vapostproc: Make cb max values symmetrical to their min values.

Intel drivers expose some colorbalance's maximum values much more
bigger than their minimum values, given their middle values (default
value). This means, in practice, that the real middle point between
the maximum and minimum values implies a major change in the color
balance, which is not expected by the GStreamer color balance logic.

This patch makes the given maximum value symmetrical to the minimum
value, given the middle one (default value).

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1580>

diff --git a/subprojects/gst-plugins-bad/sys/va/gstvavpp.c b/subprojects/gst-plugins-bad/sys/va/gstvavpp.c
index d3ff5ea..be0453e 100644 (file)
--- a/subprojects/gst-plugins-bad/sys/va/gstvavpp.c
+++ b/subprojects/gst-plugins-bad/sys/va/gstvavpp.c
@@ -2160,6 +2160,21 @@ gst_va_vpp_colorbalance_list_channels (GstColorBalance * balance)
   return self->channels;
 }
 
+/* This assumes --as happens with intel drivers-- that max values are
+ * bigger than the simmetrical values of min values */
+static float
+make_max_simmetrical (GParamSpecFloat * fpspec)
+{
+  gfloat max;
+
+  if (fpspec->default_value == 0)
+    max = -fpspec->minimum;
+  else
+    max = fpspec->default_value + ABS (fpspec->minimum - fpspec->default_value);
+
+  return MIN (max, fpspec->maximum);
+}
+
 static gboolean
 _set_cb_val (GstVaVpp * self, const gchar * name,
     GstColorBalanceChannel * channel, gint value, gfloat * cb)
@@ -2167,7 +2182,7 @@ _set_cb_val (GstVaVpp * self, const gchar * name,
   GObjectClass *klass = G_OBJECT_CLASS (GST_VA_VPP_GET_CLASS (self));
   GParamSpec *pspec;
   GParamSpecFloat *fpspec;
-  gfloat new_value;
+  gfloat new_value, max;
   gboolean changed;
 
   pspec = g_object_class_find_property (klass, name);
@@ -2175,14 +2190,16 @@ _set_cb_val (GstVaVpp * self, const gchar * name,
     return FALSE;
 
   fpspec = G_PARAM_SPEC_FLOAT (pspec);
-  new_value = (value - channel->min_value) * (fpspec->maximum - fpspec->minimum)
+  max = make_max_simmetrical (fpspec);
+
+  new_value = (value - channel->min_value) * (max - fpspec->minimum)
       / (channel->max_value - channel->min_value) + fpspec->minimum;
 
   GST_OBJECT_LOCK (self);
   changed = new_value != *cb;
   *cb = new_value;
   value = (*cb + fpspec->minimum) * (channel->max_value - channel->min_value)
-      / (fpspec->maximum - fpspec->minimum) + channel->min_value;
+      / (max - fpspec->minimum) + channel->min_value;
   GST_OBJECT_UNLOCK (self);
 
   if (changed) {
@@ -2217,16 +2234,18 @@ _get_cb_val (GstVaVpp * self, const gchar * name,
   GObjectClass *klass = G_OBJECT_CLASS (GST_VA_VPP_GET_CLASS (self));
   GParamSpec *pspec;
   GParamSpecFloat *fpspec;
+  gfloat max;
 
   pspec = g_object_class_find_property (klass, name);
   if (!pspec)
     return FALSE;
 
   fpspec = G_PARAM_SPEC_FLOAT (pspec);
+  max = make_max_simmetrical (fpspec);
 
   GST_OBJECT_LOCK (self);
   *val = (*cb + fpspec->minimum) * (channel->max_value - channel->min_value)
-      / (fpspec->maximum - fpspec->minimum) + channel->min_value;
+      / (max - fpspec->minimum) + channel->min_value;
   GST_OBJECT_UNLOCK (self);
 
   return TRUE;