mfvideosrc: Expose sorted caps

Sort the list of supported caps for downstream to be able to select
the best image in terms of quality (resolution and framerate) by default.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1452>

sys/mediafoundation/gstmfcapturewinrt.cpp

@@ -27,6 +27,7 @@
 #include "mediacapturewrapper.h"
 #include <memorybuffer.h>
 #include <memory>
+#include <algorithm>
 
 using namespace Microsoft::WRL;
 using namespace Microsoft::WRL::Wrappers;
@@ -161,6 +162,13 @@ gst_mf_capture_winrt_main_loop_running_cb (GstMFCaptureWinRT * self)
   return G_SOURCE_REMOVE;
 }
 
+static bool
+winrt_compare_caps_func (const GstWinRTMediaDescription & a,
+    const GstWinRTMediaDescription & b)
+{
+  return gst_mf_source_object_caps_compare (a.caps_, b.caps_) < 0;
+}
+
 static gpointer
 gst_mf_capture_winrt_thread_func (GstMFCaptureWinRT * self)
 {
@@ -232,30 +240,33 @@ gst_mf_capture_winrt_thread_func (GstMFCaptureWinRT * self)
     goto run_loop;
   }
 
+  if (target_group->source_list_.empty ()) {
+    GST_WARNING_OBJECT (self, "No available source list");
+    goto run_loop;
+  }
+
   self->capture->SetSourceGroup(*target_group);
 
-  for (auto iter: target_group->source_list_) {
-    if (!self->supported_caps)
-      self->supported_caps = gst_caps_ref (iter.caps_);
-    else
-      self->supported_caps =
-          gst_caps_merge (self->supported_caps, gst_caps_ref (iter.caps_));
-  }
+  std::sort (target_group->source_list_.begin (),
+      target_group->source_list_.end (), winrt_compare_caps_func);
+
+  self->supported_caps = gst_caps_new_empty ();
+
+  for (auto iter: target_group->source_list_)
+    gst_caps_append (self->supported_caps, gst_caps_copy (iter.caps_));
 
   GST_DEBUG_OBJECT (self, "Available output caps %" GST_PTR_FORMAT,
       self->supported_caps);
 
-  source->opened = !!self->supported_caps;
+  source->opened = TRUE;
 
-  if (source->opened) {
-    g_free (source->device_path);
-    source->device_path = g_strdup (target_group->id_.c_str());
+  g_free (source->device_path);
+  source->device_path = g_strdup (target_group->id_.c_str());
 
-    g_free (source->device_name);
-    source->device_name = g_strdup (target_group->display_name_.c_str());
+  g_free (source->device_name);
+  source->device_name = g_strdup (target_group->display_name_.c_str());
 
-    source->device_index = index;
-  }
+  source->device_index = index;
 
 run_loop:
   GST_DEBUG_OBJECT (self, "Starting main loop");

sys/mediafoundation/gstmfsourceobject.c

@@ -338,3 +338,64 @@ gst_mf_source_object_new (GstMFSourceType type, gint device_index,
 
   return NULL;
 }
+
+gint
+gst_mf_source_object_caps_compare (GstCaps * caps1, GstCaps * caps2)
+{
+  GstStructure *s1, *s2;
+  const gchar *n1, *n2;
+  gboolean m1_is_raw, m2_is_raw;
+  gint w1 = 0, h1 = 0, w2 = 0, h2 = 0;
+  gint r1, r2;
+  gint num1 = 0, den1 = 1, num2 = 0, den2 = 1;
+  gint fraction_cmp;
+
+  /* sorting priority
+   * - raw video > comprssed
+   *   - raw video format
+   * - higher resolution
+   * - higher framerate
+   */
+  s1 = gst_caps_get_structure (caps1, 0);
+  n1 = gst_structure_get_name (s1);
+
+  s2 = gst_caps_get_structure (caps2, 0);
+  n2 = gst_structure_get_name (s2);
+
+  m1_is_raw = g_strcmp0 (n1, "video/x-raw") == 0;
+  m2_is_raw = g_strcmp0 (n2, "video/x-raw") == 0;
+
+  if (m1_is_raw && !m2_is_raw)
+    return -1;
+  else if (!m1_is_raw && m2_is_raw)
+    return 1;
+
+  /* if both are raw formats */
+  if (m1_is_raw) {
+    gint format_cmp = g_strcmp0 (gst_structure_get_string (s1, "format"),
+        gst_structure_get_string (s2, "format"));
+    if (format_cmp)
+      return format_cmp;
+  }
+
+  /* resolution */
+  gst_structure_get_int (s1, "width", &w1);
+  gst_structure_get_int (s1, "height", &h1);
+  gst_structure_get_int (s2, "width", &w2);
+  gst_structure_get_int (s2, "height", &h2);
+
+  r1 = w1 * h1;
+  r2 = w2 * h2;
+
+  /* higher resolution first */
+  if (r1 != r2)
+    return r2 - r1;
+
+  gst_structure_get_fraction (s1, "framerate", &num1, &den1);
+  gst_structure_get_fraction (s2, "framerate", &num2, &den2);
+
+  fraction_cmp = gst_util_fraction_compare (num1, den1, num2, den2);
+
+  /* higher framerate first */
+  return fraction_cmp * -1;
+}

sys/mediafoundation/gstmfsourceobject.h

@@ -108,6 +108,10 @@ GstMFSourceObject * gst_mf_source_object_new      (GstMFSourceType type,
                                                    const gchar * device_name,
                                                    const gchar * device_path);
 
+/* Utility methods */
+gint            gst_mf_source_object_caps_compare (GstCaps * caps1,
+                                                   GstCaps * caps2);
+
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GstMFSourceObject, gst_object_unref)
 
 G_END_DECLS

sys/mediafoundation/gstmfsourcereader.cpp

@@ -244,6 +244,17 @@ gst_mf_stream_media_type_free (GstMFStreamMediaType * media_type)
   g_free (media_type);
 }
 
+static gint
+compare_caps_func (gconstpointer a, gconstpointer b)
+{
+  GstMFStreamMediaType *m1, *m2;
+
+  m1 = (GstMFStreamMediaType *) a;
+  m2 = (GstMFStreamMediaType *) b;
+
+  return gst_mf_source_object_caps_compare (m1->caps, m2->caps);
+}
+
 static gboolean
 gst_mf_source_reader_open (GstMFSourceReader * self, IMFActivate * activate)
 {
@@ -280,13 +291,15 @@ gst_mf_source_reader_open (GstMFSourceReader * self, IMFActivate * activate)
   self->source = source.Detach ();
   self->reader = reader.Detach ();
 
+  self->media_types = g_list_sort (self->media_types,
+      (GCompareFunc) compare_caps_func);
+
+  self->supported_caps = gst_caps_new_empty ();
+
   for (iter = self->media_types; iter; iter = g_list_next (iter)) {
     GstMFStreamMediaType *mtype = (GstMFStreamMediaType *) iter->data;
-    if (!self->supported_caps)
-      self->supported_caps = gst_caps_ref (mtype->caps);
-    else
-      self->supported_caps =
-          gst_caps_merge (self->supported_caps, gst_caps_ref (mtype->caps));
+
+    gst_caps_append (self->supported_caps, gst_caps_copy (mtype->caps));
   }
 
   GST_DEBUG_OBJECT (self, "Available output caps %" GST_PTR_FORMAT,