[libcamera-devel] [PATCH v2 02/27] gst: Add utility to convert StreamFormats to GstCaps

[Nicolas Dufresne]

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 at collabora.com>
---
 src/gstreamer/gstlibcamera-utils.cpp | 98 ++++++++++++++++++++++++++++
 src/gstreamer/gstlibcamera-utils.h   | 18 +++++
 src/gstreamer/meson.build            |  1 +
 3 files changed, 117 insertions(+)
 create mode 100644 src/gstreamer/gstlibcamera-utils.cpp
 create mode 100644 src/gstreamer/gstlibcamera-utils.h

diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp
new file mode 100644
index 0000000..dc129c3
--- /dev/null
+++ b/src/gstreamer/gstlibcamera-utils.cpp
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Collabora Ltd.
+ *     Author: Nicolas Dufresne <nicolas.dufresne at 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 inline 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);
+			gst_structure_set(s,
+					  "width", GST_TYPE_INT_RANGE, range.min.width, range.max.width, range.hStep,
+					  "height", GST_TYPE_INT_RANGE, range.min.height, range.max.height, range.vStep,
+					  nullptr);
+			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 0000000..33160b8
--- /dev/null
+++ b/src/gstreamer/gstlibcamera-utils.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Collabora Ltd.
+ *     Author: Nicolas Dufresne <nicolas.dufresne at collabora.com>
+ *
+ * gstlibcamera-utils.h - GStreamer libcamera Utility Functions
+ */
+
+#ifndef __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 832b8a5..f409107 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',
 ]
-- 
2.24.1