From c0ca12a3fbfaab9beee533be2b24384eafc5ef54 Mon Sep 17 00:00:00 2001
From: Michael Gruner <michael.gruner@ridgerun.com>
Date: Thu, 23 Jan 2020 11:02:52 -0600
Subject: [PATCH] videoscale: transform size sensitive metas

Currently, videoscale just drops all metas that have other tags
besides video. However videoscale wont change the colorspace or
the orientation of the video so metas tagged as such may be
copied safely. Additionaly, given that videoscale will change
the frame size, we invoke the meta transform implementation
to give it the opportunity to scale accordingly.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/548>
---
 gst/videoscale/gstvideoscale.c | 64 +++++++++++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 1 deletion(-)

diff --git a/gst/videoscale/gstvideoscale.c b/gst/videoscale/gstvideoscale.c
index e7b82ec5f0..1d73406293 100644
--- a/gst/videoscale/gstvideoscale.c
+++ b/gst/videoscale/gstvideoscale.c
@@ -127,6 +127,9 @@ static GstStaticCaps gst_video_scale_format_caps =
     GST_STATIC_CAPS (GST_VIDEO_CAPS_MAKE (GST_VIDEO_FORMATS) ";"
     GST_VIDEO_CAPS_MAKE_WITH_FEATURES ("ANY", GST_VIDEO_FORMATS));
 
+GQuark _size_quark;
+GQuark _scale_quark;
+
 #define GST_TYPE_VIDEO_SCALE_METHOD (gst_video_scale_method_get_type())
 static GType
 gst_video_scale_method_get_type (void)
@@ -191,6 +194,8 @@ static GstCaps *gst_video_scale_transform_caps (GstBaseTransform * trans,
     GstPadDirection direction, GstCaps * caps, GstCaps * filter);
 static GstCaps *gst_video_scale_fixate_caps (GstBaseTransform * base,
     GstPadDirection direction, GstCaps * caps, GstCaps * othercaps);
+static gboolean gst_video_scale_transform_meta (GstBaseTransform * trans,
+    GstBuffer * inbuf, GstMeta * meta, GstBuffer * outbuf);
 
 static gboolean gst_video_scale_set_info (GstVideoFilter * filter,
     GstCaps * in, GstVideoInfo * in_info, GstCaps * out,
@@ -283,10 +288,15 @@ gst_video_scale_class_init (GstVideoScaleClass * klass)
       GST_DEBUG_FUNCPTR (gst_video_scale_transform_caps);
   trans_class->fixate_caps = GST_DEBUG_FUNCPTR (gst_video_scale_fixate_caps);
   trans_class->src_event = GST_DEBUG_FUNCPTR (gst_video_scale_src_event);
+  trans_class->transform_meta =
+      GST_DEBUG_FUNCPTR (gst_video_scale_transform_meta);
 
   filter_class->set_info = GST_DEBUG_FUNCPTR (gst_video_scale_set_info);
   filter_class->transform_frame =
       GST_DEBUG_FUNCPTR (gst_video_scale_transform_frame);
+
+  _size_quark = g_quark_from_static_string (GST_META_TAG_VIDEO_SIZE_STR);
+  _scale_quark = gst_video_meta_transform_scale_get_quark ();
 }
 
 static void
@@ -487,6 +497,57 @@ gst_video_scale_transform_caps (GstBaseTransform * trans,
   return ret;
 }
 
+static gboolean
+gst_video_scale_transform_meta (GstBaseTransform * trans, GstBuffer * inbuf,
+    GstMeta * meta, GstBuffer * outbuf)
+{
+  GstVideoFilter *videofilter = GST_VIDEO_FILTER (trans);
+  const GstMetaInfo *info = meta->info;
+  const gchar *const *tags;
+  const gchar *const *curr = NULL;
+  gboolean should_copy = TRUE;
+  const gchar *const valid_tags[] = { GST_META_TAG_VIDEO_STR,
+    GST_META_TAG_VIDEO_COLORSPACE_STR,
+    GST_META_TAG_VIDEO_ORIENTATION_STR,
+    GST_META_TAG_VIDEO_SIZE_STR
+  };
+
+  tags = gst_meta_api_type_get_tags (info->api);
+
+  /* No specific tags, we are good to copy */
+  if (!tags) {
+    return TRUE;
+  }
+
+  /* We are only changing size, we can preserve other metas tagged as
+     orientation and colorspace */
+  for (curr = tags; *curr; ++curr) {
+
+    /* We dont handle any other tag */
+    if (!g_strv_contains (valid_tags, *curr)) {
+      should_copy = FALSE;
+      break;
+    }
+  }
+
+  /* Cant handle the tags in this meta, let the parent class handle it */
+  if (!should_copy) {
+    return GST_BASE_TRANSFORM_CLASS (parent_class)->transform_meta (trans,
+        inbuf, meta, outbuf);
+  }
+
+  /* This meta is size sensitive, try to transform it accordingly */
+  if (gst_meta_api_type_has_tag (info->api, _size_quark)) {
+    GstVideoMetaTransform trans =
+        { &videofilter->in_info, &videofilter->out_info };
+
+    return info->transform_func (outbuf, meta, inbuf, _scale_quark, &trans);
+  }
+
+  /* No need to transform, we can safely copy this meta */
+  return TRUE;
+}
+
 static gboolean
 gst_video_scale_set_info (GstVideoFilter * filter, GstCaps * in,
     GstVideoInfo * in_info, GstCaps * out, GstVideoInfo * out_info)
@@ -659,7 +720,8 @@ gst_video_scale_fixate_caps (GstBaseTransform * base, GstPadDirection direction,
   GstStructure *ins, *outs;
   const GValue *from_par, *to_par;
   GValue fpar = { 0, }, tpar = {
-  0,};
+    0,
+  };
 
   othercaps = gst_caps_truncate (othercaps);
   othercaps = gst_caps_make_writable (othercaps);