEO_FORMAT_RGB, DRM_FORMAT_BGR888 },
+	{ GST_VIDEO_FORMAT_BGR, DRM_FORMAT_RGB888 },
+	{ GST_VIDEO_FORMAT_ARGB, DRM_FORMAT_BGRA8888 },
+	{ GST_VIDEO_FORMAT_NV12, DRM_FORMAT_NV12 },
+	{ GST_VIDEO_FORMAT_NV21, DRM_FORMAT_NV21 },
+	{ GST_VIDEO_FORMAT_NV16, DRM_FORMAT_NV16 },
+	{ GST_VIDEO_FORMAT_NV61, DRM_FORMAT_NV61 },
+	{ GST_VIDEO_FORMAT_NV24, DRM_FORMAT_NV24 },
+	{ GST_VIDEO_FORMAT_UYVY, DRM_FORMAT_UYVY },
+	{ GST_VIDEO_FORMAT_VYUY, DRM_FORMAT_VYUY },
+	{ GST_VIDEO_FORMAT_YUY2, DRM_FORMAT_YUYV },
+	{ GST_VIDEO_FORMAT_YVYU, DRM_FORMAT_YVYU },
+	/* \todo NV42 is used in libcamera but is not mapped in GStreamer yet. */
+};
+
+static GstVideoFormat
+drm_to_gst_format(guint drm_fourcc)
+{
+	for (const auto &item : format_map) {
+		if (item.drm_fourcc == drm_fourcc)
+			return item.gst_format;
+	}
+	return GST_VIDEO_FORMAT_UNKNOWN;
+}
+
+static GstStructure *
+bare_structure_from_fourcc(guint fourcc)
+{
+	GstVideoFormat gst_format = drm_to_gst_format(fourcc);
+
+	if (gst_format == GST_VIDEO_FORMAT_UNKNOWN)
+		return nullptr;
+
+	if (gst_format != GST_VIDEO_FORMAT_ENCODED)
+		return gst_structure_new("video/x-raw", "format", G_TYPE_STRING,
+					 gst_video_format_to_string(gst_format), nullptr);
+
+	switch (fourcc) {
+	case DRM_FORMAT_MJPEG:
+		return gst_structure_new_empty("image/jpeg");
+	default:
+		return nullptr;
+	}
+}
+
+GstCaps *
+gst_libcamera_stream_formats_to_caps(const StreamFormats &formats)
+{
+	GstCaps *caps = gst_caps_new_empty();
+
+	for (unsigned int fourcc : formats.pixelformats()) {
+		g_autoptr(GstStructure) bare_s = bare_structure_from_fourcc(fourcc);
+
+		if (!bare_s) {
+			GST_WARNING("Unsupported DRM format %" GST_FOURCC_FORMAT,
+				    GST_FOURCC_ARGS(fourcc));
+			continue;
+		}
+
+		for (const Size &size : formats.sizes(fourcc)) {
+			GstStructure *s = gst_structure_copy(bare_s);
+			gst_structure_set(s,
+					  "width", G_TYPE_INT, size.width,
+					  "height", G_TYPE_INT, size.height,
+					  nullptr);
+			gst_caps_append_structure(caps, s);
+		}
+
+		const SizeRange &range = formats.range(fourcc);
+		if (range.hStep && range.vStep) {
+			GstStructure *s = gst_structure_copy(bare_s);
+			GValue val = G_VALUE_INIT;
+
+			g_value_init(&val, GST_TYPE_INT_RANGE);
+			gst_value_set_int_range_step(&val, range.min.width, range.max.width, range.hStep);
+			gst_structure_set_value(s, "width", &val);
+			gst_value_set_int_range_step(&val, range.min.height, range.max.height, range.vStep);
+			gst_structure_set_value(s, "height", &val);
+			g_value_unset(&val);
+
+			gst_caps_append_structure(caps, s);
+		}
+	}
+
+	return caps;
+}
diff --git a/src/gstreamer/gstlibcamera-utils.h b/src/gstreamer/gstlibcamera-utils.h
new file mode 100644
index 00000000..2e4e3042
--- /dev/null
+++ b/src/gstreamer/gstlibcamera-utils.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Collabora Ltd.
+ *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
+ *
+ * gstlibcamera-utils.h - GStreamer libcamera Utility Functions
+ */
+
+#ifndef __GST_LIBCAMERA_UTILS_H__
+#define __GST_LIBCAMERA_UTILS_H__
+
+#include <gst/gst.h>
+#include <gst/video/video.h>
+
+#include <libcamera/stream.h>
+
+GstCaps *gst_libcamera_stream_formats_to_caps(const libcamera::StreamFormats &formats);
+
+#endif /* __GST_LIBCAMERA_UTILS_H__ */
diff --git a/src/gstreamer/meson.build b/src/gstreamer/meson.build
index 490e030e..9b11a46f 100644
--- a/src/gstreamer/meson.build
+++ b/src/gstreamer/meson.build
@@ -1,4 +1,5 @@
 libcamera_gst_sources = [
+    'gstlibcamera-utils.cpp',
     'gstlibcamera.c',
     'gstlibcamerasrc.cpp',
 ]