libs: video-format: add a helper function of get_formats_by_chroma.

The function iterates all supported video formats and returns the
formats belong to the specified chroma type.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-vaapi/-/merge_requests/315>

gst-libs/gst/vaapi/video-format.c

@@ -476,6 +476,39 @@ gst_vaapi_video_format_get_best_native (GstVideoFormat format)
   return gst_vaapi_video_format_from_chroma (chroma_type);
 }
 
+/**
+ * gst_vaapi_video_format_get_formats_by_chroma:
+ * @chroma: a #GstVaapiChromaType
+ *
+ * Get all #GstVideoFormat which belong to #GstVaapiChromaType.
+ *
+ * Returns: an array of #GstVideoFormat.
+ **/
+GArray *
+gst_vaapi_video_format_get_formats_by_chroma (guint chroma)
+{
+  const GstVideoFormatMap *entry;
+  GArray *formats;
+  guint i;
+
+  formats = g_array_new (FALSE, FALSE, sizeof (GstVideoFormat));
+  if (!formats)
+    return NULL;
+
+  for (i = 0; i < gst_vaapi_video_formats_map->len; i++) {
+    entry = &g_array_index (gst_vaapi_video_formats_map, GstVideoFormatMap, i);
+    if (entry->chroma_type == chroma)
+      g_array_append_val (formats, entry->format);
+  }
+
+  if (formats->len == 0) {
+    g_array_unref (formats);
+    return NULL;
+  }
+
+  return formats;
+}
+
 struct ImageFormatsData
 {
   VAImageFormat *formats;

gst-libs/gst/vaapi/video-format.h

@@ -64,6 +64,9 @@ gst_vaapi_video_format_from_chroma (guint chroma);
 GstVideoFormat
 gst_vaapi_video_format_get_best_native (GstVideoFormat format);
 
+GArray *
+gst_vaapi_video_format_get_formats_by_chroma (guint chroma);
+
 gboolean
 gst_vaapi_video_format_create_map (VAImageFormat * formats, guint n);